Datasheet

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LTC4052-4.2

405242f

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

Lithium-Ion Battery

Pulse Charger with

Overcurrent Protection

Single Cell 4.2V, 1A, Standalone Li-Ion Battery Charger

The LTC

4052 is a complete standalone pulse charger

with integrated MOSFET for 1-cell lithium-ion batteries.

An external sense resistor provides overcurrent limiting as

a safety precaution against a user connecting a wall

adapter with the incorrect or no current limit. The internal

MOSFET prevents reverse battery current from flowing if

the input voltage is shorted to ground, eliminating the

need for a blocking diode.

As the battery accepts charge and approaches the

programmed float voltage, the internal MOSFET begins

switching off and on with the duty cycle gradually decreas-

ing as the battery approaches a fully charged condition.

A programmable timer terminates the charge cycle. The

near end-of-charge C/10 condition is indicated at the

CHRG pin when the average charge current falls to one-

tenth of the wall adapter current. Removing the input

voltage puts the LTC4052 into a sleep mode, dropping the

battery current drain to less than 1µA.

The LTC4052 is available in a tiny 8-pin thermally

enhanced MSOP package.

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Handheld Computers

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Cellular Telephones

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Cradle Chargers

, LTC and LT are registered trademarks of Linear Technology Corporation.

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Very Low Power Dissipation: 350mW at 1A

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Complete Standalone Pulse Charger for 1-Cell

Lithium-Ion Batteries

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Requires No Microcontroller, MOSFET or

Blocking Diode

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Sense Resistor Limits Maximum Current for Safety

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Programmable Charge Termination Timer for

Maximum Capacity Charging

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±1% Float Voltage Accuracy

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Near End-of-Charge (C/10) Detection Output

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AC Wall Adapter Present Output

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Low Battery Drain when Input Supply Is Removed

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Automatic Trickle Charge for Low Battery

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Automatic Battery Refresh

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Thermal Shutdown Protection

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Tiny Thermally Enhanced MSOP Package

10k

4.7Ω

SENSE

0.05Ω

1-CELL 4.2V

Li-Ion

BATTERY

CHRG

ACPR

GATE

BAT

TIMER

0.1µF

GND

LTC4052

SENSE

1µF

0.047µF

0.022µF

= 4.5V TO 10V

WITH 1A

CURRENT LIMIT

CHARGE STATUS

4052 TA01

AC PRESENT

TIME (HOURS)

0 0.5

BATTERY

VOLTAGE (V)CHRG (V)

CHARGE

CURRENT (A)

1.0 2.01.5

2.5

3.0

4052 • TA01b

4.5

4.0

3.5

3.0

1.0

0.5

CONSTANT

CURRENT

PULSING

CURRENT

CHARGE

CYCLE

ENDS

C/10

LTC4052 Charge Profile

Summary of content (12 pages)

