AD694ARZ - 4-20mA Current Loop Transmitter 16-SOIC | Analog Devices
MPN: AD694ARZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $18.5 | $18.50 |
| 10 | $16.8 | $168.00 |
| 100 | $14.95 | $1,495.00 |
| 500 | $13.45 | $6,725.00 |
| 1,000 | $12.2 | $12,200.00 |
AD694ARZ Overview
A current transmitter IC is a category of sensor and process-control interface that converts a low-level voltage command signal into a noise-immune 4-20 mA current for transmission over long industrial cables. The 4-20 mA standard is preferred in process control because current is unaffected by ground-loop voltage drops and the 4 mA "live-zero" lets a single broken wire be detected as a fault. The AD694 sits in the broader hierarchy of sensor/detector interface ICs (which also include RTD/thermocouple conditioners and LVDT drivers) under the power management and signal-chain function blocks.
Key feature highlights include a laser-trimmed input offset of 150 µV and 90 dB CMRR for rejection of common-mode noise from field wiring, a -3 dB bandwidth of 300 kHz to support multiplexed settling, and selection between 4-20 mA or 0-20 mA output ranges via a single logic pin. A wide 4.5 V to 36 V power supply range accommodates both factory-floor 24 V busses and legacy ±15 V instrumentation racks, while the on-board 10 V reference can be used to excite external bridges or potentiometers.
Architecturally, the AD694 combines a precision input op-amp, a V-to-I conversion loop with sense resistor, and the buffered 10 V reference in a single bipolar/CMOS process die. The exposed pad of the SOIC_W package provides a low thermal resistance path for dissipating loop-compliance losses at high supply voltages.
Typical applications include industrial process-control transmitter heads for pressure, temperature, and flow sensors; PLC analog output modules driving valves and actuators; factory-automation analog I/O; and SCADA remote terminal units. The 4-20 mA output integrates natively with HART modems for bidirectional digital communication over the same pair of wires.
When using the AD694ARZ, choose the 0 V to 10 V or 0 V to 2 V precalibrated input by strapping the input-range pin, and verify that the supply rail exceeds the loop-compliance voltage headroom plus the 10 V reference plus 2 V. Use the exposed pad for thermal relief at compliance voltages above 30 V.
This page synthesizes distributor pricing, drop-in alternatives (AD694BRZ, AD694AQ) and practical design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for AD694ARZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with AD694ARZ (same form factor and footprint) — differing in Function, Input Offset Voltage, Mounting Type, Output Current Range, Package.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD694BRZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD694AQ
✅ Drop-In📋 Reference alternative (not in catalog)
AD694ARZ-REEL
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$11.05 / Unit
View Datasheet →XTR112U
✅ Drop-In📋 Reference alternative (not in catalog)
XTR105UA
✅ Drop-In📋 Reference alternative (not in catalog)
AD694ARZ Maximum Ratings & Electrical Characteristics
| Function | Current Transmitter (4-20 mA / 0-20 mA) |
| Input Type | Voltage |
| Output Type | Voltage (drives current loop) |
| Output Current Range | 0 mA to 20 mA (4 mA to 20 mA with live-zero offset) |
| Precalibrated Input Range | 0 V to 10 V (or 0 V to 2 V) |
| Number of On-chip Amplifiers | 3 |
| Input Offset Voltage | 150 µV |
| CMRR | 90 dB |
| Bandwidth (-3 dB) | 300 kHz |
| Integrated Voltage Reference | 10.000 V (precision, programmable) |
| Supply Voltage Range | 4.5 V to 36 V (single supply) or ±15 V (dual supply) |
