February 2001 Mixed-Signal Products

Users Guide

SLOU031A

IMPORTANT NOTICE

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TI warrants performance of its products to the specifications applicable at the time of sale in accordance withTIs standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessaryto support this warranty. Specific testing of all parameters of each device is not necessarily performed, exceptthose mandated by government requirements.

Customers are responsible for their applications using TI components.

In order to minimize risks associated with the customers applications, adequate design and operatingsafeguards must be provided by the customer to minimize inherent or procedural hazards.

TI assumes no liability for applications assistance or customer product design. TI does not warrant or representthat any license, either express or implied, is granted under any patent right, copyright, mask work right, or otherintellectual property right of TI covering or relating to any combination, machine, or process in which suchproducts or services might be or are used. TIs publication of information regarding any third partys productsor services does not constitute TIs approval, license, warranty or endorsement thereof.

Reproduction of information in TI data books or data sheets is permissible only if reproduction is withoutalteration and is accompanied by all associated warranties, conditions, limitations and notices. Representationor reproduction of this information with alteration voids all warranties provided for an associated TI product orservice, is an unfair and deceptive business practice, and TI is not responsible nor liable for any such use.

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Also see: Standard Terms and Conditions of Sale for Semiconductor Products. www.ti.com/sc/docs/stdterms.htm

Mailing Address:

Texas InstrumentsPost Office Box 655303Dallas, Texas 75265

Copyright 2001, Texas Instruments Incorporated

iii Read This First

Preface

How to Use This Manual

This document contains the following chapters:

Chapter 1Introduction

Chapter 2Quick Start

Chapter 3Details

Information About Cautions and Warnings

This book may contain cautions and warnings.

This is an example of a caution statement.A caution statement describes a situation that could potentiallydamage your software or equipment.

This is an example of a warning statement.A warning statement describes a situation that could potentiallycause harm to you.

The information in a caution or a warning is provided for your protection.Please read each caution and warning carefully.

Running TitleAttribute Reference

iv

Related Documentation From Texas Instruments TI Plug-N-Play Audio Amplifier Evaluation Platform (literature

number SLOU011) provides detailed information on the evaluationplatform and its use with TI audio evaluation modules.

TLC2274 Advanced LinCMOS Rail-to-Rail OperationalAmplifiers (literature number SLOS190) This is the data sheet forthe TLC2274 Quad operational amplifier integrated circuit used in thetone control EVM.

TLV2231 Advanced LinCMOS Rail-to-Rail Low-Power SingleOperational Amplifier (literature number SLOS158) This is thedata sheet for the TLV2231 operational amplifier integrated circuitused in the tone control EVM.

FCC Warning

This equipment is intended for use in a laboratory test environment only. Itgenerates, uses, and can radiate radio frequency energy and has not beentested for compliance with the limits of computing devices pursuant to subpartJ of part 15 of FCC rules, which are designed to provide reasonable protectionagainst radio frequency interference. Operation of this equipment in otherenvironments may cause interference with radio communications, in whichcase the user at his own expense will be required to take whatever measuresmay be required to correct this interference.

Running TitleAttribute Reference

v Chapter TitleAttribute Reference

Contents

1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Feature Highlights 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Description 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Tone Control EVM Specifications 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 Quick Start 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Precautions 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Quick Start List for Platform 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Quick Start List for Stand-Alone 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 Details 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Precautions 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 The Tone Control Evaluation Module 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2.1 Tone Control EVM Circuit Description 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Tone Control EVM Frequency Response 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3 Using The Tone Control EVM With the Plug-N-Play Evaluation Platform 3-7. . . . . . . . . . . 3.3.1 Installing and Removing EVM Boards 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Signal Routing 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Mute/Mode 3-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 Power Requirements 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 Inputs and Outputs 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4 Using The Tone Control EVM Stand-Alone 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Tone Control EVM Connected for Stand-Alone Operation 3-11. . . . . . . . . . . . . . . .

