Thankyou GSM MAN for the prompt and helpful reply.
Can we design a circuit using only discrete components and an op- amp for the same purpose??
This is how I assume:
When main supply is ON:
The op-amp will provide the constant current required for the LI-Ion recharge until the maximum rating is reached.
When the main supply is OFF:
The supply should switch to the battery backup without any reset in the load,which I suppose a diode can do.
But I don't have a clear picture of a final circuit.
Can anyone share/suggest?
The Lithium-ion chemistry is very sensitive to the charging current and voltage, and they have to be carefully controlled. The cells are easily destroyed if not charged properly. Before attempting to design your own charging circuit I'd look carefully at the charging requirements. Maxim has some good application notes on their web site **broken link removed**
It was really a helpful link ,Thank you for the support.
But I didn't get a single IC in DIP package(that will be helpful to develop the prototype)
Can you suggest me any IC in DIP package which serves the same purpose.
The big market for battery chargers addressing those chemistries is in small devices (cell phones, PDA, laptops, etc.). Those apps require small device packages so the manufacturers don't make those chips in DIP packages. Personnally, I don't know of any battery charger that will fit your requirement that's available in a DIP package.
TI has various components for Battery charging, Battery Monitoring especially in 3.7V battery LI-ion area. And they claim an accuracy of 1% considering all the factors like aging, no of time charged discharged etc etc in estimating the available back up.