MAX712CPE Maxim Integrated Products, MAX712CPE Datasheet - Page 11

• Manufacturer Part Number: MAX712CPE
• Description: IC BATT FASTCHRG NICD/NIMH 16DIP
• Manufacturer: Maxim Integrated Products

Specifications of MAX712CPE

• Function: Charge Management
• Battery Type: Nickel Cadmium (NiCd), Nickel Metal-Hydride (NiMH)
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Configuration:
Settings:
Since PGM3 = BATT-, the voltage on R
ed to 31.3mV during trickle charge, and the current is
20.7mA. Thus the trickle current is actually C/25, not
C/16.
The trickle-charge current can be reduced to less than
C/16 using the circuit in Figure 7. In trickle charge,
some of the current will be shunted around the battery,
since Q2 is turned on. Select the value of R7 as follows:
where
The regulation loop controls the output voltage between
the BATT+ and BATT- terminals and the current
through the battery via the voltage between BATT- and
GND. The sink current from DRV is reduced when the
Table 5. Trickle-Charge Current
Determination from PGM3
Typical Operating Circuit
2 x Panasonic P-50AA 500mAh AA NiCd batteries
C/3 fast-charge rate
264-minute timeout
Negative voltage-slope cutoff enabled
Minimum DC IN voltage of 6V
Use MAX713
PGM0 = V+, PGM1 = open, PGM2 = BATT-,
PGM3 = BATT-, R
I
FAST
PGM3
OPEN
BATT-
REF
V+
R7 = (V
= 167mA), R1 = (6V - 5V)/5mA = 200Ω
Further Reduction of Trickle-Charge
V
I
current setting
I
BATT
TRlCKLE
BATT
BATT
= desired battery trickle-charge current
FAST-CHARGE
= battery voltage when charged
______________________________________________________________________________________
Nonstandard Trickle-Charge
+ 0.4V)/(l
= MAX712/MAX713 trickle-charge
SENSE
Current for NiMH Batteries
RATE
C/2
4C
2C
C
= 1.5Ω (fast-charge current,
TRlCKLE
Current Example
Regulation Loop
CURRENT (I
TRICKLE-CHARGE
- I
SENSE
BATT
I
I
I
FAST
FAST
FAST
I
FAST
)
/64
/32
/16
is regulat-
/8
TRICKLE
)
Fast-Charge Controllers
output voltage exceeds the number of cells times
V
grammed charging current.
For a linear-mode circuit, this loop provides the following
functions:
1) When the charger is powered, the battery can be
2) If the load is connected as shown in the Typical
The voltage loop sets the maximum output voltage
between BATT+ and BATT-. If V
2.5V, then:
Maximum BATT+ voltage (referred to BATT-) = V
(number of cells as determined by PGM0, PGM1)
VLIMIT should be set between 1.9V and 2.5V. If VLIMIT
is set below the maximum cell voltage, proper
termination of the fast-charge cycle might not occur.
Cell voltage can approach 1.9V/cell, under fast charge,
in some battery packs. Tie V
operation.
With the battery removed, the MAX712/MAX713 do not
provide constant current; they regulate BATT+ to the
maximum voltage as determined above.
Figure 7. Reduction of Trickle Current for NiMH Batteries
(Linear Mode)
LIMIT
DC IN
GND
removed without interrupting power to the load.
Operating Circuit, the battery current is regulated
regardless of the load current (provided the input
power source can supply both).
MAX712
MAX713
, or when the battery current exceeds the pro-
DRV
NiCd/NiMH Battery
Q1
FASTCHG
V+
10k
10k
LIMIT
LIMIT
to V
is set to less than
Voltage Loop
R7
Q2
D1
REF
for normal
BATTERY
R
SENSE
LIMIT
11
x