19-0100; Rev 5; 4/02
KIT
ATION
EVALU
E
BL
AVAILA
NiCd/NiMH Battery
Fast-Charge Controllers
Features
o
Fast-Charge NiMH or NiCd Batteries
o
Voltage Slope, Temperature, and Timer
Fast-Charge Cutoff
o
Charge 1 to 16 Series Cells
o
Supply Battery’s Load While Charging
(Linear Mode)
o
Fast Charge from C/4 to 4C Rate
o
C/16 Trickle-Charge Rate
o
Automatically Switch from Fast to Trickle Charge
o
Linear or Switch-Mode Power Control
o
5µA (max) Drain on Battery when Not Charging
o
5V Shunt Regulator Powers External Logic
General Description
The MAX712/MAX713 fast-charge Nickel Metal Hydride
(NiMH) and Nickel Cadmium (NiCd) batteries from a DC
source at least 1.5V higher than the maximum battery
voltage. 1 to 16 series cells can be charged at rates up
to 4C. A voltage-slope detecting analog-to-digital convert-
er, timer, and temperature window comparator determine
charge completion. The MAX712/MAX713 are powered
by the DC source via an on-board +5V shunt regulator.
They draw a maximum of 5µA from the battery when not
charging. A low-side current-sense resistor allows the
battery charge current to be regulated while still
supplying power to the battery’s load.
The MAX712 terminates fast charge by detecting zero
voltage slope, while the MAX713 uses a negative
voltage-slope detection scheme. Both parts come in 16-
pin DIP and SO packages. An external power PNP tran-
sistor, blocking diode, three resistors, and three
capacitors are the only required external components.
For high-power charging requirements, the MAX712/
MAX713 can be configured as a switch-mode battery
charger that minimizes power dissipation. Two evaluation
kits are available: Order the MAX712EVKIT-DIP for quick
evaluation of the linear charger, and the MAX713EVKIT-
SO to evaluate the switch-mode charger.
MAX712/MAX713
Ordering Information
PART
MAX712CPE
MAX712CSE
MAX712C/D
MAX712EPE
MAX712ESE
MAX712MJE
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
16 Plastic DIP
16 Narrow SO
Dice*
16 Plastic DIP
16 Narrow SO
16 CERDIP**
________________________Applications
Battery-Powered Equipment
Laptop, Notebook, and Palmtop Computers
Handy-Terminals
Cellular Phones
Portable Consumer Products
Portable Stereos
Cordless Phones
Ordering Information continued at end of data sheet.
*Contact
factory for dice specifications.
**Contact
factory for availability and processing to MIL-STD-883.
Typical Operating Circuit
DC IN
C4
0.01µF
Q1
2N6109
R2
150Ω
R1
Pin Configuration
TOP VIEW
VLIMIT 1
BATT+ 2
PGM0 3
PGM1 4
THI 5
TLO 6
TEMP 7
FASTCHG 8
16 REF
15 V+
14 DRV
C1
1µF
R3
68kΩ
TEMP
10µF
R4
22kΩ
LOAD
CC BATT- TLO GND
C2
0.01µF
VLIMIT
REF
BATT+
C3
10µF
WALL
CUBE
THI
V+
DRV
D1
1N4001
MAX712
MAX713
13 GND
12 BATT-
11 CC
10 PGM3
9
PGM2
MAX712
MAX713
BATTERY
R
SENSE
DIP/SO
SEE FIGURE 19 FOR SWITCH-MODE CHARGER CIRCUIT.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
NiCd/NiMH Battery
Fast-Charge Controllers
MAX712/MAX713
ABSOLUTE MAXIMUM RATINGS
V+ to BATT- .................................................................-0.3V, +7V
BATT- to GND ........................................................................±1V
BATT+ to BATT-
Power Not Applied............................................................±20V
With Power Applied ................................The higher of ±20V or
±2V x (programmed cells)
DRV to GND ..............................................................-0.3V, +20V
FASTCHG
to BATT- ...................................................-0.3V, +12V
All Other Pins to GND......................................-0.3V, (V+ + 0.3V)
V+ Current.........................................................................100mA
DRV Current. .....................................................................100mA
REF Current.........................................................................10mA
Continuous Power Dissipation (T
A
= +70°C)
Plastic DIP (derate 10.53mW/°C above +70°C............842mW
Narrow SO (derate 8.70mW/°C above +70°C .............696mW
CERDIP (derate 10.00mW/°C above +70°C ................800mW
Operating Temperature Ranges
MAX71_C_E .......................................................0°C to +70°C
MAX71_E_E .................................................... -40°C to +85°C
MAX71_MJE ................................................. -55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(I
V+
= 10mA, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Refer to the
Typical Operating Circuit.
All measurements are with respect to
BATT-, not GND.)
