SCHOTTKY BARRIER TYPE DIODE(CATHODE COMMAND) # Technical Documentation: KDR721S Schottky Barrier Diode
Manufacturer : KEC
Component Type : Schottky Barrier Diode
Document Version : 1.0
Date : October 26, 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The KDR721S is a surface-mount Schottky barrier diode designed for high-frequency, low-voltage applications where fast switching and low forward voltage drop are critical. Its primary use cases include:
* Power Supply Protection : Employed as a reverse polarity protection diode in DC input stages of power supplies, consumer electronics, and automotive systems. Its low forward voltage (Vf) minimizes power loss.
* Freewheeling/Clamping Diode : In switching regulator circuits (buck, boost) and motor drive circuits, it provides a path for inductive current when the main switch turns off, preventing voltage spikes and protecting MOSFETs or IGBTs.
* OR-ing Diode : Used in redundant power supply systems or battery backup circuits to allow current flow from the highest voltage source while isolating others, preventing back-feeding.
* Signal Demodulation/Rectification : Suitable for high-frequency signal rectification in RF detection circuits and mixer stages due to its fast recovery characteristics.
### 1.2 Industry Applications
* Consumer Electronics : Smartphones, tablets, laptops (for DC jack protection, USB power path management).
* Automotive Electronics : Infotainment systems, body control modules (BCM), lighting systems (for reverse battery protection and load dump suppression).
* Industrial Control : PLC I/O modules, sensor interfaces, low-voltage DC/DC converter modules.
* Telecommunications : Network switches, routers, and base station power subsystems.
* Renewable Energy : Solar charge controllers and low-power MPPT circuits.
### 1.3 Practical Advantages and Limitations
Advantages:
* Low Forward Voltage Drop (Vf) : Typically 0.55V at 1A, significantly lower than standard PN junction diodes (~0.7V), leading to higher efficiency and reduced heat generation.
* Fast Switching Speed : Virtually no reverse recovery time (trr), minimizing switching losses and enabling operation at high frequencies (up to several MHz).
* Low Leakage Current : Ensures good blocking performance in off-state conditions.
* SMD Package (SOD-123FL) : Saves board space and is compatible with automated assembly processes.
Limitations:
* Lower Reverse Voltage Rating : The maximum repetitive peak reverse voltage (VRRM) is typically 100V for this series, making it unsuitable for high-voltage applications (e.g., offline AC/DC converters).
* Higher Reverse Leakage vs. PN Diodes : Leakage current increases more significantly with temperature compared to standard diodes, which can be a concern in high-temperature environments.
* Sensitivity to Voltage Transients : Schottky diodes are generally more susceptible to damage from voltage surges (ESD, surge); external transient voltage suppression (TVS) may be required in harsh environments.
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## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
* Pitfall 1: Thermal Runaway Due to High Leakage
* Issue : At high ambient temperatures, reverse leakage current (IR) can increase substantially, causing additional power dissipation and further temperature rise.
* Solution : Carefully calculate worst-case power dissipation (P_diss = Vf * If_avg + VR * IR) at maximum junction temperature (Tj). Ensure adequate PCB copper area (thermal pad) for heat sinking. Derate the diode's current capability at high temperatures.
* Pitfall
