MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
14 ______________________________________________________________________________________
The voltage-slope, fast-charge termination circuitry
might become disabled if attempting to charge a
different number of cells than the number programmed.
The switching frequency (nominally 30kHz) can be
decreased by increasing the value of the capacitor
connected between CC and BATT-. Make sure that
the two capacitors connected to the CC node are
placed as close as possible to the CC pin on the
MAX712/MAX713 and that their leads are of minimum
length. The CC node is a high-impedance point, so do
not route logic lines near the CC pin. The circuit of
Figure 19 cannot service a load while charging.
Order the MAX713SWEVKIT-SO for quick evaluation of
the MAX712/MAX713 in switch-mode operation. For
more information on switch-mode operation and
ordering information for external components, order the
MAX713EVKIT data sheet.
Battery-Charging Examples
Figures 13 and 14 show the results of charging 3 AA,
1000mAh, NiMH batteries from Gold Peak (part no.
GP1000AAH, GP Batteries (619) 438-2202) at a 1A rate
using the MAX712 and MAX713, respectively. The
Typical Operating Circuit
is used with Figure 9a’s
thermistor configuration .
DC IN = Sony AC-190 +9VDC at 800mA AC-DC adapter
PGM0 = V+, PGM1 = REF, PGM2 = REF, PGM3 = REF
R1 = 200Ω, R2 = 150Ω, R
SENSE
= 0.25Ω
C1 = 1µF, C2 = 0.01µF, C3 = 10µF, V
LIMIT
= REF
R3 = 10kΩ, R4 = 15kΩ
T1, T2 = part #13A1002 (Alpha Thermistor: (800) 235-5445)
R5 omitted, T3 omitted, TLO = BATT-
11
6
5
0 200 600 1000
7
10
MAX712/713
OUTPUT VOLTAGE (V)
400
LOAD CURRENT (mA)
800
9
8
LOW PEAK
HIGH PEAK
120Hz
RIPPLE
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
MAX712/713
BATTERY VOLTAGE (V)
BATTERY TEMPERATURE (°C)
60
TIME (MINUTES)
4.8
4.6
∆V
∆t
CUTOFF
26
24
30
40
38
34
28
36
32
V
T
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
∆V
∆t
CUTOFF
V
T
Figure 14. NiMH Cells Charged with MAX713
