A 16X oversampling CMOS ADC with 100 kHz bandwidth and 90dB SNR

摘要

Oversampled sigma-delta ADCs have considerable advantages for high-resolution applications compared to other ADC architectures, including relaxed requirements for component matching, amplifier and comparator performance, and improved noise immunity. These advantages have led to their widespread adoption for applications such as instrumentation, seismology and digital audio, with signal bandwidths of a few hertz to a few tens of kilohertz. Their use in wider bandwidth applications with high dynamic range has been limited by the need for high oversampling ratios (OSR), typically 64 or more, in order to obtain sufficient rejection of quantisation noise. ADC sampling rates of tens of megahertz are required to obtain signal bandwidths of 100kHz and above, and the consequences of this include high amplifier power consumption, large and high-power digital filters, and difficulty in driving the ADC signal and reference inputs. Reduction of the required oversampling ratio to 16 or less while preserving the other advantages of these ADCs can be used to reduce power consumption, increase signal-to-noise ratio (SNR), or increase signal bandwidth. This makes them suitable for applications such as high dynamic range ADCs for digital cellular radio, where the increased SNR can be used to simplify other parts of the system.