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

3

HalfSwing

EQ1

Short

4 Std

5 Long

6 Short/Std

NT 7 Long

8

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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