Is it common for internal pull-up resistors to fail? or what would cause them to become intermittent?
I have a board based on an ASIC ARM Cortex-M3 that after months of work suddenly started to report spurious button presses. The ASIC is not our design, but a reputable company's.
The buttons schematic is given below. The pin is configured as input with pull-up resistor enabled. The resistor's value is about 30KOhm.
When measuring the pin-side with a DMM, I see the value floats around. Sometimes it is 3.2V (=VCC, chip range: 2.1V to 3.6V) and other times jumps around floating between 0.6V to 1.0V.
There are no issues of humidity/condensation (9% RH), no dust or other objects on traces. And this is the ONLY board that suffers this. Other manufactured clones of this board work without any issues (so far anyway).
The only thing I can think of is that something is making the internal pull-up flicker. Is it common for the internal pull-ups to give way? What else could be causing this?
R9,R12 are 2.2Kohm, and C10,C11 are 33nF.
I have a board based on an ASIC ARM Cortex-M3 that after months of work suddenly started to report spurious button presses. The ASIC is not our design, but a reputable company's.
The buttons schematic is given below. The pin is configured as input with pull-up resistor enabled. The resistor's value is about 30KOhm.
When measuring the pin-side with a DMM, I see the value floats around. Sometimes it is 3.2V (=VCC, chip range: 2.1V to 3.6V) and other times jumps around floating between 0.6V to 1.0V.
There are no issues of humidity/condensation (9% RH), no dust or other objects on traces. And this is the ONLY board that suffers this. Other manufactured clones of this board work without any issues (so far anyway).
The only thing I can think of is that something is making the internal pull-up flicker. Is it common for the internal pull-ups to give way? What else could be causing this?
R9,R12 are 2.2Kohm, and C10,C11 are 33nF.
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