LTC1731EMS8-4.1#TRPBF Linear Technology, LTC1731EMS8-4.1#TRPBF Datasheet - Page 9

• Manufacturer Part Number: LTC1731EMS8-4.1#TRPBF
• Description: IC CTRLR BATT CHRGR LI-ION 8MSOP
• Manufacturer: Linear Technology

Specifications of LTC1731EMS8-4.1#TRPBF

• 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

APPLICATIONS
After an internal time delay of 320ms, this state is then
latched. This delay will help prevent false triggering due to
transient currents. The end-of-charge comparator is dis-
abled in trickle charge mode.
Gate Drive
Typically the LTC1731 controls an external P-channel
MOSFET to supply current to the battery. The DRV pin is
internally clamped to 6.5V below V
low voltage P-channel MOSFETs with gate to source
breakdown voltage rated at 8V to be used.
An external PNP transistor can also be used as the pass
transistor instead of the P-channel MOSFET. Due to the
low current gain of the current amplifier (CA), a high gain
Darlington PNP transistor is required to avoid excessive
charge current error. The gain of the current amplifier is
around 0.6 A/mV. For every 1 A of base current, a 1.6mV
of gain error shows up at the inputs of CA. With R
19.6k (100mV across R
error in charging current.
TYPICAL APPLICATIO
CONDITION
NO WALL ADAPTER
CHARGING (I > C/10)
CHARGING (I < C/10)
TIMER EXPIRED
U
INFORMATION
SENSE
U
GREEN
OFF
OFF
ON
ON
), it represents 1.67% of
U
AMBER
CC
W
OFF
OFF
OFF
ON
. This feature allows
MMBT3906
Using CHRG Pin to Indicate Charge Status
GREEN
1k
U
OPTIONAL: FOR REVERSE
20k
PROG
INPUT PROTECTION
MMBT3906
2.2k
=
AMBER
0.1 F
1k
Constant-Current Only Mode
The LTC1731 can be used as a programmable current
source by forcing the TIMER pin to V
useful for charging NiMH or NiCd batteries. In the con-
stant-current only mode, the timer and voltage amplifier
are both disabled. An external termination method is
required to properly terminate the charge.
Stability
The charger is stable without any compensation when a
P-channel MOSFET is used as the pass transistor.
However, a 10 F capacitor is recommended at the BAT
pin to keep the ripple voltage low when the battery is
disconnected.
When a PNP transistor is chosen as the pass transistor, a
1000pF capacitor is required from the DRV pin to V
capacitor is needed to help stablize the voltage loop. A
10 F capacitor at the BAT pin is also recommended when
a battery is not present.
MMSD4148
1.5k
4.7k
2
3
LTC1731-4.1/LTC1731-4.2
CHRG
TIMER
LTC1731-4.2
V
IN
GND
V
CC
= 6V
4
7
SENSE
PROG
DRV
MBRM120T3
BAT
8
6
1
5
R
19.6k
PROG
+
Si9430DY
R
0.2
Li-ION
CELL
SENSE
CC
. This is particularly
1731 TA04
1 F
10 F
CC
. This
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