MIPI D-PHY℠ - Physical Layer Test
& Measurement Challenges
Parthasarathy Raju, & Suryakant Kumar,
Tektronix
Agenda
• MIPI D-PHY℠ Spec Overview • New in v2.0
• PHY layer Testing • Transmitter & Receiver Needs • Equipment • Device Test Modes
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MIPI: Mobile System Diagram
MIPI D-PHY℠ Applications: MIPI Camera (CSI℠) & MIPI Display (DSI℠)
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Camera&
Display
D-PHY Lanes and Modes • Data & Clock Lane
• Minimum configuration with 4 wires • Data+, Data- & Clock+, Clock-
• Lane operating modes • High Speed Mode(HS)
• Terminated • Low swing, Differential signal • Non-Return to Zero(NRZ) coding • Data transmission
• Low Power Mode(LP) • Non-Terminated • Single-ended transmission • Spaced-One-Hot coding • Control
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Data+Data-
D-PHYClock+Clock-
HS Data Transmission in Bursts • Continuous Mode & Burst Mode • Four LP states
• LP-00, LP01, LP-10, LP-11 • Stop state(LP-11) – Standby state
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Clock:BurstMode
Data to Clock Timing • Differential Data to Clock has a quadrature phase
relationship
• Data-Clock Timing Specification • Data to Clock Skew • Setup time & Hold time • Deterministic and Random Jitter( data rate > 1.5Gbps)
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Parameter Min Max
TSKEW[TX](UI) -0.2 0.2 TSETUP[RX](UI) 0.2 THOLD[RX](UI) 0.2 TSKEW[TLIS](UI) -0.1 0.1
Parameter Min Max
TJTX(UI) 0.3
DJTX(UI) 0.2
RJTX(UI) 0.1
TSKEW[TX]staAc(UI) -0.2 0.2
HS-Transmitter • Half Swing Mode
• Differential swing of Tx is half with respect to default swing mode • Option for reduced operating power
• De-emphasis • Two equalization ratios are defined • Data rates >2.5Gbps
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SSC & Eye Diagram • Spread Spectrum Clocking
• Triangular Down spreading, deviation 5000ppm at 33KHz
• Transmitter & Receiver Eye Diagram • Data Rates >1.5Gbps & <= 4.5 Gbps • Reference channel included • Mask prorated to BER 10e-6
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BER TEYE VDIF
10-12 0.5UI 40mV
10-6 0.53UI 47mV
Interconnect Spec & System Configurations • Three Differential Insertion loss templates
• Short, Standard & Long Reference • Uniform reference across all MIPI PHYs
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Mode#
DataRate
Gbps
TransmiPer
SwingEQ ReferenceChannel
Receiver
Term
(ohm) 1
Default EQ2 Short/Std
80-125
2 Long
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HalfSwing
EQ1
Short
4 Std
5 Long
6 Short/Std
NT 7 Long
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None
Short
9 Std
10 Long
Receiver De-skew Calibration • Operating data rates >1.5Gbps • Initial and Periodic Calibration modes • De-skew burst
• Sync : all one’s (16UI) • Payload: 0101 (215 UI)
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LP-Transmitter, LP-Receiver • Line Levels
• VOL(Min)= -50mV, VOH(mx) = 1.3V
• Slew rate spec for various load conditions • LP Receiver - Interference and Noise performance
• Input pulse rejection(eSpike) • Minimum pulse width response(TMIN-RX) • Peak Interference(VINT, fINT)
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MIPI D-PHY℠
Test & Measurement Challenges
Elements of Testing • Test Methodology
• Waveform/Pattern/Region • Measurement Procedure/Post processing Algorithm
• Test Equipment • Oscilloscopes • Waveform Generators • Probes & Accessories
• Device -Test Modes, Test Points • Test Sequences • Bit Error Detector • Replica Traces
• Test Modes Needs special focus!
