Author Topic: ST92163 Microcontroller reset stuck on low.  (Read 512 times)

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Offline gkmaia

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ST92163 Microcontroller reset stuck on low.
« on: August 23, 2019, 07:02:44 am »
I got a ST microcontroler that is stuck in low.

If you look at the attached image pin 36 seems to connect to the base of an NPN transistor and at the same time connects to ground.
Pin 35 is the reset, seems to connect to the emitter.
The NPN collector if feed from a 5v rail.

If I momentarily short the reset pin to the 5v rail then disconnect it the IC boots up.

The transistor circuit itself cannot boot the IC but manually I can do it.

Anyone out there with some ideas of what could be going wrong here?
 

Offline fzabkar

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Re: ST92163 Microcontroller reset stuck on low.
« Reply #1 on: August 23, 2019, 07:26:59 am »
An NPN transistor in that position makes no sense, but a reset supervisor IC would.
 

Offline gkmaia

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Re: ST92163 Microcontroller reset stuck on low.
« Reply #2 on: August 23, 2019, 07:30:45 am »
An NPN transistor in that position makes no sense, but a reset supervisor IC would.

Yes, I agree. Struggling to make sense of that too. I will do some research on a reset IC and see if I can find anything.
 

Offline fzabkar

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Re: ST92163 Microcontroller reset stuck on low.
« Reply #3 on: August 23, 2019, 08:09:43 am »
What are the markings on the "transistor"?

There are hundreds of candidates with the correct pinout:

http://www.ti.com/lit/ds/symlink/tlv803.pdf
« Last Edit: August 23, 2019, 08:18:38 am by fzabkar »
 

Offline gkmaia

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Re: ST92163 Microcontroller reset stuck on low.
« Reply #4 on: August 23, 2019, 09:19:35 am »
I researched all over for the marking. Nothing no where.

Fzabkar was right. It is a microcontroller reset monitor. TCM809 is probably the right part.

The output of my faulty one is not holding the voltage low for the first ╬╝secs.

I added a 4.7uf capacitor between the RESET and GND and a 10k resistor between the 5v rail and RESET.
Now as the voltage raises slowly the microcontroller detects the raise slope on RESET and the thing booted up just fine.
« Last Edit: August 23, 2019, 10:29:50 pm by gkmaia »
 


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