3.5 Tone Control Evaluation Module Parts List 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Running TitleAttribute Reference

vi

Figures

11 The Tone Control Evaluation Module 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Quick Start Platform Map 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Quick Start Module MapStand-Alone 2-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 The TI Plug-N-Play Audio Amplifier Evaluation Platform 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Tone Control EVM 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Tone Control EVM Schematic Diagram 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Tone Control Evaluation Module Frequency Response 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Tone Control EVM Block Diagram 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Bass and Treble Tone Control Response 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Platform Signal Routing and Outputs 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Tone Control EVM Stand-Alone Operation 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tables

31 Tone Control EVM Parts List 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1Introduction

Introduction

This chapter provides an overview of the Texas Instruments (TI) tone controlevaluation module (SLOP109). It includes a list of EVM features, a briefdescription of the module illustrated with a diagram, and a list of EVMspecifications.

Topic Page

1.1 Feature Highlights 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Description 12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Tone Control EVM Specifications 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 1

Feature Highlights

1-2 Introduction

1.1 Feature HighlightsThe TI tone control evaluation module and the TI plug-n-play audio amplifierevaluation platform include the following features:

Tone Control Evaluation Module Individual slide pots for left and right channel volume control Individual slide pots for bass and treblethe bass control adjusts both

channels simultaneously and the treble control adjusts both channelssimultaneously 20-dB cut and 15-dB boost for both bass and treble 3.3-V and 5-V operation Quick and Easy Configuration with The TI Plug-N-Play Audio Amplifier

Evaluation Platform Evaluation module is designed to simply plug into the platform,

automatically making all signal, control, and power connections Platform provides flexible power options Jumpers on the platform select power and module control options Switches on the platform route signals Platform provides quick and easy audio input and output connections Platform Power Options External 5-V 15-V DC VCC supply inputs External regulated VDD supply input Socket for onboard 5-V/3.3-V VDD voltage regulator EVM Onboard overvoltage and reverse polarity power protection Platform Audio Input and Output Connections Left and right RCA phono jack inputs Miniature stereo phone jack input Left and right RCA phono jack outputs Left and right compression speaker terminal outputs Miniature stereo headphone jack output

1.2 DescriptionThe tone control evaluation module is a complete audio volume level and baseand treble control board that is designed primarily for use with the TIplug-n-play audio amplifier evaluation platform. It consists of separate slidepotentiometers for the right- and left-channel volume control, a slidepotentiometer for controlling the bass response of both channels, a slidepotentiometer for adjusting the treble response of both channels, asingle-channel operational amplifier IC, a quad operational amplifier IC, anda small number of passive components mounted on a circuit board thatmeasures approximately 2 1/4 inches by 1 3/4 inches (Figure 11).

Tone Control EVM Specifications

1-3Introduction

Figure 11. The Tone Control Evaluation Module

LT Vol Tone Control BoardR2

R1 RT Vol Max

1998SLO

P109R

ev. B

R10Bass

R18Treble C14

R13

Vdd

GND

R Out

L Out

+

+

+

J5

C16R

4C15

R19

R20

C4

R8

R5 R6

U1 C5 J4J3

R16C9

R15

R17

C10C12R

11

R14

C11C7R9R12C8C13

R7

U2 C6R In

L In

+

+ C1

C2

C3

R3

J1J2

Max

Single in-line header pins extend from the underside of the module circuitboard to allow the EVM to be plugged into the TI plug-n-play audio amplifierevaluation platform, or to be wired directly into existing circuits and equipmentwhen used stand-alone.

The platform, with room for a single tone control evaluation module, is aconvenient vehicle for evaluating TIs audio power amplifier and relatedevaluation modules. The EVMs plug into the platform, which automaticallyprovides power to the modules, interconnects them correctly, and connectsthem to a versatile array of standard audio input and output jacks andconnectors. Configuration controls allow the platform and EVMs to quicklymodel many possible end-equipment configurations.

There is nothing to build, nothing to solder, and nothing but the speakersincluded with the platform to hook up.

1.3 Tone Control EVM SpecificationsSupply voltage range, VDD 3 V to 5.5 V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supply current, IDD 6.85 mA max. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Audio input voltage, VI 4 Vpp max. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Audio output voltage, VO 4 Vpp max. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4 Introduction

2-1Quick Start

Quick Start

Follow the steps in this chapter to quickly prepare the tone control EVM for use.Using the tone control EVM with the TI plug-n-play audio amplifier evaluationplatform is a quick and easy way to connect power, signal, and control inputs,and signal outputs to the EVM using standard connectors. However, the tonecontrol EVM can be used stand-alone by making connections directly to themodule pins and can be wired into existing circuits or equipment.

