A CMOS sensor signal conditioner for an automotive pressure sensor based on a piezo-resistive bridge transducer

This paper describes the design of a Sensor Signal Conditioner for a pressure sensor transducer in automotive applications. The circuit has been implemented in a 0.35 um CMOS process and comprises an Instrumentation Amplifier (IA), a 2
^nd
order Chebyshev active low pass filter and an 1
^st
order incremental ADC. The IA consumes 3mA with a supply voltage of 5V. Measured gain is 30 dB with 10° of phase margin. The PSRR and CMRR are 60 dB and 90 dB, respectively. Measured input referred offset voltage is 22 uV. The IA shows good linearity up to an amplitude of 2.5 Vpp at the output. With this output swing of 2.5 Vpp harmonics are 60dBc for a 1 KHz input tone. The PSD of the input referred noise is below 150 nV/VHz. The ADC current consumption of the ADC is 1.3 mA at 400 S/s. Its INL ±2.5 LSB for a 13 bit resolution, which gives an ENOB of 11.4 bits. Input referred noise results in 0.85 LSB or an ENOB of 11.4 bits. The IA combined with the ADC has an overall area of 0.71 mm
²
. Its INL of ±4 LSB. Again, the input referred noise is in 0.85 LSB or 11.5 bits.