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 capability. All DAC reads and writes are done through a single-ended microprocessor-compatible I/O port.
The I/O port can handle 4-, 8-, or 12-bit parallel words, allowing easy interfacing with a variety of microprocessors. The device has a reset-to-zero control pin that allows the user to reset all DAC outputs to zero simultaneously, regardless of what's in the input latch. Either or all DACs can be placed in transparent mode so that the output reacts immediately to the input data.
The analog section of the AD664 consists of four DAC units, four output amplifiers, one control amplifier, and switches. Each DAC unit is of type inverting R-2R. The output current of each DAC is switched to the on-chip application resistors and output amplifier. The output range of each DAC unit is programmed through a digital I/O port and can be set to a unipolar or bipolar range with a gain of 1 or 2 times the reference voltage. All DACs operate with an external reference.
The versatility of the AD664 is the result of using Analog Devices' BiMOS II process combined with laser trimming of thin-film resistors and double-layer metal interconnects.