ps_aux on TE0817

[benm]

Hello,
I have a problem powering up a TE0817 module:
LP_DCDC is 3.3V
3.3VIN is 3.3V
EN_LPD is 0
LP_0V85 is 0 as expected
DCDC_2V0 is 0 as expected
PS_PLL is 0 as expected
but
PS_AUX is 0.47V
PS_1V8 is 0.86V
I don't understand how this is happens. I don't use PS_1V8 on my carrier board, it is just connected to a power plane but nothing else is there.
Do you have a hint on what is going on?
Thanks,
Ben

[Martin R @Trenz]

Hi,
sorry for not answering for such a long time, this should not happen.
Without making more measurements and test, it is hard to guess what is going on.
I would expect some back sourcing or loading of the rails.
I checked our oscilloscope bring up measurements for TE0817 REV02 on a TEBF0818 base board:
At the state you describe (LP_DCDC is up) there is no other voltage visible  until they are powered up in their sequence. To be fair, we measured only the normal startup sequence without stopping. So we see that zero of PS_AUX and PS_1V8 only a few hundred milliseconds. Meaning if there would be a very slow loading we would have missed it.
Did you already find out what is going on?
Did you measure the time dependency when this voltage appears? Who does the rise look like? Does it coincide with some other rail? Adding a small load (e.g. 1K) to the Testpoint of the rail could also give you a hint, e.g. does it respond like a voltage divider?

Best regards