Topic Page

2.1 Precautions 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.2 Quick Start List for Platform 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Quick Start List for Stand-Alone 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 2

Precautions

2-2 Quick Start

2.1 Precautions

Power Supply Input Polarity and Maximum VoltageAlways ensure that the polarity and voltage of the external powerconnected to VCC power input connector J1, J2, and/or VDD powerinput connector J6 are correct. Overvoltage or reverse-polaritypower applied to these terminals can open onboard soldered-infuses and cause other damage to the platform, installed evaluationmodules, and/or the power source.

Inserting or Removing EVM BoardsDo not insert or remove EVM boards with power applieddamageto the EVM board, the platform, or both may result.

Figure 21. Quick Start Platform Map

Signal Conditioning

****CAUTION****Do not insert or removeEVM boards with power

applied

ICC

JP4

F1

VR1

R1

JP3

JP2

JP1AC/DC(J2)VCC(J1)

D1

D2

D3

D4

J2

J3J4

J5

AC/DCIn

VCCIn+

J1

DCSO

URCE

LED1

VCC

LED2

VDD

R2JP5

IDD

B1

U6PO

WER

SUPPLY

U3U4

U5

U1 U2

AudioPowerAmps

On

Off

ConditioningS2

J7J8

Right

Out

LeftO

ut+

+

JP6 ModeMute

Spk(U2-U4)JP8

J9LeftO

utJP7

S3HPSourceU2-U4

U5

PolarityLoHi

HP(U5)

C3C2

++R3

R5

J10

Stereo

HP Out

TP1G

ND

Plug-N-Play Audio AmplifierEvaluation PlatformSLOP097 Rev. C.1

StereoInR

ightInLeftIn

J6In/Out

VDD

F2

VR2

+

DCPowerIn/Out

SpeakerOutput

HeadphoneOutput

AudioInput

PowerInput

Batt

C1+

Right

Out

On

Off

Pwr

S1

TEXASINSTRUM

ENTS1997

R4

6a

1

3

6b

6b

6b 6b

910

11

10

2

Quick Start List for Platform

2-3Quick Start

2.2 Quick Start List for PlatformFollow these steps when using the tone control EVM with the TI plug-n-playaudio amplifier evaluation platform (see the platform users guide, SLOU011,for additional details). Numbered callouts for selected steps are shown inFigure 21, and details appear in Chapter 3.

Platform preparations

1) Ensure that all external power sources are set to OFF and that the platformpower switch S1 is set to OFF.

2) Install the tone control module in the signal conditioning platform socketU1, taking care to align the module pins correctly.

3) Set switch S2 to ON to select signal conditioning by the tone control EVM.4) Install power amplifiers and/or a headphone amplifier module in the

appropriate platform sockets (see the amplifier module users guide fordetails).

5) Set platform jumpers and switches in accordance with the users guide foreach amplifier module installed on the platform.

Power supply

6) Select and connect the power supply (ensure power supply is set to OFF ):a) Connect an external regulated power supply set to 5 V to platform VDD

power input connector J6 taking care to observe marked polarity, or

b) Install a voltage regulator EVM (SLVP097 or equiv.) in platform socketU6. Connect a 7 V 12 V power source to a platform VCC power inputJ1 or J2 and jumper the appropriate power input (see platform usersguide). Inputs and outputs

7) Ensure that the audio signal source level is set to minimum.8) Set the EVM right and left volume slide pots to minimum.9) Connect the audio source to left and right RCA phono jacks J3 and J5 or

stereo miniature phone jack J4.10) Connect 3- 8- speakers to left and right RCA jacks J7 and J9 or to

stripped wire speaker connectors J8, or plug headphones into J10.

Power Up

11) Verify correct voltage and input polarity and set the external power supplyto ON. If VCC and an onboard regulator EVM are used to provide VDD, setplatform power switch S1 to ON.

Platform LED2 should light indicating the presence of VDD, and the evaluationmodules installed on the platform should begin operation.12) Adjust the signal source and tone control EVM audio levels as needed.

