LTC4080X_技术文档

LTC4080X

500mA Standalone Li-Ion

Charger with Integrated 300mA

Synchronous Buck in 3mm

×

3mm DFN

U

DESCRIPTIO

FEATURES

■

Complete Linear Battery Charger with Integrated

Buck Converter in 3mm x 3mm DFN Package

Battery Charger:

The LTC4080X is a complete constant-current/constant-

voltage linear battery charger for a single-cell 4.2V

lithium-ion/polymer battery with an integrated 300mA

synchronousbuckconverter. A3mm×3mmDFNpackage

and low external component count make the LTC4080X

especially suitable for portable applications. Furthermore,

the LTC4080X is speciﬁcally designed to work within USB

power speciﬁcations.

■

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

The CHRG 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 LTC4080X battery charger also includes

automatic recharge and soft-start to limit inrush current.

If trickle charging is desired, please see the LTC4080

datasheet.

■

C/10 Charge Current Detection Output

■

5µA Supply Current in Shutdown Mode

Switching Regulator:

■

High Efﬁciency Synchronous Buck Converter

■

300mA Output Current (Constant-Frequency Mode)

■

2.7V to 4.5V Input Range (Powered from BAT Pin)

■

0.8V to V Output Range

BAT

■

The LTC4080X 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.

MODE Pin Selects Fixed (2.25MHz) Constant-Frequency

PWM Mode or Low I (23µA) Burst Mode^®

CC

Operation

■

2µA BAT Current in Shutdown Mode

U

APPLICATIO S

TheLTC4080Xisavailablein10-lead, lowproﬁle(0.75mm)

3mm × 3mm DFN and 10-lead MSE packages.

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

Burst Mode is a registered trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents,

including 6522118.

■

Wireless Headsets

■

Bluetooth Applications

■

Portable MP3 Players

Multifunction Wristwatches

■

U

Buck Efﬁciency vs Load Current

TYPICAL APPLICATIO

(V

= 1.8V)

OUT

100

80

60

40

20

0

1000

100

10

Li-Ion Battery Charger with 1.8V Buck Regulator

EFFICIENCY

(Burst)

500mA

V

EFFICIENCY

(PWM)

CC

V

BAT

CC

4.2V

POWER

LOSS

(3.75V

to 5.5V)

+

LTC4080X

Li-Ion/

1OµH

4.7µF

POLYMER

BATTERY

(PWM)

EN_CHRG

SW

FB

1

POWER LOSS

1M

10pF

4.7µF

EN_BUCK

(Burst)

V

OUT

V

= 3.8V

= 1.8V

(1.8V/300mA)

BAT

OUT

0.1

0.01

MODE GND PROG

L = 10µH

C = 4.7µF

C

OUT

4.7µF

806Ω

806k

0.01

0.1

1

10

100

1000

4080X TA01a

LOAD CURRENT (mA)

4080X TA01b

4080Xf

1

LTC4080X

W W U W

ABSOLUTE AXI U RATI GS

(Note 1)

BAT Short-Circuit Duration............................Continuous

BAT Pin Current ...................................................800mA

PROG Pin Current....................................................2mA

Junction Temperature ...........................................125°C

Operating Temperature Range (Note 2) .. – 40°C to 85°C

Storage Temperature Range.................. – 65°C to 125°C

V , t < 1ms and Duty Cycle < 1%.............. – 0.3V to 7V

CC

V

Steady State......................................... – 0.3V to 6V

BAT, CHRG.................................................. – 0.3V to 6V

EN_CHRG, PROG, ACPR.................– 0.3V to V + 0.3V

CC

MODE, EN_BUCK.......................... – 0.3V to V + 0.3V

BAT

FB ............................................................... – 0.3V to 2V

PIN CONFIGURATION

TOP VIEW

BAT

1

2

3

4

5

10 SW

BAT

CC

EN_CHRG

1

2

3

4

5

10 SW

V

CC

9

8

7

6

EN_BUCK

V

9

8

7

6

EN_BUCK

11

EN_CHRG

PROG

MODE

FB

11

MODE

FB

CHRG

PROG

ACPR

CHRG

MSE PACKAGE

10-LEAD PLASTIC MSOP

DD PACKAGE

10-LEAD (3mm × 3mm) PLASTIC DFN

T

= 125°C, θ = 40°C/W

JA

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

JMAX

T

JMAX

= 110°C, θ = 43°C/W (NOTE 3)

