LTC4009
LTC4009-1/LTC4009-2
High Efficiency,
Multi-Chemistry
Battery Charger
FEATURES
DESCRIPTION
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General Purpose Battery Charger Controller
TheLTC4009isaconstant-current/constant-voltagebattery
charger controller. It uses a synchronous quasi-constant
frequency PWM control architecture that will not generate
audible noise with ceramic bulk capacitors. Charge cur-
rent is set by the combination of external sense, input and
programming resistors. With no built-in termination, the
LTC4009 family charges a wide range of batteries under
external control.
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Efficient 550kHz Synchronous Buck PWM Topology
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0ꢀ5ꢁ ꢂutput ꢃloat ꢄoltage Accuracy
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Programmable Charge Current: 4ꢁ Accuracy
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Programmable AC Adapter Current Limit:
3ꢁ Accuracy
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No Audible Noise with Ceramic Capacitors
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Wide Input Voltage Range: 6V to 28V
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Wide Output Voltage Range: 2V to 28V
TheLTC4009featuresafullyadjustableoutputvoltage,while
theLTC4009-1andLTC4009-2canbepin-programmedfor
lithium-ion/polymer battery packs of 1-, 2-, 3- or 4-series
cells. The LTC4009-1 provides output voltage of 4.1V/cell,
and the LTC4009-2 is a 4.2V/cell version.
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Indicator Outputs for AC Adapter Present, Charging,
C/10 Current Detection and Input Current Limiting
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Analog Charge Current Monitor
Micropower Shutdown
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Thermally Enhanced 20-Pin 4mm × 4mm × 0.75mm
QFN Package
ThedeviceincludesACadapterinputcurrentlimitingwhich
maximizes the charge rate for a fixed input power level. An
externalsenseresistorprogramstheinputcurrentlimit,and
theICLstatuspinindicateswhenthebatterychargecurrent
is being reduced as a result of AC adapter current limiting.
APPLICATIONS
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Notebook Computers
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Portable Instruments
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The CHRG status pin is active during all charging modes,
including special indication for low charge current.
Battery Backup Systems
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 5723970.
TYPICAL APPLICATION
FROM
ADAPTER
33mΩ
POWER TO
SYSTEM
13V TO 20V
0.1μF
DCIN
20μF
0.1μF
Efficiency at DCIN = 20ꢄ
CLP
5.1k
14.3k
1.5k
CLN
BOOST
100
95
90
85
80
75
70
10000
1000
100
DCDIV
LTC4009
0.1μF
TGATE
EFFICIENCY
CHRG
ACP
ICL
SW
INTV
DD
TO/FROM
MCU
POWER LOSS
2μF
6.8μH
33mΩ
BGATE
GND
SHDN
ITH
V
= 12.3V
= 33mΩ
FLOAT
3.01k
3.01k
R
R
R
D
SENSE
CSP
= 3.01k
IN
PROG
= 26.7k
6.04k
0.1μF
= SSB44
IN
L = IHLP-2525CZ 6.8μH
1.5 2.0 2.5 3.0
CHARGE CURRENT (A)
CSN
BAT
0
1.0
0.5
CHARGE
CURRENT
MONITOR
+
20μF
PROG
FBDIV
12.3V
Li-Ion
301k
4009 TA01b
26.7k
4.7nF
BATTERY
V
FB
4009 TA01a
32.8k
4009fb
1