The AD420 is a complete digital to current loop output converter， designed to meet the needs of the industrial control market. It provides a high precision， fully integrated， low cost single-chip solution for generating current loop signals in a compact 24-lead SOIC or PDIP package. The output current range can be programmed to 4 mA to 20 mA， 0 mA to 20 mA or to an overrange function of 0 mA to 24 mA. The AD420 can alternatively provide a voltage output from a separate pin that can be configured to provide 0 V to 5 V， 0 V to 10 V， ±5 V， or ±10 V with the addition of a single external buffer amplifier. The 3.3 M Baud serial input logic design minimizes the cost of galvanic isolation and allows for simple connection to commonly used microprocessors. It can be used in 3-wire or asynchronous mode and a serial-out pin is provided to allow daisy chaining of multiple DACs on the current loop side of the isolation barrier. The AD420 uses sigma-delta （Σ-Δ） DAC technology to achieve 16-bit monotonicity at very low cost. Full-scale settling to 0.1% occurs within 3 ms. The only external components that are required （in addition to normal transient protection circuitry） are two low cost capacitors which are used in the DAC output filter.