Suppressing signal transfer function peaking in a feedforward delta sigma converter

摘要

A modified topology for a CTDSM (referred herein as “SCFF”) can effectively deal with signal transfer function (STF) peaking, an inherent property of continuous time feedforward delta sigma converters. The SCFF approach involves providing an additional digital-to-analog (DAC) feedback path to the input of the second integrator (incurring an additional DAC in the circuitry, converting the output of the quantizer into an analog signal and feeding the analog signal to the input of the second integrator). Furthermore, the SCFF approach involves providing two feed-ins: a first feed-in to the input of the second integrator and a second feed-in to the input of the third integrator. The first feed-in can be negative. Advantageously, the modified continuous time delta sigma modulator implementing this approach alleviates some of the peaking issues in the signal transfer function while still enjoy low power consumption.

主权项

1. A modified feedforward delta sigma analog-to-digital converter, comprising:
a cascade of integrators receiving an analog input of the converter; a quantizer for quantizing a sum of the outputs of the integrators and generating a digital output of the converter, and providing feedback to input of a first one of the integrators; a feedback path from the digital output of the quantizer to an input of a second one of the integrators; and one or more feed-in paths from the analog input of the converter to inputs of one or more ones of the integrators subsequent to the first one of the integrators, the one or more feed-in paths comprising a first feed-in path from the analog input of the converter to the input of the second one of the integrators and a second feed-in path from the analog input of the converter to the input of a third one of the integrators.