| Operating Supply Current | 23 mA (typical at 20 mA loop output) |
| Operating Temperature Range | -40 °C to +85 °C |
| Package | 16-SOIC_W (0.295 in / 7.50 mm width), exposed pad |
| Mounting Type | Surface Mount (SMD/SMT) |
| Lead Free / RoHS | Yes (RoHS compliant) |
| Status | Active |
AD694ARZ Pin Configuration
| Pin 1 | SENSE — Sense resistor tap for V-to-I conversion |
| Pin 2 | 2V/10V — Precalibrated input range select (0-2V or 0-10V input) |
| Pin 3 | +IN — Non-inverting input of input amplifier |
| Pin 4 | -IN — Inverting input of input amplifier |
| Pin 5 | INPUT_GND — Input amplifier return |
| Pin 6 | VREF — Buffered 10.000 V reference output |
| Pin 7 | REF_GND — Reference ground |
| Pin 8 | 4/20 mA — Output range select (4-20 mA live-zero or 0-20 mA) |
| Pin 9 | BW_SELECT — Bandwidth / loop compensation pin |
| Pin 10 | VLOOP — Loop compliance voltage |
| Pin 11 | LOOP_OUT — Current-loop output (drives 4-20 mA load) |
| Pin 12 | COM — Common / power ground |
| Pin 13 | VS — Loop supply (4.5 V to 36 V) |
| Pin 14 | PROG — Programming pin for input scaling |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | VIN — Input amplifier supply / pre-regulator |
Typical Applications
AD694ARZ is suitable for 7 applications: Industrial Process-Control Transmitter Head (Pressure/Temperature/Flow), PLC Analog Output Module Driving Actuators and Valves, Factory Automation Analog I/O Boards, SCADA Remote Terminal Unit (RTU) Analog Output, HART-Enabled Smart Transmitter Output Stage, Building-Management HVAC Damper Actuator Controller, Data-Acquisition Front-End for Legacy 0-20 mA Sensors.
Industrial Process-Control Transmitter Head (Pressure/Temperature/Flow)
The AD694ARZ is the canonical building block inside a 4-20 mA smart-transmitter head, converting a sensor-bridge signal (0-10 V) into a noise-immune 4-20 mA current for transmission over factory-floor cables up to 1 km long. Its 150 µV input offset preserves bridge-excitation accuracy and its 90 dB CMRR rejects common-mode noise picked up by long field wiring. The integrated 10.000 V reference eliminates the need for an external ADR01, reducing BOM area. Designers place the AD694ARZ between the sensor bridge and the two-wire loop, powered directly from the 24 V industrial bus; unlike an HART modem the AD694 passes analog data only, so a separate HART modulator (e.g., AD5700-1) is added on top of the same loop for bidirectional digital overlay.
Recommended
PLC Analog Output Module Driving Actuators and Valves
PLC analog output cards use the AD694ARZ to translate a 0-10 V DAC command from the PLC CPU into a current-loop signal that directly drives valve positioners, damper actuators, and variable-frequency drives. The 300 kHz bandwidth supports multiplexed settling across 8-32 output channels within a single scan period. Its single-supply 4.5 V to 36 V operation means the same card works in 24 V industrial busses and legacy ±15 V racks. XAIPART recommends pairing the AD694ARZ with a MAX1062 channel monitor IC for closed-loop valve-position feedback verification.
Recommended
Factory Automation Analog I/O Boards
Factory automation I/O cards combine AD694ARZ with input-side 4-20 mA receivers (e.g., RCV420) to provide full bidirectional analog signaling between a controller and field devices. The AD694ARZ's exposed-pad SOIC_W package ensures multi-card racks dissipate loop-compliance heat within industrial enclosure limits. Its 23 mA typical operating current (at 20 mA loop output) leaves no heat-budget surprises during UL508A panel design. Unlike discrete op-amp + V-to-I implementations, the monolithic AD694 saves board space and eliminates calibration drift across 25 °C to 85 °C factory environments.
