LTC4413-2 Linear Technology, LTC4413-2 Datasheet - Page 11

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

APPLICATIONS INFORMATION
Introduction
The LTC4413-1/LTC4413-2 are intended for power control
applications that include low loss diode OR’ing, fully auto-
matic switchover from a primary to an auxiliary source of
power, microcontroller controlled switchover from a pri-
mary to an auxiliary source of power, load sharing between
two or more batteries, charging of multiple batteries from
a single charger and high side power switching.
Dual Battery Load Sharing With Automatic Switchover
to a Wall Adapter With Overvoltage Protection
(LTC4413-2 Only)
An application circuit for dual battery load sharing with
automatic switchover of load from batteries to a wall
adapter is shown in Figure 2. When the wall adapter is not
present, whichever battery has the higher voltage provides
the load current until it has discharged to the voltage of the
other battery. The load is shared between the two batter-
ies according to the capacity of each battery. The higher
capacity battery provides proportionally higher current to
the load. When a wall adapter input is applied, the output
voltage rises as the body diode in MP2 conducts. When
the output voltage is larger than the battery voltages, the
LTC4413 turns off and very little load current is drawn
from the batteries. At this time, the STAT pin pulls down
ADAPTER
INPUT
WALL
JACK
BATA
BATB
+
+
1
2
3
4
5
INA
ENBA
GND
ENBB
INB
LTC4413-2
IDEAL
IDEAL
R1
1Ω
C1
0.10μF
OUTB
OUTA
STAT
OVP
OVI
Figure 2
10
9
8
7
6
10nF
IRLML6402
C2
MP1
C
4.7μF
OUT
DFLZ6V2-7
OPTIONAL
6.2V
10nF
IRLML6402
C1: C1206C106K8PAC
C2: C0403C103K8PAC
C
MP2
OUT
: C1206C475K8PAC
R
470k
STAT
441312 F02
TO LOAD
STAT
OVP
the gate voltage of MP2, causing it to conduct. This status
signal can be used to provide information as to whether
the wall adapter (or BATB) is supplying the load current.
If the wall adapter voltage exceeds the OVI trip threshold
(V
external PFET, MP1. The OVI voltage can be monitored
(through a voltage divider if necessary) to determine if
an overvoltage condition is present.
Capacitor C2 is required to dynamically pull up on the
gate of PFET MP1 if a fast edge occurs at the wall adapter
input during a hot plug. In the event that capacitor C2 (or
the gate-to-source of MP1) is precharged below the OVI
rising threshold. When a high voltage spike occurs, the
OVP output cannot guarantee turning off MP1 before the
load voltage exceeds the absolute maximum voltage for
the LTC4413-2. This may occur in the event that the wall
adapter suddenly steps from 5.5V to a much higher value.
In this case, a zener diode is recommended to keep the
output voltage to a safe level.
Automatic PowerPath Control
Figure 3 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller’s analog inputs (perhaps with the aid of
a resistor voltage divider) monitor each supply input and
the LTC4413-1 status, and then commands the LTC4413-1
through the two ENBA/ENBB control inputs.
AUXILIARY
PRIMARY
SOURCE
SOURCE
OVIH
POWER
POWER
) then the wall adapter is disconnected via the
R
1Ω
R
1Ω
LTC4413-1/LTC4413-2
A
B
C
10μF
C
10μF
A
B
1
2
3
4
5
Figure 3
MICROCONTROLLER
INA
ENBA
GND
ENBB
INB
LTC4413-1
IDEAL
IDEAL
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OUTB
OUTA
STAT
10
9
6
R
470k
441312 F03
STAT
STAT
11
441312fb
C1
4.7μF
LOAD