pspice® advanced analysis user’s guide

PSpice Advanced Analysis Users GuideProduct Version 15.7July 2006

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PSpice Advanced Analysis Users Guide

July 2006 3 Product Version 15.7

Before you begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9How to use this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Symbols and conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Related documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Accessing online documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Advanced Analysis overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Project setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Validating the initial project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Advanced Analysis files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Numerical conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2Libraries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Parameterized components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Location of Advanced Analysis libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Using Advanced Analysis libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Using the online Advanced Analysis library list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Using the library tool tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Using Parameterized Part icon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Preparing your design for Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Creating new Advanced Analysis-ready designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Using the design variables table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Contents



Modifying existing designs for Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Selecting a parameterized component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Setting a parameter value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Using the design variables table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38For power users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Legacy PSpice optimizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Sensitivity overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Sensitivity strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Plan ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Sensitivity procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Setting up the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Setting up Sensitivity in Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Running Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Controlling Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Sending parameters to Optimizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Sensitivity calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

4Optimizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71Optimizer overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71Terms you need to understand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Optimizer procedure overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Setting up in the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Setting up Optimizer in Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Running Optimizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Assigning available values with the Discrete engine . . . . . . . . . . . . . . . . . . . . . . . . 105Finding components in your schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106Examining a Run in PSpice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106



Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107Optimizing a design using measurement specifications . . . . . . . . . . . . . . . . . . . . . . 107Optimizing a design using curve-fit specifications . . . . . . . . . . . . . . . . . . . . . . . . . . 125

For Power Users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131What are Discrete Tables? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131Adding User-Defined Discrete Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132Device-Level Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133Optimizer log files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Engine Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

5Smoke. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137Smoke overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137Smoke strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Plan ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Smoke procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139Setting up the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139Running Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140Configuring Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144Setting up the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144Running Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146Configuring Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

For power users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154Smoke parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154Adding Custom Derate file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160Supported Device Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

6Monte Carlo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179Monte Carlo overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179



Monte Carlo strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180Plan Ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Monte Carlo procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183Setting up the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183Setting up Monte Carlo in Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184Running Monte Carlo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185Reviewing Monte Carlo data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186Controlling Monte Carlo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190Printing results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192Saving results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194Setting up the circuit in the schematic editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194Setting up Monte Carlo in Advanced Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197Running Monte Carlo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202Reviewing Monte Carlo data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203Controlling Monte Carlo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211Printing results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215Saving results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

7Parametric Plotter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217Launching Parametric Plotter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218Sweep Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

Adding sweep parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222Specifying measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

Adding measurement expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225Adding a trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Running Parametric Plotter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227Viewing results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

Results tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227Analyzing Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228Plot Information tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229



Adding plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230Viewing the plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231Measurements Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

8Measurement Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245Measurements overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245Measurement strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246Procedure for creating measurement expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246

Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246Composing a measurement expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247Viewing the results of measurement evaluations . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248Viewing the results of measurement evaluations. . . . . . . . . . . . . . . . . . . . . . . . . . . 252Measurement definitions included in PSpice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

For power users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259Creating custom measurement definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259Definition example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261Measurement definition syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263Syntax example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

9Optimization Engines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275LSQ engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

Principles of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276Configuring the LSQ engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

Modified LSQ engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288Configuring the Modified LSQ engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

Random engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293Configuring the Random Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

Discrete engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296Commercially available values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298



10Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299In this chapter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299Troubleshooting feature overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302Setting up the example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302Using the troubleshooting function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306Analyzing the trace data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309Resolving the optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

Common problems and solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

AProperty Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327Template property file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

The model_info section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331The model_params section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332The smoke section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

The device property file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339The device_info section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340

Optional sections in a device property file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355

PSpice Advanced Analysis Users Guide 9

Before you begin

WelcomeAdvanced Analysis allows PSpice and PSpice A/D users tooptimize performance and improve quality of designs beforecommitting them to hardware. Advanced Analysis fourimportant capabilities: sensitivity analysis, optimization, yieldanalysis (Monte Carlo), and stress analysis (Smoke) addressdesign complexity as well as price, performance, and qualityrequirements of circuit design.

Advanced Analysis is integrated with OrCAD Capture and isavailable on Windows 98, Windows NT, and Windows 2000platforms.

Chapter Before you begin Product Version 15.7

10 PSpice Advanced Analysis Users Guide

How to use this guideThis guide is designed to make the most of the advantages ofonscreen books. The table of contents, index, and crossreferences provide instant links to the information you need.Just click on the text and jump.Each chapter about an Advanced Analysis tool isself-contained. The chapters are organized into thesesections:

Overview: introduces you to the tool

Strategy: gives you tips on planning your project Procedure: lists each step you need to successfully apply

the tool

Example: lists the same steps with an illustrating example

For power users: provides background information

If you find printed paper helpful, print only the section youneed at the time. When you want an in-depth tutorial, print theexample. When you want a quick reminder of a procedure,print the procedure.

Symbols and conventions

Our documentation uses a few special symbols andconventions.

Notation Examples DescriptionBold text Import Measurements,

Modified LSQ,PDF Graph

Indicates that text is a menuor button command, dialogbox option, column or graphlabel, or drop-down list option

Icon graphic , , Shows the toolbar icon thatshould be clicked with yourmouse button to accomplish atask

Product Version 15.7 Related documentation


Related documentationIn addition to this guide, you can find technical productinformation in the embedded AutoHelp, in related onlinedocumentation, and on our technical website. The table belowdescribes the type of technical documentation provided withAdvanced Analysis.

Lowercase fileextensions

.aap, .sim, .drt Indicates a file nameextension

This documentation component . . . Provides this . . .This guidePSpice Advanced Analysis UsersGuide

A comprehensive guide for understanding andusing the features available in Advanced Analysis.



Help system (automatic and manual) Provides comprehensive information forunderstanding the features in Advanced Analysisand using them to perform specific analyses.Advanced Analysis provides help in two ways:automatically (AutoHelp) and manually.AutoHelp is embedded in its own window andautomatically displays help topics that areassociated with your current activity as you moveabout and work within the Advanced Analysisworkspace and interface. It provides immediateaccess to information that is relative to yourcurrent task, but lacks the complete set ofnavigational tools for accessing other topics.The manual method lets you open the help systemin a separate browser window and gives you fullnavigational access to all topics and resourcesoutside of the help system.Using either method, help topics include: Explanations and instructions for common tasks Descriptions of menu commands, dialog boxes,

tools on the toolbar and tool palettes, and thestatus bar

Glossary terms Reference information Product support information

PSpice Users Guide An online, searchable users guidePSpice Library List An online, searchable library list for PSpice model

librariesPSpice Reference Guide An online, searchable reference manual for the

PSpice simulation software productsPSpice Quick Reference Concise descriptions of the commands, shortcuts,

and tools available in PSpiceOrCAD Capture Users Guide An online, searchable users guide

This documentation component . . . Provides this . . .

