MXR485
High-reliability RS-485 transceiver with 50Mbps data rate, ±15kV ESD protection, and radiation tolerance.
Product Overview
Description
The MXR485 is a robust RS-485/RS-422 transceiver featuring data rates up to 50Mbps and ±15kV ESD protection for harsh environments.
With extended temperature range, radiation tolerance options, and fault-protected outputs, it's ideal for aerospace and military communication networks.
The device includes fail-safe circuitry, hot-swap capability, and supports up to 256 nodes on a single bus.
Product Series
MXR
Primary Application
Satellite communication
Key Features
- High data rate up to 50Mbps
- ±15kV ESD protection
- Supports up to 256 nodes
- ±60V fault protection
- Fail-safe receiver
- Hot-swap capability
- Radiation tolerance to 100krad(Si)
- Extended temperature range
Specifications
| Data Rate | Up to 50Mbps |
|---|---|
| ESD Protection | ±15kV HBM |
| Nodes | Up to 256 |
| Supply Voltage | 3.3V or 5V |
| Common Mode Range | -7V to +12V |
| Fault Protection | ±60V |
| Radiation Tolerance | 100 krad(Si) optional |
| Temperature Range | -55°C to +125°C |
| Package | CERDIP-8, SOIC-8, QFP-16 |
Applications
Satellite communication
Communication and interface
Military vehicle networks
Automotive and EV electronics
Industrial automation
Industrial automation and control
Avionics data buses
Electronic system design
Test equipment
Electronic system design
Power system monitoring
Electronic system design
FAE Expert Insights
"The MXR485 is my go-to RS-485 transceiver for aerospace and military applications. The ±15kV ESD protection is excellent - I've seen it survive direct contact discharges in field testing. The ±60V fault protection is valuable for military vehicle applications where wiring faults can occur. In one satellite design, we used this part for the payload-to-bus communication link at 10Mbps over 50m cable with excellent signal integrity. The fail-safe feature ensures the receiver outputs a defined state (high) when the bus is idle or open - this prevents false triggering in control systems. For radiation-tolerant designs, the 100krad option covers most LEO and GEO missions. One tip: for long buses, use twisted pair cable with proper termination at both ends. The 120Ω termination resistors should match the cable characteristic impedance. For multi-drop networks, keep stub lengths (transceiver to main bus) under 0.3m to minimize reflections."
Robust RS-485 transceiver for aerospace communication networks
— Dr. Sun Lei, BeiLuo
Frequently Asked Questions
What is the difference between RS-485 and RS-422?
RS-485 and RS-422 use the same differential signaling but differ in topology: RS-485 supports multi-drop (up to 256 transceivers on one bus) with half-duplex or full-duplex operation. RS-422 is point-to-point only (1 driver, up to 10 receivers) with full-duplex. RS-485 drivers can be disabled (tri-state) to share the bus, while RS-422 drivers are always enabled. RS-485 is used for industrial networks, DMX512 lighting control. RS-422 is used for point-to-point links requiring high noise immunity. Both use differential signaling with similar voltage levels. Mxtronics MXR485 supports both modes with proper configuration.
Use RS-485 for multi-drop networks. Use RS-422 for point-to-point links. Both offer excellent noise immunity.
How do I properly terminate an RS-485 bus?
RS-485 bus termination is critical for signal integrity: 1) Place 120Ω termination resistors at both ends of the bus (not at every node). 2) Match termination to cable characteristic impedance (typically 100-120Ω for twisted pair). 3) Use resistor power rating adequate for worst-case power dissipation (typically 0.25W). 4) For short buses (<10m) at low speeds (<100kbps), termination may be optional. 5) AC termination (120Ω + 100nF in series) can reduce power consumption but complicates design. 6) Failsafe biasing resistors (pull-up to A, pull-down to B) ensure idle state when all drivers are disabled. Proper termination prevents reflections that cause signal integrity issues.
Terminate both ends with 120Ω. Match cable impedance. Use failsafe biasing for idle state definition.
What cable should I use for RS-485?
RS-485 cable recommendations: Use twisted pair cable with characteristic impedance of 100-120Ω. Shielded twisted pair (STP) provides better noise immunity than unshielded (UTP). For aerospace applications, use Teflon-insulated cable rated for temperature and radiation. Cable gauge: 24-26 AWG for typical distances, larger gauge (20-22 AWG) for long distances (>500m). Twisted pair reduces magnetic coupling between wires. Shield reduces capacitive coupling from external noise sources. Connect shield to ground at one end only (typically at master) to prevent ground loops. For critical applications, use double-shielded cable with foil and braid.
Use 100-120Ω twisted pair. Use shielded for noisy environments. Connect shield at one end only.
How do I implement failsafe in RS-485?
RS-485 failsafe ensures receiver outputs defined state when bus is idle or open. Methods: 1) External failsafe biasing: Add pull-up resistor (typically 560Ω-1kΩ) from A to VCC and pull-down resistor from B to ground. Creates ~200mV differential when idle. 2) Internal failsafe: MXR485 includes internal failsafe - outputs logic high when bus is idle or open. 3) Termination with failsafe: Combine termination and biasing resistors. External biasing recommended for long buses (>100m) or many nodes. Internal failsafe sufficient for most applications. Failsafe prevents false triggering when all drivers are disabled (bus idle state).
Use internal failsafe for most applications. Add external biasing for long buses or critical applications.
What is hot-swap capability in RS-485?
Hot-swap capability allows inserting or removing nodes from a powered RS-485 bus without disrupting communication. MXR485 hot-swap feature: 1) Prevents driver activation during power-up until supply is stable. 2) Prevents bus disturbance when node is inserted. 3) Ensures receiver is in high-impedance state during insertion. Without hot-swap, inserting a node can cause bus contention and data errors. Important for systems requiring maintenance without shutdown, such as industrial control systems and satellite payloads. Hot-swap is implemented through controlled power-up sequencing and tri-state control logic.
Use hot-swap capable transceivers for systems requiring node insertion/removal without shutdown.