AD8436 RMS-core occur overshoot

Hi

I have question about AD8436.

 

When 5Vin start-up condition at ADI EVB/LTspice, RMS-CORE occur overshoot.

Is it normal operation? Or what is this reason?

 

CH1:TRMSIN(AC123mV+DC1.65V),CH2:Output-Buffer,CH3:RMS-CORE Output,CH4:+5V

 

Best Regards,

Yu