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PDF LTC1731-8.2 Data sheet ( Hoja de datos )
| Número de pieza | LTC1731-8.2 | |
| Descripción | Lithium-Ion Linear Battery Charger Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1731-8.2/LTC1731-8.4
Lithium-Ion Linear
Battery Charger Controller
FEATURES
s Complete Linear Charger Controller for
2-Cell Lithium-Ion Batteries
s 1% Voltage Accuracy
s Programmable Charge Current
s C/10 Charge Current Detection Output
s Programmable Charge Termination Timer
s Space Saving 8-Pin MSOP Package
s Automatic Sleep Mode When Input Supply
is Removed (15µA Battery Drain)
s Automatic Trickle Charging of Low Voltage Cells
s Programmable for Constant-Current-Only Mode
U
APPLICATIO S
s Cellular Phones
s Handheld Computers
s Charging Docks and Cradles
s Programmable Current Source
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTIO
The LTC®1731-8.2/LTC1731-8.4 are complete constant-
current/constant-voltage linear charger controllers for 2-
cell lithium-ion (Li-Ion)batteries. Nickel-cadmium (NiCd)
and nickel-metal-hydride (NiMH) batteries can also be
charged with constant current using external termina-
tion. The external sense resistor sets the charge current
with 7% accuracy. An internal resistor divider and preci-
sion reference set the final float potential with 1% accu-
racy. The output float voltages are set internally to 8.2V
(LTC1731-8.2) or 8.4V (LTC1731-8.4).
When the input supply is removed, the LTC1731-8.2/
LTC1731-8.4 automatically enter a low current sleep mode,
dropping the battery drain current to typically 15µA. An
internal comparator detects the end-of-charge (C/10) con-
dition while a programmable timer, using an external
capacitor, sets the total charge time. Fully discharged cells
are automatically trickle charged at 10% of the pro-
grammed current until battery voltage exceeds 4.95V.
The LTC1731-8.2/LTC1731-8.4 are available in the 8-pin
MSOP and SO packages. For 1-cell Li-Ion battery charg-
ing, see the LTC1731-4.1 and LTC1731-4.2 data sheets.
TYPICAL APPLICATIO
400mA Li-Ion Charger
VIN = 9V
MBRM120T3
CHARGE
STATUS
CTIMER
0.1µF
2k
2
7
VCC
SENSE
CHRG DRV
8
6
LTC1731-8.4
3
TIMER
1
BAT
5
PROG
GND
4
RPROG*
19.6k
RSENSE
0.2Ω
Q1
Si9430DY
IBAT = 400mA
+
2-CELL
Li-ION
1µF
10µF
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
1731 TA01
Typical Li-Ion Charge Cycle
CONSTANT
CURRENT
CONSTANT
VOLTAGE
9
BATTERY VOLTAGE
400 8
400mA HR BATTERY
300
CHARGE CURRENT
200 7
CHRG
LED OFF TIMER
100 STOPS
06
0 0.5 1.0 1.5 2.0 2.5 3.0
TIME (HOURS)
1731 TA01b
sn1731 17318fs
1
1 page  
LTC1731-8.2/LTC1731-8.4
PIN FUNCTIONS
BAT (Pin 1): Battery Sense Input. A bypass capacitor of at
least 10µF is required to keep the loop stable when the
battery is not connected. A precision internal resistive
divider sets the final float potential on this pin. The resistor
divider is disconnected in sleep mode.
CHRG (Pin 2): Open-Drain Charge Status Output. When
the battery is being charged, the CHRG pin is pulled low by
an internal N-channel MOSFET. When the charge current
drops to 10% of the full-scale current for at least 0.32
seconds, the N-channel MOSFET turns off and a 100µA
current source is connected from the CHRG pin to GND.
When the timer runs out or the input supply is removed,
the current source will be disconnected and the CHRG pin
is forced into a high impedance state.
TIMER (Pin 3): Timer Capacitor and Constant-Voltage
Mode Disable Input Pin. A capacitor CTIMER connected
from this pin to ground sets a 30 hour/µF time period for
charge termination. When the TIMER pin is connected to
VCC, the constant-voltage mode and the timer is disabled
and the IC will operate in constant-current mode only.
Short the TIMER pin to GND to disable the internal timer
and the C/10 functions.
GND (Pin 4): Ground.
PROG (Pin 5): Charge Current Program and Shutdown
Input Pin. The charge current is programmed by connect-
ing a resistor, RPROG to ground. The charge current is IBAT
= (VPROG • 800Ω)/(RPROG • RSENSE). The IC can be forced
into shutdown by floating the PROG pin and allowing the
internal 2.5µA current source to pull the pin above the
2.457V shutdown threshold voltage.
DRV (Pin 6): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. If a PNP transistor is used, it must have
high gain (see Applications Information section). The DRV
pin is internally clamped to 6.5V below VCC.
VCC (Pin 7): Input Supply Voltage. VCC ranges from 8.8V
to 12V when charging. If VCC drops below VBAT + 54mV,
for example when the input supply is disconnected, then
the IC enters sleep mode with ICC < 30µA. Bypass this pin
with a 1µF capacitor.
SENSE (Pin 8): Current Sense Input. Connect this pin to
the sense resistor. Choose the resistor value using the
following equation:
RSENSE = (VPROG • 800Ω)/(RPROG • IBAT)
sn1731 17318fs
5
5 Page 
PACKAGE DESCRIPTION
LTC1731-8.2/LTC1731-8.4
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8 765
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157**
(3.810 – 3.988)
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
12
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
34
SO8 1298
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
sn1731 17318fs
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1731-8.2.PDF ] | |
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