Quad switched multibit digital to analog converter and continuous time sigma-delta modulator

Abstract

A quad signal generator circuit generates four 2−1 bit control signals in response to a sampling clock and a 2−1 bit thermometer coded signal. A digital-to-analog converter (DAC) circuit has 2−1 unit resistor elements, with each unit resistor element including four switching circuits controlled by corresponding bits of the four 2−1 bit control signals. Outputs of the 2−1 unit resistor elements are summed to generate an analog output signal. The quad signal generator circuit controls generation of the four 2−1 bit control signals such that all logic states of bits of the four 2−1 bit control signals remain constant for at least a duration of one cycle of the sampling clock. The analog output signal may be a feedback signal in a sigma-delta analog-to-digital converter (ADC) circuit that includes a multi-bit quantization circuit operating to quantize a filtered loop signal to generate the 2−1 bit thermometer coded signal.