Does battery charger need dc-dc converter?

[Alan_Nesta]

For example
input voltage=5v from USB
output 4.2v
need buck dc-dc?
or only use voltage feedback-loop control enough?

 

[docs]

Would it be a Li-ion charger? Then check Microchip's MCP73861

 

[Davood Amerion]

I think, in this case, you dont need buck convertor.
insted you can use Low Drop out Linear voltage regulator, because in-out voltage is low (0.8V).

 

[lylnk]

Linear charger is ok.
Both voltage feedback loop and current feedback loop are needed.
The maximum output current of USB is 500mA, the current feedback loop must limit the charge current within 500mA.
The linear charger is heater than DCDC charger. When VDD=5V, VBAT=3V and charge current 400mA, the power of charger chip is 800mW.

 

[Alan_Nesta]

OK
I know
Can Someone give me some paper or thesis about Li-Ion architecture?