Technical Whitepaper of HMSR SMS Series Integrated Current Sensors
1. One-Sentence Description
The HMSR SMS series is a new generation of high-insulation integrated current sensors launched by LEM, adopting micro-core technology and open-loop Hall effect scheme, specifically designed to provide compact and reliable solutions for high-precision and high-voltage current detection in industrial and new energy fields.
2. Core Features
- Multi-range coverage: Wide range selection from 6-30A RMS (HMSR6-SMS to HMSR30-SMS)
- Dual protection mechanism: Built-in ±2.75 times rated current overcurrent detection (OCD) and configurable external OCD
- High isolation performance: Compliant with IEC 60950-1 standard, creepage/clearance distance up to 8mm, CTI 600 rating
- Low power consumption design: Operating current only 20-26mA, static power consumption below 0.5W
- Fast response: Step response delay <2μs, bandwidth up to 300kHz (-3dB)
- Anti-interference capability: Differential output suppresses common-mode noise, EMC performance passes IEC 61000-4-2/4 testing
3. Core Technical Specifications
| Parameter | Typical Value | Limit Value | Unit |
|---|---|---|---|
| Rated Current (IPN) | 6/8/10/15/20/30 | 75 | A |
| Sensitivity (SN) | 133.33-26.67 | - | mV/A |
| Response Time | 1.5-2μs | - | μs |
| Operating Voltage (Uc) | 5V±10% | 8V | V |
| Insulation Withstand Voltage | 4.95kV RMS | - | V |
| Operating Temperature | -40~125℃ | - | ℃ |
| Hysteresis Error | ±0.5% IPN | - | % |
4. The Story Behind the Chip
LEM spent three years researching and overcoming three core technologies:
- Nano-crystalline core process: Using FeSiBCu amorphous alloy with permeability >100k to effectively suppress external magnetic field interference
- Patented ASIC design: Integrates 24-bit ADC and digital calibration engine to achieve ±0.5% linearity (25℃)
- 3D packaging technology: 6mm ultra-thin SOIC16 package with thermal resistance as low as 18K/W, supporting 30A continuous current
5. Design Philosophy
- Modular architecture: Separated primary/secondary circuit design supports multi-layer PCB routing
- Thermal management optimization: Copper substrate heat dissipation path design, junction-to-ambient thermal resistance only 19℃/W
- Scalability: Flexible range configuration via Uref voltage divider network (e.g., HMSR30-SMS supports 3.3V/5V dual versions)
- Safety redundancy: Dual OCD protection + 20kA surge withstand capability meets strict Industry 4.0 requirements
6. Application Scenarios
- New energy field: Photovoltaic inverters (MPPT control), energy storage system battery monitoring
- Industrial automation: Servo motor drives, frequency converter current loop control
- Smart grid: Power quality analyzers, harmonic detection devices
- Automotive electronics: Electric vehicle charging piles (pending automotive certification), on-board chargers (OBC)
7. Unique Advantages
- Ultra-low zero drift: ±5μV/℃ (typical), far lower than similar products (industry average ±20μV/℃)
- Transient immunity: Withstands ±1kV/20kV/μs dv/dt surges, error recovery time <4μs
- Mixed-signal output: Provides both analog voltage (Uout) and digital OCD signals, simplifying system design
- Environmental features: Lead-free packaging, compliant with RoHS/REACH standards, supports halogen-free processes
8. Key Considerations for Engineers in Selection
- Range selection formula: IPM = IPN × 2.5 (e.g., 30A model can measure ±75A peak)
- Bandwidth matching principle: Switching frequency should be lower than BW×0.3 (e.g., 300kHz sensor fits 100kHz SMPS)
- PCB layout key points:
- Main current path should maintain <5cm straight routing
- Heat sink pads should connect to ground plane (recommended 6-layer 1oz copper thickness)
- Avoid routing sensitive signal lines under the sensor
- Calibration recommendations: Use LEM calibration fixtures for zero/gain calibration at 25℃
- Certification reference: For automotive applications, choose HMSR DA series (∑Δ modulation output)
Technical Highlights Summary
The HMSR SMS series integrates three core capabilities of ±8kV insulation, 30A continuous current handling, and 300kHz bandwidth within a 6mm height through innovative magnetic circuit design and advanced packaging technology, providing a revolutionary current detection solution for high-density power electronics systems. Its unique OCD architecture and anti-interference design are particularly suitable for harsh application scenarios in new energy and industrial automation fields.