PARAMETER
V+ Voltage
I
V+
(Note 1)
BATT+ Leakage
BATT+ Resistance with Power On
C1 Capacitance
C2 Capacitance
REF Voltage
Undervoltage Lockout
External VLIMIT Input Range
THI, TLO, TEMP Input Range
THI, TLO Offset Voltage (Note 2)
THI, TLO, TEMP, VLIMIT Input Bias Current
VLIMIT Accuracy
Internal Cell Voltage Limit
Fast-Charge VSENSE
PGM3 = V+
Trickle-Charge VSENSE
PGM3 = open
PGM3 = REF
PGM3 = BATT-
Voltage-Slope Sensitivity (Note 3)
Timer Accuracy
Battery-Voltage to Cell-Voltage
Divider Accuracy
DRV Sink Current
2
V
DRV
= 10V
MAX713
MAX712
-15
-1.5
30
1.2V < V
LIMIT
< 2.5V, 5mA < I
DRV
< 20mA,
PGM0 = PGM1 = V+
V
LIMIT
= V+
0V < TEMP < 2V, TEMP voltage rising
0mA < I
REF
< 1mA
Per cell
V+ = 0V, BATT+ = 17V
PGM0 = PGM1 = BATT-, BATT+ = 30V
30
0.5
5
1.96
0.35
1.25
0
-10
-1
-30
1.6
225
1.5
4.5
12.0
26.0
1.65
250
3.9
7.8
15.6
31.3
-2.5
0
15
1.5
2.04
0.50
2.50
2
10
1
30
1.7
275
7.0
12.0
20.0
38.0
mV/t
A
per cell
%
%
mA
mV
CONDITIONS
5mA < I
V+
< 20mA
MIN
4.5
5
5
TYP
MAX
5.5
UNITS
V
mA
µA
kΩ
µF
nF
V
V
V
V
mV
µA
mV
V
mV
_______________________________________________________________________________________
NiCd/NiMH Battery
Fast-Charge Controllers
ELECTRICAL CHARACTERISTICS (continued)
(I
V
+ = 10mA, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Refer to the
Typical Operating Circuit.
All measurements are with respect to
BATT-, not GND.)
PARAMETER
FASTCHG
Low Current
FASTCHG
High Current
A/D Input Range (Note 4)
CONDITIONS
V
FASTCHG
= 0.4V
V
FASTCHG
= 10V
Battery voltage ÷ number of cells programmed
1.4
MIN
2
10
1.9
TYP
MAX
UNITS
mA
µA
V
MAX712/MAX713
Note 1:
The MAX712/MAX713 are powered from the V+ pin. Since V+ shunt regulates to +5V, R1 must be small enough to allow at
least 5mA of current into the V+ pin.
Note 2:
Offset voltage of THI and TLO comparators referred to TEMP.
Note 3:
t
A
is the A/D sampling interval (Table 3).
Note 4:
This specification can be violated when attempting to charge more or fewer cells than the number programmed. To ensure
proper voltage-slope fast-charge termination, the (maximum battery voltage) ÷ (number of cells programmed) must fall
within the A/D input range.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
CURRENT-SENSE AMPLIFIER
FREQUENCY RESPONSE (with 15pF)
20
MAX712/13 toc01
CURRENT-SENSE AMPLIFIER
FREQUENCY RESPONSE (with 10nF)
40
20
MAX712/13 toc02
40
C2 = 15pF
FASTCHG = 0V
10
GAIN (dB)
A
V
0
Φ
-40
0
PHASE (DEGREES)
GAIN (dB)
10
C2 = 10nF
FASTCHG = 0V
0
A
V
0
Φ
-10
-80
-40
PHASE (DEGREES)
35
30
25
20
15
10
5
0
0
10
20
30
40
50
60
BATTERY TEMPERATURE(°C)
BATTERY THERMISTOR RESISTANCE (kΩ)
BATT-
-10
CC
CURRENT-
SENSE
AMP
BATT-
+
+
-80
V
IN
-
V
OUT
-
GND
-20
1k
10k
100k
FREQUENCY (Hz)
1M
10M
-120
-20
10
100
1k
10k
FREQUENCY (Hz)
-120
CURRENT ERROR-AMPLIFIER
TRANSCONDUCTANCE
FASTCHG = 0V, V+ = 5V
DRV PIN SINK CURRENT(mA)
MAX712/13 toc03
SHUNT-REGULATOR VOLTAGE
vs. CURRENT
5.6
5.4
V+ VOLTAGE (V)
5.2
5.0
4.8
4.6
4.4
4.2
0.4
0.2
0
10
20
30
40
50
60
CURRENT INTO V+ PIN (mA)
DRV SINKING CURRENT
DRV NOT SINKING CURRENT
MAX712/13 toc04
ALPHA SENSORS PART No. 14A1002
STEINHART-HART INTERPOLATION
1.6
1.4
TEMP PIN VOLTAGE (V)
1.2
1.0
0.8
0.6
MAX712/13 toc05
100
5.8
10
1
0.1
1.95
4.0
1.97
1.99
2.01
2.03
2.05
VOLTAGE ON CC PIN (V)
_______________________________________________________________________________________
3
NiCd/NiMH Battery
Fast-Charge Controllers
MAX712/MAX713
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
MAX713
NiCd BATTERY CHARGING
