ZHCSF29E May 2016 – January 2021 TPS25940-Q1
PRODMIX
During a transient short circuit event, the current through the device increases very rapidly. As current-limit amplifier cannot respond quickly to this event because of its limited bandwidth, the device incorporates a fast-trip comparator, with a threshold I(FASTRIP). This comparator shuts down the pass device within 1μs, when the current through internal FET exceeds I(FASTRIP) (I(OUT) > I(FASTRIP)), and terminates the rapid short-circuit peak current. The trip threshold is set to more than 50% of the programmed overload current limit ( I(FASTRIP) = 1.5 x I(LIM)+ 0.375 ). The fast-trip circuit holds the internal FET off for only a few microseconds, after which the device turns back on slowly, allowing the current-limit loop to regulate the output current to I(LIM). Then, device behaves similar to overload condition. Figure 10-13 through Figure 10-14 illustrate the behavior of the system when the current exceeds the fast-trip threshold.