Datasheet

MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
14
Maxim Integrated
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
The current-sense resistor, R
SENSE
, causes a small
efficiency loss during battery use. The efficiency loss is
significant only if R
SENSE
is much greater than the
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
MAX712/713
OUTPUT VOLTAGE (V)
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
BATTERY VOLTAGE (V)
BATTERY TEMPERATURE (°C)
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
MAX712/713
OUTPUT VOLTAGE (V)
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
BATTERY VOLTAGE (V)
BATTERY TEMPERATURE (°C)
60
TIME (MINUTES)
4.8
4.6
26
24
30
40
38
34
28
36
32
DV
Dt
CUTOFF
V
T
Figure 14. NiMH Cells Charged with MAX713