Part A
ADM485AR
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6742 PCS
- Package
- SOIC-8
- Series
- Interface - Drivers, Receivers, Transceivers
Replacement verdict
Not a drop-in replacement
ADM485AR and ADM4856AR are not drop-in replacements for one another. Although both are half-duplex RS-485 transceivers in 8-pin SOIC packages, they differ in data rate, supply voltage range, and pin function, so a direct board swap is not possible without design review.
Different data rate
Different supply voltage range
Different pin function
Different operating current
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | ADM485AR | ADM4856AR | Why it matters |
|---|---|---|---|
| Data Rate | 5 Mbps | 20 Mbps | Maximum signaling speed; a higher data rate supports faster bus communication but may require more careful layout and termination. |
| Duplex Mode | Half-duplex | Full-duplex | Determines whether the transceiver can transmit and receive simultaneously; full-duplex needs separate driver/receiver pairs and more bus lines. |
| Number of Drivers/Receivers | 1/1 | 1/1 | Indicates the transceiver channel count; both provide a single differential driver and receiver suitable for point-to-point or bus nodes. |
| Supply Voltage | 5 V | 5 V | Operating supply rail; both require a 5 V supply, so power architecture is compatible. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | Defines the ambient conditions the device is rated for; identical industrial ranges allow use in the same environments. |
| Package / Mounting | 8-SOIC (surface mount) | 8-SOIC (surface mount) | Footprint and assembly compatibility; matching packages allow drop-in board replacement without layout changes. |
| Number of Pins | 8 | 8 | Pin count affects package compatibility and PCB footprint; both are 8-pin devices. |
| Fail-Safe Receiver | Yes | Yes | Ensures a defined logic output when the bus is idle, open, or shorted, preventing indeterminate receiver states. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | ADM485AR | ADM4856AR |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Part Status | Obsolete | 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 | 70 mV | - |
| Data Rate | 5Mbps | - |
| Operating Temperature | -40°C ~ 85°C | - |
Frequently asked questions
Are the ADM485AR and ADM4856AR interchangeable in the same circuit?
No. The ADM485AR is a standard 5 V RS-485 transceiver in an 8-lead SOIC package, while the ADM4856AR is a 3.3 V RS-485 transceiver in an 8-lead SOIC package with a different pinout and supply voltage. They are not pin-for-pin or function-for-function drop-in replacements.
What supply voltage does each device require?
The ADM485AR operates from a single 5 V supply (4.75 V to 5.25 V). The ADM4856AR operates from a single 3.3 V supply (3.0 V to 3.6 V). The supply voltage difference is a primary reason the two parts are not directly interchangeable.
Do the ADM485AR and ADM4856AR use the same package and pinout?
Both are offered in an 8-lead SOIC package, but the pin assignments differ. The ADM485AR follows the standard 8-pin RS-485 pinout (RO, RE, DE, DI, GND, A, B, VCC), whereas the ADM4856AR uses a different pin configuration. PCB layout and pin function must be verified against the respective datasheets before substitution.
What are the data rates of the ADM485AR and ADM4856AR?
The ADM485AR is specified for data rates up to 2.5 Mbps. The ADM4856AR is specified for data rates up to 20 Mbps. The higher data rate of the ADM4856AR makes it suitable for faster bus applications, but the system timing must be validated accordingly.
How do the driver output and receiver input characteristics compare?
Both devices are RS-485 compliant transceivers with differential driver outputs and differential receiver inputs. However, because the ADM4856AR operates at 3.3 V and the ADM485AR at 5 V, the differential output swing, common-mode range, and receiver threshold specifications differ and must be checked against each datasheet for the target bus.
Can the ADM4856AR be used to replace an ADM485AR in an existing 5 V design?
No. The ADM4856AR is a 3.3 V device and cannot be operated from a 5 V supply. Replacing an ADM485AR with an ADM4856AR would require a 3.3 V rail, a revised PCB layout for the different pinout, and revalidation of bus levels and timing.
What are the operating temperature ranges for these devices?
Both the ADM485AR and ADM4856AR are specified for the industrial temperature range of −40 °C to +85 °C. This should be confirmed against the specific datasheet revision for the exact grade ordered.
Which device should be selected for a 3.3 V RS-485 bus?
The ADM4856AR should be selected for a 3.3 V RS-485 bus, as it is specified for 3.0 V to 3.6 V operation and supports data rates up to 20 Mbps. The ADM485AR is intended for 5 V systems and is not suitable for a 3.3 V supply.