The LM5143-Q1 includes an optional hiccup mode protection function that is enabled when a capacitor is connected to the RES pin. In normal operation, the RES capacitor is discharged to ground. If 512 cycles of cycle-by-cycle current limiting occurs, SS is pulled low and the HO and LO outputs are disabled (see Figure 8-6). A 20-μA current source begins to charge the RES capacitor. When the RES voltage increases to 1.2 V, RES is pulled low and the SS capacitor begins to charge. The 512-cycle hiccup counter is reset if four consecutive switching cycles occur without exceeding the current limit threshold. Separate hiccup counters are provided for each channel, but the RES pin is shared by both channels. One channel can be in hiccup protection while the other operates normally. In the event that both channels are in an overcurrent condition triggering hiccup protection, the last hiccup counter to expire pulls RES low and starts the RES capacitor charging cycle. Both channels then restart together when V_RES = 1.2 V. If RES is connected to VDDA at power up, the hiccup function is disabled for both channels.

Figure 8-6 Hiccup Mode Timing Diagram

Use Equation 13 to calculate the RES capacitance.

Equation 13.

where

• t_RES is the specified hiccup delay as shown in Figure 8-6