I am designing a board for my project which is powered from 4.2V Li-Ion Battery. I am using a buck-boost converter ADP2504 for powering the board which outputs 4.0V constant voltage. I have buzzer on my board for alarm applications. Whenever I turn on my buzzer I get a huge drop of 1.4V in my regulator output (attached is my drop waveform) and comes back to 4.0V in 33 microseconds.
When I turn on buzzer, current shoots up by 200mA (buzzer current = 200mA). Question is
How to calculate a capacitor to handle this transient with the above input? Currently I don't have any capacitor in my board. Above observations are without capacitor.
If the calculated value is very high in 100's of micro Farads, how to handle inrush current caused by that?