11

LTC4412HV

sn4412hv 4412hvfs

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 charging

current until both battery voltages are equal, then both will

be charged. When both are charged simultaneously, the

higher capacity battery will get proportionally higher cur-

rent 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 pins provide information as to which

batteries are being charged. For intelligent control, the

CTL pin input can be used with a microcontroller and

back-to-back MOSFETs as shown in Figure 4. This allows

complete control for disconnection of the charger from

either battery.

TYPICAL APPLICATIO S

GND

CTL

SENSE

GATE

STAT

1

2

3

6

5

4

LTC4412HV

P-CHANNEL

MOSFET

SUPPLY

INPUT

LOGIC

INPUT

*

TO LOAD

4412HV F07

*DRAIN-SOURCE DIODE OF MOSFET

0.1

µF

Figure 7. Logic Controlled High Side Power Switch

High Side Power Switch

Figure 7 illustrates an application circuit for a logic con-

trolled high side power switch. When the CTL pin is a

logical low, the LTC4412HV will turn on the MOSFET.

Because the SENSE pin is grounded, the LTC4412HV will

apply maximum clamped gate drive voltage to the MOSFET.

When the CTL pin is a logical high, the LTC4412HV will

turn off the MOSFET by pulling its gate voltage up to the

supply input voltage and thus deny power to the load. The

MOSFET is connected with its source connected to the

power source. This disables the drain-source diode from

supplying voltage to the load when the MOSFET is off. Note

that if the load is powered from another source, then the

drain-source diode can forward bias and deliver current to

GND

CTL

SENSE

GATE

STAT

1

2

3

6

5

4

LTC4412HV

TO LOAD OR

PowerPath

CONTROLLER

TO LOAD OR

PowerPath

CONTROLLER

STATUS IS HIGH

WHEN BAT1 IS

CHARGING

STATUS IS HIGH

WHEN BAT2 IS

CHARGING

470k

4412HV F06

*

*

BAT1

BATTERY

CHARGER

INPUT

470k

BAT2

GND

CTL

SENSE

GATE

STAT

1

2

3

6

5

4

LTC4412HV

*DRAIN-SOURCE DIODE OF MOSFET

0.1

µF

Figure 6. Automatic Dual Battery Charging

from Single Charging Source

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.