Product Version 15.7 Related documentation


Accessing online documentation

To access online documentation, you must open the CadenceDocumentation window.

1 Do one of the following:

a.From the Windows Start menu, choose OrCAD 10.0programs folder and then the Online Documentationshortcut.

b.From the Help menu in PSpice, choose Manuals.2 Do one of the following:

a. From the Windows Start menu, choose CadenceAllegro 15.2 programs folder and then the OnlineDocumentation shortcut.

b.From the Help menu in AMS Simulator, choose Manuals.

The Cadence Documentation window appears.3 Click the PSpice category to show the documents in the

category.4 Double-click a document title to load that document into

your web browser.

OrCAD Capture Quick Reference Card Concise descriptions of the commands, shortcuts,and tools available in Capture

This documentation component . . . Provides this . . .


1

Introduction

In this chapter Advanced Analysis overview on page 15

Project setup on page 16 Advanced Analysis files on page 18

Workflow on page 18

Numerical conventions on page 20

Advanced Analysis overviewAdvanced Analysis is an add-on program for PSpice andPSpice A/D. Use these four Advanced Analysis tools toimprove circuit performance, reliability, and yield:

Sensitivity identifies which components have parameterscritical to the measurement goals of your circuit design.

The four Optimizer engines optimize the parameters ofkey circuit components to meet your performance goals.

Smoke warns of component stress due to powerdissipation, increase in junction temperature, secondarybreakdowns, or violations of voltage / current limits.

Chapter 1 Introduction Product Version 15.7


Monte Carlo estimates statistical circuit behavior andyield.

Project setupBefore you begin an Advanced Analysis project, you need: Circuit components that are Advanced Analysis-ready

Only those components that you want tested in AdvancedAnalysis have to be Advanced Analysis-ready. SeeChapter 2, Libraries.

Note: You can adapt passive RLC components forAdvanced Analysis without choosing them fromparameterized libraries. See Chapter 2, Libraries.

A circuit drawn in Capture and successfully simulated inPSpice.

PSpice measurements that check circuit behavior criticalto your design.

Creating measurement expressions

Sensitivity, Optimizer, and Monte Carlo require measurementexpressions as input. You should create these measurementsexpressions in PSpice so you can test the results.

You can also create measurement expressions in Sensitivity,Optimizer, or Monte Carlo which can be exported to eachother, but these measurements cannot be exported to PSpicefor testing.

Product Version 15.7 Project setup


Validating the initial projectBefore you use Advanced Analysis:1 Make your circuit components Advanced-Analysis ready

for the components you want to analyze.

See Chapter 2, Libraries for more information.2 Set up a PSpice simulation.

The Advanced Analysis tools use the followingsimulations:

3 Simulate the circuit and make sure the results andwaveforms are what you expect.

4 Define measurements in PSpice to check the circuitbehaviors that are critical for your design. Make sure themeasurement results are what you expect.

Note: For information on setting up circuits, see yourschematic editor user guide, Project setup on page 16,and Chapter 2, Libraries.

For information on setting up simulations, see yourPSpice Users Guide.

This tool... Works on these PSpice simulations...Sensitivity Time Domain (transient)

DC SweepAC Sweep/Noise

Optimizer Time Domain (transient)DC SweepAC Sweep/Noise

Smoke Time Domain (transient)Monte Carlo Time Domain (transient)

DC SweepAC Sweep/Noise



For information on setting up measurements, seeProcedure for creating measurement expressions onpage 246.

Advanced Analysis filesThe principal files used by Advanced Analysis are:

PSpice simulation profiles (.sim) Advanced Analysis profiles (.aap)Advanced users may also use these files:

Device property files (.prp)For more information, see Appendix A, Property Files.

Custom derating files for Smoke (.drt)For more information, see the technical note titledCreating Custom Derating Files for AdvancedAnalysis Smoke on www.orcadpcb.com.

Discrete value tables for Optimizer (.table)For more information, see What are Discrete Tables? onpage 131.

WorkflowThere are many ways to use Advanced Analysis. Thisworkflow shows one way to use all four features.

Product Version 15.7 Workflow




Numerical conventionsPSpice ignores units such as Hz, dB, Farads, Ohms, Henrys,volts, and amperes. It adds the units automatically, dependingon the context.

Name Numericalvalue

Usertypes in: Or:

ExampleUses

femto- 10-15 F, f 1e-15 2f2F2e-15

pico- 10-12 P, p 1e-12 40p40P40e-12

nano- 10-9 N, n 1e-9 70n70N70e-9

micro- 10-6

.000001U, u 1e-6 20u

20U20e-6

milli- 10-3.001

M, m 1e-3 30m30M30e-3.03

kilo- 103

1000K, k 1e+3 2k

2K2e32e+32000

Product Version 15.7 Numerical conventions


mega- 1061,000,000

MEG,meg

1e+6 20meg20MEG20e620e+620000000

giga- 109 G, g 1e+9 25g25G25e925e+9

tera- 1012 T, t 1e+12 30t30T30e1230e+12

Name Numericalvalue

Usertypes in: Or:

ExampleUses


2

Libraries

In this chapter Overview on page 23

Using Advanced Analysis libraries on page 27

Preparing your design for Advanced Analysis on page 30

Example on page 36

For power users on page 39

OverviewPSpice ships with over 30 Advanced Analysis librariescontaining over 4,300 components. Separate library lists areprovided for Advanced Analysis libraries and standard PSpicelibraries. The components in the Advanced Analysis librariesare listed in the Advanced Analysis library list. See Usingthe online Advanced Analysis library list on page 28 fordetails.

The Advanced Analysis libraries contain parameterized andstandard components. The majority of the components areparameterized. Standard components in the AdvancedAnalysis libraries are similar to components in the standardPSpice libraries and will not be discussed further in thisdocument.

Chapter 2 Libraries Product Version 15.7


Parameterized components

A parameter is a physical characteristic of a component thatcontrols behavior for the component model. In Capture, aparameter is called a property. A parameter value is either anumber or a variable. When the parameter value is a variable,you have the option to vary its numerical solution within amathematical expression and use it in optimization.