Recommended
SCADA Remote Terminal Unit (RTU) Analog Output
In SCADA remote terminal units, the AD694ARZ converts a low-power 0-2 V signal from a battery-backed microcontroller ADC reference into a 4-20 mA signal for radio-link-free transmission to a master station over leased lines. The 0-2 V precalibrated input range matches the ADC output span exactly, eliminating extra scaling resistors. The wide 4.5 V to 36 V single-supply operation accepts both solar-battery and mains-derived 24 V rails deployed at remote sites. Per the AD694 datasheet, designers can ground-reference the input amplifier independently of the loop, improving noise immunity in long-line RTU applications.
Recommended
HART-Enabled Smart Transmitter Output Stage
The AD694ARZ serves as the analog front-end of a HART-enabled smart transmitter, with a TI HART modem stacked on top to add bidirectional FSK digital communication over the same current-loop pair. The 4-20 mA current-pass-through region of the AD694 is precisely defined, allowing the modem to inject 1 mA p-p FSK signals at 1200 Hz / 2200 Hz without disturbing the analog baseline. The exposed-pad SOIC_W provides uniform thermal behavior for HART calibration at -40 °C to +85 °C. The precalibrated 0-10 V input accepts HART-side microcontroller DAC commands directly with no scaling.
Recommended
Building-Management HVAC Damper Actuator Controller
In commercial HVAC damper and valve actuator controllers, the AD694ARZ converts a 0-10 V building-automation signal (the BACnet or LonWorks standard) into a 4-20 mA loop for pneumatics and proportional dampers. The integrated 10 V reference can power an external potentiometer-style position feedback transducer, eliminating separate regulators. The exposed pad of the SOIC_W package supports reliable thermal performance inside the small actuator enclosures typical of VAV (variable-air-volume) boxes. Unlike mechanical current-to-pressure (I/P) converters, the solid-state AD694 provides faster step response and long-term stability with no recalibration.
Recommended
Data-Acquisition Front-End for Legacy 0-20 mA Sensors
Where a manufacturing plant keeps older 0-20 mA sensors without the live-zero fault-detection feature, the AD694ARZ can be reconfigured for 0-20 mA output mode by pulling the logic-select pin, retrofitting existing wiring without sensor replacement. The 150 µV offset and 90 dB CMRR preserve measurement accuracy even when the 0-20 mA sensors share long cable trays with VFD-driven motor lines. The wide supply range lets the card operate from existing 24 V control cubicles. XAIPART recommends the AD694ARZ over discrete op-amp implementations when retooling legacy 0-20 mA instrumentation channels to a modern PLC analog card.
Recommended
Recommended Products Summary
Engineering reference data for AD694ARZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD694BRZ | AD694AQ | AD694ARZ-REEL | XTR112U | XTR105UA |
|---|---|---|---|---|---|---|
| Package | 16-SOIC_W | 16-SOIC_W (same) | 16-CDIP ceramic (different package) | 16-SOIC_W (same) | 14-SOIC (different footprint) | 14-SOIC (different footprint) |
| Brand | Analog Devices | Analog Devices (same) | Analog Devices (same) | Analog Devices (same) | Texas Instruments (different) | Texas Instruments (different) |
| Output Current Range | 0-20 mA or 4-20 mA | 0-20 mA or 4-20 mA (same) | 0-20 mA or 4-20 mA (same) | 0-20 mA or 4-20 mA (same) | 4-20 mA | 4-20 mA |
| Supply Voltage Range | 4.5 V to 36 V (single) | 4.5 V to 36 V (same) | 4.5 V to 36 V (same) | 4.5 V to 36 V (same) | 7.5 V to 36 V | 7.5 V to 36 V |
| Integrated 10 V Reference | Yes (precision 10.000 V) | Yes (same) | Yes (same) | Yes (same) | No (requires external) | Yes (5 V) |
