Patent ID: 8400340

Claim:
A sigma-delta analog to digital converter (SD ADC) comprising a sigma delta modulator (SD modulator), wherein the SD modulator comprises: a first integrator to generate a time integral of a first difference signal at an integrator output node; a comparator to convert the time integral to a corresponding binary value at each rising edge and falling edge of a sampling clock; a first feedback block to receive the corresponding binary value and to generate a first analog pulse representing the corresponding binary value; and a first summing block to subtract the first analog pulse from a first analog signal to generate the first difference signal, wherein the first feedback block comprises a first switched-resistor circuit and a second switched-resistor circuit, wherein the first switched-resistor circuit is operable to generate a first set of analog pulses, each of a constant magnitude and a duration equal to one period of the sampling clock, in each of an interval between successive rising edges of the sampling clock, an analog pulse in the first set being generated with a first voltage if the corresponding binary value has a first logic level, the analog pulse in the first set being generated with a second voltage if the corresponding binary value has a second logic level, and wherein the second switched-resistor circuit is operable to generate a second set of analog pulses, each of a constant magnitude and a duration equal to one period of the sampling clock, in each of an interval between successive falling edges of the sampling clock, an analog pulse in the second set being generated with the first voltage if the corresponding binary value has a first logic level, the analog pulse in the second set being generated with the second voltage if the corresponding binary value has a second logic level, wherein the first analog pulse is a sum of the corresponding analog pulse in the first set of analog pulses and the corresponding analog pulse in the second set of analog pulses.