Design EntryWhen the parameter value is a variable, you havethe option to vary its numerical solution within a mathematicalexpression and use it in optimization.In the AdvancedAnalysis libraries, components may contain one or more of thefollowing parameters:

Tolerance parameters

For example, for a resistor the positive tolerance could bePOSTOL = 10%.

Distribution parameters

For example, for a resistor the distribution function usedin Monte Carlo analysis could be DIST = FLAT.

Optimizable parameters

For example, for an opamp the gain bandwidth could beGBW = 10 MHz.

Smoke parameters

For example, for a resistor the power maximum operatingcondition could be POWER = 0.25 W.

To analyze a circuit component with an Advanced Analysistool, make sure the component contains the followingparameters:

This AdvancedAnalysis tool...

Uses these componentparameters...

Sensitivity Tolerance parametersOptimizer Optimizable parametersSmoke Smoke parameters

Product Version 15.7 Overview



Tolerance parameters define the positive and negativedeviation from a components nominal value. In order toinclude a circuit component in a Sensitivity or Monte Carloanalysis, the component must have tolerances for theparameters specified. Use the Advanced Analysis librarylist to identify components with parameter tolerances.

In Advanced Analysis, tolerance information includes:

Positive tolerance

For example, POSTOL for RLC is the amount a value canvary in the plus direction.

Negative tolerance

For example, NEGTOL for RLC is the amount a value canvary in the negative direction.

Tolerance values can be entered as percents or absolutenumbers.

Distribution parameters

Distribution parameters define types of distribution functions.Monte Carlo uses these distribution functions to randomlyselect tolerance values within a range.

Monte Carlo Tolerance parameters,Distribution parameters(default parameter value is Flat /Uniform)

This AdvancedAnalysis tool...

Uses these componentparameters...



For example, in Captures property editor, a resistor couldprovide the following information:


Optimizable parameters are any characteristics of a modelthat you can vary during simulations. In order to include acircuit component in an Optimizer analysis, the componentmust have optimizable parameters. Use the AdvancedAnalysis library list to identify components with optimizableparameters.

For example, in Captures property editor, an opamp couldprovide the following gain bandwidth:

Note that the parameter is available for optimization only if youadd it as a property on the schematic instance and assign it avalue.

During Optimization, the GBW can be varied between anyuser-defined limits to achieve the desired specification.

Smoke parameters

Smoke parameters are maximum operating conditions for thecomponent. To perform a Smoke analysis on a component,define the smoke parameters for that component. You can stilluse non-smoke-defined components in your design, but thesmoke test ignores these components. Use the onlineAdvanced Analysis library list to identify components withsmoke parameters.

Property ValueDIST FLAT

Property ValueGBW 1e7

Product Version 15.7 Using Advanced Analysis libraries


Most of the analog components in the standard PSpicelibraries also contain smoke parameters. Use the onlinePSpice library list to identify components in the standardPSpice libraries that have smoke parameters.

See also Smoke parameters on page 154.

For example, in Captures property editor, a resistor couldprovide the following smoke parameter information:

Use the design variables table to set the values of RMAX andRTMAX to 0.25 Watts and 200 degrees Centigrade,respectively.

See Using the design variables table on page 33.

Location of Advanced Analysis libraries

The program installs the Advanced Analysis libraries to thefollowing locations:

Capture symbol libraries

\Capture\Library\PSpice\AdvAnls\

PSpice Advanced Analysis model libraries

\ PSpice \ Library

Using Advanced Analysis librariesIn Capture, there are three ways to quickly identify if acomponent is from an Advanced Analysis library:

Property ValuePOWER RMAXMAX_TEMP

RTMAX



Looking in the online Advanced Analysis library list

Using the library tool tip in the Place Part dialog box

Using the Parameterized Part icon in the Place Partdialog box

Using the online Advanced Analysis library list

You can find the online Advanced Analysis library list fromyour Windows Start menu.1 Do one of the following:

From the Windows Start menu, choose theOrCAD 10.0 programs folder and then the OnlineDocumentation shortcut.

From the Help menu in PSpice, choose Manuals.

The Cadence Documentation window appears.2 Click the PSpice category to show the documents in the

category.3 Double-click Advanced Analysis library list to load the

document into your web browser.

The Advanced Analysis library list contains the names ofparameterized and standard libraries. Most of the libraries areparameterized. Standard components in the AdvancedAnalysis libraries are similar to standard PSpice librarycomponents. Each library contains the following items:

Component names and part numbers

Manufacturer names

Lists of component parameters for each component



Smoke parameters

Some component libraries, primarily opamp libraries, containcomponents with all of the parameter types.

Product Version 15.7 Using Advanced Analysis libraries


Examples from the library list are shown below:

The parameter columns are the three columns on the right inthe list. The abbreviations in the parameter columns have thefollowing meanings:

Using the library tool tip

One easy way to identify if a component comes from anAdvanced Analysis library is to use the tool tip in the PlacePart dialog box.1 From the Place menu, select Part.

Device Type GenericName

Part Name PartLibrary

Mfg. Name TOL OPT SMK

Opamp AD101A AD101A OPA AnalogDevices

Y Y Y

BipolarTransistor

2N1613 2N1613 BJN Motorola N Y Y

AnalogMultiplier

AD539 AD539 DRI AnalogDevices

N N N

This library listcolumnheading...

With thefollowingnotation... Means the component...

TOL Y Has tolerance parameters in the modelTOL N Does not have tolerance parameters in the modelOPT Y Has optimizable parameters in the modelOPT N Does not have optimizable parameters in the modelSMK Y Has smoke parameters in the modelSMK N Does not have smoke parameters in the modelDIST Y Has a distribution parameter associated with the modelDIST N Does not have a distribution parameter associated with

the model



The Place Part dialog box appears.2 Enter a component name in the Part text box.3 Hover your mouse over the highlighted component name.

A library path name appears in a tool tip.4 Check for ADVANLS in the path name.

If ADVANLS is in the path name, the component comesfrom an Advanced Analysis library.

Using Parameterized Part icon

Another easy way to identify if a component comes from anAdvanced Analysis library is to use the Parameterized Particon in the Place Part dialog box.1 From the Place menu, select Part.

The Place Part dialog box appears.2 Enter a component name in the Part text box.

Or:

Scroll through the Part List text box3 Look for in the lower right corner of the dialog box.

