Power MOSFET Avalanche Guidelines: Ensuring Reliable Operation

Understanding avalanche capability in power MOSFETs is crucial for designing robust power electronics systems. This technical guide explores the key parameters, testing methodologies, and design considerations for managing avalanche events effectively.

Fundamentals of Avalanche Behavior

Avalanche breakdown occurs when the voltage across a MOSFET’s drain-source junction exceeds its rated breakdown voltage (V_BRDSS). During this phenomenon, the device must safely dissipate the stored energy without suffering permanent damage.

Parameter	Symbol	Description	Critical Factors
Avalanche Energy	E_AS	Maximum energy absorbable during avalanche	Temperature, current density
Avalanche Current	I_AS	Maximum current during avalanche event	Pulse width, duty cycle
Breakdown Voltage	V_BRDSS	Voltage at which avalanche occurs	Temperature coefficient, design margin

Critical Design Considerations

Temperature Effects on Avalanche Operation

Temperature significantly impacts a MOSFET’s avalanche capability. As junction temperature increases, both the breakdown voltage and avalanche energy handling capability typically decrease.

Critical Warning: Operating MOSFETs near their maximum temperature rating during avalanche events can lead to catastrophic failure. Always maintain adequate thermal margins in your design.

Design Guidelines for Avalanche-Rated Applications

Always calculate the maximum possible avalanche energy in your application
Include a safety margin of at least 30% for avalanche energy ratings
Consider the impact of parasitic inductances in your PCB layout
Implement proper thermal management solutions
Use snubber circuits when necessary to limit voltage spikes

Winsok’s Advanced Avalanche-Rated MOSFETs

Winsok’s latest generation of power MOSFETs features enhanced avalanche capability through advanced cell design and optimized silicon processing. These devices offer:

Superior avalanche energy handling capacity
Excellent thermal performance
Consistent breakdown voltage across temperature
Comprehensive datasheet specifications for avalanche parameters

Avalanche Testing Methodologies

Proper avalanche testing is essential for validating MOSFET reliability in demanding applications. Here’s a comprehensive overview of industry-standard testing approaches and best practices.

Unclamped Inductive Switching (UIS) Test

The UIS test is the primary method for evaluating a MOSFET’s avalanche capability. This test simulates worst-case avalanche conditions by forcing the device into avalanche mode using an inductor to store energy.

Test Parameter	Typical Range	Considerations
Test Current (I_AS)	1A – 100A	Device rating dependent
Inductance (L)	100µH – 1mH	Energy storage calculation critical
Pulse Width	50µs – 500µs	Temperature rise consideration
Case Temperature	25°C – 150°C	Multiple temperature points needed

Test Setup Requirements

High-precision current measurement capability
Fast voltage probes with adequate bandwidth
Temperature-controlled test fixture
Accurate timing control for pulse generation
Protection circuits for equipment safety

Laboratory Safety Notice: Avalanche testing involves high voltages and currents. Always follow proper safety protocols and use appropriate personal protective equipment (PPE).

Data Analysis and Interpretation

Key Parameters to Monitor

During avalanche testing, several critical parameters must be carefully monitored and analyzed:

Peak avalanche current and duration
Voltage waveform characteristics
Temperature rise during avalanche
Recovery characteristics post-avalanche
Device degradation indicators

Failure Analysis Techniques

Failure Mode	Indicators	Preventive Measures
Thermal Runaway	Sudden current spike, device shorting	Proper thermal design, current limiting
Gate Oxide Breakdown	Increased leakage current, gate failure	Gate voltage control, proper driving
Hot Carrier Degradation	Gradual Vth shift, increased RDS(on)	Operating within safe area

Expert Testing Support from Olukey

As Winsok’s authorized distributor, Olukey provides comprehensive testing support and validation services:

Advanced testing facilities with state-of-the-art equipment
Expert analysis of test results and recommendations
Custom testing solutions for specific applications
Detailed reporting and documentation

Schedule Your Device Testing

Practical Implementation Guidelines

Design Verification Checklist

Before finalizing your design, ensure these critical aspects are addressed:

Calculate maximum possible avalanche energy in the application
Verify temperature rise under worst-case conditions
Implement appropriate derating factors
Consider environmental factors affecting performance
Plan for regular maintenance and monitoring

Design Tip: Always validate your design under various operating conditions and temperatures. Winsok’s MOSFETs undergo rigorous testing to ensure reliable performance across their entire operating range.

For detailed specifications and availability of Winsok’s avalanche-rated MOSFETs, contact Olukey’s technical support team. Our engineers can help you select the optimal device for your application and provide comprehensive design support.