SLUAAY0 September   2025 UCC57102 , UCC57102-Q1 , UCC57102Z , UCC57102Z-Q1 , UCC57108 , UCC57108-Q1 , UCC57132 , UCC57132-Q1 , UCC57138 , UCC57138-Q1 , UCC57142 , UCC57142-Q1 , UCC57148 , UCC57148-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2TI Non-Isolated SiC MOSFET Gate Drivers Overview
  6. 3SiC MOSFET Gate Driver Design Considerations
    1. 3.1 Undervoltage Lockout (UVLO)
    2. 3.2 Negative Bias Supply (Bipolar Drive)
    3. 3.3 Short-Circuit Protection
      1. 3.3.1 Desaturation Protection
      2. 3.3.2 Overcurrent Protection
      3. 3.3.3 Soft Turn-Off
  7. 4PFC CCM Boost Low-Side Gate Driver Example
    1. 4.1 Gate Driver Requirements
    2. 4.2 Gate Driver Selection
    3. 4.3 Gate Driver Power Dissipation
  8. 5Summary
  9. 6References

3.3.1 Desaturation Protection

Desaturation (DESAT) protection is a type of short-circuit protection that is voltage-based. Figure 3-3 shows a typical DESAT circuit.

When the SiC MOSFET is on during normal operation, then ID is within specifications, keeping the drain voltage low ( V D S = I D × R D S ( o n ) ) . This keeps the high-voltage blocking diode (DHV) forward-biased, allowing the current sourced from ICHG (indicated in the figure by the down arrow from VDD) to flow through DHV without charging the blanking capacitor (CBLK).

When a short-circuit occurs, then large ID causes the drain voltage to rise high. This causes DHV to become reverse-biased, blocking the flow of current sourced from ICHG. The charging current now charges CBLK, and once the CBLK voltage exceeds the internal DESAT voltage threshold (VDESAT), the comparator indicates that short-circuit is detected.

The time to charge the capacitor is the blanking time, which can be calculated in Equation 1 by using the internal VDESAT and ICHG. Reducing the capacitor value can shorten the time to trigger DESAT protection, which can be useful for SiC MOSFET applications.

Equation 1. t B L K = V D E S A T × C B L K I C H G

While the internal VDESAT is set by design, the drain voltage needed to trigger DESAT protection can be adjusted by modifying the components in series between the DESAT pin and SiC MOSFET drain, which can be calculated in Equation 2. VDESAT(actual) refers to the drain voltage that triggers DESAT.

Equation 2. V D E S A T ( a c t u a l ) = V D E S A T - ( I C H G × R B L K ) - V F ( D H V )
DESAT Protection Circuit Figure 3-3 DESAT Protection Circuit