A Low Power Fully Differential Level-Crossing ADC With Low Power Charge Redistribution Input for Biomedical Applications

A low-power fully differential level-crossing analog-to-digital converter (LC-ADC) for biomedical applications is presented. Different from conventional ADCs based on the uniform sampling rate, LC-ADC generates fewer samples for biomedical signals and leads to less power consumption in the following blocks. In this design, the power consumption of n-bit DAC and digital parts is reduced significantly with respect to the conventional LC-ADCs. The proposed method uses a charge redistribution block (CRB) instead of the n-bit DAC, which leads to a large reduction in average switching energy. Besides energy-saving, the proposed switching scheme also reduces the complexity of the controlling logic circuit, providing reduced complexity and low power consumption. Another advantage of the proposed LC-ADC is its fully differential structure. As a result, SNDR is improved by decreasing the levels of even harmonics. The proposed LC-ADC is designed in 0.18
$\mu {\mathrm{ m}}$
CMOS technology. Post-layout simulation results show an effective number of bits (ENOB) of up to 6.8 bits with about 97–188 nW power consumption under 0.8 V supply voltage and input signal bandwidth from 1 Hz to 4 kHz. The ADC occupies a silicon area of only
$60\mathbf {\times }65\,\,\mu \text{m}^{2}$