Quick Start List for Stand-Alone

2-4 Quick Start

2.3 Quick Start List for Stand-AloneFollow these steps to use the tone control EVM stand-alone or whenconnecting it into existing circuits or equipment. Connections to the tonecontrol module header pins can be made via individual sockets, wire-wrapping, or soldering to the pins, either on the top or the bottom of the modulecircuit board. The tone control EVM is shown in Figure 22 and details appearin Chapter 3.

Figure 22. Quick Start Module MapStand-Alone

LT Vol Tone Control BoardR2

R1 RT Vol Max

1998SLO

P109R

ev. B

R10Bass

R18Treble C14

R13

Vdd

GND

R Out

L Out

+

+

+

J5

C16R

4C15

R19

R20

C4

R8

R5 R6

U1 C5 J4J3

R16C9

R15

R17

C10C12R

11

R14

C11C7R9R12C8C13

R7

U2 C6

R In

L In

+

+ C1

C2

C3

R3

J1J2

Max

Power supply

1) Ensure that all external power sources are set to OFF.

2) Connect an external regulated power supply set to 5 V to the module VDDand GND pins taking care to observe marked polarity.

Inputs and outputs

3) Ensure that audio signal source level adjustments are set to minimum.

4) Set the tone control EVM volume slide pots to minimum.5) Connect the audio source to the module R IN and L IN pins, taking care

to observe marked polarity. Power Up

6) Verify correct voltage and input polarity and set the external power supplyto ON.

The EVM should begin operation.

7) Adjust the signal source and tone control EVM audio levels as needed.

3-1Details

Details

This chapter provides details on the tone control EVM, the steps in the Quick-Start List, additional application information, and a parts list for the tone controlevaluation module.

Topic Page

3.1 Precautions 32. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 The Tone Control Evaluation Module 33. . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Using the Tone Control EVM With the Plug-N-Play

Evaluation Platform 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4 Using The Tone Control EVM Stand-Alone 311. . . . . . . . . . . . . . . . . . . . . 3.5 Tone Control Evaluation Module Parts List 312. . . . . . . . . . . . . . . . . . . .

Chapter 3

Precautions

3-2 Details

3.1 Precautions

Power Supply Input Polarity and Maximum VoltageAlways ensure that the polarity and voltage of the external powerconnected to VCC power input connector J1, J2, and/or VDD powerinput connector J6 are correct. Overvoltage or reverse-polaritypower applied to these terminals can open onboard soldered-infuses and cause other damage to the platform, installed evaluationmodules, and/or the power source.

Inserting or Removing EVM BoardsDo not insert or remove EVM boards with power applieddamageto the EVM board, the platform, or both may result.

Figure 31. The TI Plug-N-Play Audio Amplifier Evaluation Platform

Signal Conditioning

****CAUTION****Do not insert or removeEVM boards with power

applied

ICC

JP4

F1

VR1

R1JP3

JP2

JP1AC/DC(J2)VCC(J1)

D1

D2

D3

D4

J2

J3J4

J5

AC/DCIn

VCCIn+

J1

DCSO

URCE

LED1

VCC

LED2

VDD

R2JP5

IDD

B1

U6PO

WER

SUPPLY

U3U4

U5

U1 U2

AudioPowerAmps

On

Off

ConditioningS2

J7J8

Right

Out

LeftO

ut+

+

JP6 ModeMute

Spk(U2-U4)JP8

J9LeftO

utJP7

S3HPSourceU2-U4

U5

PolarityLoHi

HP(U5)

C3C2

++R3

R5

J10

Stereo

HP Out

TP1G

ND

Plug-N-Play Audio AmplifierEvaluation PlatformSLOP097 Rev. C.1

StereoInR

ightInLeftIn

J6In/Out

VDD

F2

VR2

+

DCPowerIn/Out

SpeakerOutput

HeadphoneOutput

AudioInput

PowerInput

Batt

C1+

Right

Out

On

Off

Pwr

S1

TEXASINSTRUM

ENTS1997

R4

The Tone Control Evaluation Module

3-3Details

3.2 The Tone Control Evaluation Module

The tone control evaluation module provides a convenient way to control theaudio volume and the tonal response of audio amplifier EVMs plugged into theTI plug-n-play audio amplifier evaluation platform. Tone controls allow thefrequency response of the audio system to be adjusted to compensate for theresponse of speakers and their enclosures, or to simply provide a morepleasing sound. A pair of slide potentiometers adjusts the volume of eachchannel independently, while a single slide potentiometer adjusts the bassresponse of both channels simultaneously and another slide potentiometeradjusts the treble response of both channels. The module provides a gain of2 at the maximum volume setting when both tone controls are at theirmidpoints (flat).

