DAC features dynamic power control

There are ICs which are low-power by design, and then there are those which are low-power in operation, as demonstrated by the Analog Devices AD5755 quad-channel 16-bit voltage/current-out digital/analog converter (DAC). By incorporating dynamic power control, the DAC throttles it voltage and power to the load by sensing load impedance, thus reducing its own power dissipation and self-heating, and allowing four channels in a tiny package. The vendor maintains the result is that power needs are reduced by 80% while net thermal rise (silicon die temperature plus ambient temperature) is reduced by 75%, compared to available comparable products.

Basic DAC performance is not sacrificed in this design. The 16-bit resolution DAC has total unadjusted error is0.05%, and relative inaccuracy of ±0.003% maximum, thus eschewing the need for system calibration. All associated functions are included on-chop, such as internal power converters, a 5- ppm/°C reference, drivers, interfaces, and buffers, to reduce external component count to near zero while increasing reliability and mean time to failure (MTTF). For enhanced reliability, the ADC includes various self-test and reporting modes.

The AD5755 supports industry-standard Highway Addressable Remote Transducer (HART) protocol modems, and uses a 30MHz SPI port for processor interface. The output can be set to provide voltage or current output on the same pin. Current output ranges include 0-20, 4-20, or 0-24 mA, and output voltage range are 0-5, 0-10, ±5, ±10, ±6, and ±12 V. The IC is specified over a -40°C to +105°C temperature range.

The AD5755 is sampling now with full production in October 2010. It is available as a 9×9 mm, 64-lead LFCSP device, with prices starting at $11.56 (1000 pieces) depending on specific I/O version. Analog Devices also offers a full-scale evaluation board as well as a reference design complete with schematics, layout, and driver code.

- Bill Schweber
EE Times