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TUSB212: Asking for the TUSB212 design consideration

Part Number: TUSB212
Other Parts Discussed in Thread: TUSB216

Hi Team,

Customer is designing TUSB212 on switch application

Would you please provide comment for the following questions?

1. This chip should close to USB Tx source side (host) or Rx receive side (device) ?

2. customer found one symptom. When customer enable TUSB212, even TUSB212 can enhance the eye diagram, but it also make the jitter become worse. How to improve eye diagram and still keep jitter not to worse?? Which gain setting will affect more jitter?? DC_boost setting or EQ gain setting ?? 

 

BR,

SHH

 

  • Hi SHH,

    1. I recommend that TUSB212 should be placed nearest the USB 2 connector. If the connection is embedded (no exposed USB port), I would like to know the total trace length between Host and device. Than I can make a recommendation.
    2. Can you provide an eye diagram? I recommend using Low/No DC boost and Mid AC boost to prevent amplification of jitter/noise coming for host/device. What is does the USB connection (i.e. trace length, flat cable connection, etc)?   

  • Hi Malik,

    The whole system block diagram and detail are in the link here.


    1. Now we have two TUSB212 in whole trace, one is in Puck board and the other is in 5 meter active cable type C side connector.
    We found that if we use two TUSB212 in whole system, some laptop can't enumerate to device.
    And in the Puck board, the TUSB212 is closed to type A connector.
    Please suggest us to keep which TUSB212 is better.

    2. About the eye diagram, jitter, and frequency shift issue. When we enable TUSB212, even TUSB212 can enhance the eye diagram, but it also make the jitter become worse, and also may cause USB signal rate to over the spec.
    Source eye :

    Source connect to Puck board typeA and measure to host connect eye. We remove the TUSB212 in this test.

    Source connect to Puck board typeA and measure to host connect eye. Gain setting is DC_Boost is high, and EQ is level 3.

    Source connect to Puck board typeA and measure to host connect eye. Gain setting is DC_Boost is low, and EQ is level 2.

    When we put TUSB212 on the cable, we can obviously observe that jitter and signal rate are getting worse.
    Source connect to 5 meter active cable typeC side and measure cable typeA side connect eye. Remove TUSB212 from the cable.

    Source connect to 5 meter active cable typeC side and measure cable typeA side connect eye. Gain setting is DC_boost high and EQ level 2

    About USB signal rate ove spec issue, please reference the attached test report.
    Please help to check why TUSB212 will make jitter worse and signal rate over spec when we set large gain issue. Thanks.

    BR,

    SHH

  • Hi SHH,

    Sorry for the delay, i had a illness late last week. I recommend using TUSB212 on with medium DC boost and level 2. Also there seems to be something on the Puck board causing an abnormal eye. Is there a schematic for the Puck board that I can review? TUSB216 should be used on the puck board. TUSB216 has greater re-driving capability on both the rising and failing edge of the eye, which could help in this case. Does the design have a I2C master available?  Is there an evaluation where the whole systems, puck board plus cable, is connected and measured?

  • Hi Malik,

    customer's test is test with 5 meter cable.

    Would you please help for the questions?

    1. Is TUSB216 BOM to BOM with TUSB212?

    2. Can TUSB216 use as HW mode? In I2C mode, what else flexibility can be get?

    3. Will TUSB212 increase the jitter and frequency shift problem? the eye from source jitter looks good, but it seem jitter is worsen after TUSB212.

    Please refer to the schematic here.

    txn.box.com/.../j0ybue7vagf6vbal27yjttn4lnd0jwon

    BR,

    SHH

  • Hi SHH,

    1. TUSB216 and TUSB212 are P2P but some resistor option may need to be changed for tuning without I2C.

    2. TUSB216 can use HW mode with predefined drive settings. I2C allow you to modify these drive settings with more voltage resolution.

    3.  TUSB212 will amplify some noise/ISI caused by the 5 meter cable. DC boost will increase this amplification and can cause variation in the data rate check. TUSB216 can turn off DC boost to prevent this.

    Looking at the schematic the customer should be able to use TUSB216 now. They will have Boost Level 2 and Medium RX_SEN settings. 

  • Hi Malik,

    for Boost Level 2 and Medium RX_SEN, should customer use 5V? or 3.3V is ok for this setting?

    BR,

    SHH

  • Hi SHH,

    Are you referring to VCC? If so, both voltages are OK for this setting.