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PDF LTC4080X Data sheet ( Hoja de datos )
| Número de pieza | LTC4080X | |
| Descripción | 500mA Standalone Li-Ion Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC4080X
FEATURES
500mA Standalone Li-Ion
Charger with Integrated 300mA
Synchronous Buck in 3mm × 3mm DFN
DESCRIPTIO
■ Complete Linear Battery Charger with Integrated
Buck Converter in 3mm x 3mm DFN Package
Battery Charger:
■ Constant-Current/Constant-Voltage Operation
with Thermal Feedback to Maximize Charge Rate
Without Risk of Overheating
■ Internal 4.5 Hour Safety Timer for Termination
■ Charge Current Programmable Up to 500mA with
5% Accuracy
■ C/10 Charge Current Detection Output
■ 5µA Supply Current in Shutdown Mode
Switching Regulator:
■ High Efficiency Synchronous Buck Converter
■ 300mA Output Current (Constant-Frequency Mode)
■ 2.7V to 4.5V Input Range (Powered from BAT Pin)
■ 0.8V to VBAT Output Range
■ MODE Pin Selects Fixed (2.25MHz) Constant-Frequency
PWM Mode or Low ICC (23µA) Burst Mode®
Operation
■ 2µA BAT Current in Shutdown Mode
U
APPLICATIO S
■ Wireless Headsets
■ Bluetooth Applications
■ Portable MP3 Players
■ Multifunction Wristwatches
The LTC4080X is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion/polymer battery with an integrated 300mA
synchronous buck converter. A 3mm × 3mm DFN package
and low external component count make the LTC4080X
especially suitable for portable applications. Furthermore,
the LTC4080X is specifically designed to work within USB
power specifications.
The ⎯C⎯H⎯R⎯G pin indicates when charge current has
dropped to ten percent of its programmed value (C/10).
An internal 4.5 hour timer terminates the charge cycle.
The full-featured LTC4080X battery charger also includes
automatic recharge and soft-start to limit inrush current.
If trickle charging is desired, please see the LTC4080
datasheet.
The LTC4080X integrates a synchronous buck converter
that is powered from the BAT pin. It has an adjustable
output voltage and can deliver up to 300mA of load cur-
rent. The buck converter also features low-current high-
efficiency Burst Mode operation that can be selected by
the MODE pin.
The LTC4080X is available in 10-lead, low profile (0.75 mm)
3mm × 3mm DFN and 10-lead MSE packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6522118.
TYPICAL APPLICATIO
Li-Ion Battery Charger with 1.8V Buck Regulator
VCC
(3.75V
to 5.5V)
4.7µF
VCC BAT
LTC4080X
EN_CHRG
SW
EN_BUCK
FB
MODE GND PROG
1OµH
500mA
+
4.7µF
4.2V
Li-Ion/
POLYMER
BATTERY
10pF 1M
806Ω
806k
VOUT
(1.8V/300mA)
COUT
4.7µF
4080X TA01a
Buck Efficiency vs Load Current
(VOUT = 1.8V)
100 1000
EFFICIENCY
80 (Burst)
EFFICIENCY
(PWM)
60
100
POWER
LOSS 10
(PWM)
40
20
0
0.01
POWER LOSS
(Burst)
1
VBAT = 3.8V
VOUT = 1.8V
0.1
L = 10µH
C = 4.7µF
0.01
0.1 1 10 100 1000
LOAD CURRENT (mA)
4080X TA01b
4080Xf
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LTC4080X
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, VCC = 5V, VBAT = 3.8V, unless otherwise
specified)
Battery Regulation (Float) Voltage
vs Charge Current
4.21
RPROG = 2k
4.20
4.19
4.18
Battery Regulation (Float) Voltage
vs Temperature
4.210
4.205
4.200
4.195
4.190
Battery Regulation (Float) Voltage
vs VCC Supply Voltage
4.25
4.20
4.15
4.10
4.17
4.16
4.15
4.14
4.13
0
50 100 150 200
CHARGE CURRENT (mA)
250
4080X G01
Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)
250 VCC = 6V
VBAT = 3V
200 RPROG = 2k
4.185
4.180
4.175
4.170
4.165
4.160
– 50 – 30 – 10 10 30 50
TEMPERATURE (°C)
70 90
4080X G02
PROG Pin Voltage
vs Charge Current
1.0
RPROG = 2k
0.8
4.05
4.00
3.95
3.90
3.85
4
4.5 5 5.5
VCC SUPPLY VOLTAGE (V)
6
4080X G03
Charger FET On-Resistance
vs Temperature
0.9
VCC = 4V
0.8 IBAT = 350mA
0.7
150
THERMAL CONTROL
LOOP IN OPERATION
100
0.6
0.4
0.6
0.5
0.4
0.3
50 0.2
0.2
0.1
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4080X G04
0
0 25
⎯E⎯N⎯_⎯C⎯H⎯R⎯G, EN_BUCK and
MODE Pin Threshold Voltage
vs Temperature
0.95
50 75 100 125 150 175 200
CHARGE CURRENT (mA)
4080X G05
0
– 50 – 30
–10 10 30 50
TEMPERATURE (°C)
⎯E⎯N⎯_⎯C⎯H⎯R⎯G Pin Pulldown
Resistance vs Temperature
1.7
70 90
4080X G06
0.90
RISING
0.85
0.80
0.75 FALLING
1.6
1.5
1.4
0.70 1.3
0.65
1.2
0.60
0.55 1.1
0.50
–50 –30 –10 10 30 50
TEMPERATURE (°C)
70 90
4080X G07
1.0
–50 –30 –10 10 30 50
TEMPERATURE (°C)
70 90
4080X G08
4080Xf
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U
OPERATIO
The LTC4080X is a full-featured linear battery charger
with an integrated synchronous buck converter designed
primarily for handheld applications. The battery charger
is capable of charging single-cell 4.2V Li-Ion batteries.
