Electronics > Beginners

Help finding PCB design flaw

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aliarifat794:
Before printing, did you simulate your circuit? Or implement it at home (perhaps on a breadboard or veroboard)? 

tooki:
A potential issue I see is that all of your input capacitors are ceramic. This can cause voltage spikes if you connect a power supply that is already turned on, connected through a long (more than a few cm) cable. See https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf

Previous threads that at least mention this issue:
https://www.eevblog.com/forum/beginners/boost-converter-explodes-when-connected-to-battery/ <— really nice explanation in words in reply #4
https://www.eevblog.com/forum/beginners/do-lc-power-on-spikes-usually-matter/
https://www.eevblog.com/forum/beginners/hot-swapping-killing-ics/
https://www.eevblog.com/forum/chat/why-did-my-lt3042-die/
https://www.eevblog.com/forum/projects/tmc5160-keeps-dying-on-24v-input/
https://www.eevblog.com/forum/projects/protecting-against-voltage-regulator-failure/
https://www.eevblog.com/forum/projects/regulator-dies-and-takes-whole-circuit-down-with-him/
https://www.eevblog.com/forum/projects/buck-converter-ic-fail-vin-shorted-to-ground/
https://www.eevblog.com/forum/projects/synchronous-buck-ic-with-internal-power-switches-failing/

If it is this, don’t be like most of the people in the above threads, who never gave any update on whether that was the problem or not: please leave an update!

mrburns:

--- Quote ---please leave an update!
--- End quote ---
Thanks for the info! I will definetely keep updating. I was not able to break any components when testing with lab power supply. I did find one thing that could have caused these issues:
- The Q3 P-mosfet was acting weirdly and showing 1V voltage drop across it until I jumped the gate to ground. It would also not open after I removed 5V from the gate.
- Also with low voltages like 3-3.5 it would really slowly start rising the voltage through it, so it must have been in some unstable state.

I now added 10k pull down resistor between the gate and ground on the U7 Attiny10 gnd and PB0 (driving the Q3 gate) breakouts and now it seems to be working..
I dont have any code on the attiny yet but just jumping Vin to the PB0 seems to work correctly and it cuts the power to the board and resumes operating when the gate is low again.

gamalot:
Those vias make my head spin, are they really necessary?  |O

amwales:
I'm new to all this, so this may be a silly question but is the bag you are standing your board on conductive?

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