TUSB1002A: Optional pulldown resistor for RX port with HD3SS3320

TerryU

Part Number: TUSB1002A

Hi Experts,

TUSB1002A document mentions an optional pulldown resistor, 220kohm, for RX port for discharging . I would use TUSB1002A with HD3SS3320, Type-C MUX, for Type-C configuration. In this case, should I consider about this pulldown resistor? And if so, which is put the pulldown pre-MUX or post-MUX?

Best regards,

Tetsu

over 1 year ago

0 David (ASIC) Liu over 1 year ago

TI__Guru**** 152641 points

Tetsu-san

The 220k resistors help to further reduce the discharge time to be well within the spec limit of 250 ms. As stated in the TUSB1002A these resistors are not required assuming leakage current from external components is enough to discharge capacitor. There will only be signal integrity impact to USB performance if the resistors are added. The stub created from placing the optional (not necessary) pull down resistor should be minimized to avoid negative affects.

Thanks

David

0 TerryU over 1 year ago in reply to David (ASIC) Liu

Prodigy 145 points

Hi David,

Thank you for your rapid response. This optinal resistor works quick discahrage of coupling capasitors, and TUSB1002A RX port does not have discharge system. What will occur, if charge remains a bit large term?

Best regards,

Tetsu

+1 David (ASIC) Liu over 1 year ago in reply to TerryU

TI__Guru**** 152641 points

Tetsu-san

The Tdischarge spec is there to ensure that the USB receiver, at the connector, does not hold a previous common mode voltage and prevent a newly plugged device form seeing this common mode.

Thanks

David

0 TerryU over 1 year ago in reply to David (ASIC) Liu

Prodigy 145 points

Hi David,

Thank you for your useful comment. I will consider about discharge.

Thanks,

Tetsuj

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TUSB1002A: Optional pulldown resistor for RX port with HD3SS3320