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Capacitor mismatch error shaping switching circuit and method suitable for oversampling SAR ADC

A capacitance mismatch and oversampling technology, applied in electrical components, electrical signal transmission systems, analog/digital conversion calibration/testing, etc., can solve problems such as increased complexity, and achieve low driving force requirements, simple logic, and error shaping. good effect

Active Publication Date: 2020-01-31
SOUTHEAST UNIV
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Problems solved by technology

When the number of digits in the capacitor array is small, this method is simple to implement and the cost is low, but because the complexity increases exponentially with the number of digits, it is not suitable for the case of large digits, usually no more than 5 digits

Method used

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  • Capacitor mismatch error shaping switching circuit and method suitable for oversampling SAR ADC
  • Capacitor mismatch error shaping switching circuit and method suitable for oversampling SAR ADC
  • Capacitor mismatch error shaping switching circuit and method suitable for oversampling SAR ADC

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Embodiment Construction

[0025] In the following, the present invention will be further explained in conjunction with the figures and simulation results.

[0026] Taking the MSB DAC as a reference, first consider the case where the high-level capacitor has only 1 bit. The high-level capacitor itself can be considered as having no error, and the value of the low-level capacitor (LSB DAC) has an error relative to the MSB capacitor, which is specifically reflected in the analog domain. There is an error between the bit weight and the ideal value, so only the mismatch error of the low-level capacitor needs to be considered. In order to realize the shaping of the capacitance mismatch error, in the nth conversion, the combination of the previous two LSB DAC comparison results, 2D i (n-1)-D i (n-2), together with the mismatch error of the LSB DAC part 2E i (n-1)-E i (n-2) Feed back to the nth conversion to realize the error shaping.

[0027] figure 1 Is the behavioral model of the present invention, where E is t...

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Abstract

The invention provides a capacitor mismatch error shaping switching circuit and method suitable for an oversampling SARADC, and belongs to the technical field of analog-digital hybrid integrated circuits. According to the invention, the second-order shaping of the capacitor mismatch error can be realized by feeding back the quantization results of the previous two low-order (LSB) and the capacitormismatch error. Compared with a traditional switching algorithm, a reference voltage needs to be additionally introduced, and the LSB capacitance value is changed into three times of the original capacitance value. The circuit is simple in logic, low in circuit overhead, easy to implement, excellent in capacitor mismatch error shaping effect and suitable for high-precision application occasions.

Description

Technical field [0001] The invention designs a capacitance mismatch error shaping switch circuit and method suitable for oversampling SAR ADCs, and belongs to the technical field of analog-digital hybrid integrated circuits. Background technique [0002] The successive approximation analog-to-digital converter (SAR ADC) is usually used in low- and medium-precision analog-to-digital conversion occasions. Because of its simple structure, small area and low power consumption, it has been widely used. However, the capacitance mismatch error limits the linearity of the structure. Generally, when the sampling capacitance does not exceed 2pF, the spurious-free dynamic range (SFDR) of the SAR ADC does not exceed 75dB. [0003] Capacitance mismatch is a relative concept, and a capacitor should be used as a reference when studying this problem. By increasing the capacitance value of the capacitor array, the capacitance mismatch error can be reduced, but it will bring about negative effects ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03M1/10H03M1/38
CPCH03M1/1009H03M1/38
Inventor 吴建辉王鹏李红
Owner SOUTHEAST UNIV
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