RSM485
RS-485 isolated transceiver, 2500VDC isolation, 500Kbps, automatic flow control, integrated isolated power
Product Overview
Description
The RSM485 is a high-performance RS-485 isolated transceiver in Aipu's RSM series, featuring integrated signal isolation, power isolation, and RS-485 transceiver in a single compact module.
This module provides 2500VDC galvanic isolation between RS-485 bus and logic side, protecting sensitive control electronics from ground loops, common-mode noise, and bus fault conditions. The integrated DC-DC converter generates isolated power, eliminating the need for external isolation power supply.
The RSM485 supports data rates up to 500Kbps with automatic flow control, making it ideal for industrial automation, building automation, and process control applications requiring reliable RS-485 communication with isolation.
Product Series
RSM
Primary Application
Industrial automation networks
Key Features
- RS-485 transceiver with automatic flow control
- 2500VDC galvanic isolation
- Integrated isolated DC-DC converter
- Data rate up to 500Kbps
- Up to 256 nodes on bus
- ESD protection HBM 4kV
- Bus fault protection
- Thermal shutdown protection
- Compact PCB mount package
Specifications
| Protocol | RS-485 |
|---|---|
| Isolation Voltage | 2500VDC |
| Data Rate | Up to 500Kbps |
| Max Nodes | 256 |
| ESD Protection | HBM 4kV |
| Bus Fault Protection | +/-36V |
| Operating Temperature | -40C ~ +85C |
| Package | DIP/SMD |
Applications
Industrial automation networks
Industrial automation and control
Building automation systems
Industrial automation and control
Process control systems
Industrial automation and control
Smart grid communication
Communication and interface
Security systems
Electronic system design
Instrumentation
Electronic system design
FAE Expert Insights
"I have deployed RSM485 in hundreds of industrial automation and building automation projects. This integrated isolated RS-485 transceiver is excellent for reliable communication in noisy environments. The most significant advantage is the elimination of external isolation power supply - simply connect 5V or 3.3V to the logic side, and the module handles all isolation power generation internally. This saves significant PCB space and reduces BOM cost. In one large building management system with over 300 RS-485 nodes, we used RSM485 throughout the network. The 2500VDC isolation proved essential in this installation with multiple ground references across different building zones. The automatic flow control simplifies software design - no need to manually control driver enable. For any isolated RS-485 application, I strongly recommend RSM485 for its reliability and ease of use."
No external isolation power needed, automatic flow control, excellent noise immunity
— Wang Hua, BeiLuo
Frequently Asked Questions
What is the maximum number of nodes on RS-485 bus with RSM485?
The RSM485 supports up to 256 nodes on a single RS-485 bus segment. This high node count is achieved through high-input-impedance receiver design (1/8 unit load). For larger networks, use RS-485 repeaters or bridges to create multiple bus segments. In practice, most industrial RS-485 networks have 32-64 nodes for optimal performance. The maximum bus length is 1200m at lower data rates (up to 100Kbps), decreasing at higher speeds.
RSM485 supports up to 256 nodes. Use repeaters for larger networks or longer distances.
What is the maximum bus length with RSM485?
The maximum RS-485 bus length with RSM485 depends on data rate: 1) 100Kbps and below: up to 1200m; 2) 250Kbps: up to 500m; 3) 500Kbps: up to 250m. These lengths assume proper bus termination (120 ohm resistors at both ends), twisted pair cable, and maximum 256 nodes. For longer distances, reduce data rate or use RS-485 repeaters. The RSM485's 500Kbps maximum speed is suitable for most industrial automation applications.
Maximum bus length 1200m at 100Kbps, 250m at 500Kbps. Use proper termination for reliable operation.
What is automatic flow control in RSM485?
The RSM485 features automatic flow control (also called auto-direction control) that eliminates the need for software to manually control the driver enable signal. The module automatically detects when data is being transmitted and enables the driver, then disables it when transmission is complete. This simplifies software design and prevents bus contention issues that can occur with manual control. The automatic flow control ensures proper timing and reduces software complexity, making RSM485 easier to implement than traditional RS-485 transceivers requiring manual direction control.
Automatic flow control eliminates manual driver enable control, simplifying software design and preventing bus contention.
What is the isolation voltage of RSM485?
The RSM485 provides 2500VDC galvanic isolation between the logic side (microcontroller) and the bus side (RS-485 network). This high isolation voltage effectively protects sensitive control electronics from ground loops, common-mode noise, and high-voltage faults on the RS-485 bus. The 2500VDC isolation exceeds the requirements of most industrial and commercial applications, providing excellent protection in harsh environments with multiple ground references or electrical noise.
2500VDC isolation provides excellent protection against ground loops and noise in industrial environments.
What is the data rate of RSM485?
The RSM485 supports data rates up to 500Kbps, which is suitable for most industrial automation and building automation applications. At 500Kbps, the maximum bus length is approximately 250m. For longer distances, lower data rates can be used: 250Kbps supports up to 500m, and 100Kbps supports up to 1200m. The module automatically handles the data rate set by the host microcontroller, making it easy to integrate into existing systems. The 500Kbps maximum speed provides good balance between communication speed and bus length for typical industrial applications.
500Kbps maximum suitable for industrial automation. Use lower rates for longer distances.