TIDUF43 Design guide

TIDUF43 August 2024

3.3 Short-Circuit Protection

The TPS1213-Q1 features configurable short-circuit protection. R8 (R_ISCP) sets the SC protection threshold, whose value can be calculated using Equation 5.

Equation 5.

R_{I S C P} (Ω) = \frac{I_{S C} \times R_{D S (o n)} - 19 m V}{2 μ A}

where

R_DS(on) = 1.06mΩ

For pre-release TPS1213-Q1 silicon, use Equation 6 instead of Equation 5.

Equation 6.

R_{I S C P} (Ω) = \frac{I_{S C} \times R_{D S (o n)} - 10 m V}{2 μ A}

To set 100A as the SC protection threshold, R8 is calculated to be 48kΩ using Equation 6. The closest standard value of 47kΩ was selected.

By leaving C8 (C_TMR) depopulated, a fast SC response time less than 6μs is selected. Nonetheless, refer to Equation 7 to modify the short-circuit response time.

Equation 7.

C_{T M R} = \frac{I_{T M R} \times t_{S C}}{1.1}

where

I_TMR is internal pullup current of 80μA
t_SC is the short-circuit response time

R10 (R_TMR) serves to keep the TMR pin clamped low for latch-off behavior during SC events. nFLT asserts low at the same time, requiring the user to attempt to clear the latch using S2 or S3. To change from latch-off to auto-retry behavior, refer to Equation 8 for automatically recovering from SC events:

Equation 8.

t_{R E T R Y} = 22.7 \times 10^{6} \times C_{T M R}