![]() The corresponding current will also be very low. This forces the diode to limit the reverse polarity voltage to a very low value (less than the -300 mV limit on CMOS I/Os). Once a reverse polarity event occurs, the diode will be driven in reverse bias. The circuit diagram below shows the correct placement.Ī simple series diode can provide significant reverse polarity protection. The simplest method for adding DC reverse polarity protection to a circuit is to place a series diode in front of the protected load or circuit. There are three principle components used for reverse polarity protection: During reverse polarity, the device should have high impedance so that the voltage reaching the protected circuit is dropped across the protection circuit. When operating normally (positive voltage), the device has low impedance and minimal voltage drop. Reverse polarity components are normally placed as a series element before the protected circuit. The purpose of reverse polarity protection components and circuits is to drop excess voltage such that it does not reach a protected load once the polarity of the applied voltage is reversed. ![]() These options apply to batteries, power supplies, and regulator circuits providing DC power to integrated circuits or other loads sensitive to overvoltage. ![]() In this article, we’ll briefly examine some simple options for protecting integrated circuits from reverse polarity. A common reverse polarity limit on single-ended integrated circuit I/Os built with the standard CMOS process is -0.3 V, and your reverse polarity protection measures should protect against this level of reverse overvoltage. In an extreme case of high overvoltage under reverse polarity, an integrated circuit could be destroyed and would need to be replaced. Voltage applied to semiconductors can push them into reverse bias, which can then damage inputs on an integrated circuit.
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