ZMD announced a new addition to its family of resistive bridge (RBic-Lite) signal conditioner ICs. Developed for correction of resistive bridge sensors, the ZMD31014 combines high accuracy amplification with analog-to-digital conversion of a differential input. The CMOS device is ideal for all-types of microcontroller-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 the highest possible accuracy, the ZMD31014 features a 14-bit low-noise analog-to-digital converter, four times more precise than the 12-bit units found in most devices in this class. 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 bill-of materials as well as the overall system power consumption. The ZMD31014 uses 40% less power than previous designs during operation, and features a standby mode of less than 2µA to further reduce current consumption in battery-powered equipment.
The ZMD31014 supports the two IC interconnect busses I2C 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 microcontroller to continuously test the entire sensor system and improve the safety and reliability of the system. In addition, the ZMD31014 has a 32-bit 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 microcontroller can custom-calibrate the sensor in a very short time, typically a fraction of a second. The microcontroller can even recalibrate in-system if desired. Eliminating the need for external trimming components reduces the overall bill of materials as well as manufacturing costs and shortens time-to-market. The ZMD31014 operates on supply voltages from 2.7 to 5.5 volts and over a temperature range of -40°C to +125°C. Accuracy is 0.1% of full scale over the range of 0°C to 70°C, and 0.25% over the full temperature range. Power consumption during normal operation is as low as 150 µA while standby current is below 2 µA. 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.
Package, Price, and Availability
The ZMD31014 is sampling now and will be available for production in Q2 of 2008. It comes in an SOP8 package and is priced at Euro 1.75 for 1K units.
