A Low Power Analog Front-end for Implantable Intraocular Pressure Detection Chip

For implantable, high-resolution and real-time intraocular pressure detection, a low power analog front-end (AFE) consisting of full-integrated, subthreshold front-end amplifier and 10bit, 20ks/s low power successive approximation analog-to-digital converter (SAR ADC) is proposed in this paper. The subthreshold transistors are adopted as pseudo-resistor with GΩ value, which is paralleled with feedback capacitor to generate high-pass path to restrict DC offset voltage and low-frequency noise. SAR ADC with charge-retribution DAC structure is optimized to realize tradeoff between performance and power consumption. The circuit is fabricated with SMIC 0.18 μm CMOS process and the poset-simulation results show that in 1.8 V supply voltage, the signal-to-noise plus distortion ratio (SNDR) is 58.3 dB, effective number of bits (ENOB) reaches 9.4 bit with 20 kS/s clock frequency, and consumes only 76 μW power consumption.