TPS22971: Maximum rise time

Kuramoch-san,

There is not an explicit maximum specified for the rise time or CT capacitance, however it is best design practice to use the lowest possible value that will account for the inrush current. You should determine the maximum inrush current that is acceptable for the upstream power supply and then calculate a slew rate by the following formula:

From here can plug it into the corresponding formula in the datasheet in order to calculate the appropriate capacitor size for CT.

One important thing to note here is regarding power dissipation. If the rise time is so long that the power dissipated over the internal FET causes device to go into thermal shutdown then obviously the rise time will not work. Refer to section 9.1.1 Thermal Consideration in the datasheet for the appropriate method to calculate the max power dissipation.