AN INTEGRATED CMOS INTERFACE FOR LAMBDA SENSOR

Automotive pollution can be reduced by suitably controlling the mixtur e that is fed to the cylinders. This can be performed by means of a fe edback loop including a lambda sond and a processing unit which contro ls the electronic fuel injectors. This paper describes a CMOS interfac e which adapts the output signal of a lambda sensor to allow its feedi ng into the processing unit. It provides a differential to a single-en ded conversion with a good common mode rejection, a level shifting aro und a given reference voltage, and an accurate voltage gain. Both desi gn considerations and the measurements performed on an integrated test structure are presented. The measured variation of the large-signal v oltage gain for an input signal of 0 to 1 V is within +/- 5% when the input common mode voltage ranges from -I V to 1 V with respect to the negative supply voltage. An output voltage with a precision within +/- 1 mV is obtained in the presence of an input voltage corresponding to the stochiometric composition of the mixture.