Datasheet
LTC4413-1/LTC4413-2
13
441312fd
APPLICATIONS INFORMATION
Automatic Switchover from a Battery to a Wall
Adapter and Charger with Overvoltage Protection
Figure 6 illustrates the LTC4413-2 performing the function
of automatically switching a load over from a battery to a
wall adapter while controlling an LTC4059 battery charger.
When no wall adapter is present, the LTC4413-2 connects
the load at OUTA from the Li-Ion battery at INA. In this
condition, the STAT voltage is high, thereby disabling
the battery charger. If a wall adapter of a higher voltage
than the battery is connected to MP1 (but below the OVI
threshold), the load voltage rises as the second ideal di-
ode conducts. As soon as the OUTA voltage exceeds the
INA voltage, the BAT is disconnected from the load and
the STAT voltage falls, turning on the LTC4059 battery
charger and beginning a charge cycle. If a high voltage
wall adapter is inadvertently attached above the OVI rising
threshold, the OVP pin voltage rises, disconnecting both
the LTC4413-2 and the LTC4059 from potentially hazard-
ous voltages. When this occurs, the load voltage collapses
until it is below the BAT voltage causing the STAT voltage
to rise, disabling the battery charger. At the same time,
the LTC4413-2 automatically reconnects the battery to the
load. One major benefi t of this circuit is that when a wall
adapter is present, the user may remove the battery and
replace it without disrupting the load.
Capacitor C2 is required to dynamically pull up on the
gate of MP1 if a fast edge occurs at the wall adapter input
during a hot plug. If the wall adapter voltage is precharged
when an overvoltage spike occurs, the OVP voltage may
not discharge capacitor C2 in time to protect the output.
In this event, a Zener diode is recommended to protect
the output node until MP1 is turned off.
INA
IDEAL
LTC4413-2
INB
OVP
OVI
IDEAL
ENBA
ENBB
GND
100k
D1
OPTIONAL
DFLZ6V2-7
OUTA
Li-Ion
1
4
3
5
2
10
9
R
STAT
560k
6
OUTB
STAT
441312 F06
TO
LOAD
STAT
C
OUT
4.7μF
C1
10μF
1μF
C2
10nF
+
BAT
PROG
GND
ENB
V
CC
LTC4059
Li/CC
MP1
IRLML6402
WALL
ADAPTER
INPUT
JACK
Figure 6