CAPACITOR SENSING SYSTEM

摘要

A capacitor sense system includes a pad for coupling to an external capacitor. A current digital to analog converter (DAC) supplies current to charge the external capacitor. A reference capacitor is charged by a current source. A first comparator compares a voltage across the external capacitor sensed at the pad to a reference voltage and generates a first comparison. A second comparator compares a voltage across a reference capacitor to the reference voltage and generates a second comparison. The stored first and second comparisons are used to control the current DAC. First and second AC coupling capacitors are coupled respectively between the pad and the first comparator and between the reference capacitor and the second comparator. Sensing at the pad allows more accuracy and the AC coupling capacitors provide better matching and allow for different DC biases to be set for the external capacitor and the first comparator.

主权项

1. An apparatus comprising:
a pad for coupling to an external capacitor; a first current source coupled to the pad through a first path, the first current source to supply current to charge the external capacitor; and a first comparator coupled to the pad through a second path to compare a first voltage at the pad corresponding to voltage across the external capacitor to a predetermined voltage and provide a first compare indication indicative thereof.