The buck converter is powered from the BAT pin and has
a programmable output voltage providing a maximum load
current of 300mA. The converter and the battery charger
can run simultaneously or independently of each other.
BATTERY CHARGER OPERATION
Featuring an internal P-channel power MOSFET, MP1, the
battery charger uses a constant-current/constant-voltage
charge algorithm with programmable current. Charge
current can be programmed up to 500mA with a final
float voltage of 4.2V ±0.5%. The ⎯C⎯H⎯R⎯G open-drain status
output indicates when C/10 has been reached. No blocking
diode or external sense resistor is required; thus, the basic
charger circuit requires only two external components. The
⎯A⎯C⎯P⎯R open-drain output indicates if the VCC input voltage,
and the difference between VCC and BAT, are sufficient for
charging. An internal charge termination timer adheres to
battery manufacturer safety guidelines. Furthermore, the
LTC4080X battery charger is capable of operating from a
USB power source.
A charge cycle begins when the voltage at the VCC pin
rises above 3.6V and approximately 82mV above the BAT
pin voltage, a 1% program resistor is connected from the
PROG pin to ground, and the ⎯E⎯N⎯_⎯C⎯H⎯R⎯G pin is pulled below
the shutdown threshold (VIL).
When the BAT pin approaches the final float voltage of
4.2V, the battery charger enters constant-voltage mode
and the charge current begins to decrease. When the
current drops to 10% of the full-scale charge current, an
internal comparator turns off the N-channel MOSFET driving
the ⎯C⎯H⎯R⎯G pin, and the pin becomes high impedance.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 115°C. This feature protects
the LTC4080X from excessive temperature and allows the
user to push the limits of the power handling capability
of a given circuit board without the risk of damaging the
LTC4080X or external components. Another benefit of the
LTC4080X
thermal limit is that charge current can be set according
to typical, rather than worst-case, ambient temperatures
for a given application with the assurance that the battery
charger will automatically reduce the current in worst-case
conditions.
An internal timer sets the total charge time, tTIMER (typi-
cally 4.5 hours). When this time elapses, the charge cycle
terminates and the ⎯C⎯H⎯R⎯G pin assumes a high impedance
state even if C/10 has not yet been reached. To restart
the charge cycle, remove the input voltage and reapply
it or momentarily force the ⎯E⎯N⎯_⎯C⎯H⎯R⎯G pin above VIH. A
new charge cycle will automatically restart if the BAT pin
voltage falls below VRECHRG (typically 4.1V).
Constant-Current / Constant-Voltage /
Constant-Temperature
The LTC4080X battery charger uses a unique architecture
to charge a battery in a constant-current, constant-volt-
age and constant-temperature fashion. Figure 1 shows a
Simplified Block Diagram of the LTC4080X. Three of the
amplifier feedback loops shown control the constant-cur-
rent, CA, constant-voltage, VA, and constant-temperature,
TA modes. A fourth amplifier feedback loop, MA, is used to
increase the output impedance of the current source pair,
MP1 and MP3 (note that MP1 is the internal P-channel
power MOSFET). It ensures that the drain current of MP1
is exactly 400 times the drain current of MP3.
Amplifiers CA and VA are used in separate feedback loops
to force the charger into constant-current or constant-
voltage mode, respectively. Diodes D1 and D2 provide
priority to either the constant-current or constant-voltage
loop, whichever is trying to reduce the charge current the
most. The output of the other amplifier saturates low which
effectively removes its loop from the system. When in
constant-current mode, CA servos the voltage at the PROG
pin to be precisely 1V. VA servos its non-inverting input
to 1.22V when in constant-voltage mode and the internal
resistor divider made up of R1 and R2 ensures that the
battery voltage is maintained at 4.2V. The PROG pin volt-
age gives an indication of the charge current anytime in
the charge cycle, as discussed in “Programming Charge
Current” in the Applications Information section.
4080Xf
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC4080X.PDF ] | |
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