A/D conversion system

Abstract

An input signal (Vin) is quantized by a quantizer (7) after being passed through plural loop filters (13,14). A last-stage loop filter is formed of an operational amplifier (15) for generating an output signal (Vin), a sampling capacitor (Cs) for sampling the input signal, an integrating capacitor for integrating the signal sampled by the capacitor and plural switches (S1 to S7) for switching over signal paths. A control circuit controls on / off states of the switches to discharge the sampling capacitor and the integrating capacitor and causes the loop filter to repeat a sampling operation and an integrating operation plural times. The control circuit (20) lastly connects the sampling capacitor and the integrating capacitor to a state, which is opposite to the state of the integrating operation time and turns on a converting switch (S8) so that the A / D converter A / D-converts the output signal of the loop filter.

Description

technical field [0001] The present invention relates to an A / D conversion system configured in a cascade type by employing delta-sigma (ΔΣ) modulators. Background technique [0002] In an A / D conversion system configured by employing a delta-sigma modulator, an input signal, that is, a voltage signal is filtered by a loop filter, and an output of the loop filter is quantized by a quantizer. When there is an error (variation) in the capacitance value of the capacitor used in the loop filter, the gain of the loop filter including the capacitor becomes erroneous, and thus the A / D conversion result becomes erroneous. In the case where an input signal is A / D-converted by a single-loop type A / D conversion system configured without cascading, the above-mentioned error is negligible. However, this requires many operation cycles and a longer time to output the A / D conversion result. [0003] When successively A / D converting input signals output from a plurality of sensors by switch...

AI Technical Summary

Problems solved by technology

If an amplifier with a wide output signal range is used to solve the above problems, the circuit area and power consumption need to be increased

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