AD421是一款完整的环路供电、数字4-20 mA转换器，专为满足工业控制领域智能发射器制造商的需求而设计。它提供一种高精度、全集成、低成本解决方案，采用紧凑型16引脚封装。AD421特别适合扩展4-20 mA智能发射器的分辨率，而且成本极低。
The AD421 has an optional regulator that powers itself and other devices in the transmitter. The regulator is available with +5 V, +3.3 V, or +3 V regulated output voltage. The device also has built-in +1.25 V and +2.5 V precision references. As a result, the AD421 does not require a discrete regulator and a voltage reference. The external components require only a few passives and a regulating tube to extend the large loop voltage range.
The AD421 can be used in combination with standard HART FSK protocol communication circuits without compromising rated performance. The high-speed serial interface is capable of operating at 10 Mbps and allows for simple connection to commonly used microprocessors and microcontrollers via a standard three-wire serial interface.
The DAC uses a sigma-delta architecture that guarantees 16-bit monotonicity and integral nonlinearity of ±0.01%. The device provides 4 mA zero-level output current with an offset error of ±0.1%) and 20 mA full-scale output current with a gain error of ±0.2%).
The AD421 is available in two packages: a 16-pin, 0.3-inch-wide, plastic DIP package and a 16-pin, 0.3-inch-wide, SOIC package. Rated for an industrial temperature range of -40°C to +85°C.