16-bit low-power analog front end (AFE) with DAC, ADC and HART® modem for sensor transmitters

The 16-bit AFE881H1 and 14-bit AFE781H1 ( AFEx81H1) are highly-integrated, high-accuracy,

extremely low-power digital-to-analog converters (DACs) with voltage outputs

designed for HART-enabled sensor-transmitter applications.

The AFEx81H1 devices include most of the components required to design a 4‑mA

to 20‑mA, 2‑wire (loop-powered) sensor transmitter. In addition to the highly

accurate DAC, these parts include a HART-certified FSK modem, 10‑ppm/°C voltage

reference, and diagnostic analog-to-digital converter (ADC). To accommodate

intrinsic and functional safety concerns, external voltage-to-current conversion and

power regulation are required.

The internal diagnostic ADC is

multiplexed to several internal nodes that enable an automatic self-health check. 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 fail-safe

state corresponding to a standard NAMUR output value or user-specified custom value,

or both.

These devices operate from supplies as

low as 1.71 V with 220 µA maximum quiescent current. The devices are specified over

the temperature range of –40°C to +125°C, but are functional from –55°C to

+125°C.