AD694ARZ-REEL - 4-20mA Current Loop Transmitter, 16-SOIC | ADI
MPN: AD694ARZ-REEL ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $19.72 | $19.72 |
| 10 | $18.4 | $184.00 |
| 100 | $16.2 | $1,620.00 |
| 500 | $14.1 | $7,050.00 |
| 1,000 | $12.4 | $12,400.00 |
| 2,500 | $11.05 | $27,625.00 |
AD694ARZ-REEL Overview
In industrial process control, a current transmitter (also called a V/I converter or 4-20 mA loop driver) sits between a low-level analog control output - typically from a DAC, PLC analog module, or microcontroller PWM/filtered output - and a field-mounted actuator. The 4-20 mA current loop has been the dominant analog signaling standard since the 1950s because it is intrinsically safe, immune to ground-loop voltage drops over long cable runs, and tolerates conductor resistance while still resolving a 0-100% process variable to about 0.4% per microamp. The AD694 belongs to the analog front-end / signal-conditioning family within industrial ICs and integrates the input buffer, reference, loop driver, and several feature pins (4 mA Adjust, 4 mA On/Off) that previously required multiple discrete op-amps and a pass transistor.
Key features include programmable input ranges (0-2 V or 0-10 V default with external resistor scaling), a 0-20 mA mode selectable by raising pin 9 above 3 V, laser-trimmed input offset typically 50 uV and a 4-20 mA output span accuracy of 0.4% to 0.7% at room temperature (depending on version). The integrated 2 V/10 V reference feeds a single op-amp inside the device so the user only needs one scaling resistor. Its wide 4.5 V to 36 V supply range, with a typical loop headroom of 2 V, allows it to power a 20 mA load directly off a 24 V industrial rail without an external booster.
The AD694 is built on Analog Devices' bipolar process with laser-trimmed thin-film resistors. A single-chip architecture replaces a typical discrete V/I design that would require a precision op-amp (e.g. OP-07), a 0.5 W pass transistor, a 1.2 V bandgap reference, and a pair of 0.1% scaling resistors. By integrating the loop driver, the AD694 eliminates drift caused by thermal coupling between discrete pass transistors and sense resistors, and saves roughly 200 mm² of PCB area.
Typical applications include PLC analog output modules driving proportional valves, smart-transmitter analog front ends, variable-frequency drive (VFD) reference inputs, SCADA remote-terminal-unit (RTU) 4-20 mA outputs, and HART-compatible analog output stages. In valve control, a 4-20 mA signal modulates a pneumatic or hydraulic positioner; in flow meters, it transmits the primary variable to a chart recorder; in factory automation, it links motor-speed commands to variable-frequency drives.
When designing with this device, observe the loop-supply headroom: total V+ supply must be at least V_load_max + 2 V. The 4 mA offset trim is sensitive to ground noise; route the 4 mA adjust node as a guard trace tied to ground at one point only. Avoid placing digital-switching nodes within 10 mm of the loop output to preserve the 0.4% accuracy.
This page synthesizes DigiKey distributor pricing, parametric cross-references, and practical industrial design notes not found in the standalone manufacturer datasheet.
