Abstract
The thesis presents a 12-bit 500KS/s successive approximation register (SAR) analog-to-digital (A/D) converter for biomedical applications. The A/D converter is designed in a standard 0.13μm CMOS process and operates at supply voltage 1.2V. The SAR A/D converter includes the sample-and-hold (S/H) stage, the comparator, the digital-to-analog (D/A) converter and the SAR control logic. In this design, we use bootstrapped switch for S/H stage is to improve the circuit linearity and reduce the signal distortion. The comparator is composed of the dynamic latched regenerative circuit which gives the output of comparator better accuracy because of its positive feedback. Adopting the split capacitor array in D/A converter is to decrease the total capacitance and average power dissipation. Finally, the SAR control logic circuit uses a form of level shift control conversion process and a row of D filp-flops for controlling the split capacitor array. The performance of converter can be reduced due to the process mismatch and layout deviation, and thus the accuracy of the digital output declines. So the thesis proposes a self-correction circuits which improves the performance of the converter. Since the comparator and capacitor array are important in SAR A/D converter, and the output signal will be wrong at the slightest error. So we calibrate the comparator, attenuation capacitor and capacitors in capacitor array individually. In the comparator correction circuit, we use coarse and fine correction two stage procedures to reduce the area and power consumption. The correction circuit can effectively reduce the offset of comparator, and correct the mismatch in the attenuation capacitor and capacitors in capacitor array. The output accuracy of the converter is improved significantly for medical applications.