Although the tone control EVM is designed to be used with the TI plug-n-playaudio amplifier evaluation platform (Figure 31), it can be wired directly intocircuits or equipment. The module has single in-line header connector pinsmounted to the underside of the board. These pins allow the module to beplugged into the TI platform, which automatically makes all the signal input andoutput, power, and control connections to the module.

The module connection pins are on 0.1-inch centers to allow easy use withstandard perf board and plug board-based prototyping systems. Or, the EVMcan be wired directly into existing circuits and equipment when usedstand-alone.

The module appears in Figure 32 and its schematic is shown in Figure 33.

Figure 32. Tone Control EVM

LT Vol Tone Control BoardR2

R1 RT Vol Max

1998SLO

P109R

ev. B

R10Bass

R18Treble C14

R13

Vdd

GND

R Out

L Out

+

+

+

J5

C16R

4C15

R19

R20

C4

R8

R5 R6

U1 C5 J4J3

R16C9

R15

R17

C10C12R

11

R14

C11C7R9R12C8C13

R7

U2 C6

R In

L In

+

+ C1

C2

C3

R3

J1J2

Max

The Tone Control Evaluation Module

3-4 Details

Figure 33. Tone Control EVM Schematic DiagramVDD

C6 0.1 F

R Out

R In

C80.033 F

C22.2 F

_

+

R610 k

R820 k

R250 k

AT

76

5

_

+

C143300 pF

R1310 k

9

108

midmid

C16 1.0 F

R20100 k

R10B100 k R17

2.2 k

R1510 k

R1210 k

C100.033 F

+

R18B100 k

mid

7

+

7

+

7

+

7

+

7

+

7

+

7

+

777

+

7

+

7

+

7

+

7

+

7

L In

L Out

U2 = TLC2274 Quad Op-AmpU1 = TLV2231 Single Op-Amp

+C3 10 F

C133300 pF

C70.033 F

C12.2 F

_

+

R510 k

R720 k

R150 k

AT

76

5

_

+

C123300 pF

R1110 k

9

108

midmid

C15 1.0 F

R19100 k

R10A100 k

R163.3 k

R1410 k

R1910 k

C90.033 F

R18A100 k

mid

777777777777777

C113300 pF

U2:D

U2:CU2:B

U2:A

VDD

4

VDD

C42.2 F

_

+

R420 k

R320 k

12

34

5

U1

C5 0.1 F

mid

GND

Bass

11

Treble

Vol

Vol

The tone control EVM is a variation of the classic and popular Baxandallnegative feedback tone control. This circuit allows a range of adjustment fromcut, through flat, to boost in bass response with a single potentiometer.Another potentiometer provides the same range of adjustment for the trebleresponse. The component values indicated in the schematic provide theresponse curve shown in Figure 34. Each of the tone adjustingpotentiometers is a dual unit, allowing the simultaneous adjustment of bothchannels with a single control. A separate volume control for each channelallows the adjustment of balance between the channels as well as volume.A single TLC2274 quad rail-to-rail operational amplifier IC contains all theamplifiers required for both channels. A TLV2231 operational amplifier IC isconnected to provide a midpoint voltage (and signal ground) for properoperation of the TLC2274.

The Tone Control Evaluation Module

3-5Details

Figure 34. Tone Control Evaluation Module Frequency Response

5

5

15

100f Frequency Hz

10

0

10

20

10K

15

15

Out

put L

evel

dB

20

20K1K

Flat

Full Boost

Full Cut

3.2.1 Tone Control EVM Circuit DescriptionEach of the two separate channels on the tone control EVM is basically anactive filter built around an IC operational amplifier. An active filter design waschosen over a passive filter circuit because active filters have thefrequency-response adjusting components located in the feedback loop of thefilter amplifiers, providing much lower THD, little or no insertion loss, and asymmetrical response about the axis in both boost and cut, compared withmost passive designs. Each channel also includes an input buffer amplifier toprovide some gain, isolation from source impedance variations, signalinversion, and a low-impedance drive for the filter circuit.

