During an output short-circuit event, the current through the device increases very rapidly. When a severe overcurrent condition is detected, the device triggers a fast-trip response to limit the current to a safe level. For the TPS259480x/2x variants, the internal fast-trip comparator employs a scalable threshold (I_SC = 2 × I_LIM). This enables the user to adjust the fast-trip threshold rather than using a fixed threshold which can be too high for some low current systems. The device also employs a fixed fast-trip threshold (I_FFT) to protect fast protection against hard short-circuits during steady state. The fixed fast-trip threshold is higher than the maximum recommended user adjustable scalable fast-trip threshold. The TPS259481x variants employ only the fixed fast-trip threshold. Once the current exceeds I_SC or I_FFT, the HFET is turned off completely within t_SC or t_FT. Thereafter, the devices tries to turn the HFET back on after a short de-glitch interval (30 μs) in a current limited manner instead of a dVdt limited manner. This ensures that the HFET has a faster recovery after a transient overcurrent event and minimizes the output voltage droop. However, if the fault is persistent, the device will stay in current limit causing the junction temperature to rise and eventually enter thermal shutdown. See Overtemperature Protection (OTP) section for details on the device response to overtemperature.

Figure 8-8 TPS259480x/2x Short-Circuit Response

Figure 8-9 TPS259481x Short-Circuit Response