In the XRX, I use a voltage monitor chip from Texas Instruments, which also serves as the input for the reset button. It’s the TPS3828.

If the supply voltage drops below 4.55V (typical), the chip generates a reset signal for the circuit. In addition, during power-up, it also ensures a 200ms reset pulse.

The watchdog function, although present, is not being used in this project.

Well, it turns out that the board would randomly reboot on its own. It didn’t happen all the time, but it did happen.

There’s another reset trigger in the circuit, coming from the power supply. The “Power Good” signal is buffered and can also trigger a reset, but the oscilloscope showed everything was normal.

The supply voltage also didn’t goes down 4.55V—it didn’t even come close to that. So, what could it be?

Using the old “put your finger on it and see if it burns” technique, when I touched one of the pins on the reset switch connector, the board rebooted. A missing ground? It didn’t seem like it, but I resoldered the connector anyway.

The problem persisted.

I decided to replace the TPS3828, using the one from the old board. And… it worked.

This is something to keep in mind when producing this board… but, for now, I can continue with my work.