LTC4012/
LTC4012-1/LTC4012-2
High Efficiency,
Multi-Chemistry Battery Charger
with PowerPath Control
DESCRIPTION
FEATURES
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General Purpose Battery Charger Controller
The LTC4012 is a constant-current/constant-voltage
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Efficient 550kHz Synchronous Buck PWM Topology
0ꢀ5ꢁ ꢂutput ꢃloat ꢄoltage Accuracy
Programmable Charge Current: 4ꢁ Accuracy
Programmable AC Adapter Current Limit:
3ꢁ Accuracy
No Audible Noise with Ceramic Capacitors
INꢃET Low Loss Ideal Diode PowerPath™ Control
Wide Input Voltage Range: 6V to 28V
Wide Output Voltage Range: 2V to 28V
Indicator Outputs for AC Adapter Present, Charging,
C/10 Current Detection and Input Current Limiting
Analog Charge Current Monitor
battery charger controller. It uses a synchronous
quasi-constant frequency PWM control architecture
that will not generate audible noise with ceramic
bulk capacitors. Charge current is set by external
resistors and can be monitored as an output voltage.
With no built-in termination, the LTC4012 family charges
a wide range of batteries under external control.
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TheLTC4012featuresfullyadjustableoutputvoltage,while
theLTC4012-1andLTC4012-2canbepin-programmedfor
Lithium-Ion/Polymerbatterypacksof1-, 2-, 3-or4-series
cells. The LTC4012-1 provides output voltage of 4.1V/cell
and the LTC4012-2 is a 4.2V/cell version.
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Micropower Shutdown
20-Pin 4mm × 4mm × 0.75mm QFN Package
ThedeviceincludesACadapterinputcurrentlimiting,which
maximizes charge rate for a fixed input power level. An
external sense resistor programs the input current limit,
and the ICL status pin indicates reduced charge current as
a result of AC adapter current limiting. Ideal diode control
at the adaptor input improves charger efficiency.
APPLICATIONS
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Notebook Computers
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Portable Instruments
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Battery Backup Systems
The CHRG status pin is active during all charging modes,
including special indication for low charge current.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath
is a trademark 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
25mΩ
Efficiency at DCIN = 20ꢄ
POWER TO
SYSTEM
0.1μF
13V TO 28V
20μF
100
95
90
85
80
75
70
10000
1000
100
5.1k
INFET
DCIN
CLP
EFFICIENCY
CLN
BOOST
0.1μF
0.1μF
TGATE
ACP
POWER LOSS
SW
CHRG INTV
DD
TO/FROM
MCU
2μF
ICL
BGATE
GND
6.8μH
33mΩ
V
= 12.3V
OUT
R
R
R
= 33mΩ
SENSE
= 3.01k
SHDN
ITH
IN
PROG
3.01k
3.01k
= 26.7k
CSP
6.04k
0
1
1.5
2
2.5
3
0.5
LTC4012
CHARGE CURRENT (A)
0.1μF
CSN
BAT
PIN NAME
FBDIV
PROG
20μF
PART INꢃET DCDIꢄ
301k
+
LTC4009
LTC4012
X
26.7k
4.7nF
12.3V
V
FB
X
4012 TA02
Li-Ion
32.8k
BATTERY
4012 TA01
4012f
1