JA

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

TAPE AND REEL

PART MARKING

PACKAGE DESCRIPTION

10-Lead (3mm × 3mm) DFN

10-Lead Plastic MSE

TEMPERATURE RANGE

0°C to 70°C

LTC4080XEDD#PBF

LTC4080XEMSE#PBF

LTC4080XEDD#TRPBF

LTC4080XEMSE#TRPBF LTCVW

LCVV

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

4080Xf

2

LTC4080X

ELECTRICAL CHARACTERISTICS ^The

●

denotes speciﬁcations which apply over the full operating tempera-

ture range, otherwise speciﬁcations are at T = 25°C, V = 5V, V = 3.8V, V

= 0V, V

= V , V = 0V. (Note 2)

BAT MODE

A

CC

BAT

EN_CHRG

EN_BUCK

SYMBOL

PARAMETER

CONDITIONS

(Note 4)

MIN

3.75

2.7

TYP

5

MAX

5.5

UNITS

●

V

Battery Charger Supply Voltage

V

CC

Input Voltage for the Switching

Regulator

(Note 5)

3.8

4.5

BAT

●

I

Quiescent Supply Current (Charger On,

Switching Regulator Off)

V

= 4.5V (Forces I and I = 0),

PROG

EN_BUCK

110

300

10

µA

CC

BAT

= 0

Supply Current in Shutdown (Both

Battery Charger and Switching

Regulator Off)

V

= 5V, V

= 4V, V

= 0, V > V

5

2

µA

CC_SD

EN_CHRG

BAT

EN_BUCK

CC

BAT

= 0, V (3.5V) <

CC

(4V)

●

I

Battery Current in Shutdown (Both

Battery Charger and Switching

Regulator Off)

V

= 5V, V

= 4V, V

= 0, V > V

BAT

0.6

2

5

µA

BAT_SD

EN_CHRG

BAT

EN_BUCK

CC

= 0, V (3.5V) <

CC

(4V)

Battery Charger

V

BAT

Regulated Output Voltage

I

= 2mA

4.179

4.158

4.2

4.221

4.242

V

FLOAT

BAT

= 2mA, 4.3V < V < 5.5V

●

CC

●

I

Current Mode Charge Current

Undervoltage Lockout Voltage

R

= 4k; Current Mode; V

= 0

EN_BUCK

90

100

500

110

525

mA

BAT

PROG

EN_BUCK

= 0.8k; Current Mode; V

= 0

475

●

V

CC

V

Rising

Falling

3.5

2.8

3.6

3.0

3.7

3.2

V

UVLO_CHRG

PROG

CC

●

V

PROG Pin Servo Voltage

0.8k ≤ R

≤ 4k

0.98

1.0

1.02

V

PROG

V

ASD

Automatic Shutdown Threshold Voltage (V – V ), V Low to High

60

15

82

32

100

45

mV

CC

BAT

CC

(V – V ), V High to Low

CC

BAT

CC

t

Battery Charger Soft-Start Time

Bad Battery Threshold Voltage

Recharge Battery Threshold Voltage

180

2.9

µs

V

SS_CHRG

V

BADBAT

ΔV

V

– V , 0°C < T < 85°C

70

100

130

mV

RECHRG

FLOAT

BAT

A

ΔV

(V – V ) Undervoltage Current

I

= 0.9 I

180

90

300

130

mV

UVCL1,

UVCL2

CC

BAT

CHG

Limit Threshold Voltage

Charge Termination Timer

Recharge Time

= 0.1 I

●

t

3

4.5

2.25

1.125

0.1

6

3

hrs

TIMER

1.5

Low-Battery Charge Time

End of Charge Indication Current Level

V

= 2.5V

0.75

0.085

1.5

BAT

I

R

= 2k (Note 6)

