Completely Isolated 4-Channel Multiplexed HART Analog Output Circuit

Circuit combines the AD5755-1 (quad channel voltage and current output DAC with dynamic power control) and the AD5700-1 HART modem, to give a completely isolated multiplexed HART1 analog output solution. Power can be provided either from the transformer isolated power circuit provided on the board (±13 V and +5.2 V outputs, dependent on the load current) or from external power supplies connected to terminal blocks. Circuit is suitable for use in programmable logic controllers (PLCs) and distributed control system (DCS) modules that require multiple HART-compatible 4 mA to 20 mA current outputs, along with unipolar or bipolar voltage outputs. External transient protection circuitry is also included, which is important for applications located in harsh industrial environments