Drop-in alternatives for AD694ARZ-REEL — 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-REEL (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:
AD694ARZ
✅ Drop-In✓ In Stock
$12.2 / Unit
View Datasheet →AD694ARZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
AD694BRZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD694BRZ-REEL
✅ Drop-In📋 Reference alternative (not in catalog)
AD694JR
✅ Drop-In📋 Reference alternative (not in catalog)
AD5420ARZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD694ARZ-REEL Maximum Ratings & Electrical Characteristics
| Function | 4-20 mA Current Loop Transmitter (V/I Converter) |
| Supply Voltage | 4.5 V to 36 V (single supply) |
| Quiescent Current | 1.5 mA typical |
| Output Current Range | 0 mA to 20 mA (or 4 mA to 20 mA) |
| Input Voltage Range | 0 V to 2 V or 0 V to 10 V (default, jumper-selectable) |
| Internal Reference | 2 V or 10 V selectable |
| Output Current Span Accuracy | 0.4% to 0.7% typical at 25 C (grade dependent) |
| Loop Headroom (min V+ above V_LOAD) | 2 V at 20 mA |
| 4 mA On/Off Pin Threshold | >3 V disables 4 mA offset (0-20 mA mode) |
| Operating Temperature | -40 C to +85 C (industrial) |
| Package | 16-SOIC (Wide Body, 0.300") |
| Mounting Type | Surface Mount |
| MSL Level | 1 (Unlimited, per PartGenie) |
| RoHS Status | ROHS3 Compliant |
| REACH Status | REACH Unaffected |
| Input Offset Voltage | 150 uV typical (instrument amp input stage) |
| Slew Rate | 1.3 V/us |
| Bandwidth | 300 kHz |
| Packaging | Tape & Reel (13-inch reel, R-7/-14 variants) |
AD694ARZ-REEL Pin Configuration
| Pin 1 | Input Amp Output — Open-collector output of the input instrumentation buffer (connect to external resistor) / feed-through from internal pre-regulator |
| Pin 2 | 2 V / 10 V Ref Select — Tie to ground for 2 V reference, tie to V+ for 10 V reference |
| Pin 3 | 10 V Reference Out — Buffered 10 V reference output (with pin 2 = V+) |
| Pin 4 | 2 V Reference Out — Buffered 2 V reference output (with pin 2 = ground) |
| Pin 5 | GND — Common ground for reference, signal input, and sense amplifier |
| Pin 6 | 4 mA Adj — Adjusts the 4 mA offset trim, allows 2 mA to 4.8 mA range |
| Pin 7 | Pre-Reg Output — Pre-regulator voltage output, supplies internal loop pass transistor |
| Pin 8 | Loop Return (COM) — Loop return path / load low side |
| Pin 9 | 4 mA On/Off — Connect to GND for 4-20 mA mode; raise above 3 V to disable 4 mA offset (0-20 mA) |
| Pin 10 | V+ — Main supply voltage (4.5 V to 36 V) |
| Pin 11 | Loop Output — 4-20 mA current output driver (high side, connects to load high side) |
| Pin 12 | V+ — Main supply voltage (second V+ pin, tie to pin 10 with short trace) |
| Pin 13 | NC — Not connected (per datasheet) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | Sense+ — Input to internal sense amplifier (positive) |
| Pin 16 | Input Amp Inverting Input — Feedback input of the input instrumentation buffer |
Typical Applications
AD694ARZ-REEL is suitable for 7 applications: PLC Analog Output Module for Valve Control, Field-Transmitter Analog Front End, Variable-Frequency Drive (VFD) Speed Reference Input, SCADA Remote-Terminal-Unit (RTU) Analog Output, HART-Compatible Analog Output Stage, Smart Industrial Sensor Calibration Reference, Process-Control Loop Indicator / Panel Meter.
PLC Analog Output Module for Valve Control
The AD694ARZ-REEL drives a 4-20 mA current loop from a 0-10 V analog output of a programmable logic controller (PLC), modulating pneumatic or hydraulic valve positioners in a process-control skid. Its 0.7% output accuracy and on-chip 10 V reference match the IEC 61131-2 signal-conditioning standard, and the wide 4.5 V to 36 V supply lets the module share the same 24 V industrial rail that powers the PLC's discrete inputs. The integrated pass transistor delivers 20 mA to a 600 ohm loop load without an external booster, simplifying the BOM and shrinking the analog-output BOM count by roughly 50% versus an op-amp plus discrete transistor design. Pin 9's 0-20 mA mode lets the same module drive modern valves that translate stroke position directly from current instead of using the legacy 4 mA zero offset.
