How does the TPS26620 determine if there is a short circuit on the output at startup? Based on my initial reading of the datasheet, I had expected one of two behaviors - either the current output would hit I_fastrip and the FET would turn off right away, or the current would be limited to I_Lim for T_cl, and then the fault condition would occur.
My system has some inrush currents and I was hoping that the part would simply limit the current to 880mA and the output capacitors would be charged well before the 512mS of T_cl had expired. But what I am seeing is that 880mA is provided for only about 5-10mS (the soft-start time set by the 0.022uF C_dvdt, possibly), and then the FET shuts off.
This seems to match Figure 42, which shows I_in turning on for several mS before turning off for the auto-retry delay. But in this case I cannot figure out what is causing the FET to turn off. The current is limited to I_lim, but I would have expected it to remain on for T_cl. Perhaps it is turning off due to thermal overload? That would make sense but isn't stated in the section.
