LINEAR Technology has released the LTC4068, a standalone linear single-cell Li-Ion lithium polymer battery charger. It is available from Soanar .
The charger allows system designers to program charge cycle termination properly with a system load concurrently applied to the battery. The LTC4068 allows adjustment of the level of charge termination current relative to the amount of current needed by the system during battery charging. This removes the risk that the system load might demand so much current that the charge current termination threshold is never reached. When this happens the charge cycle continues indefinitely, overcharging the battery. This can lead to reduced battery life, thermal runaway, and permanent damage to the cell.
With the use of a single resistor, charge termination current can be accurately set to a value less than, more than, or equal to C/10. The LTC4068 has a thermal regulation scheme which maximises charger rate without the risk of overheating. It has a charge current monitor, trickle charge for battery pre-conditioning, undervoltage lockout, automatic recharge, charge status indicator, and input voltage detection/indicator. Applications include PDAs, lightweight portable medical and test equipment, and large colour screen cell phones.
The LTC4068 is offered in a 0.75mm profile 3mm x 3mm DFN package. The total footprint is less than 25mm2 since an external MOSFET, sense resistor, and blocking diode are not required. The LTC4068 can also charge a Li-Ion battery from a USB port. The LTC4068 draws only 6μA from the battery terminal in standby and 2μA in shutdown mode.
The IC's soft-start function limits the inrush current to ensure safety at turn-on. The LTC4068 is also equipped with a 1ms filter to ensure that transient loads do not force premature charge cycle termination. The LTC4068 is rated for operation from -40°C to 85°C.