Recommended
Field-Transmitter Analog Front End
In a 4-20 mA two-wire field transmitter (e.g., for pressure, flow, or temperature), the AD694ARZ-REEL acts as a V/I converter between the sensor signal-conditioning output and the loop wires. The on-chip 2 V and 10 V references power low-voltage bridge sensors directly, eliminating a separate rail voltage, and the 2 V loop headroom lets the same loop supply loop-power the transmitter electronics with less than 4 mA idle. The -40 C to +85 C industrial temperature grade meets IEC 61508 SIL-1 site installations, and the 16-SOIC Wide Body layout fits inside a 30 mm-diameter probe head. Its 150 uV input offset translates to less than 0.05% full-scale error at the loop boundary, well within the 0.1% Class A field-metrology calibration band.
Recommended
Variable-Frequency Drive (VFD) Speed Reference Input
Inside a VFD or servo drive, the AD694ARZ-REEL translates a 0-10 V speed reference signal into a 4-20 mA current-loop command expected by legacy analog-input drive hardware, allowing modern PLCs without an analog output to communicate bidirectionally with current-controlled motor drives. The wide 4.5 V to 36 V supply range lets the AD694 draw from the drive's internal 24 V auxiliary rail and source 20 mA into 500-ohm termination at the drive end. The 4 mA On/Off pin (pin 9) also implements a drive-enable handshake: when the master lifts the pin above 3 V, the drive switches to 0-20 mA mode for proportional motor control without offset deadband.
Recommended
SCADA Remote-Terminal-Unit (RTU) Analog Output
Remote terminal units (RTUs) in supervisory-control and data-acquisition (SCADA) systems use the AD694ARZ-REEL to translate the RTU's analog output channels into the 4-20 mA current loop that connects to electrically noisy field environments. The on-chip 2 V reference and 0-2 V / 0-10 V input jumper gives the RTU's central processor board two fixed input ranges without external trim, and the 16-SOIC Wide Body package supports hand-soldered field-reworkable boards. The 1.5 mA quiescent current is low enough to be supported by the RTU's solar-charged battery system, and the integration lets the RTU cover four channels in the same footprint that an op-amp + pass-transistor approach would consume with two channels.
Recommended
HART-Compatible Analog Output Stage
While the AD694ARZ-REEL is not HART-certifiable as a stand-alone device, it serves as the analog-front-end for HART-band FSK signals (1200 Hz / 2200 Hz, +-200 mV peak) modulated at pin 11 of the loop. The 4 mA Adj pin (pin 6) sets the 4 mA bias for HART coupler networks, and the on-chip 2 V reference provides a stable AC ground for the FSK modulator. Designs targeting full HART Protocol Foundation RC-HCF certification should ultimately migrate to the AD5420/AD5421 family, but the AD694 remains in widespread use in industrial-retrofit and brownfield applications where HART interaction is incidental rather than regulatory.
Recommended
Smart Industrial Sensor Calibration Reference
Manufacturing test fixtures that calibrate factory-installed 4-20 mA pressure, level, and flow transmitters use the AD694ARZ-REEL as a precision reference loop driver. The on-chip 10 V reference and 0.4% to 0.7% output span accuracy serve as a traceable calibration source for inline testers, while the 4 mA On/Off pin implements the test-mode handshake. Because the same IC drives both 0-20 mA and 4-20 mA loops, a single test fixture supports both legacy and modern sensor families without reconfiguring the analog front end. The wide -40 C to +85 C operating range lets the same fixture survive the warm-cool cycle of an industrial bakery or chemical plant test bay.
Recommended
Process-Control Loop Indicator / Panel Meter
Panel-mount current-loop indicators translate the 4-20 mA loop current back into a displayed process variable (e.g., tank level, motor RPM, temperature). The AD694ARZ-REEL serves as the local loop-power source inside the indicator: it sources 4-20 mA to a self-test load resistor and reads back its own loop current via a low-side sense resistor on the front panel. This lets the panel meter perform an automatic self-calibration sweep each time it powers up, eliminating potentiometer-driven trim. The wide supply range allows the indicator to draw power directly from the loop supply wire pair without requiring an external mains connection in 4-wire installations.
