The buck regulator cycle-by-cycle current limit on both the peak and valley of the inductor current. Hiccup mode will be activated if a fault condition persists to prevent over-heating.

High-side MOSFET overcurrent protection is implemented by the nature of the Peak Current Mode control. The HS switch current is sensed when the HS is turned on after a set blanking time. The HS switch current is compared to the output of the Error Amplifier (EA) minus slope compensation every switching cycle. Refer to the Functional Block Diagram for more details. The peak current of HS switch is limited by a clamped maximum peak current threshold I_{HS_LIMIT} which is constant. So the peak current limit of the high-side switch is not affected by the slope compensation and remains constant over the full duty cycle range.

The current going through LS MOSFET is also sensed and monitored. When the LS switch turns on, the inductor current begins to ramp down. The LS switch will not be turned OFF at the end of a switching cycle if its current is above the LS current limit I_{LS_LIMIT}. The LS switch will be kept ON so that inductor current keeps ramping down, until the inductor current ramps below the LS current limit I_{LS_LIMIT}. Then the LS switch will be turned OFF and the HS switch will be turned on after a dead time. This is somewhat different than the more typical peak current limit, and results in Equation 8 for the maximum load current.

Equation 8.

If V_CSN/OUT < 2-V typical due to a short circuit for 128 consecutive cycles, hiccup current protection mode will be activated. In hiccup mode, the regulator will be shut down and kept off for 118 ms typically, then TPS2583x-Q1 go through a normal re-start with soft start again. If the short-circuit condition remains, hiccup will repeat until the fault condition is removed. Hiccup mode reduces power dissipation under severe overcurrent conditions, prevents over-heating and potential damage to the device and serves as a backup to the programmable current limit see Current Limit Sensing using R_ILIMIT. Once the output short is removed, the hiccup delay is passed and the output voltage recovers normally as shown in Figure 11-23.