TPS65986: PD_P3V3 (C140) or PD_LDO_3V3(C141) output is unstable (ring) when did the Adapter DC cable or USB cable plug in-out test

Hi,

Thanks for sharing the data. I'll review it and get back to you.

Thanks,
Rahul

Report 05112018-A1-AL.pptxHi Rahul,

    Please refer  attached file for the update and added the failure symptom waveform. The project will phase in MP  and need your help to have the comment and suggestion for the issue in time.

   1. The comment for the current build circuit. ( Note. NM of R309  means this location is open). As the mentioned the device works in dead battery mode.  Especially for the VIN_3V3, VDDIO, and LDO_3V3 are connected together as circuit.

   2. The glitch waveform  of PD_P3V3 (VIN_3V3) during power on.  Does is in theory?

Best regards,

Albert Lee.

Hi Albert,

Can you please remove R350 from the board, LDO_3V3 & PD_P3V3 rails shouldn't be shorted together.

Please try this and let us know the result.

Thanks,
Rahul

Hi Rahul,

In previous attached file has listed the waveform after removed R350. ( Unfortunately the random failed IC was damaged during test from customer side, it unable to check this one with the failed IC now)

For LDO_3V3 & PD_P3V3 rails shouldn't be shorted together:
1. Would you please help to have more specify explaining for it? And does the output unstable is relate to this one due to the failaure symptom is random and not in all system sets?

Note. From cusotmer's info that they do this kind of connection is due to they need to let PD_GPIO7 to control U38.

2. Do you have any suggestion for it? From customer side exception, they would like to see if any checking or sorting method can screen out the failure from production line with the solid analysis or evaulating.


Best regards,
Albert Lee.

Hi Albert,

As per the device datasheet the LDO_3V3 and VIN_3V3 needs isolation to ensure there's no leakeage of internal power from the internal LDO_3V3 rail to the system. LDO3V3 can be generated from internal regulator which is powered from VBUS, shorting VIN_3V3 to LDO_3V3 would cause powring up of all the devices in VIN3V3 rail which will cause unpredictable behaviour due to LDO overload of PD controller.

From all the data available the only reason I could see it the unstable VIN_3V3 and I would request you to figure out why the PD_P3V3 rail is dropping.

PD should work fine if PD_P3V3 is stable.

Thanks,
Rahul

Hi Albert,

Do let me know if this issue is resolved or you need more support on this?

Thanks,
Rahul

Hi Rahul,

     Not yet. Here are the additional questions and need your help to confirm it.

     As our opinion  that LDO_3V3 & PD_P3V3 rails shouldn't be shorted together. As per the device datasheet the LDO_3V3 and VIN_3V3 needs isolation to ensure there's no leakage of internal power from the internal LDO_3V3 rail to the system.

     Customer plans to open VIN_3V3 (unconnected other, means it is operating in dead battery mode). 

     VDDIO connects to LDO_3V3 and there has three GPIO pins will connect to driver parts.

      Would you please help to check and comemmt if it's okay?