Part A
ADM3485EAR
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 3150 PCS
- Package
- SOIC-8
- Series
- Interfaces - pilotes, récepteurs, émetteurs - récepteurs
Replacement verdict
Compatible functional replacement candidate
The ADM3491ARZ and ADM3485EAR are both 3.3 V RS-485/RS-422 transceivers from Analog Devices in the same 8-lead SOIC package, sharing identical supply voltage, pin function, and communication protocol, so the ADM3485EAR can serve as a functional substitute for the ADM3491ARZ in most designs. However, the ADM3491ARZ offers full-duplex operation and a higher 12 Mbps data rate versus the half-duplex, 250 kbps ADM3485EAR, so the replacement is only valid where half-duplex, lower-speed operation is acceptable. Verify the duplex configuration and data-rate requirements of the target application before substituting.
Duplex Configuration
Validation required
Data Rate
Validation required
Supply Voltage
High match
Package Type
High match
Parts at a glance
Part B
ADM3491ARZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 2506 PCS
- Package
- SOIC-14
- Series
- Interfaces - pilotes, récepteurs, émetteurs - récepteurs
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADM3491ARZ | ADM3485EAR | Why it matters |
|---|---|---|---|
| Data Rate | 10 Mbps | 12 Mbps | Maximum signaling speed; the faster device supports higher throughput but both are adequate for most RS-485 networks. |
| Duplex Mode | Full duplex | Half duplex | Full duplex allows simultaneous transmit and receive over four wires, while half duplex shares a two-wire bus; this fundamentally changes bus topology and pinout. |
| Number of Drivers / Receivers | 1 driver, 1 receiver | 1 driver, 1 receiver | Both are single-channel transceivers, so channel count is not a differentiator, but duplex configuration still differs. |
| Supply Voltage | 3.0 V to 3.6 V | 3.0 V to 3.6 V | Both operate from a 3.3 V nominal rail, so power-supply compatibility is maintained. |
| ESD Protection (Bus Pins) | ±15 kV (HBM) | ±15 kV (HBM) | Robust ESD ratings protect the bus pins in harsh industrial environments; both meet the same level. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Industrial temperature range ensures reliable operation across demanding environments; both are equivalent. |
| Package / Pin Count | 14-lead SOIC | 8-lead SOIC | Different package footprints and pinouts prevent direct drop-in replacement on an existing PCB. |
| Fail-Safe Receiver | Yes | Yes | Fail-safe receivers guarantee a defined logic output when the bus is idle or open, preventing spurious data; both provide this feature. |
| Receiver Input Impedance (Unit Loads) | 1 unit load | 1 unit load | Standard 1-unit-load receivers allow up to 32 nodes on a bus; both are equivalent in this respect. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM3485EAR | ADM3491ARZ |
|---|---|---|
| Part Status | Obsolete | Active |
| 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 | 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 |
Frequently asked questions
What are the primary differences between the ADM3491ARZ and ADM3485EAR?
The ADM3491ARZ is a 3.3 V, full-duplex RS-485/RS-422 transceiver in an 8-lead SOIC package, while the ADM3485EAR is a 3.3 V, half-duplex RS-485/RS-422 transceiver in an 8-lead SOIC package. The key distinction is duplex configuration: the ADM3491ARZ supports simultaneous transmit and receive (four-wire bus), whereas the ADM3485EAR supports two-wire, half-duplex communication.
Are the ADM3491ARZ and ADM3485EAR pin-compatible?
No. Although both are 8-lead SOIC devices, their pin functions differ because the ADM3491ARZ is full-duplex and the ADM3485EAR is half-duplex. The ADM3491ARZ uses separate A/B receiver inputs and Y/Z driver outputs, while the ADM3485EAR combines driver and receiver onto shared A/B pins with a DE/RE direction control. They are not drop-in replacements.
What data rate does each device support?
The ADM3491ARZ is specified for data rates up to 10 Mbps. The ADM3485EAR is specified for data rates up to 12 Mbps. Both are 3.3 V RS-485/RS-422 transceivers, but the ADM3485EAR offers a slightly higher maximum data rate.
Do both parts include enhanced ESD protection?
The ADM3485EAR is part of Analog Devices' enhanced ESD protection family, with bus-pin ESD protection specified to ±15 kV (Human Body Model) on the RS-485 bus pins. The ADM3491ARZ provides standard ESD protection and is not specified to the same ±15 kV HBM bus-pin level. Designs requiring high ESD robustness on the bus should verify the exact ESD rating in the respective datasheet.
What is the difference in quiescent supply current between the two devices?
Both devices are low-power 3.3 V transceivers. The ADM3485EAR typically draws around 1.1 mA quiescent current, while the ADM3491ARZ typically draws around 1.5 mA. Exact values should be confirmed against the manufacturer datasheet for the specific grade and test conditions.
Can the ADM3485EAR replace the ADM3491ARZ in an existing full-duplex design?
No. The ADM3485EAR is a half-duplex transceiver and cannot directly replace a full-duplex ADM3491ARZ without redesigning the bus topology, because full-duplex operation requires separate driver and receiver pairs. A half-duplex device shares the same bus pins for transmit and receive and requires direction control via DE/RE.
What are the operating temperature ranges for these devices?
Both the ADM3491ARZ and ADM3485EAR are specified for the industrial temperature range of −40 °C to +85 °C. This makes both suitable for industrial RS-485/RS-422 communication applications.
Which device is better suited for multi-point bus applications?
Both devices support multi-point RS-485 bus configurations and feature receiver input impedance compliant with the RS-485 standard (1/8 unit load or better, allowing up to 256 nodes on the bus). The choice depends on duplex requirement: the ADM3491ARZ for full-duplex multi-point links and the ADM3485EAR for standard half-duplex multi-point buses.