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-REEL7 are both half-duplex RS-485/RS-422 transceivers in 8-pin SOIC packages with overlapping supply voltage ranges, making them viable functional substitutes in many designs. However, the ADM3491AR-REEL7 offers a wider supply range and higher ESD immunity, while the ADM3485EAR provides lower quiescent current and a reduced driver output swing suited to lower-power buses. Engineers should validate supply headroom, ESD requirements, and bus loading before substituting one for the other in a qualified design.
Package Type
High match
Supply Voltage Range
High match
Data Rate
Validation required
ESD Immunity
Validation required
Parts at a glance
Part B
ADM3491AR-REEL7
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4131 PCS
- Package
- SOIC-14
- 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-REEL7 | Why it matters |
|---|---|---|---|
| Data Rate | 10 Mbps | 10 Mbps | Both support the same maximum signaling rate, so timing compatibility is preserved for the bus. |
| Duplex Mode | Half-duplex | Full-duplex | Half-duplex uses a single shared pair while full-duplex uses separate transmit and receive pairs, affecting wiring and simultaneous bidirectional communication. |
| Number of Drivers/Receivers | 1 driver / 1 receiver | 1 driver / 1 receiver | Identical transceiver count means the same point-to-point or bus node capability. |
| Supply Voltage | 3.3 V | 3.3 V | Matching supply voltage allows drop-in use in the same 3.3 V rail design. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Same industrial temperature range ensures equivalent environmental robustness. |
| Package / Pin Count | 8-lead SOIC | 14-lead SOIC | Different package and pin count means the PCB footprint and pinout are not interchangeable without redesign. |
| Receiver Input Impedance (Unit Loads) | 1 unit load (32 nodes) | 1 unit load (32 nodes) | Equal unit-load rating allows the same number of nodes on a standard RS-485 bus. |
| Fail-Safe Receiver | Yes (open-circuit fail-safe) | Yes (open-circuit fail-safe) | Both define a known output state on an idle or open bus, preventing indeterminate logic levels. |
| ESD Protection (Bus Pins) | ±15 kV (HBM) | ±15 kV (HBM) | Equivalent ESD robustness supports similar field reliability and handling tolerance. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM3485EAR | ADM3491AR-REEL7 |
|---|---|---|
| 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 | 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 ADM3485EAR and ADM3491AR-REEL7?
The ADM3485EAR is a half-duplex RS-485/RS-422 transceiver, while the ADM3491AR-REEL7 is a full-duplex RS-485/RS-422 transceiver. The ADM3485EAR offers data rates up to 12 Mbps, whereas the ADM3491AR-REEL7 supports data rates up to 10 Mbps. Additionally, the ADM3491AR-REEL7 includes a driver enable and receiver enable pin configuration suited for full-duplex communication, while the ADM3485EAR is configured for half-duplex operation with a single driver/receiver enable pair.
Are the ADM3485EAR and ADM3491AR-REEL7 pin-compatible?
No, they are not pin-compatible. The ADM3485EAR is supplied in an 8-lead SOIC package, while the ADM3491AR-REEL7 is supplied in a 14-lead SOIC package. The pinouts differ because the ADM3491AR-REEL7 provides separate driver and receiver enable pins and full-duplex A/B and Y/Z signal pairs, whereas the ADM3485EAR uses a half-duplex configuration with shared A/B lines.
What are the supply voltage and operating temperature ranges for these devices?
Both the ADM3485EAR and ADM3491AR-REEL7 operate from a single 3.3 V supply. The ADM3485EAR is specified over the industrial temperature range of −40°C to +85°C. The ADM3491AR-REEL7 is specified over the industrial temperature range of −40°C to +85°C as well, per the Analog Devices datasheet.
Can the ADM3485EAR be used as a drop-in replacement for the ADM3491AR-REEL7?
No. The ADM3485EAR is a half-duplex transceiver in an 8-lead package, while the ADM3491AR-REEL7 is a full-duplex transceiver in a 14-lead package. They differ in pin count, pinout, duplex configuration, and data rate. A direct drop-in replacement is not possible without redesigning the PCB and validating the communication topology.
What data rates do the ADM3485EAR and ADM3491AR-REEL7 support?
The ADM3485EAR supports data rates up to 12 Mbps. The ADM3491AR-REEL7 supports data rates up to 10 Mbps. Both are suitable for high-speed RS-485/RS-422 communication, but the ADM3485EAR offers a slightly higher maximum data rate.
Do both devices include fail-safe receiver inputs?
Yes. Both the ADM3485EAR and ADM3491AR-REEL7 incorporate fail-safe receiver inputs that ensure a known logic-high output when the receiver inputs are open, shorted, or idle. This prevents indeterminate output states during bus idle conditions, as specified in the Analog Devices datasheets for both products.
What ESD protection is specified for the ADM3485EAR and ADM3491AR-REEL7?
Both the ADM3485EAR and ADM3491AR-REEL7 are specified with ±15 kV ESD protection on the RS-485/RS-422 bus pins using the human body model (HBM), and ±8 kV using the IEC 61000-4-2 contact discharge method, per the Analog Devices datasheets. This protection applies to the driver outputs and receiver inputs.
Which device should be selected for a full-duplex RS-485 network?
The ADM3491AR-REEL7 should be selected for full-duplex RS-485 networks because it provides independent driver and receiver enable pins and separate differential driver outputs (Y/Z) and receiver inputs (A/B). The ADM3485EAR is a half-duplex device and cannot support simultaneous transmit and receive over a four-wire full-duplex bus without external configuration changes.