PAGE 1
LTC4052-4.
PAGE 2
LTC4052-4.2 U W W W ABSOLUTE AXI U RATI GS U W U PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (VIN)....................................... 12V BAT Voltage ...............................................– 0.3V to 12V GATE (Note 2) .............................................– 0.3V to 8V SENSE, TIMER .................................. – 0.3V to VIN +0.3V CHRG, ACPR .............................................– 0.3V to 12V SENSE, BAT Peak Current ...................................... 1.
PAGE 3
LTC4052-4.2 ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Absolute Maximum Rating for GATE pin applies only to externally applied voltage. During normal operation the LTC4052-4.2’s internal charge pump can generate GATE pin voltage exceeding absolute maximum but it is internally current limited. Note 3: The LTC4052EMS8E-4.2 is guaranteed to meet performance specifications from 0°C to 70°C.
PAGE 4
LTC4052-4.2 U W TYPICAL PERFOR A CE CHARACTERISTICS Switch On-Resistance vs Temperature Overcurrent Sense Voltage 105.8 650 600 105.6 550 RDS(ON) (mΩ) VIMAX (mV) 105.4 105.2 105.0 500 VBAT = 2.6V 450 VBAT = 4V 400 350 104.8 104.6 –50 –25 300 50 25 75 0 TEMPERATURE (°C) 100 125 250 –50 –25 0 25 50 75 100 125 TEMPERATURE (°C) 4053 G07 4053 G08 U U U PI FU CTIO S SENSE (Pin 1): Overcurrent Sense Input.
PAGE 5
LTC4052-4.2 U U U PI FU CTIO S A series RC network from the GATE to the VIN pin is required to control the slew rate at the VIN pin when the switch is turned on or off. The slew rate control prevents excessive current from the capacitor usually located in the wall adapter from flowing into the battery when the pass transistor turns on. BAT (Pin 8): Battery Sense Input Pin. An internal resistor divider presets the final float voltage to 4.2V. If the BAT pin drops below 4.
PAGE 6
LTC4052-4.2 U OPERATIO The LTC4052 is a complete lithium-ion battery pulse charger with an internal 0.35Ω N-MOSFET switch driven by an internal charge pump. The charge current is set by the current limit of the input supply (wall adapter). An external RSENSE sets the maximum allowable charge overcurrent and prevents a wall adapter with a high current limit from damaging the battery.
PAGE 7
LTC4052-4.2 U W U U APPLICATIO S I FOR ATIO Input Voltage (Wall Adapter) The input voltage to the LTC4052 must have some method of current limit capability. The current limit level of the input power source must be lower than the overcurrent limit (IMAX) set by the sense resistor IMAX = 105mV/(RSENSE + 10mΩ). The 10mΩ represents bond wire resistance internal to the IC.
PAGE 8
LTC4052-4.2 U W U U APPLICATIO S I FOR ATIO C/10 Detection (Near End-of-Charge) The LTC4052 includes a comparator to monitor the duty cycle at the GATE pin to detect when the battery is nearing full charge. When the duty cycle falls below 10%, the comparator trips and turns off the N-MOSFET at the CHRG pin and switches in a weak (40µA) current source to ground. The 40µA turns off when the timer terminates the charge cycle. C/10 detection is disabled in trickle charge mode.
PAGE 9
LTC4052-4.2 U W U U APPLICATIO S I FOR ATIO In addition, feedthrough vias or plated through holes (located directly beneath the package and elsewhere) connecting internal copper and backside copper layers help transfer and spread the heat generated by the package. soldered to the PC board is approximately 35°C/W depending on the copper area.
PAGE 10
LTC4052-4.2 U TYPICAL APPLICATIO External N-MOSFET for Higher Charge Current VIN = 5V TO 10V WITH 2A CURRENT LIMIT MBRS120T3 3 4.7Ω 1µF AC PRESENT STATUS CHARGE STATUS 1k 10k VIN 1k 0.047µF LTC4052 SENSE 6 2 CHRG ACPR GATE BAT 1 7 CTIMER 0.1µF 5 GND 4 Si2302DS 8 0.022µF TIMER RSENSE 25mΩ 1-CELL 4.
PAGE 11
LTC4052-4.2 U PACKAGE DESCRIPTIO MS8E Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1662) BOTTOM VIEW OF EXPOSED PAD OPTION 2.06 ± 0.102 (.080 ± .004) 1 5.23 (.206) MIN 1.83 ± 0.102 (.072 ± .004) 0.889 ± 0.127 (.035 ± .005) 2.794 ± 0.102 (.110 ± .004) 2.083 ± 0.102 3.2 – 3.45 (.082 ± .004) (.126 – .136) 8 0.42 ± 0.04 (.0165 ± .0015) TYP 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.206) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .
PAGE 12
LTC4052-4.2 U TYPICAL APPLICATIO Minimum Component Count 4.2V Li-Ion Battery Charger VIN = 5V TO 10V WITH 600mA CURRENT LIMIT 3 10k VIN 0.047µF LTC4052 SENSE NC NC 6 2 CHRG GATE ACPR BAT TIMER CTIMER 0.1µF 5 1 7 8 0.022µF GND 4 1-CELL 4.2V 600mA Li-Ion BATTERY 4052 TA04 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1510-5 500kHz CC/CV Battery Charger Most Compact, Up to 1.