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PDF LTC4080 Data sheet ( Hoja de datos )
| Número de pieza | LTC4080 | |
| Descripción | 500mA Standalone Li-Ion Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC4080 (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
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FEATURES
■ Complete Linear Battery Charger with Integrated
Buck Converter
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
■ 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
LTC4080
500mA Standalone Li-Ion
Charger with Integrated
300mA Synchronous Buck
DESCRIPTIO
The LTC4080 is a complete constant-current/constant-
voltage linear battery charger for a single-cell 4.2V
lithium-ion battery with an integrated 300mA synchron-
ous buck converter. The small packages and low external
component count make the LTC4080 especially suitable for
portable applications. Furthermore, LTC4080 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 LTC4080 battery charger also includes
trickle charge, automatic recharge and soft-start (to limit
inrush current).
The LTC4080 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 LTC4080 is available in 10-lead, low profile (0.75 mm)
3mm × 3mm DFN and MSOP Exposed Pad packages.
, LT, LTC, LTM and Burst Mode are registered trademarks 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)
CIN
4.7μF
VCC BAT
LTC4080
EN_CHRG
SW
L1, 1OμH
500mA
CBAT +
4.7μF
4.2V
Li-Ion
BATTERY
EN_BUCK
FB
MODE GND PROG
CPL
10pF
RPROG
806Ω
R1
1M
R2
806k
4080 TA01a
VOUT
(1.8V/300mA)
COUT
4.7μF
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)
0
VBAT = 3.8V
VOUT = 1.8V
0.1
L = 10μH
C = 4.7μF 0.01
0.1 1 10 100 1000
LOAD CURRENT (mA)
4080 TA01b
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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
4.17
4.16
4.15
4.14
4.13
0
50 100 150 200
CHARGE CURRENT (mA)
250
4080 G01
Battery Regulation (Float) Voltage
vs Supply Voltage
4.25
4.20
4.15
Battery Regulation (Float) Voltage
vs Temperature
4.210
4.205
4.200
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
– 50 – 30 – 10 10 30 50 70 90
TEMPERATURE (°C)
4080 G02
Charge Current vs Temperature
with Thermal Regulation
(Constant-Current Mode)
250 VCC = 6V
VBAT = 3V
200 RPROG = 2k
4.10 150 THERMAL CONTROL
4.05 LOOP IN OPERATION
4.00 100
3.95
50
3.90
3.85
4
4.5 5 5.5
INPUT VOLTAGE (V)
6
4080 G03
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
4080 G04
Charger FET On-Resistance
vs Temperature
0.9
VCC = 4V
0.8 IBAT = 350mA
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
– 50 – 30
–10 10 30 50
TEMPERATURE (°C)
70 90
4080 G06
⎯E⎯N⎯_⎯C⎯H⎯R⎯G, EN_BUCK and
MODE Pin Threshold Voltage
vs Temperature
0.95
0.90
RISING
0.85
0.80
0.75 FALLING
0.70
0.65
0.60
0.55
0.50
–50 –30 –10 10 30 50
TEMPERATURE (°C)
70 90
4080 G07
LTC4080
Charge Current
vs Battery Voltage
250
RPROG = 2k
VBAT RISING
200
150
100
50
0
0
TRICKLE CHARGE
1 2 34
BATTERY VOLTAGE (V)
5
4080 G02a
PROG Pin Voltage
vs Charge Current
1.0
RPROG = 2k
0.8
0.6
0.4
0.2
0
0 25 50 75 100 125 150 175 200
CHARGE CURRENT (mA)
4080 G05
⎯E⎯N⎯_⎯C⎯H⎯R⎯G Pin Pulldown
Resistance vs Temperature
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
–50 –30 –10 10 30 50
TEMPERATURE (°C)
70 90
4080 G08
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OPERATIOU
The LTC4080 is a full-featured linear battery charger with
an integrated synchronous buck converter designed pri-
marily 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 termination
timer adheres to battery manufacturer safety guidelines.
Furthermore, the LTC4080 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 80mV 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). If the battery voltage is less
than 2.9V, the battery charger begins trickle charging at
10% of the programmed charge current.
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 LTC4080 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
LTC4080
LTC4080 or external components. Another benefit of the
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 LTC4080 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 LTC4080. 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.
4080fb
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11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTC4080.PDF ] | |
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