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Sensor signal conditioner has 14bit ADC

Posted: 28 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:ADC? sensor? signal conditioner?

ZMD AG has announced a new addition to its family of resistive bridge (RBic-Lite) signal conditioner ICs. According to the company, the ZMD31014 has been developed for correction of resistive bridge sensors and combines high accuracy amplification with analog-to-digital conversion of a differential input. The CMOS device is suitable for all-types of MCU-based portable equipment, such as white goods, wireless pressure transmitters, medical infusion pumps, wearable blood-pressure meters and temperature measurement equipment.

Resistive sensor bridges for conversion of physical measurements into an electrical signal are frequently used for pressure, temperature or humidity sensors. Since their conversion characteristics are generally non-linear and temperature-dependent, signal processing for amplification, linearization and compensation of the effects of the temperature is required. To deliver accuracy, the ZMD31014 features a 14bit low-noise ADC, four times more precise than the 12bit units found in most devices in this class, the company said. On-chip digital logic provides sophisticated second-order error correction for temperature offset, drift and non-linearity. Performing all of the error correction in the ZMD31014 simplifies designing the rest of the system and helps minimize the overall BOM as well as the overall system power consumption. The ZMD31014 uses 40-percent less power than previous designs during operation, and features a standby mode of less than 2?A to further reduce current consumption in battery-powered equipment.

"When we created the ZMD31014 we leveraged the comprehensive experience we gained when designing many different high-precision automotive and industrial sensor signal conditioning ICs," says Dirk Behrens, VP of marketing at ZMD. "Integrated diagnostics and low-power stand-by mode make the ZMD31014 attractive for a variety of battery operated applicationsparticularly ones involving the use of a microcontroller for networking sensors."

The ZMD31014 supports I?C and SPI. These busses support an addressing scheme so that multiple sensors can be used in the same design. The ZMD31014's on-chip diagnostics includes a bridge-connection check and a bridge short-circuit detection, allowing the MCU to continuously test the entire sensor system and improve the safety and reliability of the system. In addition, the ZMD31014 has a 32bit programmable customer ID field. This feature lets system designers customize sensor modules for specific purposes. For example, it can be used to determine if the correct sensor is attached to a system, or to uniquely identify each system in the field, thus providing easier field maintenance and diagnostics.

Using ZMD's unique one-shot/single-pass calibration, the MCU can custom-calibrate the sensor in a very short time, typically a fraction of a second. The MCU can even recalibrate in-system if desired. Eliminating the need for external trimming components reduces the overall BOM as well as manufacturing costs and shortens time-to-market.

The ZMD31014 operates on supply voltages from 2.7V to 5.5V and over a temperature range of -40C to 125C. Accuracy is 0.1 percent of full scale over the range of 0 to 70C, and 0.25 percent over the full temperature range. Power consumption during normal operation is as low as 150?A while standby current is below 2?A.

ZMD's RBic-Lite development kit supports the ZMD31014 with a range of evaluation and calibration tools that demonstrate the ease of use and the single pass calibration capabilities of the mixed-signal throughput used in the IC.

The ZMD31014 is already sampling and will be available for production Q2 2008. It comes in an SOP8 package and is priced at $2.6 for 1,000 units.

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