This is the Parameterized Part icon. If this icon appearswhen the part name appears in the Part text box, thecomponent comes from an Advanced Analysis library.

Preparing your design for Advanced Analysis

You may use a mixture of standard and parameterizedcomponents in your design, but Advanced Analysis isperformed on only the parameterized components.

You may create a new design or use an existing design forAdvanced Analysis. There are several steps for making yourdesign Advanced Analysis-ready.

Product Version 15.7 Preparing your design for Advanced Analysis


See Modifying existing designs for Advanced Analysis onpage 35.

Creating new Advanced Analysis-ready designs

Select parameterized components from Advanced Analysislibraries.

1 Open the online Advanced Analysis library list foundin Cadence Online Documentation.

2 Find a component marked with a Y in the TOL, OPT, orSMK columns of the Advanced Analysis library list.

Components marked in this manner are parameterizedcomponents.

3 For that component, write down the Part Library andPart Name from the Advanced Analysis library list.

4 Add the library to your design in your schematic editor.5 Place the parameterized component on your schematic.

For example, select the resistor component from thepspice_elem Advanced Analysis library.

Setting a parameter value

For each parameterized component in your design, set theparameter value individually on the component using yourschematic editor.

A convenient way to add parameter values on a global basisis to use the design variable table.


Note: If you set a value for POSTOL and leave the value forNEGTOL blank, Advanced Analysis will automaticallyset the value of NEGTOL equal to the value of POSTOLand perform the analysis.



Note: As a minimum, you must set a value for POSTOL. If youset a value for NEGTOL and leave the POSTOL valueblank, Advanced Analysis will not include theparameter in Sensitivity or Monte Carlo analyses.

Adding additional parameters

If the component does not have Advanced Analysisparameters visible on the symbol, add the appropriateAdvanced Analysis parameters using your schematic editor.

For example: For RLC components, the parameters requiredfor Advanced Analysis Sensitivity and Monte Carlo are listedbelow. The values shown are those that can be set using thedesign variables table.


For RLC components, the parameter required for AdvancedAnalysis Optimizer is the value for the component. Examplesare listed below:

Part Tolerance Property Name ValueResistor POSTOL RTOL%Resistor NEGTOL RTOL%Inductor POSTOL LTOL%Inductor NEGTOL LTOL%Capacitor POSTOL CTOL%Capacitor NEGTOL CTOL%

Part Optimizable Property Name ValueResistor VALUE 10KInductor VALUE 33mCapacitor VALUE 0.1u

Product Version 15.7 Preparing your design for Advanced Analysis


For example: For RLC components, the parameters requiredfor Advanced Analysis Smoke are listed below. The valuesshown are those that can be set using the design variablestable.


If you use RLC components from the analog library, you willneed to add parameters and set values; however, instead ofsetting values for the POSTOL and NEGTOL parameters, youset the values for the TOLERANCE parameter. The positiveand negative tolerance values will use the value assigned tothe TOLERANCE parameter.

Using the design variables table

The design variables table is a component available in theinstalled libraries that allows you to set global values forparameters. For example, using the design variables table,you can easily set a 5% positive tolerance on all your circuitresistors. The default information available in the designvariables table includes variable names for tolerance andsmoke parameters. For example, RTOL is a variable name in

Part Smoke Property Name ValueResistor MAX_TEMP RTMAXResistor POWER RMAXResistor SLOPE RSMAXResistor VOLTAGE RVMAXInductor CURRENT DIMAXInductor DIELECTRIC DSMAXCapacitor CURRENT CIMAXCapacitor KNEE CBMAXCapacitor MAX_TEMP CTMAXCapacitor SLOPE CSMAXCapacitor VOLTAGE CMAX



the design variables tables, which can be used to set POSTOL(and NEGTOL) tolerance values on all your circuit resistors.1 From Captures Place menu, select Part.2 Add the PSpice SPECIAL library to your design libraries.3 Select the Variables component from the PSpice

SPECIAL library.4 Click OK.

A design variable table of parameter variable names willappear on the schematic.

5 Double click on a number in the design variable table.

The Display Properties dialog box will appear.6 Edit the value in the Value text box.

7 Click OK.

The new numerical value will appear on the designvariables table on the schematic and be used as a globalvalue for all applicable components.

Parameter values set on a component instance will overridevalues set in the design variables table.

Product Version 15.7 Modifying existing designs for Advanced Analysis


Modifying existing designs for Advanced AnalysisExisting designs that you construct with standard componentswill work in Advanced Analysis; however, you can only performAdvanced Analysis on the parameterized components. Tomake sure specific components are Advanced Analysis-ready(parameterized), do the following steps: Set tolerances for the RLC components

Note: For standard RLC components, the TOLERANCEproperty can be used to set tolerance values required forSensitivity and Monte Carlo. Standard RLC componentscan also be used in the Optimizer.

Replace active components with parameterizedcomponents from the Advanced Analysis libraries

Add smoke parameters and values to RLC components



ExampleThis example is a simple addition of a parameterizedcomponent to a new design.

Well add a parameterized resistor to a schematic and showhow to set values for the resistor parameters using theproperty editor and the design variables table.

Selecting a parameterized component

We know the pspice_elem library on the AdvancedAnalysis library list contains a resistor component withtolerance, optimizable, and smoke parameters. Well use thatcomponent in our example.1 In Capture, from the Place menu, select Part.

The Place Part dialog box appears.

2 Use the Add Library browse button to add thepspice_elem library from the advanls folder to theLibraries text box.

3 Select Resistor and click OK.

The resistor appears on the schematic.

Add thepspice_elemlibrary from theadvanls folder

Note ADVANLSin library pathname

Icon tells you thepart isparameterized

Select resistorfrom thepspice_elemlibrary

Product Version 15.7 Example


Setting a parameter value1 Double click on the Resistor symbol.

The Property Editor appears. Note the AdvancedAnalysis parameters already listed for this component.

2 Verify that all the parameters required for Sensitivity,Optimizer, Smoke, and Monte Carlo are visible on thesymbol.

Refer to the tables in Adding additional parameters onpage 32.

3 Set the resistor VALUE parameter to 10k.4 Set the resistor POSTOL parameter to RTOL%.

Toleranceparameters

Smokeparameter

Optimizableparameter

Smokeparameters

Smokeparameter

Distributionparameter



Using the design variables tableSet the resistor parameter values using the design variablestable.

Well do one parameter for this resistor.1 Select the Variables part from the PSpice SPECIAL

library.

The design variables table appears on the schematic.

