Chapter · Power and protection
Diodes and surge protection
A battery fitted backwards, two supplies feeding each other, and a spike arriving down the cable. Three problems, and four parts that answer them.
- 03Diodes in the supply7 minA diode in the supply is the cheapest insurance in electronics and the most expensive to run. It survives a battery fitted backwards, and it charges you half a volt and a watt of heat on every day that nobody fits anything backwards.
- 04The ideal diode8 minAn ideal diode is a MOSFET with a comparator watching which way the current wants to go. It behaves like a diode with almost no forward drop, and the LM66100 does it in a package smaller than the diode it replaces.
- 05Diode and limit in one chip7 minThe CH213 datasheet describes itself as a Schottky barrier diode plus a self-resetting fuse, and that is exactly what it is — at a fifth of the drop, reacting in twenty microseconds instead of a hundred and fifty milliseconds, in a three-pin package.
- 06TVS diodes and the surge8 minA TVS diode does nothing at all until the voltage goes somewhere it should not, and then it conducts tens of amps for a millisecond to stop it. The number that decides whether it saved your board is not the one in its part number.
Start at 03 and read down — the order is the order things get easier in. Or take the one with your part in it; every article stands on its own, and links back to whatever it needs.