TPS65987D: Long delay in booting.

Eric,

What do you have connected to the HRESET pin?  This is the most likely pin to cause a boot issue.

Regards,

Chuck

Both boards have a pull down through a 3.3k. The voltage on HRESET is 0.098v.  If I short HRESET to ground it does not make it boot.

Eric,

The issue would have been if HRESET was floating or driven high by a MCU.  This will cause boot to be controlled by the MCU rather than being consistent.

Are you able to capture the SPI signals on the 2 boards?  It would be useful for me to see exactly what is happening on the 4 SPI signals for each board.

Don't try to zoom in, I don't need to exact details. Seeing a full boot sequence for the 2 systems will be enough for me to take the next step in figuring out what is going wrong.

Regards,

Chuck

But that is the issue.  The offending TPS65987D doesn't initiate any activity on the SPI lines.  I have a single sequence trigger set before the DFP (host) reset and nothing happens on my UFP TPS65987 after getting VBUS of 5V.  Many minutes later it will finally start and I get the capture. Both waveforms look identical.

ERic,

Can you put a scope on the LDO_3V3, VIN_3V3, and LDO_1V5 pins?

This huge delay could be an incorrectly sized capacitor that is taking a long time to charge or a potentially damaged part.  This is definitely nor correct behavior.

Regards,

Chuck

Green: VBUS

Yellow: LDO_3V3

Teal: LDO_1V8

Pink: VIN_3V3

Eric,

Are you able to rework the board to replace the TPS65987?

Based on all of your board results, I do not see any external issues, so Ii am suspicious that the TPS65987D is damaged and not performing correctly.

Unfortunately, while observing the voltage I bumped the probe on the LDO_1V8 cap and tore it off the board.  Once it was soldered back the PD wouldn't work at all.  We replaced the IC twice.  I just figured out that the cap was shorted so when the cap was replaced the board works flawlessly.

Here is the issue. We have a different design with the same issue.  It seems suspect to me that we have two marginal ICs in a short run of 5 different protos.  I will replace the LDO_1V8 cap to see if that helps.  If it doesn't help do you have the ability to diagnose what is occurring internally to the TPS65987?

Eric,

Have you checked the solder mask clearance around the LDO_1V8?

If you are seeing weak shorts across the LDO_1V8 cap, then that could cause the extremely long boot time because the LDO would not be able to provide current and would likely look unstable.

The solder mask clearance is correct on both boards.  If I remove the LDO_1V8 4.7uF capacitor the delay goes away and the boot is immediate.  I measured the cap and it is 4.8uF.  Upon returning the cap to the circuit the delay returns.  I will try the minimum capacitance of 2.2uF to see if there is an improvement. 

Even 1uF causes a delay, albeit, shorter.  TI should be interested in why this occurs.

Eric,

I have asked around internally and the best way to take care of this is to follow the Customer returns process detailed here: https://www.ti.com/support-quality/additional-information/customer-returns.html?keyMatch=RETURNS

Please reference this thread with any communication.

Regards,

Chuck

So I remove the IC from the board and return it to be analyzed?