ADM2491EBRWZ - Isolated 16Mbps RS-485/422 Transceiver | Analog Devices
MPN: ADM2491EBRWZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $7.1 | $7.10 |
| 10 | $6.39 | $63.90 |
| 100 | $5.65 | $565.00 |
| 500 | $5.1 | $2,550.00 |
| 1,000 | $4.55 | $4,550.00 |
ADM2491EBRWZ Overview
A digital isolator is a semiconductor device that transfers digital signals across a galvanic isolation barrier using chip-scale transformers, giant magnetoresistance (GMR), or RF-coupled techniques. In RS-485 systems, the isolator breaks ground loops between the host controller and the fieldbus, allowing common-mode voltages of hundreds of volts to exist between nodes without damaging low-voltage controller ICs. The ADM2491E sits at the intersection of the digital isolator hierarchy (digital isolator -> isolator -> interface IC) and the line transceiver hierarchy (RS-485 transceiver -> transceiver -> interface IC), replacing a discrete opto-isolated RS-485 implementation with a single chip.
Key specifications include a 25 kV/µs common-mode transient immunity (CMTI), low loop latency, 1 unit-load (allowing up to 256 nodes on the bus), current limiting and thermal shutdown on the driver outputs, and compliance with ANSI TIA/EIA RS-485-A-1998 and ISO 8482:1987(E). The differential driver outputs (Y, Z) and differential receiver inputs (A, B) can be externally tied for half-duplex operation. The wide-body SOIC-16 footprint provides the required 7.5 mm minimum clearance and creepage across the isolation barrier.
The internal architecture pairs a differential RS-485 driver/receiver pair with an iCoupler transformer-based isolation channel, eliminating the optocoupler LED aging, current-transfer-ratio (CTR) drift, and slow edges typical of optoisolated RS-485 designs. The integrated isolated DC/DC converter provides power to the bus side, so only a single 3.3 V or 5 V supply is required on the controller side. This reduces board area, BOM count, and the multi-channel timing skew inherent in discrete optocoupler designs.
Typical applications include isolated PROFIBUS, Modbus RTU, and other RS-485 fieldbus nodes in industrial automation; isolated motor-drive communication links (e.g., encoder feedback, drive-to-controller UART); building-automation HVAC and lighting control buses; and any microcontroller/UART port that must survive large ground potential differences or harsh electrical environments. The high CMTI and on-chip ESD protection make it well suited to long-cable installations near variable-frequency drives or switching power supplies.
When designing with the ADM2491E, observe the 7.5 mm creepage/clearance requirement on the SOIC-16 footprint, place 0.1 µF decoupling capacitors close to VDD and VISO pins, and provide a low-impedance ground return on each side of the barrier. For half-duplex operation, externally short Y to A and Z to B; for full-duplex leave the four pins independent.
This page synthesizes distributor pricing, drop-in compatible alternatives, and practical design notes that extend the information in the manufacturer datasheet.
Drop-in alternatives for ADM2491EBRWZ — 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 ADM2491EBRWZ (same form factor and footprint) — differing in Isolation Voltage, Package, Data Rate, Number of Channels, Standards Compliance.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
ADM2491EBRWZ-REEL7
✅ Drop-In📋 Reference alternative (not in catalog)
ADM2490EBRWZ
✅ Drop-In✓ In Stock
$4.16 / Unit
View Datasheet →ADM2486BRWZ
✅ Drop-In✓ In Stock
$3 / Unit
View Datasheet →ADM2485BRWZ
✅ Drop-In✓ In Stock
$9.12 / Unit
View Datasheet →ADM3052BRWZ-RL7
✅ Drop-In✓ In Stock
$2.72 / Unit
View Datasheet →ADM2491EBRWZ Specifications
| Function | Isolated RS-485/RS-422 transceiver (full-/half-duplex) |
| Isolation Voltage | 5000 Vrms |
| ESD Protection (Bus Pins) | ±8 kV (HBM) |
| Data Rate (max) | 16 Mbps |
| Common-Mode Transient Immunity (CMTI) | 25 kV/µs |
| Number of Channels | 3 (1 Tx + 1 Rx + iso) |
| Supply Voltage (VDD, logic side) | 3.0 V to 5.5 V |
| Bus-side Supply | Internally generated from VDD (isolated DC/DC) |
| Operating Temperature Range | -40°C to +105°C |
| Number of Nodes on Bus | Up to 256 (1 unit load) |
| Standards Compliance | ANSI TIA/EIA RS-485-A-1998; ISO 8482:1987(E) |
| Package | 16-lead SOIC-W (RW-16), 0.295" (7.50 mm) width |
| Mounting Type | Surface Mount |
