TPS65988DK: Port 1 path not disabled when Port 2 Path enabled to sink - power back to PC killed motherboard

Here is the .prj file used.TPS65988DK_2023_10_02-PortA EXT sw fix-USE THIS.pjt

Hi,

The issue is likely not related to you pin strapping. This sound like the PPHV path got shorted and power fed from port B to port A because both port are sinking at the same time. If an Type A to Type C cable is connected to port A, port A will become a sink because the far end type A port is always and only source.

Do you have an EC talking to the PD in the system?

Regards

Yes, we have an EC talking to the PD in the system. 

Hi,

Forgot to ask by the time port A is plugged in to a USBA port on PC is the PD in dead battery mode? Will the system be starting up in dead battery mode?

Regards

When initially connecting power via either of the ports,  the PD comes up in dead battery mode. I do not know if the DeadBattery Flag Clear (DBfg) command had been executed before port A was plugged in.

Hi,

It seems like the two type-C ports are the only power source of this system hence why you are using BP_ECWait_External. And it is likely that the device is still in dead battery operation when port A is plugged in.

Is port B using external power path or internal power path to sink power? 

Regards

Port B uses the internal power path to sink power.  The external power path for Port B is not used.

Hi

You might want to try with BP_ECWait_Internal for Port B so the external sink path on port A is disabled in dead battery operation. However you will still want to add RCP on PPHV in case where port A and Port B are sinking different voltage PDO.

Regards

We had things initially set with BP_WaitFor3V3_Internal.  When connecting to port A via a USBA port, the internal switch would turn on, power would go back the wrong way through the variable DC DC buck regulator.  How would BP_WaitFor3V3_Internal function different than this? 

What is " add RCP on PPHV"  

Hi,

Does VIN3V3 (system side power) comes up before connector is plugged in to Type-C port? Based on the diagram none of the dead battery operation mode will work for your power path setup. If you use any DB config that enables internal power path port B can sink power but port A will back feed to DC/DC. If you use any DB config that enables external power path, port B will not be able to sink power.

david hilderman said:

What is " add RCP on PPHV"  

You will need Reverse Current Protection on PPHV to prevent current back feeding from port B to port A due to PPHV2 and PPHV1 voltage difference when you have a 60W source (likely 20V3A) on port B and a 5V source (USB A PC port connected ) on port A.

Regards