A block diagram of the right channel of the tone control EVM is shown inFigure 35. The left channel is identical.

Figure 35. Tone Control EVM Block Diagram

In

Buffer Amplifier

Feedback Network

Filter Amplifier

Out

U2:A U2:D

Mid

C1

Tone Control

R1(Log)

2

The input buffer amplifier provides a gain of approximately 2 (RF/RIN) with theresistor values installed on the module. Input capacitor C1 blocks DC and setsthe overall low-frequency rolloff of the EVM at approximately 16 Hz with theinstalled value of 2.2 F. Volume control R1 has an audio taper to provide aperceived response in volume that is proportional to the physical position ofthe slider and gives an adjustment range at the output of the buffer amplifierof from 0 V to approximately 2 the audio signal input voltage.

The Tone Control Evaluation Module

3-6 Details

The tone adjusting action in each channel of the tone control EVM is providedby an equalized amplifier (or active filter) created by placing a frequency-dependent negative feedback network around an operational amplifier.Almost any overall gain-versus-frequency characteristic can be defined by thedesign of the feedback network.

The EVM provides the familiar Hi-Fi tone control, in which the low audiofrequencies can be boosted or cut approximately 20 dB with the bass controland the high audio frequencies can be boosted or cut approximately 20 dB withthe treble control. Middle frequencies are not affected by the tone controls. Anoverall flat response (no boost or cut at frequency extremes) is obtained whenthe tone controls are at their mid-point position.

3.2.2 Tone Control EVM Frequency ResponseThe overall tone control EVM frequency response can be shifted up or downby changing the values of capacitors C7, C9, C11, and C12 in the toneadjusting networks on the module. Care must be taken, however, because thesurface-mount solder pads on the board are somewhat fragile and will notsurvive a large number of soldering/desoldering operations.

To shift the EVM frequency response downward, for example, increase thevalues of the capacitors in the tone adjusting networks. Doubling the valuesof C7, C9, C11, and C12 shifts the break frequency downward a full octave(Case B, Figure 36). Conversly, halving the values of C7, C9, C11, and C12shifts the break frequency upward a full octave.

Note that to keep the boost and cut break frequencies the same, the value ofC7 must equal that of C9, and the value of C11 must equal that of C12. Inaddition, although the bass and treble break frequencies can be adjustedseparately if desired, to maintain the overall shape and symmetry of theresponse, all four capacitors must be increased or decreased by the samefactor.

Figure 36. Bass and Treble Tone Control Response

5

5

15

100f Frequency Hz

10

0

10

20

10K

15

15

Out

put L

evel

dB

20

20K1K

Case B Case A

Case A: C7, C9 = 0.033 F C11, C12 = 3300 pF

Case B: C7, C9 = 0.068 F C11, C12 = 6800 pF

Using The Tone Control EVM With the Plug-N-Play Evaluation Platform

3-7Details

3.3 Using The Tone Control EVM With the Plug-N-Play Evaluation PlatformThe tone control evaluation module was designed to be used with the TIplug-n-play audio amplifier evaluation platform. It simply plugs into socket U1.

The following paragraphs provide additional details for using the tone controlEVM with the platform.

3.3.1 Installing and Removing EVM Boards

TI plug-n-play evaluation modules use single-in-line header pins installed onthe underside of the module circuit board to plug into sockets on the platform.The EVM pins and the platform sockets are keyed such that only the correcttype of EVM can be installed in a particular socket, and then only with theproper orientation.

Evaluation modules are easily removed from the platform by simply pryingthem up and lifting them out of their sockets. Care must be taken, however,to prevent bending the pins.

3.3.1.1 EVM Insertion

1) Remove all power from the evaluation platform.2) Locate the appropriate socket on the platform.3) Orient the module correctly.4) Carefully align the pins of the module with the socket pin receptacles.5) Gently press the module into place.6) Check to be sure that all pins are seated properly and that none are bent

over.

3.3.1.2 EVM Removal

1) Remove all power from the evaluation platform.2) Gently pry up one side of the module a small amount.3) Change to the opposite side of the module and pry that side up a small

amount.

