The AD766 is a 16-bit DSP DACPORT with a 3-wire interface that interfaces directly to popular DSP processor serial ports such as the ADSP-2101, TMS320CXX, and DSP56001 without additional glue logic. In addition, the AD766 is fully configured with on-chip serial-to-parallel input format conversion, a 16-bit current guidance DAC, a voltage reference, and a voltage output op amp. Fabricated using Analog Devices' BiMOS II mixed-signal process, the AD766 offers bipolar transistors, MOS transistors, and thin-film resistors for precision analog circuits in addition to CMOS logic.
The design and layout of the AD766 has been optimized for ac performance and has been tested to guarantee signal-to-noise ratios of 94 dB (20 kHz) and 79 dB (250 kHz). The silicon-chromium thin-film resistor is laser trimmed to reduce the total harmonic distortion to less than -81 dB (1 kHz), a feature that is also production-tested. An optional linearity adjustment pin eliminates midscale differential linearity errors, resulting in lower total harmonic distortion for small signals.
The output amplifier of the AD766 provides ±3 V signals with high slew rate, small glitches, and fast settling. The output amplifier is short-circuit protected and can withstand an infinite short-circuit voltage to ground.
The serial interface consists of a bit clock input, a data input, and a latch-enable input. Twos complement data words are fed into a serial parallel converter along the falling clock in an MSB-first manner, which is consistent with the serial protocol of commonly used DSP processors. The input clock can support data transmission up to 12.5 MHz. On the falling edge of the latch enable, the 16-bit data that was recently read into the serial input register updates the internal DAC input register at the sample rate.
The AD766 operates from a ±5 V to ±12 V supply. Digital power +VLand -VLCan be connected with analog signal power +VSand -VS, separate to reduce digital crosstalk. Separate analog ground and digital ground pins are also provided. An internal bandgap reference provides the output amplifier with a precision voltage source that does not vary with temperature and time.
Typical power consumption is 120 mW when operating from a ±5 V supply; Typical power consumption is 300 mW when operating from a ±12 V supply. The AD766 is available in commercial (0°C to +70°C), industrial (-40°C to +85°C), and military (-55°C to +125°C) grades. Commercial and industrial grade devices are available in 16-pin plastic DIP packages; The military-grade device is MIL-STD-883B production compliant and is available in a 16-pin ceramic DIP package. For features of the military version, refer to Analog Devices' Military Data Sheet or current military-grade data sheets.