Overview
The ADM1485JR is a high-speed, low-power RS-485 transceiver designed by Analog Devices Inc. This device is suitable for bidirectional data communication on multipoint bus transmission lines and complies with both EIA RS-485 and RS-422 standards. It features a differential line driver and a differential line receiver, both of which can be enabled independently. The ADM1485JR operates from a single 5 V power supply and includes thermal shutdown protection to prevent excessive power dissipation during fault conditions. It is fabricated using BiCMOS technology, combining the benefits of low power CMOS with fast switching bipolar technology.
Key Specifications
| Parameter | Min | Typ | Max | Unit | Test Conditions/Comments |
|---|---|---|---|---|---|
| Supply Voltage | 4.75 | 5 | 5.25 | V | |
| Driver Differential Output Voltage (VOD) | 1.5 | 5.0 | V | R = 27 Ω (RS-485), Test Circuit 1 | |
| Receiver Input Sensitivity | ±200 mV | ||||
| Receiver Input Voltage Range | -7 | +12 | V | ||
| Driver Propagation Delay | 10 | ns | |||
| Receiver Propagation Delay | 15 | ns | |||
| Operating Temperature Range | -40 | +85 | °C | ||
| Package Type | SOIC-8, DIP-8 |
Key Features
- Fast Data Rates: Supports data rates up to 30 Mbps, ensuring high-speed communication.
- Robust Communication: Complies with EIA RS-485 and RS-422 standards, providing reliable data transmission in noisy environments.
- Thermal Shutdown Protection: Protects the device from excessive power dissipation during fault conditions by disabling the driver outputs when a significant temperature increase is detected.
- High-Z Outputs with Power Off: Maintains high impedance driver output even when powered down, minimizing bus loading effects.
- Fail-Safe Receiver Input: Ensures a logic high output state if the receiver inputs are open circuit or floating.
- ESD Protection: Includes protection against electrostatic discharge (ESD) for all inputs and outputs.
Applications
- Industrial Automation: Suitable for industrial automation systems requiring reliable RS-422/RS-485 communication.
- Building Automation: Used in building automation systems for efficient and reliable data communication.
- Data Acquisition Systems: Ideal for data acquisition systems where high-speed communication is critical.
- Local Area Networks (LANs): Applicable in packet switching and data concentration within LANs.
- Integrated Services Digital Network (ISDN): Used in ISDN applications for reliable data transmission.
Q & A
- What are the primary standards that the ADM1485JR complies with?
The ADM1485JR complies with both EIA RS-485 and RS-422 standards.
- What is the operating voltage range of the ADM1485JR?
The ADM1485JR operates from a single 5 V power supply, with a tolerance of ±5%.
- What is the maximum data rate supported by the ADM1485JR?
The ADM1485JR supports data rates up to 30 Mbps.
- What protection features does the ADM1485JR include?
The ADM1485JR includes thermal shutdown protection, ESD protection, and fail-safe receiver input features.
- How many transceivers can be connected simultaneously on a bus?
Up to 32 transceivers can be connected simultaneously on a bus, but only one driver should be enabled at any time.
- What is the operating temperature range of the ADM1485JR?
The operating temperature range is -40°C to +85°C.
- What package types are available for the ADM1485JR?
The ADM1485JR is available in SOIC-8 and DIP-8 packages.
- How does the thermal shutdown protection work?
The thermal shutdown protection disables the driver outputs if the die temperature reaches 150°C and re-enables them when it cools down to 140°C.
- What is the significance of the high-Z output state when the driver is disabled or powered down?
The high-Z output state minimizes the loading effect on the bus when the transceiver is not being utilized.
- What happens to the receiver output if the inputs are open circuit or floating?
The receiver output defaults to a logic high state if the inputs are open circuit or floating.
