MXI124
Precision isolation amplifier with 5kVrms isolation, 0.05% linearity, and radiation tolerance for high-voltage sensing.
Product Overview
Description
The MXI124 is a precision isolation amplifier featuring 5kVrms reinforced isolation with excellent linearity of 0.05%.
With isolation mode rejection of 140dB and radiation tolerance options, it's ideal for high-voltage sensing in aerospace and industrial systems.
The device provides galvanic isolation between input and output, protecting low-voltage circuits from high-voltage transients.
Product Series
MXI
Primary Application
Motor current sensing
Key Features
- 5kVrms reinforced isolation
- Excellent linearity 0.05%
- High IMRR 140dB
- 100kHz bandwidth
- Radiation tolerance to 50krad(Si)
- Hermetic ceramic packages
- Extended temperature range
- UL and VDE safety certifications
Specifications
| Isolation Voltage | 5kVrms reinforced |
|---|---|
| Linearity | 0.05% |
| Gain Error | 0.1% |
| Offset | 2mV |
| Bandwidth | 100kHz |
| IMRR | 140dB at 60Hz |
| Rise Time | 5μs |
| Radiation Tolerance | 50 krad(Si) optional |
| Temperature Range | -55°C to +125°C |
| Package | CERDIP-16, QFP-24 |
Applications
Motor current sensing
Motor drive and control systems
Power supply monitoring
Power conversion and supply
High-voltage instrumentation
Electronic system design
Medical equipment
Medical electronics
Industrial controls
Industrial automation and control
Battery management systems
Battery and charging management
FAE Expert Insights
"The MXI124 is my standard recommendation for high-voltage isolation in aerospace and industrial systems. The 5kVrms isolation rating provides excellent safety margin for 1000V+ systems. In one satellite power system design, we used this part to monitor the 120V battery bus from the low-voltage control electronics. The 140dB IMRR effectively rejected the high common-mode transients during switching. The 0.05% linearity is excellent for current sensing - I've achieved better than 0.5% accuracy in motor current monitoring applications. The 100kHz bandwidth is sufficient for most power electronics applications. For radiation-tolerant designs, the 50krad rating covers most LEO missions. One important consideration: the isolation barrier requires careful PCB layout with adequate creepage and clearance distances - typically 8mm for 5kVrms. Always follow the datasheet layout recommendations."
High-performance isolation amplifier for high-voltage aerospace systems
— Dr. Zhao Feng, BeiLuo
Frequently Asked Questions
How does isolation amplifier work?
Isolation amplifiers transmit analog signals across an isolation barrier using one of several techniques: 1) Transformer isolation - modulates signal onto carrier, couples through transformer, demodulates on output side. 2) Capacitive isolation - uses capacitive coupling with modulation. 3) Optical isolation - uses LED and photodetector (less common for precision). MXI124 uses transformer isolation with sigma-delta modulation for excellent linearity. The input signal is digitized by a sigma-delta modulator, transmitted across the isolation barrier as digital pulses, then reconstructed by a DAC on the output side. This provides excellent accuracy and linearity while maintaining isolation.
Transformer isolation provides best linearity. Choose based on isolation voltage and bandwidth requirements.
What is IMRR and why is it important?
IMRR (Isolation Mode Rejection Ratio) measures how well the isolation amplifier rejects common-mode transients across the isolation barrier. MXI124 IMRR is 140dB at 60Hz, meaning a 1000V common-mode transient produces only 0.1mV output error. This is critical in power electronics where high dv/dt transients occur during switching. High IMRR ensures accurate measurement even with large common-mode noise. For motor drives, the common-mode voltage can swing rapidly with PWM switching - high IMRR prevents this from corrupting the current measurement. Always check IMRR at the frequencies present in your application.
Select isolation amps with high IMRR at your switching frequencies. 140dB provides excellent rejection.
How do I power the isolated side of MXI124?
MXI124 requires isolated power for the input side. Options: 1) Use isolated DC-DC converter (like MXP34063RT with transformer) to generate isolated supply from main power. 2) Use dedicated isolated power module. 3) For some applications, the sensor being measured may provide power. The isolated supply must be referenced to the input common (not output ground). Typical power requirements: 5V at 10mA for input side. Output side can use system power. Ensure adequate isolation between input and output power supplies - don't share grounds. For high-reliability systems, consider isolated power supply redundancy.
Use isolated DC-DC converter to power input side. Ensure no ground connection between input and output supplies.
What PCB layout is required for 5kV isolation?
PCB layout for 5kV isolation requires: 1) Creepage distance (along surface): minimum 8mm for 5kVrms in pollution degree 2. 2) Clearance (through air): minimum 5mm. 3) Use slots or barriers to increase creepage if space limited. 4) Keep high-voltage traces on one side of isolation barrier, low-voltage on other. 5) No traces or copper under the isolation barrier region. 6) Use conformal coating to reduce pollution degree and allow smaller creepage. 7) Follow UL and IEC standards for your application. Mxtronics provides recommended PCB layouts in the datasheet.
Maintain 8mm creepage and 5mm clearance for 5kV. Use slots or conformal coating if space limited.
Can isolation amplifiers be used for current sensing?
Yes, isolation amplifiers are commonly used for high-side current sensing. Configuration: 1) Place current sense resistor in high-side of load. 2) Connect isolation amp input across sense resistor. 3) Isolation barrier separates high-voltage power side from low-voltage control side. 4) Output provides ground-referenced voltage proportional to current. Advantages: measures current without ground reference, rejects high common-mode voltage, provides safety isolation. For best accuracy, use four-wire (Kelvin) connection to sense resistor. MXI124's 140dB IMRR provides excellent accuracy even with switching noise. For motor drives, this is the preferred current sensing method.
Use for high-side current sensing in motor drives and power supplies. Use Kelvin connection for best accuracy.