AN2407 Datasheet, PDF (1/14 Pages) Freescale Semiconductor, Inc – Reed Solomon Encoder/Decoder on the StarCore SC140/SC1400 Cores, With Extended Examples

AN2407
Application note
800mA standalone linear Li-Ion
battery charger with thermal regulation
Introduction
One way to minimize the size and complexity of a battery charger is to use a linear-type
charger. The linear charger drops the AC adapter voltage down to the battery voltage. The
number of external components is low: linear chargers require input and output bypass
capacitors, and sometimes need an external pass transistor, and resistors for setting voltage
and current limits.
The main pitfall of a linear charger is power dissipation. The charger simply drops the AC
adapter voltage down to the battery voltage.
In the case of an 800mA charger, a 5V±10% regulated AC adapter voltage, and battery
voltage that varies between 4.2V and 2.5V, the power dissipation can range from 0.6W to
2.0W.
This type of charger is simpler than the switch-mode type, mainly because the passive LC
filter is not required. It dissipates the most power when the battery voltage is at its minimum,
since the difference between the fixed input voltage and the battery voltage is greatest
during this condition.
Application diagram
September 2006
Rev 2
1/14
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