Super Speed USB USB 3'0

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Super Speed USB (USB 3.0)

• End-to-end interoperability and compliance test

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USB 3.0 Basic Architecture
TX testing
Impedance, loss, crosstalk

RX testing
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Transmitter Electrical Parameters



At device output
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Fixture De-embedding
Improves accuracy for voltage and de-emphasis
measurements
2 dB _at_ 2.5 GHz
Eye Doctor software
Measured signal at the probing point. The signal
amplitude and slew rate are altered by the fixture
Signal at the transmitter output
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USB3 Clocking and Jitter
Separate SSC domains
Jitter transfer function is determined by PLL and
Phase interpolator
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Jitter Transfer Function

• Jitter in the non-tracking frequency range of the
  PLL causes eye closure i.e. Total Jitter
• SSC and other jitter sources must be minimized
  outside the loop bandwidth of the PLL (inside the
  CDR error region)
• Maximum phase difference between SSC domains
  cannot exceed transient tracking ability of the
  PLL (slew rate limit)

Jitter Transfer Function
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SSC and CDR Slew

• Frequency (red), phase (blue) and 1st difference
  of phase (light blue)
• Phase is filtered by the CDR (low pass filter)
• Peak of derivative of phase must be less than 10
  ms/s
• Maximum slew rate is based on the ability of CDR
  to track phase change

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Transmitter Compliance
Reference test channel
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Compliance Test Channels and Reference Cable
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Equalization
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(No Transcript)
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Equalization
USB 3.0 sec. 6.8.2
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Transmitter Compliance Test
DUT
fixture
Scope
TP1
1 or 3m cable
Reference channel
CTLE
Eye Doctor software
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Eye Doctor Software
CTLE
S-parameters of compliance channel
Emulate compliance channel
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Differential Impedance
DUT (TX and RX power off)
fixture

• 50 ps rise time
• Time to open with DUT disconnected
• Time to termination with DUT connected
• 72 lt Z lt 120 ohms differential

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Example TX Impedance Measurement
90 ohm differential trace
Mated connector
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USB 3.0 Cable Assembly
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Cable Measurements
Cable parameters measured using TDR/TDT
B receptacle fixture
A receptacle fixture

• Differential insertion and return loss
• Differential crosstalk
• FEXT
• NEXT
• Differential to common mode conversion
• Intra-pair skew
• Impedance
• Normalized to 90 ohm differential impedance

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Signal quality/receiver tolerance margins decrease
Higher throughput/speed reduces signal quality
and receiver tolerance margins
? receivers need to work with smaller margins
Transmitter Eye
Receiver Eye
1.5 Gbps
3.0 Gbps
6.0 Gbps
Receiver tolerance testing is not optional any
more!
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SuperSpeed USB - Receiver Compliance Is A
Requirement

• Super Speed USB Specifications require Receiver
  Tolerance compliance as a Normative Compliance
  Test
• The following information is based on version Rev
  1.0 Draft of USB 3.0 specification

Electrical Compliance Test Specification
SuperSpeed Universal Serial Bus Date
Sept 12 2009 Rev 0.9
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Receiver Compliance Procedure

• Step 1 Calibration/Channel Setup
• Calibrate amplitude, signal conditions and jitter
  sources to TP1
• Apply specified amplitude, Rj, SSC, De-emphasis,
  Reference channel and cable for RX Jitter
  tolerance
• Step 2 Loopback
• Put Device Under Test in loopback mode
• Step 3 Sj Sweep
• Sweep through specified Sj values and measure
  jitter tolerance based on BER

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Step 1 Calibration / Channel Setup

• PeRT3 Tx differential channel connects to 2 input
  channels on Scope including the Reference Channel
  and Reference Cable in between
• Calibration is done at TP2

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Step 1 Calibration / Channel Setup

