A low voltage sigma delta modulator for temperature sensor

Abstract

A sigma delta modulator is proposed to transform the analog front end of temperature sensor to digital signal. By adding additional poles and altering the zero of the transfer function, the SNR and dynamic range can be enhanced. The chopper stabilization scheme is included to reduce the DC offset and 1/f noise. A low voltage circuitry is invented to reduce the power consumption. The circuit is simulated using a 0.18μm 1p6m CMOS process with a signal bandwidth of 40Hz and oversampling ratio (OSR) of 64. The post-layout simulations of a test chip show 70dB SNR, 78dB dynamic range and 12.6 bits ENOB. The power dissipation is 32 μW at a 1-V supply voltage and the core area is 0.445 × 0.675 mm2.