SPC5744 RESET_B (31) the voltage after power-on is only 1.1V

[drogonsky]

 

For the RESET_B reset pin of SPC5744, part of the boards do not work after the circuit is powered on, and the abnormal reset voltage measured is only 1.1V. The reset circuit is used the RC reset. Has this ever happened to any of you?

The reset circuit is like this :

 

[petervlna]

Hello,

For the RESET_B reset pin of SPC5744, part of the boards do not work after the circuit is powered on

Could you be more specific? Is that on NXPs EVB or custom board?

Reset should be in specified range tied to 3.3V or to GND.

What about your supply voltages, are they in specified range? VDD_HV and VDD_LV.

Best regards,

Peter

[SindoreiZeng]

Dear petervlna,

          I had a similar problem.I left the RESET_B pin dangling, started the power supply, and the oscilloscope observation showed that the RESET_B was always low.

        Is this normal,Or in the normal case where RESET_B is dangling what is the waveform of this pin during power-up?

        Thank you!

[drogonsky]

Circuit board is the customer board, has been produced thousands of pieces, the production process has found a dozen pieces of board appeared this problem.

The reset circuit on the board uses RC reset circuit, just like what I wrote in the post, the resistance is 5.1K connected to 3.3V power supply, the capacitance is 1nF.

Supply voltage VDD_HV:3.275V, VDD_LV:1.253V

[petervlna]

Hello,

Then the simplest you can do is to swap the chips between good and bad board to see if is it chip issue.

On the other hand, you can place chip from failing unit into NXPs EVB to see if the issue persist.

As your voltages seems correct to me, micro should be working correctly.

You can also try to erase the device, to see if it is not caused by SW. Erased device, wont have any issues to get out of reset.

Best regards,

Peter

[drogonsky]

I swapped the MCUS of the problem board and the good board, and found the same thing happened to the good board after the swap.

Later, the oscilloscope was used to test the working condition of the reset signal, and it was found that the reset signal of the MCU with problems after power-on had been doing the reset action repeatedly.

The waveform of the reset signal in the case of problem MCU is as follows:

The waveform of the reset signal in the case of normal MCU is as follows:

[petervlna]

Hello,

From the photos it looks to me like the reset escalation cause by unhanded reset source.

Since your device will get out of reset for a while and then it will reset again.

What is the content of your RGM [FES/DES] when you attach to failing device. I see that reset is toggling  so you must be able to attach to running target and break the code.

One more thing you can do it to place failing micro into the EVB and run some NXP reference code on it.

But this looks like application corner case issue to me. We will be wiser after RGM is read.

Best regards,

Peter