The TPS1663x devices feature accurate overload current limiting and fast short circuit protection feature. If the load current exceeds the programmed current limit I_OL, the device regulates the current through it at I_OL eventually reducing the output voltage. The power dissipation across the device during this operation is (V_IN – V_OUT) × I_OL and this can heat up the device and eventually enter into thermal shutdown. The maximum duration for the overcurrent through the FET is t_{CL_PLIM(dly)}, 162 msec (typical). If the thermal shutdown occurs before this time the internal FET turns OFF and the device operates either in auto-retry or latch off mode based on MODE pin configuration in Table 9-1. Set the current limit using Equation 4.

Equation 4.

where

• I_(OL) is the overload current limit in Ampere
• R_(ILIM) is the current limit resistor in kΩ

During the overload current limiting if the overload condition exists for more than t_{CL_PLIM_FLT(dly)}, 1.3 msec (typical), the FLT asserts to warn of impending turnoff of the internal FETs due to the subsequent thermal shutdown event or due to t_{CL_PLIM(dly)} timer expiry. The FLT signal remains asserted until the fault condition is removed and the device resumes normal operation. Figure 9-6 and Figure 9-7 illustrate overload current limiting performance.

VIN = 50 V

MODE = GND

RILIM = 18 kΩ

Figure 9-6 Overload Performance During Load Step from 140 Ω to 40 Ω

VIN = 50 V

MODE = GND

RILIM = 18 kΩ

Figure 9-7 Coming Out of Overload With Load Step from 40 Ω to 140 Ω

The TPS1663x devices features ILIM pin short and open fault detection and protection. The internal FET is turned OFF when ILIM pin is detected short or open to GND and it remains OFF till the ILIM pin fault is removed.