8.1.5 Overcurrent Fault

The V_DS Fault Comparator can be used to implement an Over-Current shutdown function. The V_DS Fault Comparator monitors the voltage difference between the SENSE pin and the OUT pin. This is, essentially, the same voltage that is across the N-Channel MOSFET R_DS(ON) less the threshold voltage that is set by the series resistor on the SENSE pin. The value of capacitor on the TIMER pin, the capacitor charge current (I_TIMERH, 11 μA typical), along with the TIMER pin fault threshold (V_TMRH) will determine the how long the N-Channel MOSFET will be allowed to conduct excessive current before the MOSFET is turned-off. When this delay time expires, the gate is discharged at a 80 mA rate.

The LM5060 is intended for applications where precise current sensing is not required, but some level of fault protection is needed. Examples are applications where inductance or impedance in the power path limits the current rise in a short circuit condition.

The Safe Operating Area (SOA) of the external N-Channel MOSFET should be carefully considered to ensure the peak drain-to-source current and the duration of the fault delay time is within the SOA rating of the MOSFET. Also note that the R_DS(ON) variations of the external N-Channel MOSFET will affect the accuracy of the Over-Current detection.