0.115

mA/mA

°C

C/10

PROG

T

LIM

Junction Temperature in Constant-

Temperature Mode

115

R

Power FET On-Resistance (Between

CC

I

= 350mA, V = 4V

750

2

mΩ

Hz

ON_CHRG

BADBAT

BAT

CC

V

and BAT)

f

Defective Battery Detection CHRG Pulse V = 2V

Frequency

BAT

D

Defective Battery Detection CHRG Pulse V = 2V

75

%

BADBAT

BAT

Frequency Duty Ratio

Buck Converter

●

V

FB Servo Voltage

0.78

–50

1.8

0.80

0.82

50

V

nA

FB

I

f

I

FB Pin Input Current

Switching Frequency

V = 0.85V

FB

2.25

1.9

2.75

MHz

mA

OSC

No-Load Battery Current (Continuous

Frequency Mode)

No-Load for Regulator, V

L = 10µH, C = 4.7µF

= 5V,

EN_CHRG

BAT_NL_CF

4080Xf

3

LTC4080X

ELECTRICAL CHARACTERISTICS ^The

●

denotes speciﬁcations which apply over the full operating tempera-

ture range, otherwise speciﬁcations are at T = 25°C, V = 5V, V = 3.8V, V

= 0V, V

= V , V

BAT MODE

= 0V. (Note 2)

A

CC

BAT

EN_CHRG

EN_BUCK

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

I

No-Load Battery Current (Burst Mode

Operation)

No-Load for Regulator, V

= 5V,

23

µA

BAT_NL_BM

EN_CHRG

MODE = V , L = 10µH, C = 4.7µF

BAT

●

I

Battery Current in SLEEP Mode

V

= 5V, MODE = V

,

10

15

20

µA

BAT_SLP

EN_CHRG

BAT

> Regulation Voltage

OUT

●

V

Buck Undervoltage Lockout Voltage

V

BAT

V

BAT

Rising

Falling

2.6

2.4

2.7

2.5

2.8

2.6

V

UVLO_BUCK

Ω

R

PMOS Switch On-Resistance

NMOS Switch On-Resistance

PMOS Switch Current Limit

NMOS Switch Current Limit

NMOS Zero Current in Normal Mode

0.95

0.85

520

700

15

ON_P

ON_N

I

t

375

700

mA

µs

LIM_P

LIM_N

ZERO_CF

PEAK

Peak Current in Burst Mode Operation MODE = V

50

20

100

35

150

50

BAT

Zero Current in Burst Mode Operation

Buck Soft-Start Time

MODE = V

ZERO_BM

SS_BUCK

BAT

From the Rising Edge of EN_BUCK to 90%

of Buck Regulated Output

400

Logic

●

V

Input High Voltage

EN_CHRG, EN_BUCK, MODE Pin Low to High

EN_CHRG, EN_BUCK, MODE Pin High to Low

1.2

V

IH

IL

Input Low Voltage

0.4

Output Low Voltage (CHRG, ACPR)

Input Current High

I

= 5mA

60

105

1

mV

µA

MΩ

µA

OL

SINK

I

IH

I

IL

EN_BUCK, MODE Pins at 5.5V, V = 5V

–1

1

BAT

Input Current Low

EN_CHRG, EN_BUCK, MODE Pins at GND

1

R

EN_CHRG Pin Input Resistance

CHRG Pin Leakage Current

ACPR Pin Leakage Current

V

= 5V

1.45

3.3

1

EN_CHRG

CHRG

EN_CHRG

●

I

= 4.5V, V

= 5V

CHRG

BAT

= 3V, V = 5V

CHRG

1

ACPR

CC

Note 4: Although the LTC4080X charger functions properly at 3.75V, full

charge current requires an input voltage greater than the desired ﬁnal

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

battery voltage per ΔV

speciﬁcation.

UVCL1

Note 5: The 2.8V maximum buck undervoltage lockout (V

) exit

UVLO_BUCK

threshold must ﬁrst be exceeded before the minimum V speciﬁcation

applies.

Note 2: The LTC4080X is guaranteed to meet performance speciﬁcations

from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls.

BAT

Note 6: I

is expressed as a fraction of measured full charge current

C/10

with indicated PROG resistor.

Note 3: Failure to solder the exposed backside of the package to the PC

board ground plane will result in a thermal resistance much higher than

43°C/W.

