TPS3809: 200ms step on RESET at VDD power on

Hi team,

For TPS3809K33, my customer is getting below test scope at VDD power on, there is a ~200mV step with duration of 200ms before the RESET goes high. I assume the 200ms is the delay time, but why is there a 200mV step during this time? 

Thanks.

The schematic and scope are: