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PDF LTC1731-4.1 Data sheet ( Hoja de datos )
| Número de pieza | LTC1731-4.1 | |
| Descripción | Single Cell Lithium-Ion Linear Battery Charger Controllers | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Complete Linear Charger Controller for
1-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 (7µA 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
LTC1731-4.1/LTC1731-4.2
Single Cell Lithium-Ion Linear
Battery Charger Controllers
DESCRIPTIO
The LTC®1731 is a complete constant-current/constant-
voltage linear charger controller for single cell lithium-ion
batteries. Nickel-cadmium (NiCd) and nickel-metal-hy-
dride (NiMH) batteries can also be charged with constant
current using external termination. The external sense
resistor sets the charge current with 5% accuracy. An
internal resistor divider and precision reference set the
final float potential with ±1% accuracy. The output float
voltage is set internally to 4.1V (LTC1731-4.1) or 4.2V
(LTC1731-4.2).
When the input supply is removed, the LTC1731 automati-
cally enters a low current sleep mode, dropping the battery
drain current to typically 7µA. An internal comparator
detects the end-of-charge (C/10) condition while a pro-
grammable timer, using an external capacitor, sets the
total charge time. Fully discharged cells are automatically
trickle charged at 10% of the programmed current until
cell voltage exceeds 2.457V.
The LTC1731 is available in the 8-pin MSOP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
500mA Li-Ion Battery Charger
VIN = 6V
MBRM120T3
CHARGE
STATUS
CTIMER
0.1µF
1k
2
7
VCC
SENSE
CHRG DRV
8
6
LTC1731-4.2
3
TIMER
1
BAT
5
PROG
GND
4
RPROG*
19.6k
RSENSE
0.2Ω
Q1
Si9430DY
IBAT = 500mA
+ Li-ION
CELL
1µF
10µF
*SHUTDOWN INVOKED BY FLOATING THE PROG PIN
1731 TA01
1
1 page  
LTC1731-4.1/LTC1731-4.2
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 resistor
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. The timer period is set by placing
a capacitor, CTIMER, to GND. The timer period is tTIMER =
(CTIMER • 3 hours)/(0.1µF). When the TIMER pin is
connected to VCC, the constant-voltage mode and the
timer are disabled, the chip will operate in constant-
current mode only. Short the TIMER pin to GND to disable
the internal timer function and the C/10 function.
GND (Pin 4): Ground Connection.
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. An internal 2.5µA
current source will pull the pin above the shutdown
threshold voltage when the program resistor (RPROG) is
disconnected.
DRV (Pin 6): Drive Output Pin for the P-Channel MOSFET
or PNP Transistor. The impedance is high at this pin,
therefore, a high beta PNP pass transistor should be used.
The DRV pin is internally clamped to 6.5V below VCC.
VCC (Pin 7): Positive Input Supply Voltage. When VBAT is
within 54mV of VCC, the LTC1731 is forced into sleep
mode, dropping ICC to 7µA. VCC ranges from 4.5V to 12V.
Bypass this pin with a 1µF capacitor.
SENSE (Pin 8): Current Sense Input. A sense resistor,
RSENSE, must be connected from VCC to the SENSE pin.
This resistor is chosen using the following equation:
RSENSE = (VPROG • 800Ω)/(RPROG • IBAT)
5
5 Page 
LTC1731-4.1/LTC1731-4.2
PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(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)
12
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
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
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
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.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1731-4.1.PDF ] | |
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