4080Xf

4

LTC4080X

TYPICAL PERFORMANCE CHARACTERISTICS ^{(T = 25°C, V}= 5V, V = 3.8V, unless otherwise

A

CC

BAT

speciﬁed)

Battery Regulation (Float) Voltage

vs Charge Current

Battery Regulation (Float) Voltage

vs Temperature

Battery Regulation (Float) Voltage

vs V Supply Voltage

CC

4.210

4.205

4.200

4.195

4.190

4.185

4.180

4.175

4.170

4.165

4.160

4.25

4.21

4.20

4.19

4.18

4.17

4.16

4.15

4.14

4.13

R

= 2k

PROG

4.20

4.15

4.10

4.05

4.00

3.95

3.90

3.85

–30 –10

30

50

70

90

4.5

V

5

6

200

CHARGE CURRENT (mA)

250

–50

10

4

5.5

0

50

100

150

TEMPERATURE (°C)

SUPPLY VOLTAGE (V)

CC

4080X G01

4080X G03

4080X G02

Charge Current vs Temperature

with Thermal Regulation

(Constant-Current Mode)

Charger FET On-Resistance

vs Temperature

PROG Pin Voltage

vs Charge Current

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

250

200

150

100

50

1.0

0.8

0.6

0.4

0.2

0

V

= 6V

CC

V

I

= 4V

= 350mA

R

= 2k

CC

BAT

PROG

= 3V

BAT

R

= 2k

PROG

THERMAL CONTROL

LOOP IN OPERATION

0

–30 –10

30

50

70

90

–25

0

25

50

75

25 50

125 150

–50

10

–50

100 125

0

75 100

175 200

TEMPERATURE (°C)

CHARGE CURRENT (mA)

4080X G04

4080X G06

4080X G05

EN_CHRG, EN_BUCK and

MODE Pin Threshold Voltage

vs Temperature

EN_CHRG Pin Pulldown

Resistance vs Temperature

1.7

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

1.6

1.5

1.4

1.3

1.2

1.1

1.0

RISING

FALLING

0.50

–50 –30 –10 10

TEMPERATURE (°C)

90

30

50

70

–50 –30 –10 10

TEMPERATURE (°C)

90

30

50

70

4080X G07

4080X G08

4080Xf

5

LTC4080X

TYPICAL PERFORMANCE CHARACTERISTICS ^{(T = 25°C, V}= 5V, V = 3.8V, unless otherwise

A

CC

BAT

speciﬁed)

CHRG and ACPR Pin Output

Low Voltage vs Temperature

Normalized Charge Termination

Time vs Temperature

Buck Oscillator Frequency

vs Battery Voltage

80

1.05

1.00

0.95

0.90

0.85

0.80

2.28

2.27

2.26

2.25

2.24

I

, I

= 5mA

CHRG ACPR

70

60

50

40

30

20

10

2.23

2.22

0

–50 –30 –10 10

90

–50 –30 –10 10

TEMPERATURE (°C)

90

30

50

70

30

50

70

3.0

3.5

4.5

2.5

4.0

TEMPERATURE (°C)

BATTERY VOLTAGE (V)

4080X G09

4080X G10

4080X G11

Buck Oscillator Frequency

vs Temperature

Buck Efﬁciency vs Load Current

(V = 1.8V)

Buck Efﬁciency vs Load Current

(V = 1.5V)

OUT

100

80

60

40

20

0

1000

100

10

100

80

60

40

20

0

1000

100

10

2.4

2.3

2.2

2.1

2.0

1.9

1.8

V

= 3.8V

BAT

EFFICIENCY

(Burst)

V

= 4.5V

EFFICIENCY

(Burst)

BAT

EFFICIENCY

(PWM)

EFFICIENCY

(PWM)

POWER

LOSS

(PWM)

POWER

LOSS

(PWM)

V

= 2.7V

BAT

1

POWER LOSS

(Burst)

POWER LOSS

(Burst)

V

= 3.8V

= 1.5V

V

= 3.8V

= 1.8V

BAT

OUT

BAT

OUT

L = 10µH

0.1

0.01

0.1

0.01

V

L = 10µH

C = 4.7µF

40 60

–60 –40 –20

0

20

80 100

0.01

0.1

1

10

100

1000

0.01

0.1

1

10

100

1000

TEMPERATURE (°C)

LOAD CURRENT (mA)

