The AD421BNZ is a Loop-powered DAC designed to meet the needs of smart transmitter manufacturers in the industrial control industry. It provides a high precision and fully integrated solution as well it is ideal for extending the resolution of smart 4mA to 20mA transmitters at very low cost. It includes a selectable regulator that is used to power itself and other devices in the transmitter. The part also contains +1.25 and +2.5V precision references. The AD421 thus eliminates the need for a discrete regulator and voltage reference. The only external components required are a number of passive components and a pass transistor to span large loop voltages. The Sigma-Delta (Σ-Δ) architecture of the DAC guarantees 16-bit monotonicity while the integral nonlinearity for the AD421 is ±0.01%. The AD421 can be used with standard HART FSK protocol communication circuitry without any degradation in specified performance.
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