LTC4001-1
2A Synchronous
Buck Li-Ion Charger
FEATURES
DESCRIPTION
TheLTC®4001-1isa2ALi-Ionbatterychargerintendedfor
5V wall adapters. It utilizes a 1.5MHz synchronous buck
converter topology to reduce power dissipation during
charging. Low power dissipation, an internal MOSFET and
sense resistor allow a physically small charger that can be
embedded in a wide range of handheld applications. The
LTC4001-1includescompletechargeterminationcircuitry,
automatic recharge and a 1ꢀ 4.1V ꢁoat voltage. Input
short-circuit protection is included so no blocking diode
is required.
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Low Power Dissipation
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2A Maximum Charge Current
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No External MOSFETs, Sense Resistor or
Blocking Diode Required
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Remote Sensing at Battery Terminals
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Programmable Charge Termination Timer
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Preset 4.1V Float Voltage with 0.5ꢀ Accuracy
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4.1V Float Voltage Improves Battery Life and High
Temperature Safety Margin
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Programmable Charge Current Detection/
Termination
Automatic Recharge
This 4.1V version of the standard LTC4001 is intended
for applications which will be operated or stored above
approximately 60°C. Under these conditions, the reduced
ꢁoatvoltagewilltrade-offinitialcellcapacityforthebenefit
ofincreasedcapacityretentionoverthelifeofthebattery.A
reduced ꢁoat voltage also minimizes swelling in prismatic
and polymer cells, and avoids open CID (pressure fuse)
in cylindrical cells.
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Thermistor Input for Temperature Qualified
Charging
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Compatible with Current Limited Wall Adapters
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Low Profile 16-Lead (4mm × 4mm) QFN Package
APPLICATIONS
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Handheld Battery-Powered Devices
Battery charge current, charge timeout and end-of-charge
indication parameters are set with external components.
Additionalfeaturesincludeshortedcelldetection,tempera-
ture qualified charging and overvoltage protection. The
LTC4001-1 is available in a low profile (0.75mm) 16-lead
(4mm × 4mm) QFN package.
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Handheld Computers
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Charging Docks and Cradles
Digital Cameras
Smart Phones
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L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
Power Loss vs VBAT
Charging (PWM Mode)
2A Single Cell Li-Ion Battery Charger
1.5μH
1.25
1.00
0.75
0.50
0.25
SW
SENSE
V
BATSENS
BAT
INSENSE
PV
V
IN
4.5V TO 5.5V
IN
+
4.1V
Li-Ion
10μF
10μF
PGND
LTC4001-1
CHRG
NTC
FAULT
EN
V
= 5V
IN
2A CHARGER
0
PROG IDET TIMER
SS GNDSENS
3
3.25
3.5
V
3.75
(V)
4
4.25
0.22μF
0.1μF
BAT
40011 TA01b
274Ω
40011 TA01a
40011fa
1