The LM73605-Q1/6-Q1 protected from overcurrent conditions with cycle-by-cycle current limiting on both HS and LS MOSFETs.

The HS switch is turned off when HS current goes beyond the peak current limit, I_HS-LIMIT. The LS switch can only be turned off when LS current is below LS current limit, I_LS-LIMIT. If the LS switch current is higher than I_LS-LIMIT at the end of a switching cycle, the switching cycle is extended until the LS current reduces below the limit.

Current limiting on both HS and LS switches provides tighter control of the maximum DC inductor current, or output current. They also help prevent runaway current at extreme conditions. With the LM73605-Q1/6-Q1, the maximum output current is always limited to:

The LM73605-Q1/6-Q1 hiccup current protection at extreme overload conditions, including short-circuit condition. Hiccup is only activated when V_OUT droops below 40% (typical) of the regulation voltage and stays below for 128 consecutive switching cycles. Under overcurrent conditions when V_OUT has not fallen below 40% of regulation, the LM73605-Q1/6-Q1 operation with cycle-by-cycle HS and LS current limiting.

Hiccup is disabled during soft start. When hiccup is triggered, the device turns off V_OUT regulation and re-tries soft start after a re-try delay time, T_OC = 46 ms (typical). The long wait time allows the device, and the load, to cool down under such fault conditions. If the fault condition still exists when re-try, hiccup shuts down the device and repeats the wait and re-try cycle. If the fault condition has been removed, the device starts up normally.

If tracking was used for initial sequencing, the device restarts using the internal soft-start ramp. Hiccup mode helps reduce the device power dissipation and die temperature under severe overcurrent conditions and short circuits. It improves system reliability and prolongs the life span of the device.

In FPWM mode, negative current protection is implemented to protect the switches from extreme negative currents. When LS switch current reaches I_NEG-LIMIT, LS switch turns off, and HS switch turns on to conduct the negative current. HS switch is turned off once its current reaches 0 A.