Datasheet

MAX712/MAX713
NiCd/NiMH Battery
Fast-Charge Controllers
13
Maxim Integrated
Some battery packs come with a temperature-detect-
ing thermistor connected to the battery pack’s negative
terminal. In this case, use the configuration shown in
Figure 9b. Thermistors T2 and T3 can be replaced by
standard resistors if absolute temperature charge cut-
off is acceptable. All resistance values in Figures 9a
and 9b should be chosen in the 10kΩ to 500kΩ range.
__________Applications Information
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 [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 = 200Ω, R2 = 150Ω, R
SENSE
= 0.25Ω
C1 = 1µF, C2 = 0.01µF, C3 = 10µF, V
LIMIT
= REF
R3 = 10kΩ, R4 = 15kΩ
T1, T2 = part #14A1002 (Alpha Sensors: 858-549-4660) R5
omitted, T3 omitted, TLO = BATT-
0.022μF
0.022μF
NOTE: FOR ABSOLUTE TEMPERATURE CHARGE CUTOFF, T2 AND T3 CAN BE
REPLACED BY STANDARD RESISTORS.
1μF
TEMP
TLO
IN THERMAL
CONTACT WITH
BATTERY
AMBIENT
TEMPERATURE
AMBIENT
TEMPERATURE
T3
+2.0V
T2
T1
R3
R4
R5
HOT
REF
THI
BATT-
COLD
MAX712
MAX713
Figure 9a. Temperature Comparators
MAX712
MAX713
0.022μF
0.022μF
NOTE: FOR ABSOLUTE TEMPERATURE CHARGE CUTOFF, T2 AND T3 CAN BE
REPLACED BY STANDARD RESISTORS.
1μF
TEMP
TLO
AMBIENT
TEMPERATURE
AMBIENT
TEMPERATURE
IN THERMAL
CONTACT WITH
BATTERY
T3
+2.0V
T1
T2
R4
R3R5
HOT
REF
THI
BATT-
COLD
Figure 9b. Alternative Temperature Comparator Configuration
11
6
0 200 600 1000
7
10
MAX712/713
OUTPUT VOLTAGE (V)
400 800
9
8
120Hz RIPPLE
LOW PEAK
HIGH PEAK
LOAD CURRENT (mA)
Figure 10. Sony Radio AC Adapter AC-190 Load Characteristic,
9VDC 800mA