Process Measurement Field Instrument (PMFI) sensors interface to a Programmable Logic Controller with a 2-, 3- or 4-wire configuration. This slide here shows a simplified block diagram of a 2-wire 4mA - 20mA PMFI sensor transmitter configuration. In this example, power and ground are supplied through the communications line. The MAX12900 implements the main building blocks in functions required between the two external wires in the main controller. The MAX12900 can use either the microcontroller PWM output port or a DAC output. System power consumption and cost are optimized when the PWM port is used.