DELTA-SIGMA MODULATOR WITH HIGH INPUT IMPEDANCE

摘要

Measurement circuits having a delta-sigma modulator are disclosed. One example measurement circuit includes a low pass filter coupled to receive an input voltage, a switched-capacitor integrator circuit, and a switched comparator circuit. The measurement circuit may generate a digital output made up of a sequence of logic high and logic low levels that are representative of a scaled value of the input voltage output by the low pass filter circuit. Also, by virtue of its switched-capacitor configuration, the electric charge received by the switched difference amplifier circuit may be returned to the input in a manner such that the input to the delta-sigma modulator takes little to no average current from the voltage it measures. In other words, the delta-sigma modulator may have a high input impedance by virtue of its switched-capacitor circuit configuration.

主权项

1. A delta-sigma modulator circuit comprising:
a low-pass filter circuit coupled to receive an input voltage and configured to output a filtered input voltage; a switched difference amplifier circuit coupled to receive the filtered input voltage and configured to output a switched difference voltage, wherein the switched difference voltage is representative of a variable offset voltage plus a difference between the filtered input voltage and a supply voltage; a switched-capacitor integrator circuit coupled to receive the switched difference voltage and configured to output an integral voltage based on a difference between the switched difference voltage and the supply voltage; and a switched comparator circuit coupled to receive the integral voltage and configured to output an output signal based on a difference between the switched difference voltage and a reference voltage.