The AD5421 is a complete， loop-powered， 4 mA to 20 mA digital-to-analog converter （DAC） designed to meet the needs of smart transmitter manufacturers in the industrial control industry. The DAC provides a high precision， fully integrated， low cost solution in compact TSSOP and LFCSP packages. The AD5421 includes a regulated voltage output that is used to power itself and other devices in the transmitter. This regulator provides a regulated 1.8 V to 12 V output voltage. The AD5421 also contains 1.22 V and 2.5 V references， thus eliminating the need for a discrete regulator and voltage reference. The AD5421 can be used with standard HART? FSK protocol communication circuitry without any degradation in specified performance. The high speed serial interface is capable of operating at 30 MHz and allows for simple connection to commonly used microprocessors and microcontrollers via a SPI-compatible， 3-wire interface. The AD5421 is guaranteed monotonic to 16 bits. It provides 0.0015% integral nonlinearity， 0.0012% offset error， and 0.0006% gain error under typical conditions. The AD5421 is available in a 28-lead TSSOP and a 32-lead LFCSP specified over the extended industrial temperature range of ?40°C to +105°C