UCPD (USB-PD) use DBCC pins for something else if dead-battery not needed?

[Erlkoenig]

Hi,

i am using STM32G0B1KB and the UCPD peripherals to implement an USB-PD device with 2 ports:

- Port 1 is DRP
- Port 2 is Source only

I need the dead battery pulldowns for port 1, so I will connect the UCPD1_DBCCx pins with the UCPD1_CCx pins as described in the manual. However, for port 2 I don't need to present the dead battery pull-downs - when the MCU is unpowered (dead battery) and the user connects some other device (e.g. smartphone) to port 2, simply nothing should happen. The manual states:

> If dead battery behavior is not required (for example for source only products), then UCPDx_DBCC1 and UCPDx_DBCC2 pins must both be tied to ground.

What resistance can be used to connect those pins to ground? Since I don't have any pins left, can I instead use the DBCC pins for something entirely different? E.g. connect LEDs (to GND) or some other digital output with a weak external pull-down resistor (e.g. 10kOhm)? Will this prevent the MCU from enabling the pull-downs?

Thanks!

[MROUV.1 · Accepted solution]

Hello,

 TCPP protection devices (TCPP01-M12 or TCPP03-M20) handle dead battery (DB) signaling even when there's no power, making direct connections between UCPD1_DBCCx and UCPD1_CCx useless.

Thus, the pins typically used for UCPD1_DBCCx can be repurposed as GPIO for additional functionalities (LED as exemple).

Best regards,
Mathieu

[Erlkoenig]

Great to know, thank you very much!