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PDF LTC1733 Data sheet ( Hoja de datos )
| Número de pieza | LTC1733 | |
| Descripción | Monolithic Linear Lithium-Ion Battery Charger with Thermal Regulation | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1733
Monolithic Linear
Lithium-Ion Battery Charger with
Thermal Regulation
FEATURES
s Complete Linear Charger for 1-Cell Lithium-Ion
Batteries
s Thermal Regulation Maximizes Charging Rate
without Risk of Overheating*
s No External MOSFET, Sense Resistor or Blocking
Diode Required
s Up to 1.5A Charge Current
s Preset Charge Voltage with 1% Accuracy
s Programmable Charge Current with 7% Accuracy
s Programmable Charge Termination Timer
s Tiny Thermally Enhanced 10-Pin MSOP Package
s Charge Current Monitor Useful for Gas Gauging*
s C/10 Charge Current Detection Output
s Automatic Recharge
s Thermistor Input for Temperature Qualified Charging
s AC Present Logic Output
s 4.1V/4.2V Pin Selectable Output Voltage
U
APPLICATIO S
s Cellular Telephones
s Handheld Computers
s Digital Still Cameras
s Charging Docks and Cradles
DESCRIPTIO
The LTC®1733 is a standalone constant-current/
constant-voltage linear charger for lithium-ion batteries
with an on-chip power MOSFET. Internal thermal feedback
regulates the charge current to limit die temperature
during high power operation or high ambient temperature
conditions. This feature allows the user to program a high
charge current without risk of damaging the LTC1733 or
the handheld product.
No external current sense resistor is needed and no
blocking diode is required due to the internal MOSFET
architecture. The charge current and charge time can be
set externally with a single resistor and capacitor, respec-
tively. When the input supply (wall adapter) is removed,
the LTC1733 automatically enters a low current sleep
mode, dropping the battery drain current to less than 5µA.
The LTC1733 also includes NTC temperature sensing,
C/10 detection circuitry, AC present logic, 4.1V/4.2V pin
selectability and low battery charge conditioning (trickle
charging).
The LTC1733 is available in a 10-pin thermally enhanced
MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
*Patent Pending
TYPICAL APPLICATIO
Standalone Li-Ion Battery Charger
VIN = 5V
82
4.7µF
SEL VCC
9
BAT
4 LTC1733 7
TIMER PROG
GND
0.1µF 5
NTC
6
IBAT = 1A
4.2V
1-CELL
Li-Ion
1.5k BATTERY*
1%
1733TA01
*AN OUTPUT CAPACITOR MAY BE REQUIRED
DEPENDING ON BATTERY LEAD LENGTH
Charge Current vs Battery Voltage
1200
1000
TA = 0°C
CONSTANT
CURRENT
800 TA = 40°C
TA = 25°C
600
CONSTANT
POWER
400
CONSTANT
VOLTAGE
200 TRICKLE
CHARGE
0
2 2.5
VIN = 5V
θJA = 40°C/W
3 3.5
4
BATTERY VOLTAGE (V)
4.5
1733 TA01b
sn1733 1733fs
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
PROG Pin Voltage vs VCC
Constant Current Mode
1.515
1.510
TA = 25°C
VBAT = 3.5V
RPROG = 3k
VSEL = 5V
1.505
1.500
1.495
1.490
1.485
4.0 4.5 5.0 5.5 6.0 6.5 7.0
VCC (V)
1733 G10
PROG Pin Voltage vs Temperature
Constant Current Mode
1.515
1.510
VCC = 5V
VBAT = 4V
RPROG = 3k
VSEL = 5V
1.505
1.500
1.495
1.490
1.485
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1733 G11
LTC1733
Trickle Charge Current vs
Temperature
130
VCC = 5V
VBAT = 2V
120 RPROG = 1.5k
VSEL = 5V
110
100
90
80
70
–50
–25 0 25 50
TEMPERATURE (°C)
75 100
1733 G12
Trickle Charge Current vs VCC
13
TA = 25°C
VBAT = 2V
12 RPROG = 1.5k
VSEL = 5V
11
10
9
8
7
4.0 4.5 5.0 5.5 6.0 6.5 7.0
VCC (V)
1733 G13
Timer Accuracy vs Temperature
105
VCC = 5V
104 IBAT = 0mA
103
VSEL = 5V
CTIMER = 0.1µF
102
101
100
99
98
97
96
95
–50 –25
0 25 50 75 100 125
TEMPERATURE(°C)
1733 G14
Timer Accuracy vs VCC
105
TA = 25°C
104 IBAT = 0mA
103
VSEL = 5V
CTIMER = 0.1µF
102
101
100
99
98
97
96
95
4.0 4.5 5.0 5.5 6.0 6.5 7.0
VCC (V)
1733 G15
sn1733 1733fs
5
5 Page 
LTC1733
APPLICATIO S I FOR ATIO
resistance of the NTC thermistor rises. The LTC1733 is
designed to go into hold mode when the value of the NTC
thermistor increases to seven times the value of RHOT. For
a Vishay NTHS0603N02N1002J thermistor, this value is
28.2k which corresponds to approximately 0°C. The hot
and cold comparators each have approximately 2°C of
hysteresis to prevent oscillation about the trip point. The
NTC function can be disabled by grounding the NTC pin.
