LTC4054L-4.2 Datasheet, PDF (14/16 Pages) Linear Technology – 150mA Standalone Linear Li-Ion Battery Charger in ThinSOT

LTC4054L-4.2
APPLICATIO S I FOR ATIO
Reverse Polarity Input Voltage Protection
In some applications, protection from reverse polarity
voltage on V_CC is desired. If the supply voltage is high
enough, a series blocking diode can be used. In other
cases, where the voltage drop must be kept low a P-channel
MOSFET can be used (as shown in Figure 4).
DRAIN-BULK
DIODE OF FET
V_IN
LTC4054L
V_CC
4054L42 F04
Figure 4. Low Loss Input Reverse Polarity Protection
USB and Wall Adapter Power
The LTC4054L allows charging from both a wall adapter
and a USB port. Figure 5 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.
5V WALL
ADAPTER
100mA
3
BAT
SYSTEM
LOAD
USB
POWER _MP1
D1 ^LTC4054L-4.2
4
V_CC
5
PROG
+ _Li-Ion
BATTERY
1k
1.5k
4054l42 F05
Figure 5. Combining Wall Adapter and USB Power
14
4054l42f