The AD664 is a monolithic IC that integrates four complete 12-bit, voltage-output DACs. Each DAC features a double-buffered input latch structure and data readback. All DAC reads and writes are done through a single-ended microprocessor-compatible I/O port.
The I/O port can handle 4-bit, 8-bit, or 12-bit parallel words, allowing easy interfacing with a wide range of microprocessors. The device has a reset-to-zero control pin that allows the user to reset all DAC outputs to zero at the same time, regardless of what's in the input latch. Any or all of the DACs can be put into transparency mode so that the output can react immediately to the input data.
The analog portion of the AD664 consists of four DAC units, four output amplifiers, one control amplifier, and switches. Each DAC unit is of the reversed-phase R-2R type. The output current of each DAC is switched to the on-chip application resistor and output amplifier. The output range of each DAC unit is programmed through the digital I/O port and can be set to a unipolar or bipolar range with a gain of 1x or 2x the reference voltage. All DACs operate from an external reference.
The AD664 is the result of using Analog Devices' BiMOS II process combined with laser-trimmed thin-film resistors and a double-layer metal interconnect.