2 Double click on the RTOL number 0 in the designvariables table.

Note tool tipwith the librarypath name

Double click onvariable name to editvalue

Product Version 15.7 For power users


The Display Properties dialog box appears.

3 Edit the value in the Value text box.

4 Click OK.

The new numerical value will appear on the designvariable table on the schematic.

Advanced Analysis will now use the resistor with a positivetolerance parameter set to 10%. If we added more resistors tothis design, we could then set the POSTOL resistor parametervalues to RTOL% and each resistor would immediately applythe 10% value from the design variables table.

Note: Values set on the component instance override valuesset with the design variables table.

For power users

Legacy PSpice optimizations

For tips on importing legacy PSpice Optimizations intoAdvanced Analysis Optimizer, see our technical note onimporting legacy PSpice optimizations.

Technical notes are posted on the PSPice page of the OrCADcommunity web site, www.orcadpcb.com.

Edit value from 0 to10

Click OK


3

Sensitivity

In this chapter Sensitivity overview on page 41

Sensitivity strategy on page 43

Sensitivity procedure on page 44

Example on page 53

For power users on page 66

Sensitivity overviewNote: Sensitivity analysis is available with the following

products:

PSpice Advanced Optimizer Option

PSpice Advanced Analysis

Sensitivity identifies which components have parameterscritical to the measurement goals of your circuit design.

The Sensitivity Analysis tool examines how much eachcomponent affects circuit behavior by itself and in comparisonto the other components. It also varies all tolerances to createworst-case (minimum and maximum) measurement values.

Chapter 3 Sensitivity Product Version 15.7


You can use Sensitivity to identify the sensitive components,then export the components to Optimizer to fine-tune thecircuit behavior.

You can also use Sensitivity to identify which componentsaffect yield the most, then tighten tolerances of sensitivecomponents and loosen tolerances of non-sensitivecomponents. With this information you can evaluate yieldversus cost trade-offs.

Absolute and relative sensitivity

Sensitivity displays the absolute sensitivity or the relativesensitivity of a component. Absolute sensitivity is the ratio ofchange in a measurement value to a one unit positive changein the parameter value.

For example: There may be a 0.1V change in voltage for a 1Ohm change in resistance.

Relative sensitivity is the percentage of change in ameasurement based on a one percent positive change of acomponent parameter value.

For example: For each 1 percent change in resistance, theremay be 2 percent change in voltage.

Since capacitor and conductor values are much smaller thanone unit of measurement (Farads or Henries), relativesensitivity is the more useful calculation.

For more on how this tool calculates sensitivity, see Sensitivitycalculations on page 66.

Absolute sensitivity should be used when the tolerance limitsare not tight or have wide enough bandwidth. Where asrelative sensitivity should be used when the tolerance limitsare tight enough or have less bandwidth. The tolerancevariations are assumed to be linear in this case.

Product Version 15.7 Sensitivity strategy


Sensitivity strategyIf Sensitivity analysis shows that the circuit is highly sensitiveto a single parameter, adjust component tolerances on theschematic and rerun the analysis before continuing on toOptimizer.

Optimizer works best when all measurements are initiallyclose to their specification values and require only fineadjustments.

Plan ahead

Sensitivity requires:

Circuit components that are Advanced Analysis-ready

See Chapter 2, Libraries for more information.

A circuit design, that is working and can be simulated inPSpice

Measurements set up in PSpice

See Procedure for creating measurement expressions onpage 246

Any circuit components you want to include in the Sensitivitydata need to be Advanced Analysis-ready, with theirtolerances specified.

See Chapter 2, Libraries for more information.



Workflow

Sensitivity procedure

Setting up the circuit in the schematic editor

Start with a working circuit in the schematic editor. Circuitcomponents you want to include in the Sensitivity data needto have the tolerances of their parameters specified. Circuitsimulations and measurements should already be set up.

The simulations can be Time Domain (transient), DC Sweep,and AC Sweep/Noise analyses.

Product Version 15.7 Sensitivity procedure


1 Open your circuit from your schematic editor.2 Run a PSpice simulation.3 Check your key waveforms in PSpice and make sure they

are what you expect.4 Check your measurements and make sure they have the

results you expect.

Note: For information on circuit layout and simulation setup,see your schematic editor and PSpice user guides.

For information on components and the tolerances of theirparameters, see Preparing your design for Advanced Analysison page 30.

For information on setting up measurements, see Procedurefor creating measurement expressions on page 246.

For information on testing measurements, see Viewing theresults of measurement evaluations on page 248.

Setting up Sensitivity in Advanced Analysis1 From the PSpice menu in your schematic editor, select

Advanced Analysis / Sensitivity.

The Advanced Analysis Sensitivity tool opens.

Parameters Window

In the Parameters window, a list of component parametersappears with the parameter values listed in the Originalcolumn. Only the parameters for which tolerances arespecified appear in the Parameters window.

Note: Sensitivity analysis can only be run if tolerances arespecified for the component parameters.

In case you want to remove a parameter from the list, you cando so by using the TOL_ON_OFF property. In the schematicdesign, set the value of TOL_ON_OFF property attached tothe instance as OFF. If there is no TOL_ON_OFF propertyattached to the instance of the device, attach the property and



set its value to OFF. This is so, because if the tolerance valueis specified for a parameter and TOL_ON_OFF property is notattached to the component, by default Advanced Analysisassumes that the value of TOL_ON_OFF property is set toON.

In case of hierarchical designs, the value of the TOL_ON_OFFproperty attached to the hierarchical block has a higherpriority over the property value attached to the individualcomponents. For example, if the hierarchical block has theTOL_ON_OFF property value set to OFF, tolerance values ofall the components within that hierarchical design will beignored.

Specifications Window

In the Specifications window, add measurements for whichyou want to analyze the sensitivity of the parameters. You caneither import the measurements created in PSpice or cancreate new measurements in Advanced Analysis.

To import measurements:1 In the Specifications table, click on the row containing the

text Click here to import a measurement created withinPSpice.

The Import Measurement(s) dialog box appears.2 Select the measurements you want to include.



To create new measurements:

1 From the Analysis drop-down menu, chooseSensitivity / Create New Measurements.

The New Measurement dialog box appears.2 Create the measurement expression to be evaluated and

click OK.

Running Sensitivity Click on the top toolbar.

The Sensitivity analysis begins. The messages in theoutput window tell you the status of the analysis.

For more information, see Sensitivity calculations onpage 66.

