Patent ID: 8269562

Claim:
A microcontroller integrated circuit comprising: an input terminal; and an open-loop transimpedance amplifier (OLTA) having an input node and an output node, wherein the input node is coupled to the input terminal of the microcontroller integrated circuit, the input node having an input impedance less than approximately forty ohms if an input current of eight milliamperes or more is flowing into the input node, wherein the input impedance decreases as the input current in an input current operating range increases, wherein the input impedance decreases more rapidly than the input current increases such that a voltage on the input terminal is effectively clamped to an input voltage range of less than approximately 0.7 volts for input currents in the input current operating range, wherein the OLTA outputs a digital logic signal indicative of whether the input current is in a first low input current range or is in a second high input current range.