A fully integrated sensor interface chip

A single-chip sensor signal conditioning system is described. The chip contains two 20-bit sigma-delta A-D converters. The main ADC has a rail-to-rail input buffer and PGA. There is a 12-bit DAC and current sources for sensor excitation and circuitry for sensor fault detection. An 8052 microcontroller core is provided for processing the ADC outputs. There is 640 bytes of user flash memory and 8k bytes of program flash. Clocking is from a 32kHz watch crystal oscillator. An on-chip PLL multiplies up this frequency to provide programmable clocks for the microcontroller. The die area is 17mm
²
on a 0.5µm TPTM flash memory process. Power consumption is 10mW at 3V.