DESIGN IDEAS L New Dual Input USB/AC Linear
by Alfonso Centuori
Li-Ion Battery Chargers
Introduction Digital Cameras, PDAs, mobile phones
and MP3 players all use batteries that
are commonly charged via either a
wall adapter or through the USB. The
LTC4076 and LTC4077 lithium-ion
battery chargers are specifically designed to detect power at the inputs
and automatically select the appropriate source for charging. Using a
constant current/constant voltage
algorithm, the chargers can be programmed to deliver up to 950mA of
charge current with a final float voltage accuracy of ±0.6%. The LTC4076
and LTC4077 include an internal Pchannel power MOSFET and thermal
regulation circuitry with no blocking
diode or external sense resistor required. Thus, the basic dual-source
charger requires only three external
components.
The LTC4076 offers a programmable current based termination
scheme. The CHRG open-drain status
pin can be programmed to indicate
the battery charge state according to
the needs of the application. The PWR …