LTC1731EMS8-8.4#PBF Linear Technology, LTC1731EMS8-8.4#PBF Datasheet - Page 7

• Manufacturer Part Number: LTC1731EMS8-8.4#PBF
• Description: IC BATT CHRG CNTRLR LI-ION 8MSOP
• Manufacturer: Linear Technology

Specifications of LTC1731EMS8-8.4#PBF

• Function: Charge Management
• Battery Type: Li-Ion, NiCd, NiMH
• Voltage - Supply: 8.8 V ~ 12 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATIO
The LTC1731-8.2/LTC1731-8.4 are linear battery charger
controllers. The charge current is programmed by the
combination of a program resistor (R
PROG pin to ground and a sense resistor (R
tween the V
current through an internal trimmed 800 resistor that
creates a voltage drop from V
amplifier (CA). The current amplifier servos the gate of the
external P-channel MOSFET to force the same voltage
drop across R
the potential at the BAT pin approaches the preset float
voltage, the voltage amplifier (VA) will start sinking cur-
rent which shrinks the voltage drop across R
reducing the charge current.
Charging begins when the potential at V
the UVLO level and a program resistor is connected from
the PROG pin to ground. At the beginning of the charge
cycle, if the battery voltage is below 4.95V, the charger
goes into trickle charge mode. The trickle charge current
is 10% of the full-scale current. If the cell voltage stays low
for one quarter of the total charge time, the charge
sequence will terminate.
The charger goes into the fast charge constant-current
mode after the voltage on the BAT pin rises above 4.95V.
In constant-current mode, the charge current is set by the
combination of R
CC
SENSE
and SENSE pins. R
SENSE
U
which sets the charge current. When
and R
CC
PROG
to the input of the current
.
PROG
CC
PROG
sets a program
pin rises above
SENSE
) from the
SENSE
, thus
) be-
When the battery approaches the final float voltage, the
charge current will begin to decrease. When the current
drops to 10% of the full-scale charge current, an internal
comparator will turn off the N-channel MOSFET at the
CHRG pin and connect a weak current source to ground to
indicate a near end-of-charge (C/10) condition.
An external capacitor on the TIMER pin sets the total
charge time. After a time-out occurs, the charge cycle is
terminated and the CHRG pin is forced to a high imped-
ance state. To restart the charge cycle, simply remove the
input voltage and reapply it, or float the PROG pin momen-
tarily.
For batteries like lithium-ion that require an accurate final
float potential, the internal 2.457V reference, voltage
amplifier and the resistor divider provide regulation with
LTC1731-8.2/LTC1731-8.4 can be turned into a current
source by pulling the TIMER pin to V
constant-current only mode, the voltage amplifier, timer
and the trickle charge function are all disabled.
The charger can be shut down by floating the PROG pin
(I
clamp at 3.5V.
When the input voltage is not present, the charger goes
into a sleep mode, dropping I
reduces the current drain on the battery and increases the
standby time.
1% (max) accuracy. For NiMH and NiCd batteries, the
CC
1mA). An internal current source will pull it high and
LTC1731-8.2/LTC1731-8.4
CC
to 15 A. This greatly
CC
. When in the
sn1731 17318fs
7