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Renesas Singapore - Knowledgebase

What do mean by Through current?

Latest Updated:08/01/2005


Through current


This current is generated if a voltage intermediate between the high and low levels is input to a CMOS device.

CMOS is a combination of PMOS and NNOS. Both PMOS and NMOS are not completely turned off at a certain voltage, but both are on at the intermediate voltage.
Consequently, a current flows from the power supply to ground, resulting in a short circuit. This current is called a through current.

If the input signal is slow in rising or falling, the input time of the intermediate voltage is long.
Consequently, a through current is generated, weakening the internal power supply and causing malfunction in some cases.

Even if an unused CMOS input is open, the input may serve as an antenna and collect noise, causing a through current to flow.
A through current accelerates degradation because it is generated in a shorted state.

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