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PDF LTC4054X-4.2 Data sheet ( Hoja de datos )
| Número de pieza | LTC4054X-4.2 | |
| Descripción | Standalone Linear Li-Ion Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4054-4.2/LwTwCw.D4a0taS5he4etX4U.-c4om.2
Standalone Linear
Li-Ion Battery Charger with
Thermal Regulation in ThinSOT
FEATURES
s Programmable Charge Current Up to 800mA
s No MOSFET, Sense Resistor or Blocking
Diode Required
s Complete Linear Charger in ThinSOTTM Package for
Single Cell Lithium-Ion Batteries
s Constant-Current/Constant-Voltage Operation with
Thermal Regulation* to Maximize Charge Rate
Without Risk of Overheating
s Charges Single Cell Li-Ion Batteries Directly
from USB Port
s Preset 4.2V Charge Voltage with ±1% Accuracy
s Charge Current Monitor Output for Gas
Gauging*
s Automatic Recharge
s Charge Status Output Pin
s C/10 Charge Termination
s 25µA Supply Current in Shutdown
s 2.9V Trickle Charge Threshold (LTC4054)
s Available Without Trickle Charge (LTC4054X)
s Soft-Start Limits Inrush Current
s Available in 5-Lead SOT-23 Package
U
APPLICATIO S
s Cellular Telephones, PDAs, MP3 Players
s Charging Docks and Cradles
s Bluetooth Applications
DESCRIPTIO
The LTC®4054 is a complete constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its ThinSOT package and low external component count
make the LTC4054 ideally suited for portable applications.
Furthermore, the LTC4054 is specifically designed to work
within USB power specifications.
No external sense resistor is needed, and no blocking
diode is required due to the internal MOSFET architecture.
Thermal feedback regulates the charge current to limit the
die temperature during high power operation or high
ambient temperature. The charge voltage is fixed at 4.2V,
and the charge current can be programmed externally with
a single resistor. The LTC4054 automatically terminates
the charge cycle when the charge current drops to 1/10th
the programmed value after the final float voltage is
reached.
When the input supply (wall adapter or USB supply) is
removed, the LTC4054 automatically enters a low current
state, dropping the battery drain current to less than 2µA.
The LTC4054 can be put into shutdown mode, reducing
the supply current to 25µA.
Other features include charge current monitor, undervoltage
lockout, automatic recharge and a status pin to indicate
charge termination and the presence of an input voltage.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
*U.S.Patent No. 6,522,118
TYPICAL APPLICATIO
600mA Single Cell Li-Ion Charger
VIN
4.5V TO 6.5V
1µF 4
VCC BAT 3
LTC4054-4.2
5
PROG
600mA
4.2V
GND
Li-Ion
1.65k BATTERY
2
405442 TA01a
Complete Charge Cycle (750mAh Battery)
700
CONSTANT
600 CURRENT
CONSTANT
500 POWER
4.75
CONSTANT
VOLTAGE
4.50
4.25
400 4.00
300 3.75
200 3.50
VCC = 5V
100
θJA = 130°C/W
RPROG = 1.65k
0 TA = 25°C
CHARGE
TERMINATED
3.25
3.00
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0
TIME (HOURS)
405442 TAO1b
405442xf
1
1 page  
LTC4054-4.2/LwTwCw.D4a0taS5he4etX4U.-c4om.2
TYPICAL PERFOR A CE CHARACTERISTICS
CHRG Pin Current vs Temperature
(Weak Pull-Down State)
28
VCC = 5V
VBAT = 4.3V
25 VCHRG = 5V
23
19
16
13
10
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
4054 G13
Trickle Charge Threshold vs
Temperature
3.000
VCC = 5V
2.975 RPROG = 10k
2.950
2.925
2.900
2.875
2.850
2.825
2.800
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
4054 G16
Charge Current vs Ambient
Temperature
600
RPROG = 2k
500
400
VCC = 5V
300 VBAT = 4V
θJA = 80°C/W
200
ONSET OF
THERMAL
REGULATION
RPROG = 10k
100
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4054 G19
Trickle Charge Current
vs Temperature
50
RPROG = 2k
40
30
VCC = 5V
VBAT = 2.5V
20
10
RPROG = 10k
0
–50 –25 0
25 50
TEMPERATURE (°C)
75 100
4054 G14
Charge Current vs Battery Voltage
600
TA = 0°C
500
400 TA = 40°C
TA = 25°C
300
200
100
VCC = 5V
θJA = 125°C/W
RPROG = 2k
0
2.7 3.0 3.3 3.6 3.9 4.2 4.5
VBAT (V)
4054 G17
Recharge Voltage Threshold
vs Temperature
4.11
VCC = 5V
4.09 RPROG = 10k
4.07
4.05
4.03
