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.