LTC4054X-4.2_15 Datasheet, PDF (14/16 Pages) Linear Technology – Standalone Linear Li-Ion Battery Charger with Thermal Regulation in ThinSOT

LTC4054-4.2/LTC4054X-4.2
APPLICATIO S I FOR ATIO
USB and Wall Adapter Power
The LTC4054 allows charging from both a wall adapter
and a USB port. Figure 7 shows an example of how to
combine wall adapter and USB power inputs. A P-channel
MOSFET, MP1, is used to prevent back conducting into the
USB port when a wall adapter is present and a Schottky
diode, D1, is used to prevent USB power loss through the
1k pull-down resistor.
Typically a wall adapter can supply more current than the
500mA-limited USB port. Therefore, an N-channel MOSFET,
MN1, and an extra 10k program resistor are used to
increase the charge current to 600mA when the wall
adapter is present.
5V WALL
ADAPTER
600mA I_CHG
USB POWER
500mA I_{CHG MP1}
1k
D1
LTC4054-4.2 ₃
BAT
4 _VCC
5
PROG
10k
MN1
2k
I_CHG
SYSTEM
LOAD
+
Li-Ion
BATTERY
405442 F07
Figure 7. Combining Wall Adapter and USB Power
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405442xf