USB PD Dead Battery pin usage when functioning as PD Source

[JMano.2042]

I am using the STM32G071GBU6N to implement 2 USB PD interfaces. Port 1 will be sink, Port 2 will be source. On the sink interface, the dead battery support is needed and DBCC pins will be connected to cc pins. On the source, I do not need dead battery support. I want to reuse the DBCC pins for other use. The ref manual indicates that they should be connected to ground. Is this necessary, or can they be reused when operating as source only?

[Richard O]

If dead battery resistance is not desired (the case for a SRC) the DBCC pins must be at GND on power-up and until such time as the UCPDx_STROBE bits in SYSCFG_CFGR1 have been written. The recommended way to do this is shorting the pins to GND (as described in AN5225). However if re-use of DBCC pins as a GPIO is needed, it is possible after the write to UCPDx_STROBE bits has been done. In this case, an external pull-down resistor to GND (say 100 kohms to 1 Mohms) should be present on the DBCC pins to help guarantee a clean GND state at start-up.

[ChristophR]

Hi,

we would also like to reuse the DBCC pins. We implement a DRP device, do not need dead battery support, and we have a separate protection IC which does dead battery handling. Do we still have to follow your recommendations (pull-down resistor on DBCC pins during start-up) or is it safe without these pull-down resistors?

Thanks in advance!

BR,

Christoph

[waclawek.jan]

@Richard O​  ,

a simple diagram/drawing, depicting the pins and the DB logic, would be really helpful in illustrating, what's going on.

JW

[ChristophR]

Sorry, my question below should have been a reply to you @Richard O​ 

[DGaur.1]

UCPD Source Port : How to configure STM32L562 UCPD Dead Battery Pins DBCC1, DBCC2 to act both as pins for dead battery ground logic and GPIO? STMCubeMx won't allow conflicts. Any mechanism to override it?

PIN PB14 - UCPD1_DBCC2 & GPIO_EXTI14

PIN PB5 - UCPD_DBCC1 & GPIO_Output

regards,

Deepak Gaur

[OlivierR]

In AN5225 - Rev 5, there is a chapter describing DBCCx usages from system point of view:

11.2.1 DBCC1 and DBCC2 lines

Have a look in following table:

Table 12. Summary of principal Type-C application topologies 

regards.