4.01
3.99
–50 –25
0 25 50
TEMPERATURE (°C)
75 100
4054 G20
Trickle Charge Current vs
Supply Voltage
50
RPROG = 2k
40
30
VBAT = 2.5V
TA = 25°C
20
10 RPROG = 10k
0
4.0 4.5 5.0 5.5 6.0
VCC (V)
6.5 7.0
4054 G15
Charge Current vs Supply Voltage
600
RPROG = 2k
500
400
VBAT = 4V
300 TA = 25°C
θJA = 80°C/W
ONSET OF
THERMAL
REGULATION
200
RPROG = 10k
100
0
4.0 4.5 5.0 5.5 6.0
VCC (V)
6.5 7.0
4054 G18
Power FET “ON” Resistance
vs Temperature
700
VCC = 4.2V
650
IBAT = 100mA
RPROG = 2k
600
550
500
450
400
350
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4054 G21
405442xf
5
5 Page 
LTC4054-4.2/LwTwCw.D4a0taS5he4etX4U.-c4om.2
APPLICATIO S I FOR ATIO
The LTC4054 can be used above 45°C ambient, but the
charge current will be reduced from 400mA. The approxi-
mate current at a given ambient temperature can be
approximated by:
( )IBAT = 120°C – TA
VCC – VBAT • θJA
Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to approxi-
mately:
( )IBAT =
120°C – 60°C = 60°C
5V – 3.75V •150°C/W 187.5°C/A
IBAT = 320mA
Moreover, when thermal feedback reduces the charge
current, the voltage at the PROG pin is also reduced
proportionally as discussed in the Operation section.
It is important to remember that LTC4054 applications do
not need to be designed for worst-case thermal conditions
since the IC will automatically reduce power dissipation
when the junction temperature reaches approximately
120°C.
Thermal Considerations
Because of the small size of the ThinSOT package, it is very
important to use a good thermal PC board layout to
maximize the available charge current. The thermal path
for the heat generated by the IC is from the die to the
copper lead frame, through the package leads, (especially
the ground lead) to the PC board copper. The PC board
copper is the heat sink. The footprint copper pads should
be as wide as possible and expand out to larger copper
areas to spread and dissipate the heat to the surrounding
ambient. Feedthrough vias to inner or backside copper
layers are also useful in improving the overall thermal
performance of the charger. Other heat sources on the
board, not related to the charger, must also be considered
when designing a PC board layout because they will affect
overall temperature rise and the maximum charge current.
The following table lists thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with the device
mounted on topside.
Table 1. Measured Thermal Resistance (2-Layer Board*)
COPPER AREA
TOPSIDE BACKSIDE
2500mm2 2500mm2
1000mm2 2500mm2
225mm2 2500mm2
100mm2 2500mm2
50mm2 2500mm2
*Each layer uses one ounce copper
BOARD
AREA
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
THERMAL RESISTANCE
JUNCTION-TO-AMBIENT
125°C/W
125°C/W
130°C/W
135°C/W
150°C/W
Table 2. Measured Thermal Resistance (4-Layer Board**)
COPPER AREA
(EACH SIDE)
BOARD
AREA
THERMAL RESISTANCE
JUNCTION-TO-AMBIENT
2500mm2***
2500mm2
80°C/W
*Top and bottom layers use two ounce copper, inner layers use one ounce copper.
**10,000mm2 total copper area
Increasing Thermal Regulation Current
Reducing the voltage drop across the internal MOSFET
can significantly decrease the power dissipation in the IC.
This has the effect of increasing the current delivered to
the battery during thermal regulation. One method is by
dissipating some of the power through an external compo-
nent, such as a resistor or diode.
Example: An LTC4054 operating from a 5V wall adapter is
programmed to supply 800mA full-scale current to a
discharged Li-Ion battery with a voltage of 3.75V. Assum-
ing θJA is 125°C/W, the approximate charge current at an
ambient temperature of 25°C is:
IBAT
=
(5V
120°C – 25°C
– 3.75V)•125°C
/W
=
608mA
By dropping voltage across a resistor in series with a 5V
wall adapter (shown in Figure 3), the on-chip power
dissipation can be decreased, thus increasing the ther-
mally regulated charge current
IBAT
=
(VS
120°C – 25°C
– IBATRCC – VBAT )• θJA
405442xf
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC4054X-4.2.PDF ] | |
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