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Tx Testing Challenges(contd..) • Dynamic switching of terminations between LP and HS
mode
• Waveform post processing to discern the LP-HS transitions • Probing
• HS & LP transmission without loading the bus • Access to tight test locations
• Burst Mode timing measurements • Measurements on clock and data lanes
• Voltage and Timing parameters
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Tx Testing Challenges • Data rate up to 4.5Gb/s
• 800 Mbps to 4.5G
• Eye diagram and jitter measurements • Tx Equalization by de-emphasis
• Spread-spectrum clocking • Embed channel insertion loss • LP Mode
• Slew rate measurements • Bus Turn Around test
• User intervention to enable mode and measure
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Tx Testing
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• 4 Single ended Signals • Data+, Data- & Clock+, Clock-
• Termination Board • Switchable Termination
• Oscilloscope & Probes • Based on Signal data rate
• v1.0 (800 Mbps), • v1.1 (1.5 Gbps) • v1.2 (2.5 Gbps) • v2.0 (4.5 Gbps)
• High impedance probes
• 50+ CTS Tests TerminaAonBoard
Device Test Modes for Tx Testing • LP Mode Measurements
• LP sequence with open termination • BTA initiation
• HS Mode Measurements • HS entry • HS Sync & Payload
• Random Test sequences (PRBS)
• HS exit • Data and clock lanes • Continuous and Burst Modes
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Tx Test: Spread Spectrum clocking • SSC Testing
• Modulation Rate = 30KHz (min) • Measure over =>2 SSC cycles • Device Test Modes/options
• HS data length > 66 µsec • HS data ‘101010…’
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Tx Test: HS Eye Diagram • (1) Prorated Mask at BER 1E-6
• Measurement using random test pattern of 3 million UI • Continuous HS data(Recommended) or Data from multiple bursts
• (2)Mask at BER 1E-12 • Sophisticated extrapolation software on oscilloscopes
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Receiver Testing(contd..) • Philosophy
• Stimulus calibration based on parameter • Stimulus fed to the Rx • Check for error free reception
• Equipment • Waveform Generator
• Data and clock lanes • Oscilloscope for Calibration • Choice based on D-PHY spec versions
• Observables • Bit errors detected
• ~35 CTS Tests
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Receiver Testing: Stimulus(Contd..)
• Transmission Modes • LP Mode & HS Mode • Spaced-one-hot, • NRZ coding
• Data to clock timing • Setup/Hold Times • Skew
• HS Differential & Common mode voltage • LP voltage up to 1.3V
• Rise/Fall time control
• Continuous & Burst data
• Data & Clock Lanes
• Test sequences/patterns • PRBS patterns of various lengths • LP states • Escape Mode commands • De-skew calibration bursts • Standby state to trigger a test
sequence • HS entry, HS Sync & HS exit
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Receiver Testing: Stimulus • HS Mode Stressors
• Random Jitter & Deterministic Jitter • Embed Insertion loss & De-emphasis • Spread Spectrum Clocking • Dynamic Skew
• LP Mode Stressors • eSpike • Minimum Pulse TMIN-RX • Additive Square/Sine Noise (VINT, fINT)
• Data Burst Timing • THS_TRAIL, THS_PREPARE ,THS_ZERO, THS_REOT
• Clock Burst Timing • TCLK_TRAIL, TCLK_PREPARE, HS_EXIT, CLK_POST • CLK_PRE, CLK_REOT, CLK_ZERO
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Receiver Jitter Tolerance
• RT/FT Control
• Insertion Loss • Standard Channel
• DJ & VOD Control • Static Skew • DC common Mode • SSC
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HS Receiver Testing • Error Detectors
• Initiating Rx ERRDET - First Big challenge! • HS Only ERRDET Initialization Sequence – Simple and Easy!
• Rx Stress calibration • Procedure defined for standard reference channel • Better Accuracy with Replica Traces for calibration!
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References • [1] DRAFT Conformance Test Suite for D-PHY℠, Version 1.2r11, 11 March 2015
• [2] Specification for D-PHY℠, Version 1.2, 01 August 2014
• [3] Specification for D-PHY℠, Version 2.0 Revision 07, 23 November 2015
• [4] D-PHY℠ Testing, Parthasarathy, MIPI Open Day Presentation Taipei, October 2015
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