In the MP2617HGL-Z there is slight voltage fluctuation happening on the Vout pin (after the inductor) and on the battery charging pin (4.095 to 4.15), Also i noticed charging light it fluctuate also along with 6Hz pulsing (battery is not connected) and the battery is not charging. What could the issue be?
It would be good to start by evaluating the schematic if you are able to share. It could be that your Vout ripple could be too high.
is there a way to reduce the ripple?
You could add more Cout capacitance to help reduce the voltage ripple. This would also help reduce the ESR. Typically increasing the switching frequency would help too, but I believe that this battery charger IC has this fixed at 1.6MHz.
The EVB has multiple capacitors in parallel to help reduce ESR while keeping a similar Cin, Csys, and Cbatt capacitance:
Another variable that you could adjust would be to try increasing the inductance. The tradeoff here however would be the overall size of the inductor.
is the BST capacitor must be physically closed the MP2617HGL-Z and the inductor?
Yes, ideally the BST capacitor should have a very small loop.
To have a small loop, ideally this capacitor should be very close to the BST and SW pins alongside the inductor.
If the loop is too big, this can introduce a lot of di/dt noise into the SW node. When you measure this on a scope, does the SW node look very clean?