| Isolation Technology | iCoupler® (chip-scale transformer) |
| RoHS Status | Compliant (lead-free) |
ADM2491EBRWZ Pin Configuration
| Pin 1 | VDD — Logic-side supply input (3.0 V to 5.5 V) |
| Pin 2 | GND1 — Logic-side ground (return for VDD) |
| Pin 3 | RO — Receiver output (logic-side) |
| Pin 4 | RE# — Receiver enable, active-low (logic-side) |
| Pin 5 | DE — Driver enable, active-high (logic-side) |
| Pin 6 | DI — Driver input (logic-side) |
| Pin 7 | GND1 — Logic-side ground |
| Pin 8 | GND2 — Bus-side ground |
| Pin 9 | VISO — Isolated supply output (bus-side) |
| Pin 10 | A — Receiver non-inverting input (bus-side) |
| Pin 11 | B — Receiver inverting input (bus-side) |
| Pin 12 | Z — Driver inverting output (bus-side) |
| Pin 13 | Y — Driver non-inverting output (bus-side) |
| Pin 14 | GND2 — Bus-side ground |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | GND2 — Bus-side ground |
Typical Applications
ADM2491EBRWZ is suitable for 6 applications: Isolated PROFIBUS DP Fieldbus Node, Isolated Motor Drive Communication Link, Building Automation HVAC / Lighting RS-485 Bus, Isolated Data Acquisition Front End, Smart Grid / Energy Meter RS-485 Network, Industrial Sensor / Encoder UART Link.
Isolated PROFIBUS DP Fieldbus Node
The ADM2491EBRWZ is purpose-built for isolated PROFIBUS DP and other 12 Mbps industrial fieldbus nodes where the controller UART sits on a different ground potential than the cable plant. Its 16 Mbps data rate comfortably exceeds PROFIBUS DP's 12 Mbps maximum, while 5000 Vrms isolation and 25 kV/µs CMTI survive the fast transients produced by adjacent variable-frequency drives. Designers place the ADM2491EBRWZ between the microcontroller UART and the bus connector, with the bus-side ground tied only at the cable shield. Compared to optocoupler + discrete RS-485 designs, the ADM2491EBRWZ reduces part count and eliminates LED-aging reliability issues.
Recommended
Isolated Motor Drive Communication Link
Inside industrial motor drives, the controller logic and the high-voltage inverter stage share large switching transients, making galvanic isolation mandatory. The ADM2491EBRWZ's 25 kV/µs CMTI ensures data integrity even when IGBTs switch at the carrier frequency. The 5 kVrms isolation barrier protects the control board from inverter-induced surge events. Its integrated isolated DC/DC eliminates the need for a separate isolated supply, reducing PCB area. The wide-body SOIC-16 footprint provides the required creepage for 600 V motor drive systems.
Recommended
Building Automation HVAC / Lighting RS-485 Bus
Building-automation systems often span long cable runs across floors, where ground potential differences between nodes can reach tens of volts. The ADM2491EBRWZ provides the 5 kVrms isolation needed to safely connect thermostats, lighting controllers, and HVAC actuators on a shared RS-485 backbone. Its 16 Mbps capability supports modern BACnet MS/TP and high-rate Modbus traffic, while the wide-body SOIC-16 footprint simplifies UL 60747-17 compliance for safety isolation. Designers benefit from a single-chip solution that replaces optocoupler + discrete transceiver designs.
Recommended
Isolated Data Acquisition Front End
Multi-channel data acquisition systems digitize analog signals in noisy industrial environments, and the ADC must reject large common-mode voltages. The ADM2491EBRWZ isolates the host microcontroller from the field-side ADC reference and the 4-20 mA / RS-485 measurement network. The 25 kV/µs CMTI ensures ADC calibration is not corrupted by switching transients on nearby power electronics. Its single-supply architecture simplifies the BOM, and the wide-body SOIC-16 footprint gives the needed creepage for safety isolation certifications.
Recommended
Smart Grid / Energy Meter RS-485 Network
Smart electricity, water, and gas meters form RS-485 networks that connect hundreds of nodes across a utility's service area. The ADM2491EBRWZ's 5 kVrms isolation and ±8 kV ESD protection on the bus pins protect meter electronics from outdoor surge events and from cross-wiring faults during installation. The 256-node unit-load capability allows dense meter clusters, while the wide-body SOIC-16 footprint is a standard 7.5 mm creepage package accepted by UL/IEC meter safety standards. The integrated isolated DC/DC eliminates a separate isolated supply, simplifying the meter BOM.
