ltc4054x-4.2 Linear Technology Corporation, ltc4054x-4.2 Datasheet - Page 14

• Manufacturer Part Number: ltc4054x-4.2
• Description: Standalone Linear Li-ion Battery Charger With Thermal Regulation In Thinsot
• Manufacturer: Linear Technology Corporation

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.
14
U
U
W
U
USB POWER
500mA I
600mA I
ADAPTER
5V WALL
Figure 7. Combining Wall Adapter and USB Power
CHG
CHG
MP1
1k
D1
4
MN1
LTC4054-4.2
V
CC
10k
PROG
BAT
2k
3
5
I
+
CHG
405442 F07
Li-Ion
BATTERY
SYSTEM
LOAD
405442xf