11

LTC4413

4413f

APPLICATIO S I FOR ATIO

If the AUX is present when a wall adapter is applied, as the

resistive divider to ENBB rises through the turn-off thresh-

old, the STAT pin will fall and MP1 will conduct allowing the

wall adapter to power the load. When the wall adapter is

removed while the AUX supply is present, the load voltage

will fall until the voltage divider at the ENBB pin falls through

its turn-on threshold. Once this occurs, the LTC4413 will

automatically connect 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 will disconnect the battery from the load, and the

auxiliary supply will provide 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

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Figure 6

LTC4413

IDEAL

ENBA

2

4

3,11

1

5

10

9

6

ENBB

STAT

GND

INA

OUTA

470k

4413 F06

LOAD1

STAT IS HIGH

WHEN BAT1

IS CHARGING

BAT1

BATTERY

CHARGER

INPUT

IDEAL

INB

OUTB

LOAD2

BAT2

current until both battery voltages are equal, then both will

be charged. While both batteries are charging simulta-

neously, the higher capacity battery will get proportionally

higher current from the charger. For Li-Ion batteries, both

batteries will achieve the float voltage minus the forward

regulation voltage of 20mV. This concept can apply to

more than two batteries. The STAT pin provides informa-

tion 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 will be high, thereby disabling

the battery charger. If a wall adapter of a higher voltage

than the battery is connected to INB, the load voltage will

rise as the second ideal diode conducts. As soon as the

OUTA voltage exceeds INA voltage, the BAT will be discon-

nected from the load and the STAT voltage will fall, turning

on the LTC4059 battery charger and beginning a charge

cycle. If the wall adapter is removed, the voltage at INB will

collapse until it is below the load voltage. When this oc-

curs, the LTC4413 will automatically reconnect the battery

to the load and the STAT voltage will rise, 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.

Figure 7

LTC4413

IDEAL

ENBA

2

4

3,11

1

5

10

9

6

ENBB

STAT

GND

INA

OUTA

R1

560k

4413 F07

R2

100k

1-CELL

Li-Ion

IDEAL

INB

OUTB

TO LOAD

C2

4.7µF

C1

10µF

C1: C0805C106K8PAC

C2: C1206C475K8PAC

ENB

Li CC

LTC4059

PROG

WALL

ADAPTER

BAT

GND