Recommended
Industrial Sensor / Encoder UART Link
Robotic and CNC systems route UART-based encoder feedback from absolute encoders back to the motion controller. The ADM2491EBRWZ provides the high CMTI required for encoder links that run near servo amplifiers switching at 8-16 kHz. The 16 Mbps data rate exceeds the bandwidth of most encoder protocols (BiSS, SSI, EnDat), giving plenty of margin. The integrated isolated DC/DC removes the need for a separate isolated rail for the encoder interface, while the wide-body SOIC-16 footprint provides the safety isolation creepage needed for machinery safety standards.
Recommended
Recommended Products Summary
Engineering reference data for ADM2491EBRWZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | ADM2491EBRWZ-REEL7 | ADM2490EBRWZ | ADM2486BRWZ | ADM2485BRWZ | ADM3052BRWZ-RL7 |
|---|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 16-SOIC (0.295", 7.50 mm) | 16-SOIC (0.295", 7.50 mm) - same | 16-SOIC (0.295", 7.50 mm) - same | 16-SOIC (0.295", 7.50 mm) - same | 16-SOIC (0.295", 7.50 mm) - same | 16-SOIC (0.295", 7.50 mm) - same |
| Max Data Rate | 16 Mbps | 16 Mbps | 2.5 Mbps | 2.5 Mbps | 20 Mbps | 1 Mbps |
| Isolation Voltage | 5000 Vrms | 5000 Vrms | 5000 Vrms | 2500 Vrms | 2500 Vrms | 5000 Vrms |
| CMTI | 25 kV/µs | 25 kV/µs | 25 kV/µs | 25 kV/µs | 25 kV/µs | 25 kV/µs |
| ESD Protection (Bus) | ±8 kV | ±8 kV | ±8 kV | ±8 kV | ±8 kV | ±8 kV |
| Integrated Isolated DC/DC | Yes | Yes | Yes | Yes | No | Yes |
Key Differentiators
- Highest data rate in the ADM2491E / ADM248x wide-body SOIC family (vs ADM2486BRWZ)
- Integrated isolated DC/DC vs older isolated RS-485 generations (vs ADM2485BRWZ)
- Same wide-body SOIC-16 footprint for drop-in speed upgrades (vs ADM2490EBRWZ)
Design Notes
The ADM2491EBRWZ requires a wide-body SOIC-16 footprint with at least 7.5 mm of creepage and clearance between the logic-side (pins 1-7) and bus-side (pins 8-16) copper pours. Do not route any logic-side trace under or near the bus-side copper pour; this violates the safety isolation barrier and may fail UL/IEC certification. Use a slot in the PCB (milled or routed cut) directly under the IC body to physically enforce the barrier.
Place 0.1 µF X7R decoupling capacitors as close as possible to VDD (pin 1) and VISO (pin 9) on each side of the barrier. Add a 10 µF bulk tantalum or ceramic capacitor on VDD if the supply traces are longer than ~25 mm. Insufficient decoupling causes high CMTI events to corrupt logic-side data because the iCoupler transformer bias cannot ride through the transient.
For half-duplex operation, externally short pin 13 (Y) to pin 10 (A) and pin 12 (Z) to pin 11 (B) with short, matched trace lengths to minimize skew. For full-duplex, leave the four pins independent and route Y/Z as a 100 Ω differential pair and A/B as a separate 100 Ω differential pair. Use a 120 Ω termination resistor at the cable end only; do not populate both ends or stub ends to avoid reflections.
Estimated: at 5 V VDD and a fully loaded RS-485 bus at 16 Mbps, the ADM2491EBRWZ draws approximately 70-100 mA from VDD due to the integrated isolated DC/DC and high-speed driver. Ensure the host 3.3 V or 5 V regulator can supply this peak load plus the rest of the board. A separate small LDO or ferrite bead on the VDD pin of the ADM2491EBRWZ is recommended to isolate its switching noise from sensitive analog circuits.
Compliance Information
RoHS compliant per Analog Devices product page (Z suffix denotes lead-free). Not AEC-Q100 qualified - this part targets industrial / building-automation markets rather than automotive. REACH compliance stated on the Analog Devices product page.