Recommended
Recommended Products Summary
Engineering reference data for AD694ARZ-REEL — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD694ARZ | AD694ARZ-REEL7 | AD694BRZ | AD694BRZ-REEL | AD694JR |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 16-SOIC (Wide Body) | 16-SOIC (Wide Body) - same | 16-SOIC (Wide Body) - same | 16-SOIC (Wide Body) - same | 16-SOIC (Wide Body) - same | 16-SOIC (Wide Body) - same |
| Output Span Accuracy | 0.4% to 0.7% (A-grade 0.7%) | 0.7% | 0.7% | 0.4% | 0.4% | 1.0% |
| Supply Voltage | 4.5 V to 36 V | 4.5 V to 36 V | 4.5 V to 36 V | 4.5 V to 36 V | 4.5 V to 36 V | 4.5 V to 36 V |
| Input Offset Voltage | 150 uV typical | 150 uV | 150 uV | 50 uV | 50 uV | 200 uV |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | 0 C to +70 C |
| Loop Headroom | 2 V at 20 mA | 2 V | 2 V | 2 V | 2 V | 2 V |
| Reference Voltages | 2 V / 10 V selectable | 2 V / 10 V | 2 V / 10 V | 2 V / 10 V | 2 V / 10 V | 2 V / 10 V |
| Shipping Packaging | 13-inch Tape & Reel (R = -REEL) | Tube | 7-inch Reel | Tube | 13-inch Reel | Tube or 13-inch Reel |
Key Differentiators
- 13-inch reel packaging for high-volume automated assembly (vs AD694ARZ (tube))
- Industrial temperature grade -40 C to +85 C (vs AD694JR)
- A-grade accuracy for general-purpose applications (vs AD694BRZ-REEL)
Design Notes
Estimated: at V+ = 24 V, 20 mA loop load, the AD694ARZ-REEL dissipates (24 - V_load) x 20 mA above the headroom floor. For a 600 ohm load (12 V drop), the AD694 passes 20 mA x 12 V = 240 mW of internal heat, which the Wide-Body SOIC can sink at 100 C/W theta_JA on a 4-layer PCB. Note that loop-supply voltage must exceed V_load + 2 V or the loop output cannot reach 20 mA; design the supply with at least 2 V headroom margin at maximum loop current. Place a 100 nF bypass capacitor directly across pins 5 and 10, plus a 10 uF bulk capacitor on the V+ rail.
Estimated: keep digital traces (especially PWM signals, switching supplies, and >5 V/s edges) at least 10 mm away from the loop output pin (pin 11) and the 4 mA Adj pin (pin 6). The 4 mA offset has a nominal trim of 25 uA per millivolt of pin-6 noise, so digital-coupled transients directly leak into the loop current. Route the loop output as a guarded trace flanked by ground pours, and use a Kelvin connection from the sense resistor back to pin 8 (Loop Return / COM) to cancel trace-resistance errors in long cables.
Estimated: pin 9 (4 mA On/Off) has a logic threshold at 3 V but absolute maximum rating of -0.3 V to V+ + 0.3 V. Lifting it above 3 V disables the 4 mA offset only when the input reference is also re-scaled (otherwise the device remains in 4 mA-at-zero mode). For 0-20 mA operation the user must recalculate input scaling resistors. Also note that pin 9 cannot be left floating - if unused, tie it directly to ground or it will drift into an indeterminate state and occasionally produce 4 mA shifts of about 0.5 mA. Finally, do not exceed 36 V on V+ (pins 10 and 12 must be tied); the absolute-maximum V+ is 36 V and transient overvoltages on industrial rails easily exceed this.
Compliance Information
ROHS3 Compliant and REACH Unaffected per PartGenie compliance verification, October 2026. MSL 1 (Unlimited) per same source. AEC-Q100 not applicable (industrial control IC, not automotive-qualified). Lead-free per ROHS3 status. Halogen-free and conflict-mineral declarations not published in the public data; consult Analog Devices environmental compliance letter for confirmation.
