An analog-to-digital converter is used to digitalize the pressure data in Battery-less TPMS (Tire Pressure Monitoring System). To reduce power consumption

an 8-bit low-power SAR(Successive Approximation Register) ADC

with a modified switching method

is designed after analysis the requirements of the interface of pressure sensor. The DAC switching method uses /2

rather than in conventional way

as the only reference voltage to digitalize the input signals with the amplitude range of (0

). The proposed design reduces the average power consumption in the DAC by 87.5%during digitization. Post simulation results show that at the power supply of 3 V and reference voltage of 1.5 V and with the sampling rate of 2 kS/s

the average dynamic power is 0.9 W

and the ADC can digitize the input signal in a full-scale range of 3 V with ENOB of 7.6 bits and SNDR of 63.2 dB.It can work steadily with a temperature range of -40~125℃.The ADC has been applied to the Battery-less TPMS SoC and taped out in a 0.35 m BCD (Bipolar-CMOS-DMOS) automotive electronic process.