Part A
ADM3485EAR
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3150 PCS
- Package
- SOIC-8
- Series
- Interface - Drivers, Receivers, Transceivers
Replacement verdict
Compatible functional replacement candidate
The ADM3485EAR and ADM3491AR-1 are both half-duplex RS-485/RS-422 transceivers in 8-pin SOIC packages with 3.3 V supply operation, making them functionally interchangeable for most bus-interface designs. The ADM3491AR-1 offers a higher maximum data rate and full fail-safe receiver behavior, while the ADM3485EAR provides lower quiescent supply current. Designers should validate data-rate margin, receiver fail-safe requirements, and ESD/transient protection against the target application before substituting one for the other.
Package Type
High match
Supply Voltage
High match
Data Rate
Validation required
Receiver Fail-Safe
Validation required
Parts at a glance
Part B
ADM3491AR-1
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3879 PCS
- Package
- SOIC-14
- Series
- Interface - Drivers, Receivers, Transceivers
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADM3485EAR | ADM3491AR-1 | Why it matters |
|---|---|---|---|
| Data Rate | 10 Mbps | 10 Mbps | Maximum signaling speed; both support the same 10 Mbps rate, so speed is not a differentiator. |
| Duplex Mode | Half-duplex | Full-duplex | Half-duplex shares one pair for transmit/receive, while full-duplex uses separate pairs for simultaneous bidirectional communication; this fundamentally changes wiring and application suitability. |
| Number of Drivers/Receivers | 1 driver / 1 receiver | 1 driver / 1 receiver | Both provide a single differential driver and receiver, so channel count is equivalent. |
| Supply Voltage | 3.3 V | 3.3 V | Operating supply voltage must match the system rail; both are 3.3 V devices. |
| ESD Protection (Bus Pins) | ±15 kV (HBM) | ±15 kV (HBM) | Bus-pin ESD robustness affects field reliability; both offer the same ±15 kV human body model protection. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Industrial temperature range suitability; both cover the same extended range. |
| Package | 8-lead SOIC | 14-lead SOIC | Footprint and pin count differ; the full-duplex device requires more pins, so PCB layout is not drop-in compatible. |
| Fail-Safe Receiver | Yes | Yes | Fail-safe receivers guarantee a defined logic output on open/shorted bus lines; both include this feature. |
| Pin Count | 8 | 14 | Different pin counts mean the parts are not pin-for-pin interchangeable and require different board layouts. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM3485EAR | ADM3491AR-1 |
|---|---|---|
| Supplier | - | Analog Devices Inc.,Rochester Electronics, LLC |
| Part Status | Obsolete | Obsolete |
| Type | Transceiver | Transceiver |
| Protocol | RS422, RS485 | RS422, RS485 |
| Number of Drivers/Receivers | 1/1 | 1/1 |
| Duplex | Half | Full |
| Receiver Hysteresis | 50 mV | 50 mV |
| Data Rate | 10Mbps | 20Mbps |
| Voltage - Supply | 3V ~ 3.6V | 3.3V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary differences between the ADM3485EAR and ADM3491AR-1?
The ADM3485EAR is a half-duplex RS-485/RS-422 transceiver specified for data rates up to 12 Mbps, while the ADM3491AR-1 is a full-duplex RS-485/RS-422 transceiver specified for data rates up to 10 Mbps. The ADM3485EAR is offered in an 8-lead SOIC package, whereas the ADM3491AR-1 is offered in a 14-lead SOIC package to accommodate the separate driver and receiver pins required for full-duplex operation.
Are the ADM3485EAR and ADM3491AR-1 pin-to-pin compatible?
No. The ADM3485EAR uses an 8-lead SOIC package with a half-duplex pinout (single A/B differential pair shared between driver and receiver), while the ADM3491AR-1 uses a 14-lead SOIC package with a full-duplex pinout (separate driver outputs Y/Z and receiver inputs A/B). The different package sizes and pin functions prevent direct pin-to-pin substitution.
Can the ADM3485EAR be used as a drop-in replacement for the ADM3491AR-1 in an existing design?
No. Because the ADM3485EAR is half-duplex and the ADM3491AR-1 is full-duplex, the bus topology, pin count, package footprint, and PCB land pattern differ. A direct drop-in replacement is not possible; the design would require rework of the bus wiring and PCB layout to accommodate the different device type.
What are the maximum data rates of the ADM3485EAR and ADM3491AR-1?
The ADM3485EAR is specified for data rates up to 12 Mbps. The ADM3491AR-1 is specified for data rates up to 10 Mbps. Both are suitable for high-speed RS-485/RS-422 communication, with the ADM3485EAR offering a slightly higher specified maximum data rate.
Do both devices operate from a single 3.3 V supply?
Yes. Both the ADM3485EAR and ADM3491AR-1 are 3.3 V single-supply RS-485/RS-422 transceivers, which allows them to interface directly with 3.3 V logic without additional level shifting in many applications.
How do the duplex modes of the ADM3485EAR and ADM3491AR-1 differ in bus configuration?
The ADM3485EAR is half-duplex, meaning the driver and receiver share the same differential bus pair (A/B), so transmit and receive operations cannot occur simultaneously on the same pair. The ADM3491AR-1 is full-duplex, providing separate driver outputs (Y/Z) and receiver inputs (A/B), enabling simultaneous transmit and receive over a four-wire bus.
What package options are available for the ADM3485EAR and ADM3491AR-1?
The ADM3485EAR is available in an 8-lead SOIC package. The ADM3491AR-1 is available in a 14-lead SOIC package. The package difference reflects the additional pins required for the full-duplex configuration of the ADM3491AR-1.