Successive approximation register type ADC (analog-digital converter)

Abstract

The invention discloses a successive approximation register type ADC (analog-digital converter) comprising a sample holding circuit, a N-bit digital-analog converter, a comparer, a successive approximation register and a control logic, wherein the sample holding circuit finishes and holds the sample of an input signal through a sampling capacitor smaller than 2NC and a switch, and outputs sample holding voltage to a first input end of the comparer; the N-bit digital-analog converter is used for converting a digital quantization result saved in the successive approximation register into an analog quantity, and the output end of the N-bit digital-analog converter is connected with a second input end of the comparer; the comparer is used for comparing the analog quantities through conversion of the N-bit digital-analog converter with the sample holding voltage, outputting an existing result of quantizing the input signal, and writing the result into the successive approximation register; the successive approximation register is used for saving the result of quantizing the input signal and outputting the final result of analog-digital conversion; and the control logic is used for generating a control signal of a whole circuit. According to the successive approximation register type ADC disclosed by the invention, the conversion speed of ADC can be increased and the requirement on the output resistance of a signal source is reduced.

Description

technical field [0001] The present invention relates to an analog-to-digital converter, in particular to a successive approximation register type analog-to-digital converter. Background technique [0002] A successive approximation register (SAR) analog-to-digital converter (ADC) is a common structure for medium to high resolution applications with sampling rates below 5Msps (million samples per second). The resolution of SAR ADC is generally 8 to 16 bits, and it has the characteristics of low power consumption and small size. These characteristics make this type of ADC have a wide range of applications, such as portable / battery-powered instruments, pen input quantizers, industrial control, and data / signal acquisition. [0003] figure 1 It is the basic structure diagram of the current common successive approximation register type analog-to-digital converter. Such as figure 1 As shown, the successive approximation register type analog-to-digital converter in the prior art...

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Problems solved by technology

[0005] However, the existing SAR ADC has the following disadvantages: when sampling, all N+1 capacitors are connected to the input signal VIN, and its total capacitance C SUM = 2 N-1 C+2 N-2 C+......+2 1 C+2 0 C+C=2 N C is very large, which requires VIN to have a strong driving ability, and in many cases the input signal is high impedance, without much driving ability, so the use of the prior art successive approximation register (SAR) analog-to-digital converter will seriously affect the analog-to-digital Conversion accuracy and speed

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