Successive approximation type analog-to-digital converter structure

Abstract

The invention relates to a successive approximation type analog-to-digital converter (ADC) structure which comprises a comparator, a logic control unit and a digital to analog converter (DAC). The DAC comprises a capacitive sub DA structure, a resistive sub DA structure and an input common-mode setting circuit; and the resistive sub DA structure comprises a first decoding circuit, a second decoding circuit and a resistor string. The resistor string is formed by connecting 2<k-1>+1 resistors in series, the lower end of the resistor string is connected with reference ground level, the upper end of the resistor string is connected with a reference level, a lower-end tapping of each resistor of the resistor string is led out and connected with the first decoding circuit, an upper-end tapping of a (2<k-1>+1)th resistor is led out and connected with the first decoding circuit, lower-end tappings of the first to (2<k-1>)th resistors are led out and connected with the second decoding circuit, the first decoding circuit is connected to the positive input end of the comparator via a first switch, and the second decoding circuit is connected with the input common-mode setting circuit via a second capacitor. The resistor string multiplexing structure is used to reduce integral and differential nonlinearity caused by mismatching of resistors.

Description

technical field [0001] The invention belongs to the technical field of analog-to-digital conversion, and in particular relates to a successive approximation analog-to-digital converter structure. Background technique [0002] At present, with the rapid development of the digital signal processing technology, the communication technology has made great progress, which also makes the conversion accuracy requirements of the Analog-to-Digital Converter (Analog-to-Digital Converter, ADC) higher and higher. ADC has various structures, including flash type, two-step type, successive approximation type, pipeline type, folding interpolation type, Σ-Δ type, etc. Among them, although the conversion speed and conversion accuracy of the successive approximation analog-to-digital converter are medium, it has been widely used because of its low cost and low power consumption. [0003] Schematic diagram of SARADC structure figure 1 As shown, it mainly includes a comparator 101 , a success...

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Problems solved by technology

However, there will be resistance mismatch in this hybrid SARADC structure, which will cause the integral nonlinearity and differential nonlinearity of the hybrid SARADC structure

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