The AD667 is a complete voltage-output, 12-bit, monolithic digital-to-analog converter with a highly stable embedded Zener reference and double-buffered input latch. The converter uses 12 precision, high-speed, bipolar current-guided switches and a laser-adjusted thin-film resistor network to provide fast settling times and high accuracy.
Microprocessor compatibility is achieved through an on-chip double-buffered latch. The input latches can interface directly with 4-, 8-, 12-, or 16-bit buses. As a result, 12 bits of data from the first-level latch can be transferred to the second-stage latch, avoiding the generation of spurious analog output values. The latch can respond to short strobe pulses of 100 ns, allowing it to be used with the fastest microprocessors available.
The AD667's versatility and performance are the result of an advanced switch design, a high-speed bipolar manufacturing process, and proven laser wafer trimming (LWT) technology. The device is trimmed at the wafer stage with a maximum linearity error of ±1/4 LSB (K, B grades) at +25°C and a linearity error of ±1/2 LSB over the entire operating temperature range.
The chip's subsurface (embedded) Zener diode provides a low-noise reference with long-term stability and excellent temperature drift characteristics that outperform the best discrete reference diodes. The laser trimming process has excellent linearity and can also be used to adjust the absolute value of the reference and its temperature coefficient. As a result, the AD667 has a wide temperature range with a maximum linearity error of ±1/2 LSB, and monotonicity over temperature. The typical full-scale gain temperature coefficient is 5 ppm/°C.
The AD667 is classified into five levels based on performance. The AD667J and AD667K are specified over the 0°C to +70°C temperature range and are available in 28-lead injection-molded DIP (N) or PLCC (P) packages. The AD667S grade is specified over the -55°C to +125°C temperature range and is available in ceramic DIP (D) or LCC (E) packages. The AD667A and AD667B are specified over the -25°C to +85°C temperature range and are available in a 28-pin hermetically sealed ceramic DIP (D) package.