LTC4413
11
4413fd
For more information www.linear.com/LTC4413
applicaTions inForMaTion
If the AUX is present when a wall adapter is applied, as
the resistive divider to ENBB rises through the turn-off
threshold, the STAT pin voltage falls and MP1 conducts,
allowing the wall adapter to power the load. When the wall
adapter is removed while the AUX supply is present, the
load voltage falls until the voltage divider at the ENBB pin
falls through its turn-on threshold. Once this occurs, the
LTC4413 automatically connects the AUX supply to the load
when the AUX voltage exceeds the output voltage, causing
the STAT voltage to rise and disabling the external PFET.
When an AUX supply is attached, the voltage divider at
ENBA (R4 and R5) disconnects the battery from the load,
and the auxiliary supply provides load current, unless a
wall adapter is present as described earlier. If the auxiliary
supply is removed, the battery may again power the load,
depending on if a wall adapter is present.
Multiple Battery Charging
Figure 6 illustrates an application circuit for automatic dual
battery charging from a single charger. Whichever battery
has the lower voltage will receive the larger charging current
Figure 6
until both battery voltages are equal, then both are charged.
While both batteries are charging simultaneously, the
higher capacity battery gets proportionally higher current
from the charger. For Li-Ion batteries, both batteries achieve
the float voltage minus the forward regulation voltage of
20mV. This concept can apply to more than two batteries.
The STAT pin provides information as to when battery 1
is being charged. For intelligent control, the ENBA/ENBB
pin inputs can be used with a microcontroller as shown
in Figure 4.
Automatic Switchover from a Battery to a Wall
Adapter and Charger
Figure 7 illustrates the LTC4413 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 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 INB, the load voltage rises as
the second ideal diode conducts. As soon as the OUTA
voltage exceeds 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
the wall adapter is removed, the voltage at INB collapses
until it is below the load voltage. When this occurs, the
LTC4413 automatically reconnects the battery to the load
and the STAT voltage rises, disabling the LTC4059 battery
charger. One major benefit of this circuit is that when a
wall adapter is present, the user may remove the battery
and replace it without disrupting the load.
LTC4413
IDEAL
ENBA
2
4
3,11
1
5
10
9
6
ENBB
STAT
GND
INA OUTA
470k
4413 F06
LOAD1
WHEN BAT1
BAT1
BATTERY
INPUT
IDEAL
INB OUTB
LOAD2
BAT2
