Analog-to-digital converter capable of switching bit resolution and control method thereof

Abstract

The invention provides an analog-to-digital converter capable of switching bit resolution and a control method thereof. The analog-to-digital converter comprises a sampling and digital-to-analog circuit and a continuous approximation control logic unit, wherein the continuous approximation control logic unit selects the time of a signal adjusting and sampling stage and a bit circulation stage according to the bit resolution and invalidates part of the capacitance in the sampling and digital-to-analog circuit so as to switch the bit resolution of the analog-to-digital converter.

Description

technical field [0001] The present invention relates to an analog-to-digital converter (Analog to Digital Converter; ADC) comprising a continuous approximation register (Successive Approximation Register; SAR), in particular to an analog-to-digital converter with switchable bit resolution and its control method. Background technique [0002] figure 1 is a block diagram of a known SAR ADC, including a sampling circuit (Sample and Hold Circuit; S / H) 12, a comparator 14, a digital-to-analog converter (Digital-to-Analog Converter; DAC) 18 and a continuous approximation control logic unit 16. Perform continuous approximation to the sampled analog input in a binary search (Binary Search) manner. [0003] The action of ADC 10 begins with the sampling phase (Sampling Phase), during the sampling phase, the sampling circuit 12 will analog input V in Complete sampling access, then, the ADC 10 enters the bit-cycling phase (Bit-cycling Phase) to determine the conversion of the digital...

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Problems solved by technology

Under this architecture, when a 12-bit ADC is used for lower-resolution conversion, although the accuracy requirement for charging and placing the potentials of the nodes in the circuit can be reduced to 8-bit resolution to reduce the time, but the 12-bit The total capacitance value of the capacitor array of the bit is still fixed (C TOTAL = 2 N C, N=12), the charging and discharging time during conversion is still limited by this large capacitor. For example, the demand for ADC resolution of electric bicycles is only 8-bit, but requires high conversion speed, and the current built-in ADC is difficult to meet such needs

[0005] U.S. Patent No. 7265708 proposes a method of rearranging the capacitance of the ADC's internal capacitance array to obtain the desired capacitance value to achieve the required resolution, but the circuit control of this method is very complicated and requires a larger chip area, the cost also increases accordingly

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