Description

This reference design is a single-channel: 4-mA to 20-mA analog input module that supports the highway addressable remote transducer (HART) communication protocol: enabling bidirectional digital communication between field transmitters and programmable logic controllers (PLCs). The loop current: representing the primary variable: flows through a current-sense resistor producing a proportional voltage that is digitized by a precision delta-sigma analog-to-digital converter (ADC) (ADS1260). A DAC8740H modem is used in this design to implement HART communication across the current loop. The ADS1260 and DAC8740H are interfaced with an external microcontroller that controls the ADS1260 sampling and includes a HART software stack to support the HART protocol. This design also features digital isolation: a wide power-supply range: and a high-precision external voltage reference for the ADC.