AD694ARZ-REEL - 4-20mA Current Loop Transmitter, 16-SOIC | ADI
MPN: AD694ARZ-REEL ✓ Hoạt độngAD694ARZ-REEL Tóm tắt
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.
Bộ thay thế dễ dàng lắp đặt cho AD694ARZ-REEL — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Các biến thể trong loạt này
Các mẫu cùng loạt có thể lắp đặt dễ dàng tương thích với AD694ARZ-REEL (cùng hình factor và footprint) — khác nhau ở Function, Input Offset Voltage, Mounting Type, Output Current Range, Package.
AD694ARZ
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →AD694ARZ-REEL7
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694BRZ
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694BRZ-REEL
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694JR
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD5420ARZ
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694ARZ-REEL Tỷ lệ tối đa & tính chất điện
| Chức năng | 4-20 mA Current Loop Transmitter (V/I Converter) |
| Điện áp cung cấp | 4.5 V to 36 V (single supply) |
| Điện áp yên tĩnh | 1.5 mA typical |
| Output Current Range | 0 mA to 20 mA (or 4 mA to 20 mA) |
| Phạm vi điện áp đầu vào | 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) |
| Nhiệt độ hoạt động | -40 C to +85 C (industrial) |
| Hộp | 16-SOIC (Wide Body, 0.300") |
| Kiểu lắp đặt | Surface Mount |
| Cấp MSL | 1 (Unlimited, per PartGenie) |
| Trạng thái RoHS | 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) |
Cấu hình chân AD694ARZ-REEL
| Chân 1 | Input Amp Output — Open-collector output of the input instrumentation buffer (connect to external resistor) / feed-through from internal pre-regulator |
| Chân 2 | 2 V / 10 V Ref Select — Tie to ground for 2 V reference, tie to V+ for 10 V reference |
| Chân 3 | 10 V Reference Out — Buffered 10 V reference output (with pin 2 = V+) |
| Chân 4 | 2 V Reference Out — Buffered 2 V reference output (with pin 2 = ground) |
| Chân 5 | GND — Common ground for reference, signal input, and sense amplifier |
| Chân 6 | 4 mA Adj — Adjusts the 4 mA offset trim, allows 2 mA to 4.8 mA range |
| Chân 7 | Pre-Reg Output — Pre-regulator voltage output, supplies internal loop pass transistor |
| Chân 8 | Loop Return (COM) — Loop return path / load low side |
| Chân 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) |
| Chân 10 | V+ — Main supply voltage (4.5 V to 36 V) |
| Chân 11 | Loop Output — 4-20 mA current output driver (high side, connects to load high side) |
| Chân 12 | V+ — Main supply voltage (second V+ pin, tie to pin 10 with short trace) |
| Chân 13 | NC — Not connected (per datasheet) |
| Chân 14 | NC — Not connected (per datasheet) |
| Chân 15 | Sense+ — Input to internal sense amplifier (positive) |
| Chân 16 | Input Amp Inverting Input — Feedback input of the input instrumentation buffer |
Ứng dụng tiêu biểu
AD694ARZ-REEL phù hợp cho 7 Áp dụngs: 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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho AD694ARZ-REEL — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | 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 |
Bảo phân biệt quan trọng
- 13-inch reel packaging for high-volume automated assembly (vsAD694ARZ (tube))
- Industrial temperature grade -40 C to +85 C (vsAD694JR)
- A-grade accuracy for general-purpose applications (vsAD694BRZ-REEL)
Ghi chú thiết kế
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.
Thông tin tuân thủ
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.
