The AD667 is a complete voltage output 12-bit digital-to-analog converter including a high stability buried Zener voltage reference and double-buffered input latch on a single chip. The converter uses 12 precision high speed bipolar current steering switches and a laser trimmed thin-film resistor network to provide fast settling time and high accuracy.
Microprocessor compatibility is achieved by the on-chip doublebuffered latch. The design of the input latch allows direct interface to 4-, 8-, 12-, or 16-bit buses. The 12 bits of data from the first rank of latches can then be transferred to the second rank, avoiding generation of spurious analog output values. The latch responds to strobe pulses as short as 100 ns, allowing use with the fastest available microprocessors.
The functional completeness and high performance in the AD667 results from a combination of advanced switch design, high speed bipolar manufacturing process, and the proven laser wafer-trimming (LWT) technology. The AD667 is trimmed at the wafer level and is specified to ±1/4 LSB maximum linearity error (K, B grades) at +25°C and ±1/2 LSB over the full operating temperature range.
The subsurface (buried) Zener diode on the chip provides a low noise voltage reference which has long-term stability and temperature drift characteristics comparable to the best discrete reference diodes. The laser trimming process which provides the excellent linearity, is also used to trim the absolute value of the reference as well as its temperature coefficient. The AD667 is thus well suited for wide temperature range performance with ±1/2 LSB maximum linearity error and guaranteed monotonicity over the full temperature range. Typical full-scale gain TC is 5 ppm/°C.
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