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Custom I.MX28 Power Supply Hanging Problem

Question asked by Paul Hilton on Jan 19, 2015
Latest reply on Jan 30, 2015 by igorpadykov

I have a line powered, inaccessible, I.MX28 board, no batteries, working well, running Linux.

I have discovered a 'hanging state' by interrupting power for short periods.

I have 'PSWITCH' tied to VDDXTAL via a 10k resistor  to turn the thing on when power is applied, which usually works.

I believe that this was suggested as appropriate in documentation.

There is no other external dc load on VDDXTAL, and the 32.768kHz oscillator is disabled.

By interrupting line power for brief periods I can get the power supplies into a stable condition where:

VDD5V = 5.2V

VDD4P2 = 4.7V

Switching supply is stopped

VDDXTAL = 0.97V

PSWITCH = 0.97V

Various 3.3V supplies at 0.94V


By momentarily pulling PSWITCH up with an external 10k resistor to 5.2V the whole thing starts up just fine.

Changing the 10k connection to VDDXTAL to VDDIO33 would seem unlikely to fix this.


Any suggestions for a fix that does not require an external watchdog?



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