LTC4413-2 Linear Technology, LTC4413-2 Datasheet - Page 12

• Manufacturer Part Number: LTC4413-2
• Description: Fast Ideal Diodes
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
LTC4413-1/LTC4413-2
Automatic Switchover from a Battery to an Auxiliary
Supply, or a Wall Adapter with Overvoltage Protection
Figure 4 illustrates an application circuit where the LTC4413-
2 is used to automatically switch over between a battery,
an auxiliary power supply and a wall adapter. When the
battery is supplying load current, OVP is at GND and STAT
is high. If a higher supply is applied to AUX, the BAT will
be disconnected from the load and the load is powered
from AUX. When a wall adapter is applied, the body diode
of MP2 forward biases. When the load voltage exceeds the
AUX (or BAT) voltage, the LTC4413-2 senses this higher
voltage and disconnects AUX (or BAT) from the load. At
the same time it pulls the STAT voltage to GND, thereby
turning on MP2. The load current is now supplied from the
wall adapter. If the wall adapter voltage exceeds the OVI
rising threshold, the OVP voltage rises and turns off MP1,
disconnecting the wall adapter from the load. The output
voltage collapses down to the AUX (or BAT) voltage and
ADAPTER
12
BAT
AUX
INPUT
WALL
JACK
+
470k
470k
1
3
4
5
2
INA
GND
ENBB
INB
ENBA
LTC4413-2
IDEAL
IDEAL
R1
1Ω
C1
0.10μF
OUTA
OUTB
STAT
OVP
OVI
Figure 4
10
8
7
9
6
10nF
IRLML6402
C2
MP1
441312 F04
C
4.7μF
OUT
DFLZ6V2-7
OPTIONAL
6.2V
10nF
OVP
IRLML6402
C1: C1206C106K8PAC
C2: C0403C103K8PAC
C
OUT
MP2
: C1206C475K8PAC
R
560k
STAT
TO LOAD
STAT
the LTC4413-2 reconnects the load to AUX (or BAT).
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.
Multiple Battery Charging
Figure 5 illustrates an application circuit for automatic dual
battery charging from a single charger. Whichever battery
has the lower voltage will receive the larger charging cur-
rent until both battery voltages are equal, then both are
charged. While both batteries are charging simultaneously,
the higher capacity battery gets proportionally higher cur-
rent from the charger. For Li-Ion batteries, both batteries
achieve the fl oat voltage minus the forward regulation
voltage of 15mV. This concept can apply to more than
two batteries. The STAT pin provides information as to
when the battery at OUTA is being charged. For intelligent
control, the ENBA/ENBB input pins can be used with a
microcontroller as shown in Figure 3.
Automatic Switchover from a Battery to a Wall
CHARGER
BATTERY
INPUT
1
2
3
4
5
INA
ENBA
GND
ENBB
INB
LTC4413-1
IDEAL
IDEAL
Figure 5
OUTA
OUTB
STAT
10
9
6
+
V
CC
www.DataSheet4U.com
470k
441312 F05
BAT2
STAT IS HIGH
WHEN BAT1 IS
CHARGING
+
BAT1
441312fb
LOAD
LOAD