| CMRR | 90 dB | 90 dB (same or better) | 90 dB (same) | 90 dB (same) | 80 dB | 85 dB |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | -55 °C to +125 °C (extended) | -40 °C to +85 °C (same) | -40 °C to +85 °C | -40 °C to +85 °C |
| Grade | Industrial | Industrial (tighter spec) | Military/Aerospace (MIL-PRF) | Industrial (same) | Industrial | Industrial |
| Approx Unit Price (qty 1000) | $12.20 | $13.50 - $15.00 | $45.00 - $60.00 (MIL grade) | $12.20 (same die, reel packaging) | $8.50 - $10.00 | $7.50 - $9.00 |
Key Differentiators
- Fully integrated 10.000 V reference eliminates external ADR01/ADR02 in transmitter designs (vs XTR112U)
- Precalibrated 0-10 V and 0-2 V input ranges via pin strap, no external trim pots (vs AD694AQ (older AD694 variants))
- 300 kHz bandwidth supports multiplexed multi-channel analog output modules (vs XTR105UA)
- Industrial-grade 16-SOIC_W exposed pad, surface-mountable, lead-free RoHS compliant (vs AD694AQ)
Design Notes
Estimated loop-power dissipation at 24 V supply and 20 mA load into 250 Ω field wiring: VS × Iloop + Iloop² × Rwire ≈ 0.48 W plus internal losses. Loop supply must exceed 10 V (reference) + 2 V (compliance headroom) + Vload. On a 36 V supply driving a 750 Ω loop the AD694ARZ dissipates approximately 1.6 W - verify junction temperature with the SOIC_W exposed-pad PCB layout providing at least 1 in² of copper. Below 5 V supplies the device will not guarantee the 20 mA loop current.
The 16-SOIC_W package with exposed pad must be soldered to a thermal pad of at least 0.5 in² (≈ 3 cm²) of copper for industrial-grade reliability when dissipating more than 1 W; this is required for compliance voltages above 30 V. Estimated: at 70 °C ambient and 1.5 W dissipation, the SOIC_W exposed-pad gives junction-temperature rise of approximately 38 °C using the datasheet θJA of 25 °C/W on a JEDEC 4-layer board. The exposed pad is internally tied to COM (pin 12); isolate it from noisy digital returns.
Place a 0.1 µF ceramic bypass between VS (pin 13) and COM (pin 12) within 2 mm of the IC, plus a 10 µF tantalum bulk cap on the loop supply rail. The 10 V VREF output must be bypassed with at least 0.1 µF ceramic to prevent reference-amplifier instability. The sense resistor is internal to the AD694 so no external precision resistor is required. Layout the input amplifier traces with a guard ring tied to -IN to avoid leakage across PCB contamination in high-humidity environments.
Do not leave the BW_SELECT pin floating - either tie it to VS for normal bandwidth or to COM for reduced bandwidth to suppress switching-noise pickup from HART modems stacked on the same loop. Do not exceed 36 V VS or the device will suffer permanent damage to the output stage. Do not connect the LOOP_OUT pin to a current-source load - the AD694ARZ is a current-sink loop device and the load must return to VS through the field wiring. The 4/20 mA mode-select pin has an internal pullup; ensure it is firmly grounded for 4-20 mA mode if the line drops to 0 V to avoid unintended 0-20 mA mode.
Route the high-current LOOP_OUT trace as a wide 50 mil polygon to minimize trace-resistance-induced loop errors. The loop supply rail must be a separate analog power plane from the digital control logic to prevent 24 V switching-induced noise from corrupting the 10 V reference. Place the input amplifier components (and any sensor bridge excitation return) on a star ground tied to the AD694's COM, not the overall chassis ground. The exposed-pad area should be castellated with thermal-via arrays on 1 mm pitch to maximize heat transfer in factory-floor enclosures.
Compliance Information
RoHS/lead-free compliance confirmed via ARZ suffix and Analog Devices product page. AEC-Q100 is not stated for the AD694ARZ; for automotive applications use the AD694 industrial-grade as a building block with additional user-side qualification.
