Flash ADC with interpolators

摘要

An ADC is provided. The ADC includes a plurality of pre-amplifiers, dynamic comparators coupled to the pre-amplifiers, interpolators and an encoder. Each pre-amplifier provides a pair of differential outputs according to a pair of differential analog signals and a first reference voltage and a second reference voltage different from the first reference voltage. Each dynamic comparator provides a first comparing signal and a second comparing signal according to the pair of differential outputs of the corresponding pre-amplifier. Each interpolator provides an interpolating signal according to the first and second comparing signals of two of the dynamic comparators. The encoder provides a digital output according to the interpolating signals. The first and second comparing signals are the same in a reset phase, and the first and second comparing signals are complementary according to the pair of differential outputs of the corresponding pre-amplifier in an evaluation phase.

主权项

1. An analog-to-digital converter, comprising:
a plurality of pre-amplifiers, each receiving a pair of differential analog signals, a first reference voltage corresponding to one of the differential analog signals and a second reference voltage corresponding to another of the differential analog signals, and amplifying difference between the pair of differential analog signals and the first and second reference voltages to provide a pair of differential outputs, wherein the first reference voltage is different from the second reference voltage; a plurality of dynamic comparators coupled to the pre-amplifiers, each providing a first comparing signal and a second comparing signal according to the pair of differential outputs of the corresponding pre-amplifier; a plurality of interpolators, each providing an interpolating signal according to the first and second comparing signals of two of the dynamic comparators; and an encoder, providing a digital output according to the interpolating signals, wherein the first and second comparing signals are the same in a reset phase, and the first and second comparing signals are complementary according to the pair of differential outputs of the corresponding pre-amplifier in an evaluation phase, wherein the dynamic comparator comprises: a transconductance (Gm) stage unit, having a first input terminal for receiving one output among the pair of differential outputs of the corresponding pre-amplifier, a second input terminal for receiving another output among the pair of differential outputs of the corresponding pre-amplifier, a first output terminal for providing the first comparing signal, a second output terminal for providing the second comparing signal, and a command terminal; a first inverter, having an input terminal coupled to the first output terminal of the Gm stage unit, and an output terminal coupled to the second output terminal of the Gm stage unit; a second inverter, having an input terminal coupled to the second output terminal of the Gm stage unit, and an output terminal coupled to the first output terminal of the Gm stage unit; a first switch coupled between a first voltage source and the first output terminal of the Gm stage unit; a second switch coupled between the first voltage source and the second output terminal of the Gm stage unit; and a third switch coupled between a second voltage source and the command terminal of the Gm stage unit.