LM5122: schematic check

Hello Tommy,

[Question 1] For “C33(Cin)”, I plan to use the solid E/C(electrolytic capacitor), is it okay??
[Question 7] For “C41(Cout), C42(Cout), C43(Cout)”, I plan to use the solid E/C(electrolytic capacitor), is it okay??

For the bigger input and output capacitors the customer can use high quality aluminium electrolytic capacitors with Low ESR and low ESL.

[Question 8] For “C44(Coutx)”, Can I use the solid E/C(electrolytic capacitor) with positive and negative polarities to replace the original non-polarity capacitor??

No, on the input and especially on the output side you should place ceramic capacitors in parallel to the aluminium caps.
I would even recommend adding a ceramic cap on the input in parallel to C33

[Question 2] For “C35(Cvcc)”, I plan to use the solid E/C(electrolytic capacitor), is it okay??
This should ideally be a ceramic capacitor, as the part can draw short high current pulses from that external cap.
I wonder why it should be so big.
You may get around with a combination here as well (try to make the ceramic cap as big as possible)

[Question 5] For “C36(Cbst)”, Can I use the solid E/C(electrolytic capacitor) with positive and negative polarities to replace the original non-polarity capacitor??
No, this has to be a ceramic cap.

[Question 3] For “L5(L1)”, Please let me know what is the maximum current rating of this inductor??
I would expect 4A peak current as a minimum.
But be careful when selecting the inductor. At the rated current (not the satturration current) the inductor will already become hot.
So please chose an inductor with as much margin for the current as possible.

[Question 4] For “D2(Dbst)”, Please let me know what is the maximum forward current(IF) rating of this diode??
The forward current is quite low.
It is much more important that you will select a diode with a very low leakage.

[Question 6] For “Q1(M1) and Q2(M2)”, Please let me know the maximum Rds(ON) for this circuit application??
The higher the Rds(ON), the bigger the conductive losses of the FET.
At a peak current of 4A (maybe 3A average) you can calculate the resulting power dissipation yourself.

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Best regards,
Harry