4-20 mA Low Power, 14-Bit, Process Control Current Loop Transmitter

Application circuit is a 4 mA-to-20 mA current loop transmitter for communication between a process control system and its actuator. Besides being cost effective, this circuit offers the industry low power solution. The 4 to 20 mA current loop has been used extensively in programmable logic controllers (PLCs) and distributed control systems (DCS), with digital or analog inputs and outputs. Current loop interfaces are usually preferred because they offer the most cost effective approach to long distance noise immune data transmission. The combination of the low power AD8657 dual op amp, AD5641DAC, and ADR02 reference allows more power budget for higher power devices, such as microcontrollers and digital isolators. The circuit output is 0 to 20 mA of current, and it operates on a single supply from 8 to 18 V