Hi,
We are working on PCBA bring up. Two of the prototypes were damaged after a few power cycles. They have the same problem -- PMIC damage (PCA9450BHNY).
1. I measured the "resistances to GND" for each power rail, and noticed the VDD_SOC to GND was only 2ohm (damaged board).
2. For good boards, the VDD_SOC to GND were 50ohm ~ 70ohm. However, values for other power rails were around 1Kohm.
3. VDD_SOC to GND resistance on bare board was normal.
If the 50~70 ohm value is not correct, what could be the possible reason?
We are using "nano" processor, but still connected the K12, K13, L11, L13, M13, M14, N11 to VDD_SOC (like reference design).
Design guide recommended to tie MIPI-CSI to GND if unused. Should I connect them direct to GND or through a resistor?
Thanks.
How many boards do you have?each one has PMIC damage?
We made 5 sample boards. 2 of them have PMIC damaged. However, VDD_SOC to GND resistance values are in the same range for good boards. I removed the damaged PMIC, measured again and still get similar value.
If you have three boards works well, I think should be assembly or solder issue for the two issue boards.
Could you check them firstly?
The good boards also have 50ohm ~ 70ohm resistance between VDD_SOC and GND. Is this typical for imx8m nano? (After removing PMIC the value was still 50ohm ~ 70ohm)
That's a very helpful information. The value is typical, although it is a little strange to me. Let me examine the boards for other possible reason. Thanks a lot.
what's the result if you do cross test? for example change the good PMIC into bad board.
Do you mind to share with your PMIC related circuit?
Hi,
Thanks you for response. We replaced the damaged PMIC with a good one. The new PMIC damaged again after a few power cycle. May I share the design file in private?