Auto Electronics

Sensor signal conditioner features on-chip diagnostics

ZMD has introduced the ZMD31150, an automotive signal-conditioner IC with on-chip diagnostics. The part is intended for use with wheatstone bridge sensors in applications such as fuel injection, ABS, power steering, air induction, fuel tank, air conditioning, and occupant classification.

Signal conditioning is done by an internal digital signal processor that runs a correction algorithm based on calibration coefficients stored in on-chip EEPROM. The chip can be calibrated to a specific sensor via serial interface to a PC, eliminating the cost of trimming with lasers and/or external devices.

Accuracy is ±0.1% full-scale output (FSO) from -25 °C to 85 °C, ±0.25% FSO from -40 °C to 125 °C, ±0.5% FSO from -40 °C to 150 °C. Automotive business line manager Frank Schulze said the device is also two to seven times faster than other signal-conditioning chips with comparable accuracy.

Schulze added that real-time diagnostics in the ZMD31150 can detect faulty connections, shorts, and power loss events. The device’s EEPROM includes an error-correcting function and a signature check to detect uncorrectable multibit failures.

An analog pre-amp gain of 420 accommodates bridge outputs as low as 1 mV/V as well as extended sensor offset. A 16-bit analog-to-digital converter with an integrating input characteristic gives a 7.8 kHz sample rate, so the system delivers a comparable analog bandwidth of 4 kHz. internal or external temperature sensors allow more precise temperature compensation of sensor readings.

Measured and corrected bridge values are provided at the output pin, which can be configured as an analog voltage output with 12-bit resolution, as an I2C bus signal, or as ZMD’s ZACwire one-wire digital output. A programmable digital filter helps fit the sensor response to the required output behavior. The device’s output is protected against short-circuits, reverse polarity, and voltages as high as 33 V.

The ZMD31150 is available in an SSOP14 or in die form. A development kit includes printed circuit boards, samples, software and documentation. Mass calibration and circuit customization support is available.

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