9.2.2.8 Adjustable Current Limiting Resistor Selection

The converter uses the voltage drop on the high-side MOSFET to measure the inductor current. The over current protection threshold can be optimized by changing the trip resistor. Figure 17 governs the threshold of over current protection for Buck 1. When selecting a resistor, do not exceed the graph limits. In this example, the over current threshold is 3.2 A. In order to prevent a premature limit trip, the minimum line is used and the resistor is 100 kΩ.

When setting high-side current limit to large current values, ensure that the additional load immediately prior to an overcurrent condition will not cause the switching node voltage to exceed 20 V. Additionally, ensure during worst case operation, with all bucks loaded immediately prior to current limit, the maximum virtual junction temperature of the device does not exceed 125°C.