Gary Lech <[email protected]> writes: To add to what Keith said on the subject already...
Even if you put a dead short on the igniter terminals of one of our boards (not recommended, but it happens), there's always some series resistance in the wiring itself, circuit boards, screw terminals, the FET channel "on" resistance, etc. And our pyro circuit, which is designed to throttle the energy delivered to active devices just enough to keep the processor from crashing has the interesting side-effect of acting faster when there's a dead short on the igniter terminals, limiting the total energy delivered and thus helping to protect the FET which never really has time to warm up. > Should I be adding a current limiting resistor to protect the FET? No. I can't remember ever seeing a board come back with a FET blown in normal use. It's just not an issue. By the way, bench testing I did myself with a good HP scope and some commercial e-matches a few years ago showed that they usually fired within about 13 microseconds. That's why we think 50 milliseconds is more than enough on-time... but we made it configurable for those who have weird igniters, or are using our boards to switch power to some other downstream device. Bdale
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