Schottky diodes are widely favored in power design applications due to their ultra-low forward voltage drop (0.15–0.4V) and ultra-fast switching speeds. They are especially common in switching power supplies (SMPS), lithium battery protection circuits, inverters, and other low-voltage, high-current systems.
However, improper application of Schottky diodes can lead to thermal failure, efficiency loss, and circuit instability. At Tonghua Electronics, a leader in electronic component manufacturing since 2010, we have extensive experience providing high-quality diodes, MOSFETs, and TVS devices optimized for robust power electronics design.
This article details the most common mistakes engineers make with Schottky diodes and how to avoid them to ensure reliable, efficient power design.
1. Ignoring Reverse Leakage Current
Schottky diodes exhibit higher reverse leakage current compared to standard PN junction diodes. This characteristic becomes critical in high-temperature or high-voltage conditions.
Common Mistake
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Designers may assume Schottky diodes behave like regular diodes and ignore leakage, causing excessive power dissipation and thermal runaway in compact designs.
How to Avoid
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Select a diode with a reverse leakage current rating suitable for your operating temperature.
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For high-temperature applications (>85°C), consider Schottky diodes specifically rated for low leakage.
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Implement proper heatsinking or thermal vias in PCB design to mitigate heat accumulation caused by leakage.
2. Overestimating Reverse Voltage Rating
Most Schottky diodes have limited reverse voltage, often below 200V. Using them beyond this limit can result in avalanche breakdown.
Common Mistake
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Engineers may use a low-voltage Schottky diode in circuits with transient spikes or inductive load switching, risking diode failure.
How to Avoid
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Check the maximum repetitive reverse voltage (VRRM) and include a margin of at least 20–30% above expected circuit voltage.
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Consider TVS diodes or RC snubbers to absorb voltage spikes and protect the Schottky diode.
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Always review the power supply’s startup, shutdown, and fault conditions for potential voltage surges.
3. Underestimating Forward Current and Thermal Dissipation
Although Schottky diodes have low forward voltage drop, high current density can generate substantial heat, particularly in compact PCBs.
Common Mistake
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Designers may overlook the junction temperature rise, leading to reduced diode lifespan or immediate thermal failure.
How to Avoid
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Calculate power dissipation: ( P = I_{F} \times V_{F} ).
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Ensure adequate thermal management, including:
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Copper pours or thermal pads on PCB.
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Heat sinks for high-current applications.
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Airflow optimization in enclosure design.
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Select diodes with higher current ratings than the expected continuous load.
4. Improper PCB Layout
PCB layout significantly impacts Schottky diode reliability. Poor layout can cause excessive EMI, voltage overshoot, and hotspot formation.
Common Mistake
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Placing Schottky diodes far from power nodes or using long, thin traces that add resistance and inductance.
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Neglecting decoupling capacitors near the diode in SMPS applications.
How to Avoid
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Use short, wide traces for high-current paths.
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Place the diode close to switching nodes for minimal parasitic inductance.
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Implement ground planes and thermal vias to enhance both electrical and thermal performance.
5. Neglecting Reverse Recovery Time Considerations
Schottky diodes have ultra-fast switching, but in high-frequency circuits, even small deviations in reverse recovery can affect switching efficiency and EMI.
Common Mistake
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Designers may not account for circuit parasitics and assume Schottky diodes have zero reverse recovery.
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Leads to ringing, voltage spikes, or cross-talk in sensitive circuits.
How to Avoid
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Verify reverse recovery characteristics in datasheets.
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Use Schottky diodes with low junction capacitance for high-speed applications.
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Consider snubber circuits or soft-switching techniques to minimize EMI.
6. Choosing the Wrong Package
Schottky diodes come in various packages (SMA, SMB, SMC, SOT-23, DO-41, DO-15, SOD-123, etc.), each with different thermal resistance and current handling capabilities.
Common Mistake
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Selecting a physically small package for high-current applications without considering thermal limits.
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Leads to rapid junction temperature rise and eventual diode failure.
How to Avoid
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Match the package to current load and PCB cooling capability.
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SMD packages like SMA/SMB may require thermal vias or copper pours for higher currents.
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Through-hole packages like DO-41/DO-15 can dissipate more heat but occupy more space.
7. Failing to Consider Parasitic Inductance and Capacitance
In high-speed switching applications, parasitic elements can cause voltage overshoot or oscillations, especially when combined with Schottky diodes’ low forward voltage.
Common Mistake
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Not accounting for trace inductance in high-frequency SMPS designs.
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Can lead to electrical overstress and component degradation.
How to Avoid
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Keep current paths short and wide.
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Use proper decoupling and bypass capacitors.
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Consider simulation tools to analyze transient behavior before prototyping.
8. Ignoring Lifecycle and Aging Effects
Even correctly applied Schottky diodes can degrade over time due to:
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High junction temperature
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Continuous high current
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Repeated voltage spikes
Common Mistake
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Using the same diode for years without considering derating factors, resulting in unexpected failures in critical power systems.
How to Avoid
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Implement conservative derating: operate diodes at 50–70% of rated voltage/current.
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Regularly inspect and replace diodes in high-reliability systems.
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Choose diodes from reputable suppliers like Tonghua Electronics with consistent quality testing.
FAQ: Schottky Diode in Power Design
Q1: Can Schottky diodes be used in high-voltage applications?
A: Only if the reverse voltage rating exceeds maximum system voltage, otherwise use TVS or PN diodes for protection.
Q2: Why does my Schottky diode heat up under moderate current?
A: Likely due to reverse leakage current, poor thermal management, or undersized package.
Q3: Are all SMD Schottky diodes suitable for SMPS?
A: No, low-capacitance, low-inductance SMD packages are ideal for high-frequency SMPS, while some packages are better for low-frequency or low-current designs.
Q4: How can I reduce EMI when using Schottky diodes?
A: Use snubber circuits, short PCB traces, decoupling capacitors, and choose diodes with low junction capacitance.
Q5: Should I derate Schottky diodes?
A: Yes, derating by 20–30% ensures longevity and reduces risk of thermal and electrical failure.
Conclusion
Schottky diodes are indispensable in modern power electronics due to their low forward voltage drop and fast switching speed. However, their unique characteristics demand careful consideration in reverse voltage, leakage current, thermal management, PCB layout, and package selection.
At Tonghua Electronics, we provide high-quality, reliable Schottky diodes in a variety of packages (SMA, SMB, SMC, SOD-123, SOT-23, DO-41, DO-15) with strict quality control to ensure optimal performance in SMPS, lithium battery protection circuits, and low-voltage, high-current applications.
By avoiding common mistakes and implementing best practices outlined above, engineers can maximize efficiency, reliability, and longevity of their power designs.
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Tonghua Electronics Co, Ltd.