Figure 8-4 illustrates inductor current sensing using a shunt resistor. This configuration continuously monitors the inductor current to provide accurate overcurrent protection across the operating temperature range. For optimal current sense accuracy and overcurrent protection, use a low inductance ±1% tolerance shunt resistor between the inductor and the output, with a Kelvin connection to the LM25149 current sense amplifier.

If the peak voltage signal sensed from ISNS+ to VOUT exceeds the current limit threshold of 60 mV, the current limit comparator immediately terminates the HO output for cycle-by-cycle current limiting. Calculate the shunt resistance using Equation 9.

where

• V_CS-TH is current sense threshold of 60 mV.
• I_OUT(CL) is the overcurrent setpoint that is set higher than the maximum load current to avoid tripping the overcurrent comparator during load transients.
• ΔI_L is the peak-to-peak inductor ripple current.

The soft-start voltage is clamped 150 mV above FB during an overcurrent condition. Sixteen overcurrent events must occur before the SS clamp is enabled. This makes sure that SS can be pulled low during brief overcurrent events, preventing output voltage overshoot during recovery.