Part A
ADM3485EAR
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 3150 PCS
- Package
- SOIC-8
- Series
- Interface - Condutores, Receptores, Transceivers
Replacement verdict
Compatible functional replacement candidate
The ADM3485EAR and ADM3491AR are both half-duplex RS-485/RS-422 transceivers in 8-pin SOIC packages with overlapping supply voltage ranges, making them a viable functional replacement candidate. However, the ADM3491AR 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 requirements, fail-safe biasing needs, and thermal margins before substituting one for the other in a given application.
Package Type
High match
Supply Voltage Range
High match
Maximum Data Rate
Validation required
Receiver Fail-Safe Behavior
Validation required
Parts at a glance
Part B
ADM3491AR
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 8342 PCS
- Series
- Interface - Condutores, Receptores, 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 | Why it matters |
|---|---|---|---|
| Data Rate | 12 Mbps | 10 Mbps | Maximum signaling speed; determines whether the part meets the bus bandwidth requirements of the application. |
| Duplex Mode | Half-duplex | Full-duplex | Half-duplex shares one pair for transmit/receive, while full-duplex uses separate pairs; this fundamentally changes wiring and whether simultaneous bidirectional communication is possible. |
| Number of Drivers / Receivers | 1 / 1 | 1 / 1 | Defines the transceiver channel count; both are single-channel, so this is functionally equivalent. |
| Supply Voltage | 3.3 V | 5 V | Operating rail voltage must match the system supply; a 3.3 V vs 5 V difference affects logic-level compatibility and power design. |
| Receiver Input Impedance (Unit Loads) | 1/8 unit load (up to 256 nodes) | 1 unit load (up to 32 nodes) | Determines how many transceivers can share a single RS-485 bus; higher node count enables larger multi-drop networks. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Defines the environmental range over which the device is guaranteed to operate; identical here, so no substitution concern. |
| Package / Pin Count | 8-lead SOIC | 14-lead SOIC | Footprint and pinout must match the PCB layout; different packages mean the parts are not drop-in replacements. |
| Fail-Safe Receiver | Yes (open-circuit fail-safe) | Yes (open-circuit fail-safe) | Ensures a defined logic output when the bus is idle or disconnected, preventing spurious data; both provide this, so behavior is equivalent. |
| ESD Protection (Bus Pins) | ±15 kV (HBM) | ±15 kV (HBM) | Indicates ruggedness against electrostatic discharge on the bus; identical ratings mean comparable field robustness. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM3485EAR | ADM3491AR |
|---|---|---|
| Part Status | Obsolete | Obsolete |
| Type | Transceiver | Transceiver |
| Protocol | RS422, RS485 | RS422, RS485 |
| Number of Drivers / Receivers | - | 1/1 |
| Duplex | Half | Full |
| Receiver Hysteresis | 50 mV | 50 mV |
| Data Rate | 10Mbps | 10Mbps |
| Voltage - Supply | 3V ~ 3.6V | 3V ~ 3.6V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Base Product Number | - | ADM3491 |
| Number of Drivers/Receivers | 1/1 | - |
Frequently asked questions
What are the primary differences between the ADM3485EAR and ADM3491AR transceivers?
The ADM3485EAR is a half-duplex RS-485/RS-422 transceiver specified for data rates up to 12 Mbps, while the ADM3491AR is a full-duplex RS-485/RS-422 transceiver specified for data rates up to 10 Mbps. The ADM3485EAR is offered in 8-lead SOIC and 8-lead MSOP packages, whereas the ADM3491AR is offered in a 14-lead SOIC package to accommodate the separate driver and receiver pins required for full-duplex operation.
Can the ADM3485EAR be used as a direct drop-in replacement for the ADM3491AR?
No. The ADM3485EAR is a half-duplex device in an 8-lead package, while the ADM3491AR is a full-duplex device in a 14-lead package with a different pinout. The pin functions, package footprint, and duplex topology differ, so a direct drop-in substitution is not possible without a PCB redesign and validation against the manufacturer datasheets.
What are the maximum data rates of the ADM3485EAR and ADM3491AR?
Per the Analog Devices datasheets, the ADM3485EAR supports data rates up to 12 Mbps, and the ADM3491AR supports data rates up to 10 Mbps. The applicable rate depends on cable length, termination, and the specific operating conditions defined in each datasheet.
Do both devices operate from a single 3.3 V supply?
Yes. Both the ADM3485EAR and ADM3491AR are 3.3 V single-supply RS-485/RS-422 transceivers, as specified in their respective Analog Devices datasheets. Designers should still verify the specified supply tolerance and operating conditions for each part in the manufacturer documentation.
How do the duplex configurations of the ADM3485EAR and ADM3491AR differ?
The ADM3485EAR is a half-duplex transceiver, meaning the driver and receiver share the same differential bus pins (A and B), so transmit and receive cannot occur simultaneously on the same pair. The ADM3491AR is a full-duplex transceiver with separate driver outputs (Y and Z) and receiver inputs (A and B), allowing simultaneous transmit and receive over two differential pairs.
What package options are available for the ADM3485EAR and ADM3491AR?
The ADM3485EAR is available in 8-lead SOIC and 8-lead MSOP packages. The ADM3491AR is available in a 14-lead SOIC package. Package selection affects PCB land pattern, thermal behavior, and pin assignment, so the correct package variant must be confirmed against the manufacturer datasheet before layout.
Are both devices suitable for RS-485 and RS-422 bus applications?
Yes. Both the ADM3485EAR and ADM3491AR are specified as RS-485/RS-422 transceivers in the Analog Devices documentation. The choice between them depends primarily on whether the application requires half-duplex (ADM3485EAR) or full-duplex (ADM3491AR) communication and the associated data rate and package constraints.