MAX1782ETM+C8F Maxim Integrated, MAX1782ETM+C8F Datasheet - Page 5

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MAX1782ETM+C8F

Manufacturer Part Number
MAX1782ETM+C8F
Description
Battery Management Adv Smart Battery Pack Controller
Manufacturer
Maxim Integrated
Series
MAX1782r
Datasheet

Specifications of MAX1782ETM+C8F

Rohs
yes
The MAX1736 provides a simple, safe, low-cost method
of charging a single-cell Li+ battery with nearly no heat
generation. Combined with a current-limited voltage
source, the MAX1736 provides precharge, fast-charge,
and top-off-charge capabilities. After constant-current
fast charge, top-off safely finishes charging the battery
by pulse-width modulating charge current. The top-off
on-time is kept below the electrochemical time constant
of the cell. The key advantage of this method is that the
charge circuit is small and generates minimal heat
while providing a safe method of charging to ensure
maximum cell life. Figure 1 shows the MAX1736 func-
tional diagram.
To protect Li+ cells from damage that may occur if fast
charged from a dead state, the MAX1736 precharges the
Li+ cell with 6mA at the start of a charging cycle when the
cell voltage is below 2.5V. As soon as the cell voltage
reaches 2.5V, the MAX1736 begins fast charging.
In fast-charge mode, the MAX1736 turns on the exter-
nal P-channel MOSFET. Charging current is set by the
current limit of the external supply; current is not regu-
lated by the MAX1736. The P-channel MOSFET is
used only as a switch, not as a linear regulator.
Therefore, the circuit’s power dissipation is minimized,
permitting rapid charge cycles with almost no heat
generation. The external power supply should have a
PIN
1
2
3
4
5
6
NAME
GATE
BATT
GND
_______________________________________________________________________________________
EN
CT
IN
SOT23, Single-Cell Li+ Battery Charger
Detailed Description
Input Voltage from Current-Limited Voltage Source (22V max). Bypass to GND with a 0.1µF
capacitor. The charging current is set by the current limit of the external power supply.
Gate Drive for External PMOS Pass Element. The PMOS device should have a V
of 2.5V or less (see Selecting External Components).
Ground. Connect the battery’s negative terminal to GND.
Logic-Level Enable Input. Pull low to disable the MAX1736. EN is internally pulled up to V
100mV through 350kΩ, but draws no current from BATT.
Charge Time Control. Sets the minimum on-time, minimum off-time, and the IN detection interval.
Place a 0.33µF capacitor between CT and GND for most applications (see Selecting External
Components).
Cell Voltage Monitor Input, Precharge Current Output, and MAX1736 Power Source. Connect BATT
to the positive terminal of a single Li+ cell. Bypass BATT with a capacitor to GND (1.5µF per amp of
charge current).
Fast Charge
Precharge
for Current-Limited Supply
specified current limit that matches the desired fast-
charge current for the Li+ cell.
With the P-channel MOSFET on, V
equal to V
nected, the MAX1736 periodically turns the P-channel
MOSFET off and checks the voltage at IN. During fast
charge, this occurs once every input detection interval
(20s with C
detection occurs more frequently and is continuous
when the MOSFET is off (see Selecting External
Components).
When the battery approaches full charge, its instanta-
neous voltage reaches the BATT regulation voltage and
pulsed top-off begins. The MAX1736 uses a hysteretic
algorithm with a minimum on- and off-time. Cell voltage
is sampled with no charging current to minimize errors
due to battery and cell protection resistance.
If the voltage is below the BATT regulation voltage, the
P-channel MOSFET switches on for a minimum on-time.
If, at the end of the minimum on-time, the cell voltage is
still below the BATT regulation voltage, the switch
remains on until the cell voltage reaches the BATT reg-
ulation voltage. At that point, the P-channel MOSFET
then switches off for at least the minimum off-time. The
minimum on-time is set by CT and should be set below
the electrochemical time constant of the cell. A C
value of 0.33µF sets a minimum on-time of 165ms,
which is adequate for most Li+ batteries.
DESCRIPTION
BATT
CT
. To detect that an input supply is con-
= 0.33µF). During pulsed top-off, input
Pin Description
GS
Pulsed Top-Off
IN
threshold
will be nearly
BATT
+
CT
5

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