SLUAB39 January   2026 BQ76905 , BQ76907 , BQ769142 , BQ76920 , BQ76930 , BQ76940 , BQ76942 , BQ76952 , BQ76972

 

  1.   1
  2.   Abstract
  3. 1Introduction to the low-side/high-side protection solutions
  4. 2Short-circuit protection results in overvoltage damage to DFET
    1. 2.1 Low-side protection solution
    2. 2.2 High-side protection solution
    3. 2.3 Summary
  5. 3Short-circuit protection results in overtemperature damage to DFET
    1. 3.1 Low-side protection solution
    2. 3.2 High-side protection solution
    3. 3.3 Summary
  6. 4Conclusion
  7. 5References

2.1 Low-side protection solution

To simplify the analysis, the parasitic inductance on the load side and the battery side are equivalent to L1 and L2 respectively in the article.

Figure 2-1 shows the equivalent circuit of the low-side protection solution after DFET short-circuit protection is turned off.

Low-side protection solution-the discharge tube DFET shutdown equivalent circuit Figure 2-1 Low-side protection solution-the discharge tube DFET shutdown equivalent circuit

After the short-circuit protection, DSG turns off. The current flowing through L1 lacks freewheeling loop, quickly reducing from Io to zero. Consequently, a substantial induced voltage is generated across L1:

Equation 1. V L 1 = L 1 d I O d t

and the current flowing through L2 also decreases rapidly from Io to zero because there is no freewheeling loop for the current across L2. Thus, a substantial induced voltage is also generated across L2:

Equation 2. V L 2 = L 2 d I O d t

Therefore, the voltage at two terminals of DS can be expressed by the following equation:

Equation 3. V D S _ L S = V L 1 + V L 2 + V b a t = L 1 d I O d t + L 2 d I O d t + V b a t