The typical approach for setting the limit threshold voltage is to connect a resistor from the LIMIT terminal to ground. The value of this resistor, R_LIMIT, is chosen to create a corresponding voltage at the LIMIT terminal equivalent to the voltage, V_TRIP, developed by the load current flowing through the current-sensing resistor. An internal 20-µA current source is present at the LIMIT terminal that creates the corresponding voltage depending on the value of R_LIMIT. In the equations from Table 7-2, V_TRIP represents the overcurrent threshold the device is programmed to monitor for and V_LIMIT is the programmed signal set to detect the V_TRIP level. The term noise adjustment factor (NAF) is included in the V_LIMIT equation for the 10-µs delay setting. This value is equal to 500 µV and adjusts the operating point for the internal noise in this delay setting. The 50-µs and 100-µs delay settings do not use the NAF term in calculating the V_LIMIT threshold. See Section 7.3.7 for more details on the noise adjustment factor.

In Table 7-2, the process for calculating the required value for R_LIMIT to set the appropriate threshold voltage, V_LIMIT, is shown. This calculation is based on the 10-µs delay setting so the NAF term is included in the calculation. For a delay setting of 50 µs or 100 µs, the NAF term is omitted.

TI recommends using NAF in calculating the value for V_LIMIT and R_LIMIT at the 10-µs delay setting. Removing NAF from the V_LIMIT and R_LIMIT calculation at the 10-µs delay setting lowers the trigger point of the alert output. Lowering the trigger point results in the device issuing an overcurrent alert prior to reaching the corresponding V_TRIP threshold. The averaging effect included with the 50-µs and 100-µs delay settings inherently eliminates the effect internal noise has on the threshold voltage.