Li-Ion a Li-Polymer cells are becoming a No.1 choice for many applications, where they persuade by high energy density, low weight, low self-discharge and for majority of applications also by their favorable flat shape (Li-Po). Their price is also affordable (in regard to their properties) and so there´s usually only one “difficulty” – to solve charging, or more exactly – overall management of these cells. Basic principles were highlighted to you in our article “Try the most favourite types of batteries”. To reach a maximum cell lifetime, it´s also advisable to use initial (preconditioning) slow charging and also important is a proper charging termination as well as repeated recharging after reaching a certain degree of discharge.
It´s obvious, that to construct such a circuit from discrete components would be possible, but impractical, bulky and expensive. That´s why there are various charging controllers on the market and in many cases a single chip solution is an ideal solution. This is also a case of MCP73831 chip – a fully integrated linear charging controller. If you use only a single cell and maximum charging current of 500mA is sufficient for you, then MCP73831 will meet all requirements for a quality and safe recharging solution. MCP73831 has integrated output (FET) transistor, current sensing and reverse discharge protection.
Charging current can be easily adjusted by a single resistor, what´s also associated with other parameters like preconditioning current and charging termination. MCP73831 also contains a thermal regulation, which decreases output current in case of increased chip temperature (for example because of higher ambient temperature).
MCP7383x is available in four versions with factory-set regulation (max. charging) voltage. In our store can be found “the safest” first version with 4.20V regulation voltage – MCP73831T-2ATI/OT. In datasheet (p. 25) we can also read that this is the “AT“ version, which starts repeated charging at 94% Vreg (i.e. at approx. 3.95V), in a SOT23-5 package. Supply voltage can be in a range of 3.75-6V, while in respect to a thermal stress of a chip it´s better to supply it by a voltage close to max. output voltage (4,20V).
The chip can be easily supplied by a standard 5V voltage, but in cases of increased risk of overheating (operation at higher ambient temperatures, densely populated PCB,…), a common Si diode in series can be helpful. This will decrease supply voltage in 0.6-0.7V (and takes a portion of thermal loss on itself).
Charging status can be found at the “Charge status output” pin, which can drive an indication LED or can be connected to a host microcontroller.
For More Details: With MCP73831 you´ll charge lithium cells easily and safely