THREE STATE SWITCH DETECTION USING CURRENT SENSING

摘要

A three state switch detection circuit (60) converts a three state input (46) to a two-bit binary output (50, 52) readable by a micro-controller (40) or other digital logic. The circuit utilized complementary NPN and PNP transistors (Q2, Q1) having coupled emitters and coupled bases connected by a resistor (R5). The collector of the PNP transistor is connected by a resistor (R3) to ground while a complementary resistor (R4) ties the collector of the NPN transistor to VBATT. Additional circuitry preferably converts the voltage output from the collectors to a suitable voltage level readable by the micro-controller or other digital logic device.