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AN1288: Si828x external enhancement circuits
The Si828x isolated gate drivers fulfill the demands of many high voltage power applications. The Si828x series has a robust gate drive capability and includes protection circuits that maximize system efficiency for reliable operation.
For larger systems that require very large or multiple parallel switching devices, and for systems (such as SiC FET) that operate at a high switching speed, additional circuits comprised of low-cost external components can extend the Si828x capabilities. For example, it’s possible to increase the effective output current to drive larger SiC FET/IGBT modules or to adapt the Si828x to drive and protect higher switching speed SiC FET devices.
In this application note, you can explore the circuit enhancements and their associated performance improvements, including:
- A current drive booster which will increase gate current drive above 20 A.
- Circuitry for reducing DESAT protection response time below 1 µs while maintaining robust noise immunity.
- A DESAT threshold adjustment to enable a threshold below the nominal 7 V.
- A method of adjusting the soft shutdown time in the event of a fault.
- An external enhancement of the internal Miller clamp, improving the suppression. of the Miller spike which can occur when the external transistor is turned off.