A novel analog switch for high-precision switched-capacitor applications

作者：Naghavi Saeed; Sharifi Niloofar; Abrishamifar Adib^*

来源：International Journal of Circuit Theory and Applications, 2018, 46(4): 764-778.

DOI：10.1002/cta.2432

• analog switch
• channel charge injection
• clock feedthrough
• high precision
• subthreshold leakage
• switched-capacitor circuit

The performance of a switched-capacitor circuit strongly depends on its analog switches. This paper introduces a new technique to design a high-precision analog metal-oxide-semiconductor switch for switched-capacitor applications. The accuracy of analog switches is a critical parameter to determine overall performance of the discrete-time analog systems. To satisfy the accuracy requirements of the switch, a novel technique to minimize the charge injection and clock feedthrough errors by using a very simple structure is proposed. Moreover, an innovative approach to increase the OFF resistance of the switch and consequently minimizing its leakage current is presented. To evaluate the performance of the proposed switch, simulations are done in TSMC 0.18m standard complementary metal-oxide-semiconductor technology with BSIM3V3 device models. The ON and OFF resistances of the switch are one of the most important factors that should be considered while investigating analog switches. The ON resistance of the proposed switch is less than 560 over entire input signal range which completely satisfies the tracking bandwidth requirements. In addition, since the proposed switch provides an ultrahigh OFF resistance in the range of several Gs, the leakage current of the proposed switch is negligible. Simulation results also show that switch-induced errors are significantly eliminated by using the proposed cancellation technique. The output error charge due to charge injection and clock feedthrough over a wide range of input signal variation is very low (less than 1.6fC). Moreover, simulation results show that the proposed switch achieves signal to noise plus distortion ratio of 80.55dB, effective number of bits of 13.08, total harmonic distortion of -81.41dB, and spurious-free dynamic range of 87.7dB for a 2.5-MHz sinusoidal input of 800-mV peak-to-peak amplitude at 200-MHz sampling rate with a 1.8-V supply voltage. Consequently, the simulation results verify that the proposed switch can significantly improve the dynamic and static performances of a switched-capacitor circuit.

• 出版日期2018-4