Part A
ADM4851ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4442 PCS
- Package
- SOIC-8
- Series
- Interface - Drivers, Receivers, Transceivers
Replacement verdict
Compatible functional replacement candidate
The ADM4851ARZ and ADM4850AR are both half-duplex RS-485/RS-422 transceivers in an 8-lead SOIC package with matching supply voltage and pinout, making them strong functional replacement candidates. The ADM4851ARZ offers a higher maximum data rate and full fail-safe receiver behavior, while the ADM4850AR provides a lower slew-rate-limited data rate for reduced EMI. Designers should confirm data rate, fail-safe, and receiver input impedance requirements against the target application before substituting.
Package Type
High match
Supply Voltage
High match
Data Rate
Validation required
Fail-Safe Feature
Validation required
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADM4851ARZ | ADM4850AR | Why it matters |
|---|---|---|---|
| Data Rate | 500 kbps | 250 kbps | Maximum signaling speed; the faster device supports higher-throughput buses while remaining backward compatible at lower rates. |
| Duplex Mode | Half duplex | Half duplex | Determines whether transmit and receive share one pair of lines; both are half duplex, so bus wiring topology is compatible. |
| Number of Drivers/Receivers | 1 driver / 1 receiver | 1 driver / 1 receiver | Defines the transceiver channel count; identical configuration means the same node role on an RS-485 network. |
| Supply Voltage | 5 V | 5 V | Operating rail must match the system supply; both are 5 V single-supply devices, so power design is interchangeable. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Defines the environmental envelope for reliable operation; matching ranges allow use in the same industrial conditions. |
| Package / Mounting | 8-SOIC, surface mount | 8-SOIC, surface mount | Footprint and assembly compatibility; identical SOIC packages allow drop-in board replacement. |
| Receiver Input Impedance (Unit Loads) | 1 unit load | 1 unit load | Determines how many nodes can share the bus; both being 1 unit load supports up to 32 standard nodes. |
| 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 behavior. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM4851ARZ | ADM4850AR |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Part Status | Active | Obsolete |
| Type | Transceiver | Transceiver |
| Protocol | RS422, RS485 | RS422, RS485 |
| Number of Drivers/Receivers | 1/1 | 1/1 |
| Voltage - Supply | 4.75V ~ 5.25V | 4.75V ~ 5.25V |
| Mounting Type | Surface Mount | Surface Mount |
| Duplex | Half | - |
| Receiver Hysteresis | 20 mV | - |
| Data Rate | 500kbps | - |
| Operating Temperature | -40°C ~ 85°C | - |
Frequently asked questions
What are the key differences between the ADM4851ARZ and ADM4850AR?
The ADM4851ARZ is a half-duplex RS-485/RS-422 transceiver specified for data rates up to 500 kbps, while the ADM4850AR is a half-duplex RS-485/RS-422 transceiver specified for data rates up to 2.5 Mbps. Both are 5 V single-supply devices in 8-lead SOIC packages, but they differ in maximum data rate and therefore in their suitability for different bus speeds.
Are the ADM4851ARZ and ADM4850AR pin-compatible?
Yes. Both devices are offered in the standard 8-lead SOIC (R-8) package with the same pinout: RO, RE, DE, DI, GND, A, B, and VCC. This common pinout allows them to share the same PCB land pattern, although the higher data rate of the ADM4850AR should be considered when evaluating bus topology and cabling.
Can the ADM4851ARZ and ADM4850AR be used interchangeably in an existing design?
They share the same package and pinout, but they are not identical in performance. The ADM4850AR supports data rates up to 2.5 Mbps, whereas the ADM4851ARZ is limited to 500 kbps. Substitution should only be made after confirming that the bus data rate, cable length, termination, and timing margins of the target design are compatible with the selected device.
What supply voltage do the ADM4851ARZ and ADM4850AR require?
Both devices operate from a single 5 V supply (VCC). They are specified for the standard 5 V RS-485/RS-422 logic and bus interface, so they are not 3.3 V devices and should not be operated outside the supply range stated in the respective manufacturer datasheets.
Do the ADM4851ARZ and ADM4850AR support half-duplex or full-duplex operation?
Both are half-duplex transceivers. They provide separate driver enable (DE) and receiver enable (RE) pins for direction control on a two-wire RS-485 bus, and they do not provide the separate A/B and Y/Z pairs required for full-duplex operation.
What data rate does each device support?
The ADM4851ARZ is specified for data rates up to 500 kbps, while the ADM4850AR is specified for data rates up to 2.5 Mbps. The lower data rate of the ADM4851ARZ generally allows longer cable runs and more relaxed signal integrity margins, while the ADM4850AR is intended for higher-speed buses within its specified limits.
Are the ADM4851ARZ and ADM4850AR suitable for the same bus termination scheme?
Both are standard RS-485/RS-422 transceivers intended for use on terminated twisted-pair buses. Proper termination, typically a 120 Ω resistor at each end of the bus, and fail-safe biasing should be applied according to the bus length and data rate. Because the ADM4850AR operates at higher data rates, termination and stub length become more critical in systems using that device.
What package options are available for the ADM4851ARZ and ADM4850AR?
Both the ADM4851ARZ and ADM4850AR are supplied in the 8-lead SOIC package, denoted by the R suffix in the ordering code. The Z suffix on ADM4851ARZ indicates RoHS-compliant packaging per the manufacturer's ordering guide. Designers should confirm the exact orderable part number and packaging status against the current manufacturer datasheet before production release.