CHARACTERISTICS AT C RATE
MAX712/13 toc06
MAX713
NiMH BATTERY CHARGING
CHARACTERISTICS AT C RATE
MAX712/13 toc07
CELL TEMPERATURE (°C)
1.55
CELL VOLTAGE (V)
∆V
CUTOFF
∆t
T
40
1.50
V
35
1.55
V
∆V
CUTOFF
∆t
35
1.45
30
1.50
T
1.45
30
1.40
25
25
0
30
60
90
0
30
60
90
CHARGE TIME (MINUTES)
CHARGE TIME (MINUTES)
MAX713
NiCd BATTERY-CHARGING
CHARACTERISTICS AT C/2 RATE
MAX712/13 toc08
MAX713
NiMH BATTERY CHARGING
CHARACTERISTICS AT C/2 RATE
MAX712/13 toc09
CELL TEMPERATURE (°C)
35
1.50
V
1.45
1.40
T
35
1.45
V
30
30
25
T
1.40
25
0
50
100
150
0
CHARGE TIME (MINUTES)
100
50
150
CHARGE TIME (MINUTES)
MAX713
CHARGING CHARACTERISTICS OF A
FULLY-CHARGED NiMH BATTERY
1.65
V
1.60
CELL VOLTAGE (V)
∆V
CUTOFF
∆t
1.55
35
MAX712/13 toc10
MAX713
CHARGING CHARACTERISTICS OF A
FULLY CHARGED NiMH BATTERY
1.65
V
MAX712/13 toc11
5 MINUTE REST
BETWEEN CHARGES
40
CELL TEMPERATURE (°C)
CELL VOLTAGE (V)
1.60
1.55
5-HOUR REST
BETWEEN CHARGES
1.50
T
1.45
35
1.50
T
30
25
30
1.45
25
0
5
10
15
20
0
CHARGE TIME (MINUTES)
5
10
15
CHARGE TIME (MINUTES)
20
4
_______________________________________________________________________________________
CELL TEMPERATURE (°C)
∆V
CUTOFF
∆t
40
CELL TEMPERATURE (°C)
1.50
CELL VOLTAGE (V)
CELL VOLTAGE (V)
∆V
CUTOFF
∆t
1.55
∆V
CUTOFF
∆t
40
CELL TEMPERATURE (°C)
1.60
CELL VOLTAGE (V)
40
NiCd/NiMH Battery
Fast-Charge Controllers
Pin Description
PIN
1
2
NAME
VLIMIT
BATT+
FUNCTION
Sets the maximum cell voltage. The battery terminal voltage (BATT+ - BATT-) will not exceed VLIMIT x
(number of cells). Do not allow VLIMIT to exceed 2.5V. Tie VLIMIT to VREF for normal operation.
Positive terminal of battery
PGM0 and PGM1 set the number of series cells to be charged. The number of cells can be set from
1 to 16 by connecting PGM0 and PGM1 to any of V+, REF, or BATT-, or by leaving the pin open (Table
2). For cell counts greater than 11, see the
Linear-Mode, High Series Cell Count
section. Charging more
or fewer cells than the number programmed may inhibit
∆V
fast-charge termination.
Trip point for the over-temperature comparator. If the voltage-on TEMP rises above THI, fast charge ends.
Trip point for the under-temperature comparator. If the MAX712/MAX713 power on with the voltage-on
TEMP less than TLO, fast charge is inhibited and will not start until TEMP rises above TLO.
Sense input for temperature-dependent voltage from thermistors.
Open-drain, fast-charge status output. While the MAX712/MAX713 fast charge the battery,
FASTCHG
sinks current. When charge ends and trickle charge begins,
FASTCHG
stops sinking current.
PGM2 and PGM3 set the maximum time allowed for fast charging. Timeouts from 33 minutes to 264
minutes can be set by connecting to any of V+, REF, or BATT-, or by leaving the pin open (Table 3).
PGM3 also sets the fast-charge to trickle-charge current ratio (Table 5).
Compensation input for constant current regulation loop
Negative terminal of battery
System ground. The resistor placed between BATT- and GND monitors the current into the battery.
Current sink for driving the external PNP current source
Shunt regulator. The voltage on V+ is regulated to +5V with respect to BATT-, and the shunt current
powers the MAX712/MAX713.
2V reference output
MAX712/MAX713
3, 4
PGM0,
PGM1
5
6
7
8
THI
TLO
TEMP
FASTCHG
PGM2,
PGM3
CC
BATT-
GND
DRV
V+
REF
9, 10
11
12
13
14
15
16
_______________________________________________________________________________________
5
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