A New Calibration Method for Successive Approximation Register A/D Converter
Date Issued
2006
Date
2006
Author(s)
Chen, Hung-Wei Kevin
DOI
en-US
Abstract
The demand of low power electronic device is become strongly these years, especially in wireless and sensor network devices. Analog to digital converter (ADC) is the key building block of these devices. Therefore, a hot research topic is to reduce ADC power consumption. For some sensor application, the highly accuracy ADC is required. A main ADC architecture for sensor application is success approximation register (SAR). It’s accuracy is usually limited by the mismatch of capacitor array which is about 10 bit. A calibration circuit can be added to enhance the accuracy; however, it usually dissipates a lot power. This work presents a switch capacitor calibration technique to enhance the performance without consume a lot of power. The charge redistribution SAR ADC operation theory is base on charge conservation law. The mismatch of capacitor would cause the voltage shift during the comparison phase. The fundamental of this calibration idea is to store the positive and negative charge in the calibration capacitors during the sample phase. Then, during the comparison phase, these pre-stored charge injects into the main capacitor array to correct the voltage shift. This work is fabricated by TSMC 0.35um CMOS technology. The chip area is 1.88x1.88mm2, and the core area is 0.83 x 0.74mm2. The conversion rate is 200KS/s, and the measured analog power is 1.35mW at 5V and digital power is 3.3mW at 3.3V. The SNDR and SFDR before self-calibration are 63.9 and 74.7dB. After self-calibration process the SNDR and SFDR are 47.9 and 50.6dB. The performance after self calibration is degraded, and it is not expected. The cause of degrading may be noisily environment of testing board. However, the effect of this calibration circuit is only in odd harmonic, and it is the same as the prediction.
Subjects
類比數位轉換器
循漸近式逼近
A/D converter
ADC
SAR
successive approximation register
Type
thesis
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