MXI48520
High-isolation RS-485 transceiver with integrated isolated DC-DC converter, 5kV isolation, and extended temperature range for harsh environments.
Product Overview
Description
The MXI48520 is a fully isolated RS-485 transceiver featuring an integrated isolated DC-DC converter, eliminating the need for external isolation power supplies. The device provides 5kVrms galvanic isolation between the logic and bus sides, ensuring safety and noise immunity in high-voltage industrial and aerospace applications.
With data rates up to 20Mbps and enhanced ESD protection (±15kV HBM), this transceiver supports high-speed industrial networks in demanding environments. The integrated DC-DC converter generates the isolated power supply, simplifying system design and reducing component count.
The device operates from a single 3.3V or 5V supply and includes fail-safe circuitry to ensure a known bus state when inputs are open or shorted. Available in hermetic ceramic packages for aerospace applications with full military temperature range support.
Product Series
MXI
Primary Application
Satellite communication systems
Key Features
- 5kVrms galvanic isolation
- Integrated isolated DC-DC converter
- Up to 20Mbps data rate
- ±15kV ESD protection
- ±60V fault protection
- 256 node capability
- Fail-safe receiver operation
- Extended temperature range -55°C to +125°C
- Radiation tolerance option 50krad(Si)
- Hermetic ceramic packages available
Specifications
| Data Rate | Up to 20 Mbps |
|---|---|
| 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 | 50 krad(Si) optional |
| Temperature Range | -55°C to +125°C |
| Isolation | 5kVrms with integrated DC-DC |
| Package | CERDIP-16, QFP-20 |
Applications
Satellite communication systems
Communication and interface
Military vehicle networks
Automotive and EV electronics
Industrial automation
Industrial automation and control
Power generation monitoring
Electronic system design
Avionics data buses
Electronic system design
High-voltage isolated communication
Communication and interface
FAE Expert Insights
"The MXI48520 is an excellent solution for isolated RS-485 communication in aerospace and defense applications. The integrated DC-DC converter eliminates the need for external isolated power supplies, significantly simplifying system design and reducing board space. In my experience supporting satellite communication systems, the 5kV isolation provides excellent safety margins for high-voltage environments. The 20Mbps data rate supports modern high-speed industrial networks. The radiation-tolerant version has been successfully qualified for LEO satellite missions. One key advantage is the fail-safe operation - the receiver outputs a known state when the bus is idle or open, preventing system lockups. For aerospace applications, I recommend the hermetic CERDIP-16 package for maximum reliability. The device has been used successfully in satellite payload data links, military vehicle communication systems, and industrial control networks requiring isolation."
Fully isolated RS-485 with integrated DC-DC for simplified high-isolation designs
— Dr. Chen Ming, BeiLuo
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MxtronicsFrequently Asked Questions
How does the integrated DC-DC converter work?
The MXI48520 includes an integrated isolated DC-DC converter that generates the isolated power supply for the bus side. The converter uses transformer isolation to create a galvanically isolated 3.3V or 5V supply from the input voltage. This eliminates the need for external isolated DC-DC converters or isolated power supplies. The integrated converter is optimized for the transceiver power requirements, providing efficient operation with minimal external components. Only input and output filter capacitors are required. The converter operates at high frequency (typically 100-200MHz) allowing small integrated transformers.
The integrated DC-DC simplifies isolated RS-485 design. No external isolated power supply needed.
What are the PCB layout considerations for isolated transceivers?
PCB layout for isolated transceivers requires attention to creepage and clearance distances. Key guidelines: 1) Maintain minimum 8mm creepage and 5mm clearance for 5kV isolation. 2) Use slots or barriers under the device to increase creepage distance. 3) Keep logic side traces on one side of the isolation barrier, bus side on the other. 4) Place decoupling capacitors close to supply pins on both sides. 5) Use solid ground planes on both sides, do not connect across isolation barrier. 6) Minimize capacitive coupling across isolation by keeping traces on opposite sides well separated. 7) Follow the evaluation board layout for best practices.
Follow the MXI48520 layout guide for proper creepage, clearance, and isolation barrier design.
Can I use the MXI48520 in 3.3V systems?
Yes, the MXI48520 supports both 3.3V and 5V logic levels. The device has a VCC pin for logic side supply (3.3V or 5V) and automatically generates the appropriate isolated voltage for the bus side. The logic inputs are TTL/CMOS compatible with the selected VCC voltage. The RS-485 bus side operates at standard RS-485 levels (differential +/-1.5V to +/-6V) regardless of logic side voltage. This allows the MXI48520 to interface 3.3V microcontrollers with standard 5V RS-485 networks without level translation.
Connect VCC to 3.3V for 3.3V logic systems. Device handles level translation automatically.
What is the maximum bus length for 20Mbps operation?
At 20Mbps, the maximum RS-485 bus length is limited by signal integrity and propagation delay. Typical maximum lengths: 20Mbps - 10-15 meters (short bus, high-speed), 10Mbps - 30-50 meters, 1Mbps - 100-200 meters, 100kbps - 500-1000 meters. For 20Mbps operation, use proper termination (120Ω at both ends), minimize stub lengths (<0.3m), use twisted pair cable with proper impedance (120Ω), and ensure good signal quality. For longer distances, reduce data rate or use repeaters. The MXI48520's high drive strength and excellent signal integrity support maximum lengths at each data rate.
Keep bus under 15m for 20Mbps. Reduce data rate or use repeaters for longer distances.
How do I test the isolation barrier?
The MXI48520 isolation barrier is factory tested to 5kVrms per UL1577. For production testing, a reduced voltage (typically 1.2x working voltage) is applied for 1 second to verify isolation integrity without degrading the barrier. For system-level testing: 1) Hipot test - Apply 3-5kVAC for 60 seconds between logic and bus sides (isolated from ground). Current should be <5mA. 2) Insulation resistance test - Apply 500VDC and measure resistance (>1GΩ expected). 3) Functional test - Verify communication across isolation with full data rate. Do not exceed 5kVrms as this may damage the isolation barrier. Follow IEC 60747-5-5 or UL1577 for qualification testing.
Use production hipot testing at reduced voltage. Follow standards for qualification testing.