Dear all:
I have some questions about the TPS56221 overcurrent protection.
Our design is quite similar with the demo design of TPS56221, except the EN/SS and the ILIM pins.
Without the EN/SS capacitor and ILIM resistor, the TPS56221 will breakdown sometimes, and the relevant voltage before and after inductor is illustrated in Fig1.We measured the rush transient current during the startup which is almost 60A, and we are sure that is because of the large bulk capacitance (almost 5000uF), and the TPS56221 is self-protecting.
Although we know it will work properly with both EN/SS capacitor and ILIM resistor added, we cannot change the two current designs as follows, for some reason.
1) we add ILIM resistor 2.4K only, and leave the EN/SS pin floating.The current (pink) ,the voltage before and after inductor (yellow and green) are illustrated in Fig.2.
2) we add EN/SS capacitor 2.7nF only, and leave ILIM pin floating.The current (pink) ,the voltage before and after inductor (yellow and green) are illustrated in Fig.3.
Now both the two designs work properly, but are there any risks for the two designs? such as long-term reliability and safety?