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I need to drive dual coil latching relays from a single input signal. Following are my assumptions:

  • low-side drive of the coil
  • coils connected to 12V automotive
  • coil resistance unknown, assumed 1A will be more than sufficient
  • input floating -> 12V (automotive) transition generates a set pulse
  • input 12V -> floating transition generates a reset pulse
  • automotive 12V load dump is limited to 40V with 5.0SMDJ24A
  • pulses generated are ~100 ms

This is the schematic I arrived at:

enter image description here

Datasheets:

I would greatly appreciate if somebody had the time to review the schematic.

ARF
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  • The MCP1416s are probably unnecessary, given the low gate charge of the IRLML0040 and undemanding circuit conditions. You probably want a pull-down resistor on the FET gates, though, to ensure predictable startup behaviour. – Hearth Mar 27 '23 at 14:10
  • need a pull-down on the input. – John Birckhead Mar 27 '23 at 22:25
  • @JohnBirckhead Thanks for catching that. – ARF Mar 28 '23 at 08:14
  • @Hearth I checked that the MCP1416 had predictable startup behaviour. I thought that was sufficient. But of course, a floating mosfet gate when the entire gaget is without power is probably not ideal either. Thanks. – ARF Mar 28 '23 at 08:16

0 Answers0