Datasheet

LTC4062
17
4062fb
APPLICATIO S I FOR ATIO
WUUU
Figure 8. Combining Wall Adapter and USB Power
+
V
CC
D1
PROG
I
DET
3.3k
2k
MN1
5V WALL
ADAPTER
I
CHG
= 800mA
USB POWER
I
CHG
= 500mA
MP1
4062 F08
BAT
LTC4062
1.24k
Li-Ion
BATTERY
SYSTEM
LOAD
1k
C/5
USB and Wall Adapter Power
The LTC4062 allows charging from both a wall adapter
and a USB port. Figure 8 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
1kΩ 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 3.3kΩ program resistor are
used to increase the charge current to 800mA when the
wall adapter is present.