MAX712 Maxim, MAX712 Datasheet - Page 14

• Manufacturer Part Number: MAX712
• Description: NiCd/NiMH Battery Fast-Charge Controllers
• Manufacturer: Maxim

NiCd/NiMH Battery
Fast-Charge Controllers
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.
Figure 11. Sony CD Player AC Adapter AC-96N Load
Characteristic, 9VDC 600mA
Figure 13. 3 NiMH Cells Charged with MAX712
14
______________________________________________________________________________________
4.3
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.2
11
10
9
8
6
5
7
0
0
200
V
LOAD CURRENT (mA)
TIME (MINUTES)
30
400
HIGH PEAK
V
t
CUTOFF
LOW PEAK
T
600
60
RIPPLE
120Hz
800
1000
90
26
40
38
36
34
32
30
28
24
Figures 13 and 14 show the results of charging 3 AA,
1000mAh, NiMH batteries from Gold Peak (part no.
GP1000AAH, GP Batteries [phone]) 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 = 200 , R2 = 150 , R
C1 = 1 F, C2 = 0.01 F, C3 = 10 F, V
R3 = 10k , R4 = 15k
T1, T2 = part #13A1002 (Alpha Thermistor: [phone])
R5 omitted, T3 omitted, TLO = BATT-
Figure 12. Panasonic Modem AC Adapter KX-A11 Load
Characteristic, 12VDC 500mA
Figure 14. NiMH Cells Charged with MAX713
5.0
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
10
18
16
14
12
8
0
0
LOW PEAK
V
200
LOAD CURRENT (mA)
Battery-Charging Examples
TIME (MINUTES)
SENSE
30
RIPPLE
120Hz
400
V
t
CUTOFF
T
HIGH PEAK
= 0.25
600
60
LIMIT
800
= REF
90
40
38
36
34
32
28
26
24
30