LTC1732EMS-8.4 Linear Technology, LTC1732EMS-8.4 Datasheet - Page 8

• Manufacturer Part Number: LTC1732EMS-8.4
• Description: IC BATTCHRG CNTRLR LI-ION 10MSOP
• Manufacturer: Linear Technology

Specifications of LTC1732EMS-8.4

• Function: Charge Management
• Battery Type: Li-Ion, NiCd, NiMH
• Voltage - Supply: 4.5 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC1732EMS8.4

APPLICATIONS
LTC1732-8.4
Charger Conditions
The charger is off when any of the following conditions exist:
the V
V
DRV pin will be pulled to V
vider is disconnected to reduce the current drain on the
battery.
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the
input voltage and keeps the charger in shutdown mode
until V
V
Trickle Charge and Defective Battery Detection
At the beginning of the charging sequence, if the battery
voltage is below 4.9V, the charger goes into trickle mode.
The charge current drops to 10% of the full-scale current.
If the low voltage persists for one quarter of the total
charge time, the battery is considered defective, the charge
cycle is terminated and the CHRG pin output is forced to
a high impedance state.
Shutdown
The LTC1732-8.4 can be forced into shutdown by floating
the PROG pin and allowing the internal 2.5 A current
source to pull the pin above the 2.457V shutdown thresh-
old voltage. The DRV pin is pulled up to V
external P-channel MOSFET. The internal timer is reset in
the shutdown mode.
Programming Charge Current
The formula for the battery charge current (see Block
Diagram) is:
where R
ground.
8
BAT
CC
I
R
BAT
PROG
= 8.2V, the UVLO circuit has built-in hysteresis.
) is less than 54mV, or the PROG pin is floating. The
CC
CC
pin is less than 8.2V, the dropout voltage (V
PROG
rises above 8.2V. To prevent oscillation around
= (I
= (2.457V/R
= (2.457V/I
PROG
is the total resistance from the PROG pin to
)(800 /R
U
BAT
PROG
INFORMATION
)(800 /R
U
CC
)(800 /R
SENSE
and the internal resistor di-
)
SENSE
W
SENSE
CC
)
) or
turning off the
U
CC
–
For example, if 0.5A charge current is needed, select a
value for R
charge current. R
For best stability over temperature and time, 1% resistors
are recommended. The closest 1% resistor value is 19.6k.
Programming the Timer
The programmable timer terminates the charge cycle.
Typically, when charging at a 1C rate, a discharged Li-Ion
battery will become fully charged in 3 hours. For lower
charge current rates, extend the timer accordingly.The
length of the timer is programmed by an external capaci-
tor at the TIMER pin. The total charge time is:
The timer starts when an input voltage greater than 8.2V
is applied and the program resistor is connected to ground.
After a time-out occurs, the CHRG output will go into a
high impedance state to indicate that charging has stopped.
Connecting the TIMER pin to V
also puts the charger into a constant-current mode. To
only disable the timer function, short the TIMER pin to
GND.
CHRG Status Output Pin
When a charge cycle starts, the CHRG pin is pulled to
ground by an internal N-channel MOSFET that can drive an
LED. When the battery current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET is turned off
and a weak 35 A current source to ground is connected to
the CHRG pin. After a time-out occurs, the pin will go into
a high impedance state. By using two different value pull-
up resistors, a microprocessor can detect three states
from this pin (charging, C/10 and stop charging). See
Figure 1 and Table 1.
R
Time (Hours) = (3 Hours) • (C
C
TIMER
PROG
= (2.457V/500mA)(800 /0.2 ) = 19.656k
= 0.1 F • Time (Hours)/3 (Hours)
SENSE
SENSE
that will drop 100mV at the maximum
= 0.1V/0.5A = 0.2 , then calculate:
CC
TIMER
disables the timer and
/0.1 F) or
17328f