4080X G13a

4080X G12

4080X G13

No-Load Buck Input Current

(Burst Mode Operation)

vs Battery Voltage

Buck Output Voltage

vs Battery Voltage

Buck Output Voltage

vs Temperature

35

30

25

1.810

1.805

1.810

1.805

1.800

1.795

I

= 1mA

OUT

I

= 1mA

OUT

I

= 1mA

= 1.8V

Burst Mode

OPERATION

OUT

Burst Mode

V

SET FOR 1.8V

V

SET FOR 1.8V

V

OUT

OPERATION

L = 10µH

PWM MODE

1.800

1.795

20

15

10

5

1.790

1.785

1.780

1.790

1.785

1.780

0

3.5

BATTERY VOLTAGE (V)

2.5

3.0

4.0

4.5

2.5

3.0

3.5

4.0

4.5

30

–50 –30 –10 10

TEMPERATURE (˚C)

70

90

50

BATTERY VOLTAGE (V)

4080X G14

4080X G17

4080X G15

4080Xf

6

LTC4080X

TYPICAL PERFORMANCE CHARACTERISTICS ^{(T = 25°C, V}= 5V, V = 3.8V, unless otherwise

A

CC

BAT

speciﬁed)

No-Load Buck Input Current

(Burst Mode Operation)

vs Temperature

Buck Main Switch (PMOS)

On-Resistance vs Battery Voltage

Buck Main Switch (PMOS)

On-Resistance vs Temperature

1.2

1.0

0.8

0.6

0.4

0.2

0

35

30

1.2

1.0

0.8

0.6

0.4

0.2

0

L = 10µH

C = 4.7µF

V

= 4.2V

= 3.8V

BAT

V

= 1.8V

OUT

V

BAT

25

20

15

10

5

V

= 2.7V

BAT

0

30

TEMPERATURE (˚C)

70

90

–50 –30 –10 10

50

3.5

BATTERY VOLTAGE (V)

2.5

3.0

4.0

4.5

5.0

30

TEMPERATURE (°C)

70

90

–50 –30 –10 10

50

4080X G18

4080X G19

4080X G20

Buck Synchronous Switch (NMOS)

On-Resistance vs Battery Voltage

Buck Synchronous Switch (NMOS)

On-Resistance vs Temperature

1.2

1.0

0.8

0.6

0.4

1.2

1.0

0.8

0.6

0.4

0.2

0

0.2

0

3.5

BATTERY VOLTAGE (V)

2.5

3.0

4.0

4.5

5.0

30

TEMPERATURE (°C)

70

90

–50 –30 –10 10

50

4080X G21

4080X G22

Maximum Output Current

(PWM Mode) vs Battery Voltage

Maximum Output Current (Burst

Mode Operation) vs Battery Voltage

500

400

300

200

100

80

70

60

50

40

30

20

10

0

L = 10µH

V

SET FOR 1.8V

OUT

V

SET FOR 1.8V

OUT

2.7

3

3.3

3.6

3.9

4.2

4.5

2.7

3

3.3

3.6

3.9

4.2

4.5

BATTERY VOLTAGE (V)

4080X G24

4080X G23

4080Xf

7

LTC4080X

TYPICAL PERFORMANCE CHARACTERISTICS ^{(T = 25°C, V}= 5V, V = 3.8V, unless otherwise

A

CC

BAT

speciﬁed)

Output Voltage Waveform

Output Voltage Transient

Step Response (PWM Mode)

when Switching Between Burst

Output Voltage Transient

Step Response (Burst Mode)

and PWM Mode (I

= 10mA)

LOAD

V

OUT

V

OUT

50mV/DIV

20mV/DIV

AC COUPLED

V

I

MODE

LOAD

5V/DIV

250mA/DIV

50mA/DIV

I = 0

0V

I = 0

4080X G27

4080X G25

4080X G26

50µs/DIV

Buck V

LOAD

Soft-Start

OUT

Charger V

Soft-Start

(I

= 50mA)

PROG

V

OUT

1V/DIV

0V

V

PROG

200mV/DIV

V

_

EN BUCK

V = 0

5V/DIV

0V

4080X G28

4080X G29

50µs/DIV

200µs/DIV

4080Xf

8

LTC4080X

U

PI FU CTIO S

BAT (Pin 1): Charge Current Output and Buck Regulator pin will be pulled to ground; otherwise the pin is high

