TUSB321: Query on USBC_ID pull-up value

Kallikuppa Sreenivasa

Guru**** 204780 points

Part Number: TUSB321

Tool/software:

Hi TI Experts,

Please support the below query:

According to the TI's TUSB231 chip datasheet - the recommended external pull-up resistor attached to the TUSB321 USBC_ID output (open drain) shall be 200K.

In the latest AM67x TI EVM schematic –“PROC170E3B(002)_SCH.pdf” a pull-up resistor R608 with value of 10K is used.

The question came from this E2E query:

https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1554882/am67-tusb321-id-pin-resistor-value-in-am67-reference-design

Do you have a recommendation on the pullup value.

Is there a concern if 10K is used on the EVM ?

Regards,

Sreenivasa

4 months ago

0 Ryan Kitto 4 months ago

TI__Mastermind 44375 points

Hi Sreenivasa,

The ID pin on the TUSB321 acts as an open-drain pin, so an external pull-up resistor is needed to allow the pin to pull high. A value of 200Kohm helps ensure that when the ID pin is pulled-down by the TUSB321, the weak pull-up from the 200Kohm resistor won't stop the voltage on the pin from going down to 0V. 10Kohm can be used, but it would need to be tested to ensure that when the ID pin is pulled-low by the TUSB321, the voltage of the pin goes low enough to signal the power switch to enable VBUS.

Thanks,

Ryan

0 Kallikuppa Sreenivasa 4 months ago in reply to Ryan Kitto

TI__Guru**** 204780 points

Hello Ryan,

Thank you for the inputs, appreciated.

The AM67x EVM has been implemented with 10K and seems to be working.

If i understand correctly the recommendation is to use 200K but you do not see any concerns in case a 10K is used and functionally working.

Please let me know your thoughts.

Regards,

Sreenivasa

0 Ryan Kitto 4 months ago in reply to Kallikuppa Sreenivasa

TI__Mastermind 44375 points

Hi Sreenivasa,

Correct, while it's the recommendation, if you aren't seeing any functional issues then I don't see any issues.

Thanks,

Ryan

0 Kallikuppa Sreenivasa 4 months ago in reply to Ryan Kitto

TI__Guru**** 204780 points

Hello Ryan,

Thank you for the inputs and quick response.

Regards,

Sreenivasa

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TUSB321: Query on USBC_ID pull-up value