• Calibrate amplitude, signal conditions and jitter
  sources to TP2
• Calibration includes
• Signal amplitude set to 750mV
• SSC - 33khz, Triangular, Down spread,
  4000-5000ppm
• Rj set to 2.42ps RMS
• Sj - 400ps at 500khz, 200ps at 1Mhz, 100ps at
  2Mhz, 40ps at 4.9Mhz, 40ps at 50Mhz
• Pre-emphasis set to 3.5dB
• Reference channel
• Supplied by USB IF Availability TBD
• Cable
• Supplied by USB IF Availability TBD
• Note Without reference test channel, signal
  amplitude should be set to 1000mV and disable
  pre-emphasis

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Step 2 Loopback

• Two methods defined in specification for loopback

• Internal BER
• Loopback BERT
• External BER
• Loopback

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Low Frequency Periodic Signaling

• Used for side band communication between the two
  Ports across a link that is either in a low power
  state or an error state
• Generator needs to generate LFPS signal and
  transition into 5Gbps signal with timing
  requirements as specified in the USB3.0 Spec
• This will also allow the DUT to enter and exit
  from loopback mode

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Loopback BERT Method

• Loopback BERT is a new method for the DUT to
  perform internal BER measurements and record
  errors in the error register
• Generator sends known patterns to Device Under
  Test
• Device Under Test counts errors in known patterns
• Counter value is sent back to generator
• Actual command flow
• Start with LFPS signal
• Transition to 5Gbps signal
• Training sequence (TSEQ, TS1, TS2)
• BRST (error register reset)
• BDAT (compliance pattern)
• BERC (error register read)

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Loopback Method

• The traditional retimed loopback mode
• Generator sends known patterns to Device Under
  Test
• Device Under Test sends received patterns back to
  the generator
• Generator counts errors

• Note Traditional BERT systems cannot perform
  this test for USB3.0 products because USB3.0
  device and Host receiver systems will add and
  remove SKP symbols during retimed loopback. This
  will cause traditional BERT systems to lose lock
  with device under test.

Loopback pattern will have inserted/deleted SKP
symbols which may cause test tool to lose lock
PeRT3 has protocol enabled state machine to
remove SKPs before counting bits
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Step 2 Loopback - Summary

• Many products in the market may not have loopback
  BERT implemented and would prefer traditional
  retimed Loopback test mode
• Intel believes that the traditional Loopback mode
  is the best way to test receivers and is pushing
  for the specification to require this method
• PeRT3 is the only tool that can perform the
  traditional Loopback while recognizing and
  handling SKP symbols and thus correctly measure
  BER!

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Step 3 Sj Sweep

• Receiver Characterization test
• 5 frequency test (SJ)
• 10E-12 BER at 95 confidence
• 50 minutes
• Normative Compliance test
• 5 frequency test (SJ)
• 10E-10 BER at 95 confidence
• 30 seconds
• The pattern sent
• Scrambled zeros pattern when in Loopback BERT
  (CP0)

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Step 3 Sj Sweep Jitter Tolerance

• The generator will test BER at the following
  jitter configurations (with SSC On)
• Rj 2.42ps RMS, Sj 400ps at 500Khz
• Rj 2.42ps RMS, Sj 200ps at 1Mhz
• Rj 2.42ps RMS, Sj 100ps at 2Mhz
• Rj 2.42ps RMS, Sj 40ps at 4.9Mhz
• Rj 2.42ps RMS, Sj 40ps at 50Mhz

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LeCroy USB 3.0 Solution

• SDA813 or SDA816Zi oscilloscope (TX tests)
• WE100H with 2 ea. ST-20 sampling/TDR heads
  (cable, TX impedance)
• PERT3 (RX tests)
• USB 3.0 fixtures
• QualiPhy software for USB3.0 (automates tests)

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Summary of LeCroy USB 3.0 compliance test solution

• Complete set of instruments for compliance and
  development
• PERT3 for receiver tolerance test
• 13 GHz real time oscilloscope for transmitter
  tests
• Sampling oscilloscope with TDR and s-parameters
  for TX/RX impedance and cable testing
• QualiPhy software automates all tests and
  generates report
• Cost-effective solution
• Two instruments cover all PHY tests
• PERT3 provides complete receiver tolerance
  testing at less than ½ the cost of traditional
  BERT systems

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