VCC
RHOT
1%
7/8 VCC
RNTC
10k
NTC
1/2 VCC
–
+
+
–
TOO COLD
TOO HOT
3/160 VCC
+
LTC1733
–
Figure 3.
DISABLE NTC
1733 F03
Thermistors
The LTC1733 NTC trip points were designed to work with
thermistors whose resistance-temperature characteris-
tics follow Vishay Dale’s “R-T Curve 2”. The Vishay
NTHS0603N02N1002J is an example of such a ther-
mistor. However, Vishay Dale has many thermistor prod-
ucts that follow the “R-T Curve 2” characteristic in a variety
of sizes. Futhermore, any thermistor whose ratio of RCOLD
to RHOT is about 7.0 will also work (Vishay Dale R-T Curve
2 shows a ratio of RCOLD to RHOT of 2.816/0.4086 = 6.9).
NTC Layout Considerations
It is important that the NTC thermistor not be in close
thermal contact with the LTC1733. Because the LTC1733
package can reach temperatures in excess of the 50°C trip
point, the NTC function can cause a hysteretic oscillation
which turns the charge current on and off according to the
package temperature rather than the battery temperature.
This problem can be eliminated by thermally coupling the
NTC thermistor to the battery and not to the LTC1733.
Furthermore, it is essential that the VCC connection to
RHOT is made according to standard Kelvin sense tech-
niques. Since VCC is a high current path into the LTC1733,
it is essential to minimize voltage drops between the VCC
input pin and the top of RHOT.
NTC Trip Point Errors
When a 1% resistor is used for RHOT, the major error in
the 50°C trip point is determined by the tolerance of the
NTC thermistor. A typical 10k NTC thermistor has a ±10%
tolerance. By looking up the temperature coefficient of the
thermistor at 50°C, the tolerance error can be calculated
in degrees centigrade. Consider the Vishay
NTHS0603N02N1002J thermistor which has a tempera-
ture coefficient of –3.3%/°C at 50°C. Dividing the toler-
ance by the temperature coefficient, ±10%/(–3.3%/°C) =
±3°C, gives the temperature error of the hot trip point.
The cold trip point is a little more complicated because its
error depends on the tolerance of the NTC thermistor and
the degree to which the ratio of its value at 0°C and its value
at 50°C varies from 7 to 1. Therefore, the cold trip point
error can be calculated using the tolerance, TOL, the
temperature coefficient of the thermistor at 0°C, TC
(in %/°C), the value of the thermistor at 0°C, RCOLD, and
the value of the thermistor at 50°C, RHOT. The formula is:
Temperature Error (°C) =
1+ TOL
7
• RCOLD
RHOT
– 1
• 100
TC
For example, the Vishay NTHS0603N02N1002J thermistor
with a tolerance of ±10%, TC of –4.5%/°C, and RCOLD/
RHOT of 6.89, has a cold trip point error of:
Temperature
Error
(°C)
=
1±
0.10
7
•
6.89
–
1
• 100
–4.5
= –1.8°C, +2.5°C
sn1733 1733fs
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1733.PDF ] | |
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