Leakage current compensation circuit

摘要

Circuitry is described for compensating leakage currents in capacitive sensing circuits. A single active leakage compensation circuit may sense a representative leakage current and drive a plurality of output transistors, each of which provides a compensating current to a respective capacitive sensing circuit. The leakage compensation circuit may sense current flow through a device substantially equivalent to a device exhibiting leakage current in a capacitive sensing circuit, and in response, provide a signal to drive one or more output transistors to supply approximately equivalent currents to a plurality of circuit nodes. For embodiments having multiple similar capacitive sensors and capacitive sensing circuits, only one transistor need be added to each capacitive sensing circuit to compensate for leakage current.

主权项

1. A leakage compensation circuit, comprising:
an amplifier configured to sense a first current through a sense node that is substantially equal to a leakage current in a leakage device connectable to the compensation circuit at a second node; a supply transistor having a control terminal directly connected to an output of the amplifier, a first main terminal coupled to a first potential and a second main terminal directly connected to both the sense node and a first input terminal of the amplifier; and a first output transistor having a control terminal directly connected to said output of the amplifier and configured to provide a compensation current to the second node in response to a control signal output from said amplifier, wherein the compensation current is approximately equal to the leakage current.