AD694ARZ - 4-20mA Current Loop Transmitter 16-SOIC | Analog Devices
MPN: AD694ARZ ✓ Hoạt độngAD694ARZ Tóm tắt
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.
Bộ thay thế dễ dàng lắp đặt cho AD694ARZ — 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 (cùng hình factor và footprint) — khác nhau ở Function, Input Offset Voltage, Mounting Type, Output Current Range, Package.
AD694BRZ
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694AQ
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694ARZ-REEL
✅ Drop-In ⚠️ Thông số chưa được xác minhLiên hệ để biết giá
Xem tài liệu →XTR112U
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
XTR105UA
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
AD694ARZ Tỷ lệ tối đa & tính chất điện
| Chức năng | Current Transmitter (4-20 mA / 0-20 mA) |
| Input Type | Voltage |
| Kiểu đầu ra | 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) |
| Khoảng nhiệt độ hoạt động | -40 °C to +85 °C |
| Hộp | 16-SOIC_W (0.295 in / 7.50 mm width), exposed pad |
| Kiểu lắp đặt | Surface Mount (SMD/SMT) |
| Lead Free / RoHS | Yes (RoHS compliant) |
| Status | Active |
Cấu hình chân AD694ARZ
| Chân 1 | SENSE — Sense resistor tap for V-to-I conversion |
| Chân 2 | 2V/10V — Precalibrated input range select (0-2V or 0-10V input) |
| Chân 3 | +IN — Non-inverting input of input amplifier |
| Chân 4 | -IN — Inverting input of input amplifier |
| Chân 5 | INPUT_GND — Input amplifier return |
| Chân 6 | VREF — Buffered 10.000 V reference output |
| Chân 7 | REF_GND — Reference ground |
| Chân 8 | 4/20 mA — Output range select (4-20 mA live-zero or 0-20 mA) |
| Chân 9 | BW_SELECT — Bandwidth / loop compensation pin |
| Chân 10 | VLOOP — Loop compliance voltage |
| Chân 11 | LOOP_OUT — Current-loop output (drives 4-20 mA load) |
| Chân 12 | COM — Common / power ground |
| Chân 13 | VS — Loop supply (4.5 V to 36 V) |
| Chân 14 | PROG — Programming pin for input scaling |
| Chân 15 | NC — Not connected (per datasheet) |
| Chân 16 | VIN — Input amplifier supply / pre-regulator |
Ứng dụng tiêu biểu
AD694ARZ phù hợp cho 7 Áp dụngs: 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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
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.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho AD694ARZ — 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 | 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 |
Bảo phân biệt quan trọng
- Fully integrated 10.000 V reference eliminates external ADR01/ADR02 in transmitter designs (vsXTR112U)
- Precalibrated 0-10 V and 0-2 V input ranges via pin strap, no external trim pots (vsAD694AQ (older AD694 variants))
- 300 kHz bandwidth supports multiplexed multi-channel analog output modules (vsXTR105UA)
- Industrial-grade 16-SOIC_W exposed pad, surface-mountable, lead-free RoHS compliant (vsAD694AQ)
Ghi chú thiết kế
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.
Thông tin tuân thủ
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.
