S
Stefan Heinzmann
- Jan 1, 1970
- 0
Ed said:[...]Winfield said:Ed wrote...
The application is simply this. I'm building a microcontroller based
pyrotechnic firing system. The fet is needed to switch on and off the
supply to isolate the modules from the pyro. Since typically these
systems will be running from battery, and it involves reasonably long
wire lengths I want to introduce as little voltage drop as possible.
This is somewhat at odds with the current limiter. The series resistor
drops up to 0.65V, as you can see from Win's formula. It makes no sense
to use a fat MOSFET to minimize the voltage drop through it when most of
the loss occurs elsewhere.
If you are very serious about minimizing voltage drop and you still want
current limiting then you may want to use the drain-source resistance of
the MOSFET itself to measure the current. The resulting circuit is more
complicated. You may be better off to look for integrated solutions.
I would imagine I could create a zener gate voltage limiter with a
suitable resistor? This should solve the problem I would imagine, and
surely allow me to operate the fet at a suitable gate voltage level
across a wide range of supply rails?
Yes, that's a possibility. For turning off the MOSFET quickly you may
still want to have a resistor in parallel to the Zener.