Displaying run data

Sensitivity displays results in two tables for each selectedmeasurement:

Parameters table

Parameter values at minimum and maximummeasurement values

Absolute / Relative sensitivities per parameter

Linear / Log bar graphs per parameter

Specifications table

Worst-case min and max measurement values

Sorting data

Double click on column headers to sort data in ascendingor descending order.



Reviewing measurement data

Select a measurement on the Specifications table.

A black arrow appears in the left column on theSpecifications table, the row is highlighted, and the Minand Max columns display the worst-case minimum andmaximum measurement values.

The Parameters table will display the values forparameters and measurements using the selectedmeasurement only.

Interpreting @min and @max

Values displayed in the @min and @max columns are theparameter values at the measurements worst-case minimumand maximum values.

If a measurement value is insensitive to a component, thesensitivity displayed for that component will be zero. In suchcases, values displayed in the @Min and @Max columns willbe same and will be equal to the Original value of thecomponent.

Negative and positive sensitivity

If the absolute or the relative sensitivity is negative it impliesthat for one unit positive increase in the parameter value, themeasurement value increases in the negative direction.

For example, if for a unit increase in the parameter value, themeasurement value decreases, the component exhibitsnegative sensitivity. It can also be that for a unit decrease inthe parameter value, there is an increase in the measurementvalue.

On the other hand, positive sensitivity implies that for a unitincrease in the component value, there is an increase in themeasurement value.



Changing from Absolute to Relative sensitivity

1 Right click anywhere in the Parameters table.2 Select Display / Absolute Sensitivity or Relative

Sensitivity from the pop-up menu.

Note: See Sensitivity calculations on page 66.

Changing bar graph style from linear to log

Most of the sensitivity values can be analyzed using the linearscale. Logarithmic scale is effective for analyzing the smallerbut non-zero sensitivity values.

To change the bar graph style,1 Right-click anywhere in the Parameters table.2 Select Bar Graph Style / Linear or Log from the

pop-up menu.

ImportantIf 'X' is the bar graph value on a linear scale, then thebar graph value on the logarithmic scale is notlog (X). The logarithmic values are calculatedseparately.

Interpreting results

Sensitivity displays on the bar graph when sensitivityvalues are very small but nonzero.

Interpreting zero results

Sensitivity displays zero in the absolute / relative sensitivityand bar graph columns if the selected measurement is notsensitive to the component parameter value.



Controlling Sensitivity

Data cells with cross-hatched backgrounds are read-only andcannot be edited. The graphs are also read-only.

Pausing, stopping, and starting

Pausing and resuming1 Click on the top toolbar.

The analysis stops, available data is displayed, and thelast completed run number appears in the output window.

2 Click the or to resume calculations.

Stopping

Click on the top toolbar.

If a Sensitivity analysis has been stopped, you cannotresume the analysis.

Sensitivity does not save data from a stopped analysis.

Starting

Click to start or restart.

Controlling measurement specifications

To exclude a measurement specification fromSensitivity analysis: click on the applicablemeasurement row in the Specifications table.

This removes the check and excludes themeasurement from the next Sensitivity analysis.

To add a new measurement: click on the rowcontaining the text Click here to import ameasurement created within PSpice.

The Import Measurement(s) dialog box appears.



Or:

Right click on the Specifications table and selectCreate New Measurement.

The New Measurement dialog box appears.

See Procedure for creating measurementexpressions on page 246.

To export a new measurement to Optimizer or MonteCarlo, select the measurement and right click on therow containing the text Click here to import ameasurement created within PSpice.

Select Send To from the pop-up menu.

Adjusting component valuesUse Find in Design from Advanced Analysis to quicklyreturn to the schematic editor and change componentinformation.

For example: You may want to tighten tolerances oncomponent parameters that are highly sensitive or loosentolerances on component parameters that are less sensitive.1 Right click on the components critical parameter in the

Sensitivity Parameters table and select Find in Designfrom the pop-up menu.

2 Change the parameter value in the schematic editor.3 Rerun the simulation and check results.

4 Rerun Sensitivity.

Varying the tolerance range

During Sensitivity analysis, by default Advanced Analysisvaries parameter values by 40% of the tolerance range. Youcan modify the default value and specify the percentage bywhich the parameter values should be varied within thetolerance range.



To specify the percentage variation:1 From the Edit drop-down menu in Advanced Analysis,

choose Profile Settings.2 In the Profile Settings dialog box, select the Sensitivity

tab.

3 In the Sensitivity Variation text box, specify thepercentage by which you want the parameter values to bevaried.

4 Click OK to save the modifications.

If you now run the Sensitivity analysis, the value specified byyou would be used for calculating the absolute and relativesensitivity.

Sending parameters to Optimizer1 Select the critical parameters in Sensitivity.2 Right click and select Send to Optimizer from the

pop-up menu.3 Select Optimizer from the drop-down list on the top

toolbar.

This switches the active window to the Optimizer viewwhere you can double check that your critical parametersare listed in the Optimizer Parameters table.

4 Click the Sensitivity tab at the bottom of the OptimizerSpecifications table.

This switches the active window back to the Sensitivitytool.

Printing results

Click .

Or:

From the File menu, select Print.



Saving results

Click .

Or:

From the File menu, select Save.

The final results will be saved in the Advanced Analysisprofile (.aap).

Example

The Advanced Analysis examples folder contains severaldemonstration circuits. This example uses the RFAmp circuit.

The circuit contains components with the tolerances of theirparameters specified, so you can use the components withoutany modification.

Two PSpice simulation profiles have already been created andtested. Circuit measurements, entered in PSpice, have beenset up and tested.

Note: See Chapter 2, Libraries for information about settingtolerances for other circuit examples.

Setting up the circuit in the schematic editor1 In your schematic editor, browse to the RFAmp tutorials

directory.

\PSpice\tutorial\Capture\pspiceaa\rfamp



2 Open the RFAmp project.

3 Select the SCHEMATIC1-AC simulation profile.

Assign globaltolerancesusing thistable



The AC simulation included with the RF example

1 Click to run the simulation.2 Review the results.

The waveforms are what we expected.

The measurements in PSpice give the results weexpected.

In the simulator,viewmeasurementresults



Setting up Sensitivity in Advanced Analysis1 From the PSpice menu in your schematic editor, select

Advanced Analysis / Sensitivity.

The Advanced Analysis window opens, and theSensitivity tool is activated. Sensitivity automatically listscomponent parameters for which tolerances are specifiedand the component parameter original (nominal) values.

