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I have a PCB which needs a 3,3V logic signal during the start-up of a system. Then this signal needs to be irreversibly broken.
Of course this could be done by flipping a switch, but the PCB isn't accessible anymore. So this needs to be done by another logic signal from the onboard microcontroller. I can't find a component for this task.

What I have checked:

  • this post but there must not be any particles or remnants of a blown fuse (pcb needs to be very clean)
  • latching relay: no magnetic parts allowed in the system
  • OTP eFuse like in microcontrollers, but I can't find them as separate products.

Would be happy about any ideas, thank you!

brhans
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bthunder
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    See the answer to this question for some info on an electrically triggerable fuse-like device used in some battery packs. Not sure if it'll work in your application - I think it'll need to draw a little pulse of current when you trigger it, so depends on your supply. – brhans Jul 04 '23 at 10:32
  • Managed to find efuses on digikey https://www.digikey.co.za/short/2h2rbqj0 – Makoto Jul 04 '23 at 10:44
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    Before we go to a wild goose chase, can you please explain why and how there is a need for such signal? What does the signal do? Why it is needed on first boot and then never again? Start-up as in once during the lifetime of the product, or each time it is powered on? – Justme Jul 04 '23 at 10:48
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    Any reason why it can't be handled by software? As in - set some flag in flash then control an analog switch or similar depending on the state of that flag. – Lundin Jul 04 '23 at 10:52
  • Thank you for the answers! @brhans the function of these "battery-protection-fuse" device looks very promising. But the current needed to blow the fuses (smallest fuse I found was 50A) is too high. – bthunder Jul 05 '23 at 11:35
  • @Justme The system consists of several PCBs. One of them - the one we are talking about - is only needed for start-up e.g. for debugging. But when the system is ready for use, this pcb should be permanently deactivated. The 3,3V logic signal enables the power circuit and shuts down the whole PCB if broken. – bthunder Jul 05 '23 at 11:35
  • @Lundin unfourtunately it is not possible as the state of this 3,3V signal needs to be non-volatile on a physical level. The signals controls a power circuit and the microcontroller sits behind it and therefore can't power itself up. – bthunder Jul 05 '23 at 11:39
  • @brhans Correction: these 50A is the current the fuse is able to break. For blowing the fuse a heater is activated and "only" needs 10W-30W. Maybe that is possible, I will check on that. Datasheet – bthunder Jul 05 '23 at 11:49
  • A standard fuse might work, too. A super-quick research revealed nominal currents down to 2 mA, with a 2 s max blow time on factor 5 (10 mA). – the busybee Jul 05 '23 at 11:59
  • Hi guys, the idea with a fuse worked best for me. I have put a low current fuse on the logic signal and when I want to break it, I short the signal to ground via a MOSFET and the fuse blows --> signal permanently off. – bthunder Jul 10 '23 at 08:04

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