The dynamic current limit function maintains the output voltage regulation when the power source becomes weaker. The maximum current allowed through the switch depends on the voltage applied at the input terminal of the TPS6306x devices. Figure 8-5 shows this dependency, and the I_SW vs V_IN. The dynamic current limit has its lowest value when reaching the minimum recommended supply voltage at V_IN.

Given the I_SW value from Figure 8-5, is then possible to calculate the output current reached in boost mode using Equation 1 and Equation 2 and in buck mode using Equation 3 and Equation 4.

Equation 1.

Equation 2.

Equation 3.

Equation 4.

where

• η is the estimated converter efficiency (use the number from the efficiency curves or 0.80 as an assumption)
• f is the converter switching frequency (typical 2.4 MHz)
• L is the selected inductor value

If the die temperature increases above the recommended maximum temperature, the dynamic current limit becomes active. The current limit is reduced with temperature increasing.

Figure 8-5 Average Inductance Current vs Input Voltage