A 100 MS/s 9 bit 0.43 mW SAR ADC with custom capacitor array

A low power 9 bit 100 MS/s successive approximation register analog-to-digital converter（SAR ADC）with custom capacitor array is presented. A brand-new 3-D MOM unit capacitor is used as the basic capacitor cell of this capacitor array. The unit capacitor has a capacitance of 1 fF. Besides, the advanced capacitor array structure and switch mode decrease the power consumption a lot. To verify the effectiveness of this low power design, the 9 bit 100 MS/s SAR ADC is implemented in TSMC IP9M 65 nm LP CMOS technology. The measurement results demonstrate that this design achieves an effective number of bits（ENOB） of 7.4 bit, a signal-to-noise plus distortion ratio（SNDR） of 46.40 dB and a spurious-free dynamic range（SFDR） of 62.31 dB at 100 MS/s with 1 MHz input.The SAR ADC core occupies an area of 0.030 mm;and consumes 0.43 mW under a supply voltage of 1.2 V. The figure of merit（FOM） of the SAR ADC achieves 23.75 fJ/conv.