The AD664 is four complete 12-bit, voltage-output digital-toanalog converters (DACs) on one monolithic IC chip. Each DAC has a double buffered input latch structure and a data readback function. All DAC read and write operations occur through a single microprocessor-compatible input/output (I/O) port.The I/O port accommodates 4-bit, 8-bit, or 12-bit parallel words allowing simple interfacing with a wide variety of microprocessors. A reset to zero control pin is provided to allow a user to simultaneously reset all DAC outputs to zero, regardless of the contents of the input latch. Any one or all of the DACs may be placed in a transparent mode allowing immediate response by the outputs to the input data.The analog portion of the AD664 consists of four DAC cells, four output amplifiers, a control amplifier, and switches. Each DAC cell is an inverting R-2R type. The output current from each DAC is switched to the on-board application resistors and output amplifier. The output range of each DAC cell is programmed through the digital input/output port and may be set to unipolar (UNI) or bipolar (BIP) range, with a gain of one or two times the reference voltage. All DACs are operated from a single external referenceThe functional completeness of the AD664 results from the combination of the Analog Devices, Inc., BiMOS II process, laser trimmed thin film resistors, and double level metal interconnects.