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Signal conditioner IC advances automotive-sensor diagnostics

Melville, NY&#8212Optimized for the fast-changing dynamics of automotive control systems, ZMD's ZMD31150 signal conditioning IC, for fuel injection, ABS, power steering, and air conditioning applications, includes advanced on-chip diagnostics for use with Wheatstone Bridge sensors.

“In some applications, speed is of the essence,” stated Frank Schulze, business line manager for Automotive. “For optimum safety in a car
crash, the car must sense the size, weight, and orientation of the front-seat occupants&#8212quickly, in order to control the airbag's deployment. The ZMD31150 is two to seven times faster than other
signal-conditioning chips with comparable accuracy, and its diagnostic features mean increased reliability when it's needed most.”

The chip, which provides provides highly accurate amplification and sensor-specific digital correction of bridge sensor signals, includes an analog front-end (programmable gain amplifier, multiplexer, ADC), ROM, EEPROM for storing the auto system's various correction coefficients, microcontroller with correction algorithm for internal calibration, DAC, output amplifier stage (analog output) and ZACwire (digital data) I/O interface.

The chip's preamp, with a gain of 420, accommodates bridge outputs as low as 1 mV/V and accommodates an extended sensor offset. The chip's 16-bit ADC samples at 7.8 kHz (comparable analog bandwidth of about 4 kHz). The microcontroller runs its correction algorithm based on the calibration coefficients&#8212stored in (reprogrammable) EEPROM&#8212for the particular sensor in use. Calibration is accomplished with a PC-based program using the ZMD31150's serial interface.

An EEPROM signature check detects severe, uncorrectable multibit failures. To enhance hardware reliability, the output is protected against short-circuits, reverse-polarity, and voltages as high as 33 volts. Enhanced real-time diagnostics in the ZMD31150 detect faulty connections, shorts and power loss events. Additional EEPROM bytes allow storage of a
serial number or other product-traceability data.

The conditioned bridge signal at the output pin can be configured as an analog voltage output with 12-bit resolution, or as a digital output at the chip's ZACwire pin, or as an I2 C bus signal. The output is accurate to ±0.1 percent of full-scale from -25 to +85°C, &plusmn0.25 percent of full-scale from -40 to +125°C, and &plusmn0.5 percent of full-scale from -40 to +150&degC.

Click here to access the preliminary datasheet. The ZMD31150, in a SSOP14 package, is priced at $3.32 each in 1500 units, or as a die at a unit cost of $2.12 each for 1700 units. Support for industrial mass calibration is available, as is quick circuit customization for large production volumes. An evaluation kit is also available. The kit includes PCBs, samples, and the appropriate software.

ZMD America , 1-631-549-2666, www.zmd.biz

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