4) Alternate between sides, prying the module up a little more each time toavoid bending the pins, until it comes loose from the socket.

5) Lift the EVM off the platform.

Using The Tone Control EVM With the Plug-N-Play Evaluation Platform

3-8 Details

3.3.2 Signal Routing

Signal flow on the platform is controlled by two signal routing switches, asshown in Figure 37.

Figure 37. Platform Signal Routing and Outputs

U1Tone Control

EVM

On

Off

U5Stereo

HeadphoneAmplifier

S2

R

L

R

L

L

U5

U2U4

S3J10

HeadphoneOutput

R

L

AudioInput

R

L

J7, J8, J9SpeakerOutputs

R+

+

U2 U4Power

Amplifier EVM

+

+

GND

3.3.2.1 Signal Conditioning

The tone control EVM plugs into the signal conditioning socket (U1) on theplatform. The audio signal from the platform input jacks can be applied to thesignal conditioning socket (U1) or can bypass socket U1 as determined byconditioning switch S2. Switch S2 selects the tone control signal conditioning or bypasses it.

3.3.2.2 Headphone Output Jack

Switch S3 is the source select for the stereo headphone output jack, J10. Theheadphone jack is capacitively coupled (via 470 F electrolytics). The jack canoutput either the signal from the headphone amplifier in socket U5, or thesignal from the power amplifier installed in sockets U2 U4, as determinedby the setting of switch S3.

When S3 is set to the power amplifier position (U2 U4), the headphone jackis connected to the power amplifier OUT+ output lines. When a plug is insertedinto the jack, signals output through J10 are returned to platform ground,requiring single-ended power amplifier operation. A switch inside theheadphone jack produces a control signal that can be routed to the poweramplifier socket to shut down the power amplifier EVM or switch it tosingle-ended output mode when a plug is inserted.

See the users guide for the power amplifier and/or the headphone amplifierinstalled on the platform for information on the correct setting of switch S3.

Using The Tone Control EVM With the Plug-N-Play Evaluation Platform

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3.3.3 Mute/Mode

Some power amplifier EVMs have a mute or mode control input pin. Thisallows the power amplifier to enter the mute state for decreased powerconsumption or to switch output modes in response to a control signal appliedto this pin.

In typical applications, as often found in notebook computers, portable audioproducts, and such, the internal speakers mute when headphones areplugged into the headphone jack, or internal speakers mute when externalspeakers are connected. In applications using separate speaker andheadphone amplifiers, the power amplifier can be shut down (muted) toconserve power when the headphone amplifier is in use.

Output mode switching allows some power amplifier EVMs to operate in thebridge-tied load (BTL) output mode for increased power to internal speakersand then switch to single-ended mode to drive headphones when a plug isinserted into the headphone jack, eliminating the need for a separateheadphone amplifier.

The platform is equipped with mute/mode control signal select and polarityjumpers and a headphone source switch to provide the maximum flexibility inconfiguring the operation of the various power amplifier and headphoneamplifier EVMs that might be installed on the platform. See the users guidefor the power amplifier and/or the headphone amplifier installed on theplatform for information on the correct settings of platform mute, mode,polarity jumpers, and the platform headphone source switch.

Power Requirements

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3.3.4 Power RequirementsThe tone control evaluation module can operate from any voltage betweenapproximately 3 V and 5.5 V. For best performance (highest output power withlowest distortion), the module should be operated at approximately 5 V unlessthere is a specific reason for operating it from a lower voltage.

The TI plug-n-play audio amplifier evaluation platform with a voltage regulatorEVM installed on it can provide a regulated VDD supply from a wide variety ofunregulated VCC voltage inputs between approximately 5.5 V and 12 V,including an onboard 9-V battery. Or, an external regulated power source canbe used to supply VDD voltage to the platform and the tone control evaluationmodule installed on it.

Although the tone control EVM draws a very small amount of current from thesupply, power amplifiers installed on the platform can draw as much asapproximately 2 A from the power supply during continuous full power output.Any power supply connected to the platform should be capable of providingadequate current to the power amplifier installed on the platform to avoidclipping of the output signal during peaks. Current consumption drivingspeakers at normal listening levels is typically 0.5 A or less.

The platform is equipped with overvoltage and reverse-polarity supply voltageinput protection in the form of fused crowbar circuits.

