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LT8705A: used in MPPT application


I would like to use a buck-boost converter LT8705A as a core for my MPPT. LT8490 uses the simillar core switcher (it uses LT8705 exactly).
My question is - why is forced continous mode (MODE=0) prefered for a MPPT applications? All schematics in LT8490 datasheet have MODE pin connected to GND.
I'm asking this because I run the simulation in LTSpice XVII with a LT8705A, solar panel on input and battery on the output.  When the SS reach 1.6V, voltage jumps to 2.5V and at she same time current through the inductor becomes negative (it reaches also 7A+!), it flows from battery through M4, inductor and through M2 to the ground..after short time then current becomes positive and switcher starts to work. With MODE=1 (discontinous mode) I didn't saw this issue.
How do you recomend to calculate a needed input and output capacitance (and also an inductor) for a MPPT application - that type of applications are different from a normal applications, because solar panels is some type of current source, and the ripple on the output practicaly depends on battery (connected to the output of MPPT) ESR.
Is anywhere any longer procedure or recipe how did you derive the formulas for calculate needed capacitors/inductor mentioned in LT8705A datasheet?

Many thanks!

Best regards.