I am designing a power supply where I will also need to use a backup battery.
The choosen battery type was a Li-Ion (Lithium) type, which has a nominal cell voltage of 3.7V .
I have little experience with battery chargers and protection circuits (using dedicated ICs).
--> I searching for dedicated charger ICs and I think MCP73812 from Microchip is a good choice to do the automatic charge control.
Using a MCP73812 I am able to ENABLE/DISABLE and ADJUST the charge current through an external bias resistor.
--> I was also searching for a Li-Ion battery protection IC, to "disconnect" the BATT from the circuit in situations of under-voltage (over-discharge) and over-voltage (over-charge). I found this IC model on Digikey: S-8241ABKMC-GBKT2G. This IC (S-8241ABKMC-GBKT2G) controls two MOSFETs who are connected between the Li-Ion battery and the circuit's power supply.
The S-8241ABKMC-GBKT2G IC works similar to that:
1) It is powered from the Li-Ion battery and its current consumption is very very low, just some microamperes or less, when in power -down mode.
2) When the BATT voltage goes below 2.5V, it "opens" the MOSFET switch, preventing the BAT to continue supplying current to the circuit. It "closes" the MOSFET switch again only when the BATT voltage goes above 2.9V. This is a good idea, using a small voltage hysteresis between OPENING and CLOSING the MOSFET switch, preventing oscilations.
3) When the BATT is in charge process and its voltage reaches 4.325V, the S-8241ABKMC-GBKT2G "opens" the MOSFET switch, preventing the BAT to continue charging and being "over-charged". S-8241ABKMC-GBKT2G "closes" the MOSFET switch again only when the BAT voltage goes below 4.075V. This is a good idea, using a small voltage hysteresis beetwenn OPENING and CLOSING the MOSFET switch, preventing oscilations.
4) S-8241ABKMC-GBKT2G has two digital outputs to control two mosfets, one for under-volge and another for over-voltage cases. So using just the under-voltage output, we could use this same IC to protect battery circuits who uses NiMh (more than one cell in series) backup batteries.
- MCP73812 -->> Simple, Miniature Single-Cell, Fully Integrated Li-Ion / Li-Polymer Charge Management Controller
- S-8241ABKMC-GBKT2G -->> BATTERY PROTECTION IC FOR 1-CELL PACK
SOMEBODY RECOMMEND ME ANOTHER ICs for LI-ION BATTERY AUTOMATIC CHARGE AND FOR PROTECTION (OVER-VOLTAGE AND UNDER-VOLTAGE) ???
I don't want to use Lead-Acid, NiCd or NiMh battery anymore. Just Li-Ion from now on hehehe.