1 Features

? Functional Safety-Capable

– Documentation available to aid functional safety

system design: AFE881H1, AFE781H1

? Low quiescent current: 180 μA (typical)

? HART?-compliant physical layer modem

? 16-bit or 14-bit monotonic high-performance DAC

– 1.8-V supply: 0.15 V to 1.25 V, 0.2 V to 1.0 V

– 5-V supply: 0.3 V to 2.5 V, 0.4 V to 2.0 V

– 4-LSB INL at 16 bits

– 0.07 FSR (max) TUE from –40°C to +125°C

? 12-bit 3.84-kSPS ADC for advanced diagnostics

? Integrated 1.25-V reference at 10 ppm/°C (max)

? Internal 1.2288-MHz oscillator with clock output

? Digital interface

– Serial peripheral interface (SPI): Shared bus for

both DAC and HART

– Universal asynchronous receiver-transmitter

(UART): Shared bus for both DAC and HART

– Both: SPI for DAC and UART for HART

? Fault detection: CRC bit error checking, windowed

watchdog timer, diagnostic ADC

? Digital DAC slew-rate control

? Wide operating temperature: –55°C to +125°C

2 Applications

? 2-wire, 4-mA to 20-mA loop-powered transmitters

? Process control and industrial automation

? Smart transmitters

3 Description

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 HARTenabled

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.