Automotive SSP with Analog or Sent Output | E520.42

The IC E520.42 is a sensor signal processor (SSP) designed to amplify and treat the signal of piezoelectric resistive bridges. It comprises wide programming range and comprehensive diagnostic features. A low-noise instrumentation amplifier with gain and off-set tuning capability amplifies the input from the bridge to a level which fits the input range of a 14-bit delta-sigma AD-converter. The digitized input after low-pass filtering is compensated for thermal drifts of offset and gain in the digital domain. A temperature signal from an on-chip sensor or an external T-sensor is employed for this and its digitized output is fed to the compensation calculator, too. Besides compensation of thermal drifts of offset and gain, the correction engine also can com-pensate non-linearity in the signal to 3rd order. The out-put from the calculator engine is fed into a DA-converter driving an analogue voltage buffer at OUT providing a ratiometric output signal. Alternatively, a digital SENT output can be used instead of the analogue output. In configuration or diagnostic modes the OUT pin is used as a single-wire serial data interface for in-system calibration with only 3 wires to the outside. Calibration and configuration data for a specific sensor are stored in EEPROM. The IC includes also self-test and diagnostics of the sensor bridge attached and of the SSP itself. If faults occurs, they are indicated at the sensor output as failure states.