35V 20A Schottky Common Cathode Diode in a D2-Pak package# Technical Documentation: 20CTQ035S Schottky Rectifier
## 1. Application Scenarios
### Typical Use Cases
The 20CTQ035S is a dual center-tapped Schottky rectifier primarily employed in high-frequency switching power conversion applications. Typical implementations include:
Power Supply Circuits
- Switch-mode power supply (SMPS) output rectification
- DC-DC converter circuits in both buck and boost configurations
- Freewheeling diodes in inductive load applications
- OR-ing diodes in redundant power systems
Specific Implementation Examples
- Forward Converters : Used as output rectifiers in single-transistor forward converters operating at 100-500 kHz
- Flyback Converters : Secondary-side rectification in discontinuous conduction mode flyback designs
- Synchronous Rectification : Parallel operation with MOSFETs in high-efficiency designs
### Industry Applications
Telecommunications
- 48V DC input power rectification in base station power systems
- Server power supply units (PSUs) for data centers
- Network equipment power distribution
Automotive Electronics
- Electric vehicle (EV) onboard chargers
- DC-DC converters in 12V/48V automotive systems
- Battery management system (BMS) power circuits
Industrial Equipment
- Motor drive circuits
- Uninterruptible power supplies (UPS)
- Industrial automation power modules
Consumer Electronics
- High-efficiency laptop adapters
- Gaming console power supplies
- LED driver circuits
### Practical Advantages and Limitations
Advantages
- Low Forward Voltage : Typical VF of 0.55V at 10A reduces conduction losses by 30-40% compared to standard PN junction diodes
- Fast Recovery : Trr < 35ns enables efficient operation at switching frequencies up to 500 kHz
- High Temperature Operation : Capable of sustained operation at junction temperatures up to 150°C
- Dual Common-Cathode Configuration : Simplifies center-tapped transformer implementations
Limitations
- Reverse Leakage Current : Higher than PN diodes, particularly at elevated temperatures (up to 5mA at 125°C)
- Voltage Rating : Maximum 35V VRRM limits applications to low-voltage systems
- Thermal Management : Requires careful heatsinking at maximum current ratings
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Thermal Management Issues
- Pitfall : Inadequate heatsinking leading to thermal runaway
- Solution : Implement proper thermal vias, copper pours, and consider forced air cooling for currents above 15A
Voltage Spikes
- Pitfall : Voltage overshoot exceeding VRRM during switching transitions
- Solution : Incorporate snubber circuits and ensure proper PCB layout to minimize parasitic inductance
Current Sharing in Parallel Operation
- Pitfall : Unequal current distribution when paralleling devices
- Solution : Use separate current-limiting resistors or implement active current balancing
### Compatibility Issues with Other Components
Gate Driver Circuits
- Compatible with most modern PWM controllers (TI UCC28C4x, Infineon ICE5x, etc.)
- May require additional gate resistance when used with ultra-fast switching MOSFETs
Transformer Design
- Optimized for ferrite core transformers with switching frequencies 100-500 kHz
- Requires careful consideration of leakage inductance to minimize voltage spikes
Capacitor Selection
- Works well with low-ESR ceramic and polymer capacitors
- Bulk capacitance requirements reduced due to fast recovery characteristics
### PCB Layout Recommendations
Power Path Layout
- Use wide, short traces for anode and cathode connections (minimum 80 mil width for 10A)
- Implement star-point grounding for center tap connection
- Maintain clearance of at least 120 mil between high-voltage and low-voltage sections
