MAX712CPE Maxim Integrated Products, MAX712CPE Datasheet - Page 10

• 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

NiCd/NiMH Battery
Fast-Charge Controllers
Figure 6. Current and Voltage Regulator (linear mode)
Operating Circuit), the diode (D1), and the sense
resistor (R
ment is critical, because violating it can inhibit proper
termination of the fast-charge cycle. A safe rule of
thumb is to choose a source that has a minimum input
voltage = 1.5V + (1.9V x the maximum number of cells
to be charged). When the input voltage at DC IN drops
below the 1.5V + (1.9V x number of cells), the part
oscillates between fast charge and trickle charge and
might never completely terminate fast-charge.
The MAX712/MAX713 are inactive without the wall cube
attached, drawing 5µA (max) from the battery. Diode
D1 prevents current conduction into the DRV pin. When
the wall cube is connected, it charges C1 through R1
(see Typical Operating Circuit) or the current-limiting
diode (Figure 19). Once C1 charges to 5V, the internal
shunt regulator sinks current to regulate V+ to 5V, and
fast charge commences. The MAX712/MAX713 fast
10
DC IN
GND
______________________________________________________________________________________
D1
BATT-
R
SENSE
DRV
SENSE
GND
CURRENT-SENSE AMPLIFIER
BATT-
PGM3 FAST_CHARGE Av
OPEN
REF
V+
X
). This minimum input voltage require-
V+
1
0
0
0
0
BATT-
512
256
128
64
8
VLIMIT
CELL_VOLTAGE
REF
1.25V
BATT-
IN_REGULATION
BATT-
CC
C2
charge until one of the three fast-charge terminating
conditions is triggered.
If DC IN exceeds 20V, add a cascode connection in
series with the DRV pin as shown in Figure 5 to prevent
exceeding DRV’s absolute maximum ratings.
Select the current-limiting component (R1 or D4) to
pass at least 5mA at the minimum DC IN voltage (see
step 6 in the Getting Started section). The maximum
current into V+ determines power dissipation in the
MAX712/MAX713.
Sink current into the DRV pin also causes power dissipa-
tion. Do not allow the total power dissipation to exceed
the specifications shown in the Absolute Maximum
Ratings.
The MAX712/MAX713 enter the fast-charge state under
one of the following conditions:
1) Upon application of power (batteries already
2) Upon insertion of a battery, with TEMP higher than
R
fast charge, the voltage difference between the BATT-
and GND pins is regulated to 250mV. DRV current
increases its sink current if this voltage difference falls
below 250mV, and decreases its sink current if the volt-
age difference exceeds 250mV.
Selecting a fast-charge current (I
4C ensures a C/16 trickle-charge current. Other fast-
charge rates can be used, but the trickle-charge
current will not be exactly C/16.
The MAX712/MAX713 internally set the trickle-charge
current by increasing the current amplifier gain (Figure
6), which adjusts the voltage across R
Trickle-Charge V
table).
SENSE
installed), with battery current detection (i.e., GND
voltage is less than BATT- voltage), and TEMP
higher than TLO and less than THI and cell voltage
higher than the UVLO voltage.
TLO and lower than THI and cell voltage higher than
the UVLO voltage.
fast-charge current (I
sets the fast-charge current into the battery. In
maximum current into V+ =
(maximum DC IN voltage - 5V)/R1
power dissipation due to shunt regulator =
5V x (maximum current into V+)
SENSE
in the Electrical Characteristics
FAST
) = 0.25V/R
FAST
Trickle Charge
) of C/2, C, 2C, or
Fast Charge
SENSE
SENSE
(see