Low-power keypad 100 nA

Posted on Dec 3, 2012

The circuit in Figure 1 is a keypad interface that solves this problem by using an ultralow-power microcontroller. The circuit typically consumes 100 nA while awaiting a key press and consumes a maximum of only 2 µA if all keys are stuck or held down. An added bonus of the circuit is that it requires no crystal.

The circuit uses the MSP430, IC1, because it offers low power consumption, individually configurable I/O pins with interrupt on rising or falling edges, and wake-up time of less than 6 µsec. In normal mode, port pins P3.0 to P3.3 drive the rows high. T

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