Embedded SAR based active gain capacitance measurement system and method

摘要

A system for measuring a capacitor (CSENj) precharges a CDAC (23) in a SAR converter (17) to a reference voltage (VAZ) and also precharges a first terminal (3-j) of the capacitor to another reference voltage (GND). During a measurement phase, the CDAC is coupled between an output and an input of an amplifier (31) and the capacitor also is coupled to the input of the amplifier, so as to redistribute charge between the capacitor and the CDAC. The amplifier generates an output voltage (VAMP) representing the capacitance being measured. The output voltage is stored in the CDAC. The SAR converter converts the output voltage to a digital value representing the capacitance being measured.

主权项

1. An apparatus, comprising:
active gain circuitry including an amplifier and a switch coupled between an input and an output of the amplifier; a sense capacitor coupled to an input of the active gain circuitry; a plurality of switches coupled to an output of the active gain circuitry; a divider/feedback circuit having a plurality of capacitors, each of the capacitors of the plurality of capacitors being coupled to one of each of the plurality of switches; and a successive approximation register analog-to-digital conversion (SAR ADC) circuit, including:
a SAR comparator having an input that is coupled to the sense capacitor;SAR logic coupled to an output of the SAR comparator; anda SAR-DAC switch bank that is coupled to both an output of the SAR logic and each of the plurality of switches.