TPS25750: PP HV shuts off after a small amount of time

pdiddymac

Part Number: TPS25750
Other Parts Discussed in Thread: BQ25792

Hi, I have a tps25750 configured to negotiate 20V sink without using the external EEPROM and it seems to negotiate reliably. Downstream I have a BQ25792 with a battery load and a system load. When functioning correctly, I see ~25W of power provided to the battery and system over USB C power which is exactly what I wanted. However, after maybe 20 minutes or so, the FETs open on the TPS25750 and I lose power to the system.

See schematic below (note: my 3.3V LDO is not powered up in the system right now so I'm relying on 3.3V being supplied internally in the tps25750 part)

over 4 years ago

0 Chuck Branch over 4 years ago

TI__Mastermind 32661 points

When working with the BQ parts, the TPS25750 expects to have power on VIN3V3, so some unexpected behaviors may happen.

Are you able to see if VBUS is discharged at the same time?

It would be helpful to see both VBUS and PPHV when this event occurs.

Do you happen to have a PD analyzer, we use the TotalPhase PD analyzer extensively. Having a PD trace would let me look at the traffic and see if something happened on the PD bus to cause the disconnect.

0 pdiddymac over 4 years ago in reply to Chuck Branch

Intellectual 450 points

Can I use LDO_3V3 to power VIN_3V3?

VBUS was discharged, yes at the same time.

I think I can grab the PD data when it happens. I'm not sure what triggers the event so I'll have to set it up to capture the CC lines. I'll respond back with that and probably can get a snapshot of VBUS and PPHV during the event.

0 Chuck Branch over 4 years ago in reply to pdiddymac

TI__Mastermind 32661 points

VIN_3V3 is intended to be used for systems that source power and should not be connected to LDO_3V3. There is internal circuity that connects the two only in dead battery mode. LDO_3V3 will provide a 3.3V rail for the system to operate from when operating as a sink only.

0 pdiddymac over 4 years ago in reply to Chuck Branch

Intellectual 450 points

ok I got a new board up and running after troubleshooting some downstream parts. I currently have it working. I also finally figured out how to extract PD messages so if I see the issue again I'll respond with those.

Any good resources for interpreting the data between messages? I seen a "Request" message sent with a hex value but I don't know what it's requesting. 5V? 20V? Any suggestions on resources? Thanks

+1 Chuck Branch over 4 years ago in reply to pdiddymac

TI__Mastermind 32661 points

We use the Total Phase PD Analyzer: https://www.totalphase.com/products/usb-power-delivery-analyzer/

This tool is very useful because it allows you to read the voltage and current through the port at the same time as a very good visual representation of all of the PD traffic.

Regards,

Chuck

0 pdiddymac over 4 years ago in reply to Chuck Branch

Intellectual 450 points

thanks!

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TPS25750: PP HV shuts off after a small amount of time