VDD voltage applied to platform screw terminals J6 must not exceed theabsolute maximum rating for any EVM installed on the platform, or dam-age may result. In no case should VDD voltage of the incorrect polarity orin excess of 6.1 V be applied to screw terminals J6 of the platform, or thepower protection circuit on the VDD line will trip.

VCC voltage applied to the platform must not exceed the maximum voltageinput specified for the voltage regulator module installed in socket U6 (12V for the SLVP097), or damage to the voltage regulator module mayresult. In no case should VCC voltage applied to the platform exceed 15V, or the overvoltage protection circuit on the VCC bus will trip.

3.3.5 Inputs and OutputsThe TI plug-n-play audio amplifier evaluation platform is equipped with severalstandard conectors for audio inputs and outputs.

3.3.5.1 InputsAudio signals enter the platform through either a pair of RCA phono jacks (J3and J5) or a miniature (1/8) stereo phone jack (J4). The platform audio signalinput jacks (J3, J4, and J5) are of the closed-circuit type, grounding the signalinput lines when no plugs are inserted.

3.3.5.2 OutputsAmplified audio output signals leave the platform through left and right RCAphono jacks (J7 and J9), left and right pairs of compression connectors forstripped speaker wires (J8), and optionally, through a miniature (1/8) stereophone jack (J10), for headphones.

Using The Tone Control EVM Stand-Alone

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3.4 Using The Tone Control EVM Stand-AloneUsing the tone control evaluation module stand-alone is much the same asusing it with the platform. The same 5-V power supply requirement exists.

3.4.1 Tone Control EVM Connected for Stand-Alone Operation

Figure 38. Tone Control EVM Stand-Alone Operation

LT Vol Tone Control BoardR2

R1 RT Vol Max

1998SLO

P109R

ev. B

R10Bass

R18Treble C14

R13

Vdd

GND

R Out

L Out

+

+

+

J5

C16R

4C15

R19

R20

C4

R8

R5 R6

U1 C5 J4J3

R16C9

R15

R17

C10C12R

11

R14

C11C7R9R12C8C13

R7

U2 C6

R In

L In

+

+ C1

C2

C3

R3

J1J2

Max

5 V

AudioOutput(Right)

AudioOutput(Left)

AudioInput

(Right)

AudioInput(Left)

Tone Control Evaluation Module Parts List

3-12 Details

3.5 Tone Control Evaluation Module Parts List

Table 31. Tone Control EVM Parts List

Reference Description Size EVMQty.Source/

Part NumberC1, C2, C4 Capacitor, ceramic, 2.2 F, 16 V, YV5 1206 3 TDK

C3216Y5V1C225Z

C3 Capacitor, ceramic, 10 F, 16 V, YV5 1210 1 TDKC3216Y5V1C106Z

C15, C16 Capacitor, ceramic, 1 F, 16 V, YV5 1206 2 TDKC3216Y5V1C105Z

C7, C8, C9, C10 Capacitor, ceramic 0.033 F, 50 V, NPO 1206 2 Digi-Key

C5, C6 Capacitor, ceramic, 0.1 F, 50 V, X7R 1206 2 Digi-KeyPCC104BCTND

C11, C12, C13,C14

Capacitor, ceramic 3300 pF, 50 V, NPO 1206 4 Digi-Key

R10, R18 Dual potentiometer, 100 k, linear taper,slide control

2 CTS 448XC351109

R1, R2 Potentiometer, 50 k, audio taper, slidecontrol

2 CTS 448XC3503BAN

R5, R6, R9, R11,R12, R13, R14,R15

Resistor, CF, 10 k, 1/8 W, 5% 1206 8

R3, R4, R7, R8 Resistor, CF, 20 k, 1/8 W, 5% 1206 4

R16, R17 Resistor, CF, 3.3 k, 1/8 W, 5% 1206 2

R19, R20 Resistor, CF, 10 k, 1/8 W, 5% 1206 2

J1J5 Header, 2 position, 100-mil centers 5 Digi-Key S102236ND

U1 TLV2231IDBV IC operational amplifier SOT-23 1 TI

U2 TLC2274CD quad IC operational amplifier SOIC 1 TI

PCB PCB, tone control EVM 1 TI SLOP109