Sensitivity Parameters table prior to the first run

Sensitivity Specifications table before a project is set up and run



In case you want to remove some parameters from theParameters list, you can do so by modifying theparameter properties in the schematic capture tool.

2 In the Specifications table, right click the row titled, Clickhere to import a measurement created within PSpice.

The Import Measurement(s) dialog box appears withmeasurements configured earlier in PSpice .

3 Select the four ac.sim measurements.4 Click OK.

The Specifications table lists the measurements.



Running Sensitivity


Click to start



Displaying run dataResults are displayed in the Parameters and Specificationstables according to the selected measurement.

Sorting data

Double click on the Linear column header to sort the bargraph data in ascending order. Double click again to sortthe data in descending order.

Parameter values thatcorrespond tomeasurement minand max values

Themeasurementsworst-caseminimum andmaximum values

Click to select themeasurement dataset for review

Double click column headings to chathe sort order

Right click to changeDisplay to AbsoluteSensitivity

Min means that the sensitivityis very small, but not zero

A zero (0) displays if there isno sensitivity at all

Hover your mouseover a red flag toread the errormessages

Click toexcludefromanalysis

Right click to change barfrom Linear to Log



Selecting the measurement to view

Select a measurement in the Specifications table.

The data in the Parameters table relates to themeasurement you selected.

Note: To see all the parameter and measurement valuesused in Sensitivity calculations: from the View menu,select Log File.

Changing from Absolute to Relative sensitivity1 Right click anywhere on the Parameters table.

Table... Column heading... Means...Parameters Original The nominal component parameter values

used to calculate nominal measurement.@Min The parameter value used to calculate the

worst-case minimum measurement.@Max The parameter value used to calculate the

worst-case maximum measurement.absolute sensitivity The change in the measurement value

divided by a unit of change in theparameter value.

relative sensitivity The percent of change in a measurementvalue based on a one percent change inthe parameter value.

Specifications Original The nominal value of the measurementusing original component parametervalues.

Min The worst-case minimum value for themeasurement.

Max The worst-case maximum value for themeasurement.



A pop-up menu appears

2 Select Relative Sensitivity.

Note: See Sensitivity calculations on page 66.

Changing the bar graph to linear view1 Right click anywhere on the Parameters table.

A pop-up menu appears.

2 Select Linear.



Controlling Sensitivity

Pausing, stopping, and starting

Pausing and resuming1 Click on the top toolbar.

The analysis stops, available data is displayed, and thelast completed run number appears in the output window.

2 Click the depressed or to resume calculations.

Stopping


If a Sensitivity analysis has been stopped, you cannotresume the analysis.

Starting

Click to start or resume.

Controlling Measurements

Click to pause

Click to start Click to stop

Click here to edit themeasurementexpression

Click to remove this checkmark and exclude thismeasurement from analysis



Adjusting component valuesIn the RF example, we will not change any componentparameters.

With another example you may decide after reviewingsensitivity results that you want to change component valuesor tighten tolerances. You can use Find in Design fromAdvanced Analysis to return to your schematic editor andlocate the components you would like to change.1 In the Parameters table, highlight the components you

want to change.2 Right click the selected components.


3 Left click on Find in Design.



The schematic editor appears with the componentshighlighted.

4 Change the parameter value in the schematic editor.5 Rerun the PSpice simulation and check results.6 Rerun Sensitivity.

Sending parameters to Optimizer

Review the results of the Sensitivity calculations. We need touse engineering judgment to select the sensitive componentsto optimize:

We wont change R5 or R9 because they control the inputand output impedances.

We wont change R2 or R3 because they controltransistor biasing.

The linear bar graph at the Relative Sensitivity setting showsthat R4, R6, and R8 are also critical parameters. Well importthese parameters and values to Optimizer.1 In the Parameters table, hold down the Ctrl key and select

R4, R6, and R8.



2 Right click the selected components.


3 Select Send to Optimizer.4 From the View menu, select Optimizer.

Optimizer becomes the active window and your criticalparameters are listed in the Optimizer Parameters table.

Printing results

Click .

Or:

Select Optimizer view toswitch to the Optimizerwindow and see theparameters you sent overfrom Sensitivity



From the File menu, select Print.

Saving results

Click .

Or:

From the File menu, select Save.

The final results will be saved in the Advanced Analysisprofile (.aap).

For power users

Sensitivity calculations

Absolute sensitivity

Absolute sensitivity is the ratio of change in a measurementvalue to a one unit positive change in the parameter value.

For example: There may be a 0.1V change in voltage for a 1Ohm change in resistance.

The formula for absolute sensitivity is:[(Ms - Mn) / (Pn * Sv * Tol)]

Where:

Ms = the measurement from the sensitivity run for thatparameter

Mn = the measurement from the nominal run

Tol = relative tolerance of the parameter

Pn = Nominal parameter value

Sv = Sensitivity Variation. (Default = 40%)By default, the parameter value is varied within 40% of the settolerance.



You can change this value to any desired percentage usingthe Profile settings dialog box.1 From the Edit drop-down menu, choose Profile Settings.2 In the Profile setting dialog box, select the Sensitivity tab.3 In the Sensitivity Variation dialog box, specify the value by

which you want to vary the parameter value.4 Click OK to save your settings.

The values entered by you in the Profile Setting dialog box, arestored for the future use as well. Every time you load theproject, old values are used for advanced analysissimulations.

Example

For example, if you specify the Sensitivity Variation as 10%,the parameter values will be varied within 10% of the tolerancevalue.

Consider that you want to test a resistor of 100k for sensitivity.The tolerance value attached to the resistor is 10%.

By default, for sensitivity calculations, the value of resistor willbe varied from 96K to 104K. But if you change thedefaultvalue of Sensitiviy Variation to 10%, the resistor values will bevaried from 99K to 101K for sensitivity calculations.

Relative sensitivity

Relative sensitivity is the percentage of change in ameasurement based on a one percent positive change of acomponents parameter value.

For example: For each 1 percent change in resistance, theremay be 2 percent change in voltage.

The formula for relative sensitivity is: [(Ms - Mn) / (Sv*Tol)]

Where:



Ms = the measurement from the sensitivity run for thatparameter

Mn = the measurement from the nominal run

Tol = relative tolerance of the parameter

Sv = Sensitivity Variation. (Default = 40%)Relative sensitivity calculations determine the measurementchange between simulations with the component parameterfirst set at its original value and then changed by Sv percentof its positive tolerance. Linearity is assumed. This approachreduces numerical calculation errors related to smalldifferences.

