Comments on Robust digital output protection
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Robust digital output protection
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I am working on a digital output concept that I would like to have the following characteristics:
- Output voltage: 5V
- Controllable by the uC from 3.3V power supply
- I would like to be able to switch the output at <100Hz
- I don't need more than 50mA of output current drive
- Bonus, it would be nice that the output wouldn't budge (get damaged) when stressed a bit with either ESD event of 8kV or +-12V wrong wiring connection. Unit doesn't need to function properly in this case, it just can't get damaged.
I currently have something like:
How does this look like?
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That will work to switch the output on and off. You can tolerate a few ms switching time, so the slow base drives should be OK. If you needed much faster, I'd suggest a smarter topology.
Some issues to consider:
- You said you want ESD protection on the output, but you haven't given it any. Q3 will likely blow up with a proper ESD event. At minimum, I suggest diodes to 5 V and ground.
- There will typically be 200 mV or so drop across Q3 when on, so the output won't get all the way to the 5 V supply. Perhaps that's OK, but you need to at least consider it.
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