Low-power AFE with ADC for PLC and sensor transmitter applications

The Texas Instruments 16-bit AFE88201 and 14-bit AFE78201 (AFEx8201) are highly integrated, high-accuracy, extremely low-power DACs with voltage outputs designed for process-control and industrial-automation applications.

The AFEx8201 devices include most components needed to design a 4mA to 20mA, three‑wire or four-wire sensor transmitter or analog output module. As well as the highly accurate DAC, the devices include a 10ppm/C voltage reference and diagnostic ADC. External voltage-to-current conversion and power regulation must accommodate intrinsic and functional safety concerns.

The internal diagnostic ADC is multiplexed to several internal nodes, enabling an automatic self-health check. This check can detect errors or malfunctions of the internal bias sources, power regulator, voltage reference, DAC output, die temperature, and optional external voltage source. If any fault is detected from the diagnostic ADC, CRC frame-error checking, or windowed watchdog timer, the devices can optionally issue an interrupt, enter a user-specified fail-safe state, or both.