For example, assume that an analysis is run on a 100-ohmresistor which has a tolerance of 10 percent. The maximumvalue for the resistor would be 110 ohms. Assuming thedefault value of Sv, which is 40%, the analysis is run with thevalue of the resistor set to 104 ohms (40 percent of the 10 ohmtolerance) and a measurement value is obtained. Using thatvalue as a base, Sensitivity assumes that the resistancechange from 100 to 104 ohms is linear and calculates(interpolates) the measured value at 1 percent tolerance (101ohms).

Worst-case minimums and maximums

For each measurement, Sensitivity sets all parameters to theirtolerance limits in the direction that will increase themeasurement value, runs a simulation, and records themeasurement value. Sensitivity then sets the parameters tothe opposite tolerance limits and gets the resulting value.

If worst-case measurement values are within acceptable limitsfor the design, the measurements can in most cases beignored for the purpose of optimization.

Sensitivity assumes that the measured quantity variesmonotonically throughout the range of tolerances. If not (ifthere is an inflection point in the curve of output functionvalues), the tool does not detect it. Symptoms of this include



a maximum worst-case value that is less than the originalvalue, or a minimum value greater than the original value.

Sensitivity analysis runs

Sensitivity performs the following runs:

A nominal run with all parameters set at original values

The next run with one parameter varied within tolerance

Values are obtained for each measurement. View the LogFile for parameter values used in each measurementcalculation.

Subsequent runs with one parameter varied withintolerance

A minimum worst-case run for each measurement

A maximum worst-case run for each measurement

For our example circuit with 4 measurements and 12parameters with tolerances, Sensitivity performs 21 runs.

To see the details of parameter and measurementcalculations: from the View menu select Log File.

1 + 12 + (2 x 4) = 21 runs

The nominalrun using theoriginalparametervalues There is one run for each

parameter varied within tolerance.We use 12 parameters

There is one worst-caseminimum and oneworst-case maximum run permeasurement

There are four measurementsused in this example


4

Optimizer

In this chapterThis chapter introduces you to Optimizer, its function, and theoptimization process.

Optimizer overview on page 71

Terms you need to understand on page 73

Optimizer procedure overview on page 80

Example on page 107

For Power Users on page 131

Optimizer overviewNote: Advanced Analysis Optimizer is available with the

following products:

PSpice Advanced Optimizer Option

PSpice Advanced Analysis

PSpice Optimizer

Optimizer is a design tool for optimizing analog circuits andtheir behavior. It helps you modify and optimize analogdesigns to meet your performance goals.

Chapter 4 Optimizer Product Version 15.7


Optimizer fine tunes your designs faster and automaticallythan trial and error bench testing can. Use Optimizer to findthe best component or system values for your specifications.

Advanced Analysis Optimizer can be used to optimize thedesigns that meet the following criteria:

Design should simulate with PSpice.

You can optimize a working circuit design that can besimulated using PSpice and the simulation results are asdesired.

Components in the design must have variableparameters, each of which relates to an intendedperformance goal.

Optimizer cannot be used to:

Create a working design

Optimize a digital design or a design in which the circuithas several states and small changes in the variableparameter values causes a change of state. For example,a flip-flop is on for some parameter value, and off for aslightly different value.

You can use the Advanced Analysis Optimizer to importlegacy Optimizer projects. For view the detailed procedure,see the technical note posted on the OrCAD community site,www.orcadpcb.com. All PSpice related technical notes postedon the community site are available under Application Notessection of the PSpice page.

Product Version 15.7 Terms you need to understand


Terms you need to understand

Optimization

Optimization is the process of fine-tuning a design by varyinguser-defined design parameters between successivesimulations until performance comes close to (or exactlymeets) the ideal performance.The Advanced Analysis Optimizer solves four types ofoptimization problems as described in the table shown below.

Note: All four cases allow simple bound constraints; that is,lower and upper bounds on all of the parameters.

Problem Type Optimizer Action ExampleUnconstrainedminimization

Reduces the value of asingle goal

Minimize the propagationdelay through a logic cell

Constrained minimization Reduces the value of asingle goal whilesatisfying one or moreconstraints

Minimize the propagationdelay through a logic cellwhile keeping the powerconsumption of the cellless than a specifiedvalue

Unconstrained leastsquares1

Reduces the sum of thesquares of the individualerrors (differencebetween the ideal and themeasured value) for a setof goals

Given a terminatordesign, minimize the sumof squares of the errors inoutput voltage andequivalent resistance

Constrained leastsquares

Reduces the sum ofsquares of the individualerrors for a set of goalswhile satisfying one ormore constraints

Minimize the sum ofsquares of the figures ofmerit for an amplifierdesign while keeping theopen loop gain equal to aspecified value

1 Use unconstrained least squares when fitting model parameters to a set of measurements, or when minimizing more thanone goal.

Chapter 4 Optimizer Product Version 15.7


Optimizer also handles nonlinear function asconstraints.

Curve fitting

Curve fitting is a method of optimizing a model to a waveform.In this method, the specifications are represented using acollection of x-y points. These points describe the response ofa system or a part of it.

Parameter

A parameter defines a property of the design for which theOptimizer attempts to determine the best value withinspecified limits.

A parameter can:

Represent component values (such as resistance, R, fora resistor).

Represent other component property values (such asslider settings in a potentiometer).

Participate in expressions used to define componentvalues or other component property values.

Be a model parameter, such as IS for a diode.

Example: A potentiometer part in a schematic uses theSET property to represent the slider position. You canassign a parameterized expression to this property torepresent variable slider positions between 1 and 0.During optimization, the Optimizer varies theparameterized value of the SET property.

Specification

A specification describes the desired behavior of a design interms of goals and constraints.

For example: For a given design, the gain shall be 20 dB 1dB;for a given design, the 3 dB bandwidth shall be 1 kHz; for agiven design, the rise time must be less than 1 usec.

Product Version 15.7 Terms you need to understand


A design must always have at least one goal. You can haveany number of goals and constraints in any combination, but itis recommended that the number of goals should be less. Youcan easily change a goal to a constraint and vice-versa.

The Advanced Analysis Optimizer can have two types ofspecifications: internal and external.

Internal specifications

An internal specification is composed of goals and constraintsthat are defined in terms of target values and ranges. Thesespecifications are entered using the Standard tab of theAdvanced Analysis Optimizer.

External specifications

An external specification is composed of measurement datadefined in an external data file, which is read by the AdvancedAnalysis Optimizer. The external specifications are enteredusing the Curve Fit tab o

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