NiCd/NiMH Battery

Fast-Charge Controllers

14

______________________________________________________________________________________

Linear-Mode, High Series Cell Count

The absolute maximum voltage rating for the BATT+ pin

is higher when the MAX712/MAX713 are powered on. If

more than 11 cells are used in the battery, the BATT+

input voltage must be limited by external circuitry when

DC IN is not applied (Figure 15).

Efficiency During Discharge

efficiency loss during battery use. The efficiency loss is

battery stack’s internal resistance. The circuit in Figure

16 can be used to shunt the sense resistor whenever

power is removed from the charger.

Status Outputs

Figure 17 shows a circuit that can be used to indicate

charger status with logic levels. Figure 18 shows a

circuit that can be used to drive LEDs for power and

charger status.

11

6

5

0

200

600

1000

7

10

400

800

9

8

LOW PEAK

HIGH PEAK

120Hz

RIPPLE

LOAD CURRENT (mA)

Figure 11. Sony CD Player AC Adapter AC-96N Load

Characteristic, 9VDC 600mA

4.3

4.2

030

90

4.5

5.0

4.9

4.7

4.4

60

TIME (MINUTES)

4.8

4.6

ΔV

Δt

CUTOFF

26

24

30

40

38

34

28

36

32

V

T

MAX712/713

Figure 13. 3 NiMH Cells Charged with MAX712

10

8

0

200

600

12

18

400

LOAD CURRENT (mA)

800

16

14

HIGH PEAK

LOW PEAK

120Hz

RIPPLE

Figure 12. Panasonic Modem AC Adapter KX-A11 Load

Characteristic, 12VDC 500mA

4.3

4.2

030

90

4.5

5.0

4.9

4.7

4.4

MAX712/713

60

TIME (MINUTES)

4.8

4.6

26

24

30

40

38

34

28

36

32

ΔV

Δt

CUTOFF

V

T

Figure 14. NiMH Cells Charged with MAX713