AnsweredAssumed Answered

When i.MX28 does not boot with PSWITCH pulldown to GND

Question asked by George Fukutomi on Jul 12, 2018
Latest reply on Jul 16, 2018 by igorpadykov

Dear all,

 

We are manufacturing the product using i.MX280 from 5-years or more before.

One of about 1,000 products manufactured by them has condition that it does not boot.

And we began to investigate the cause recently.

 

The product uses only VDD5V and does not use a battery.
The schematics near by the power supply is as an attached file.

AN4199 was not published when we began to have manufactured the product.

Therefore, the power management method for u-boot and kernel is the same as it for EVK.

 

After power on,  the board which does not boot is in the following condition.

1)  VDD5V are supplied stably.

2)  The correct voltage is outputted from VDD4P2.

3)  XTAL is not oscillated.

4)  All DCDCs seem to have not started yet, Each DCDC outputs voltage are linear regulators outputs voltage.

5)  There is also no access to boot media and all codes seem not to read it.

6)  Even if it assert RESETN, the condition is unchangeable with the reset switch.

 

But, I found only one method of booting the board.

It is the method of supplying the about 1V to PSWITCH.

The voltage is generated by the system power supply.

 

It should recommend that NXP weak pulldown PSWITCH to GND.

It seems that however, their product may not be booted by pulldown.

 

Does their product have latent fault?

Is there anything you can think of?

 

Best Regards,

George

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