The AD542 1 are designed for smart transmitter applications from 4 mA to 20 mA powered by integrated devices. The AD542 1 provides a 16-bit DAC and a current amplifier in a single chip, which are used for digital control of loop current, power supply of the whole transmitter of the voltage regulator, fault alarm function, flexible SPI-compatible serial interface, gain and offset adjustment registers and other features and functions.