Input. Provides charge current to the battery and regulates impedance.

the ﬁnal ﬂoat voltage to 4.2V. An internal precision resistor

CHRG (Pin 6): Open-Drain Charge Status Output. The

dividerfromthispinsetstheﬂoatvoltageandisdisconnected

charge status indicator pin has three states: pulldown,

in charger shutdown mode. This pin must be decoupled

high impedance state, and pulsing at 2Hz. This output can

with a low ESR capacitor for low-noise buck operation.

be used as a logic interface or as an LED driver. When the

V (Pin2):PositiveInputSupplyVoltage.Thispinprovides battery is being charged, the CHRG pin is pulled low by an

CC

power to the battery charger. V can range from 3.75V internalN-channelMOSFET.Whenthechargecurrentdrops

CC

to 5.5V. This pin should be bypassed with at least a 1µF to 10% of the full-scale current, the CHRG pin is forced to

capacitor. When V is less than 32mV above the BAT pin a high impedance state. When the battery voltage remains

CC

voltage, the battery charger enters shutdown mode.

below 2.9V for one quarter of the full charge time, the

battery is considered defective, and the CHRG pin pulses

at a frequency of 2Hz with 75% duty cycle.

EN_CHRG(Pin3):EnableInputPinfortheBatteryCharger.

Pullingthispinabovethemanualshutdownthreshold(V )

IH

puts the LTC4080X charger in shutdown mode, thus stop- FB(Pin7):FeedbackPinfortheBuckRegulator. Aresistor

ping the charge cycle. In battery charger shutdown mode, divider from the regulator’s output to the FB pin programs

the LTC4080X has less than 10µA supply current and less the output voltage. Servo value for this pin is 0.8V.

than 5µA battery drain current provided the regulator is

MODE (Pin 8): Burst Mode Enable Pin. Tie this pin high to

not running. Enable is the default state, but the pin should

force the LTC4080X regulator into Burst Mode operation

be tied to GND if unused.

for all load conditions. Tie this pin low to force constant-

PROG (Pin 4): Charge Current Program and Charge Cur- frequency mode operation for all load conditions. Do not

rent Monitor Pin. Connecting a 1% resistor, R

, to ﬂoat this pin.

PROG

ground programs the charge current. When charging in

constant-currentmode,thispinservosto1V.Inallmodes,

the voltage on this pin can be used to measure the charge

current using the following formula:

EN_BUCK(Pin9):EnableInputPinfortheBuckRegulator.

Pull this pin high to enable the regulator, pull low to shut

down. Do not ﬂoat this pin.

SW (Pin 10): Switch Pin for the Buck Regulator. Minimize

the length of the metal trace connected to this pin. Place

the inductor as close to this pin as possible.

V_PROG

I_BAT

=

•400

R_PROG

ACPR (Pin 5): Open-Drain Power Supply Status Out- GND (Pin 11): Ground. This pin is the back of the Exposed

put. When V is greater than the undervoltage lockout PadpackageandmustbesolderedtothePCBforelectrical

CC

threshold (3.6V) and greater than V + 82mV, the ACPR connection and rated thermal performance.

BAT

4080Xf

9

LTC4080X

W

BLOCK DIAGRA

2

V

CC

+

3

CHARGER

SHUTDOWN

EN_CHRG

C3

MP3

X1

MP1

115°C

–

+

D3

–

0.82V

TA

X400

R

EN

T

DIE

D1

D2

PROG

0.1V

1

BAT

–

+

–

+

MA

C1

R1

R2

CA

VA

–

+

–

+

MP4

6

1.22V

1V

CHRG

CHARGER

ENABLE

PULSE

LOGIC

+

–

2.9V

BAT

C2

CHARGE

CONTROL

BADBAT

4

5

LOGIC

PROG

ACPR

R

PROG

+

–

V

CC

C4

C5

CHARGER

OSCILLATOR

COUNTER

3.6V

+

–

V

+ 82mV

BAT

LINEAR BATTERY CHARGER

MP2

+

–

SYNCHRONOUS BUCK CONVERTER

9

8

L1

PWM

CONTROL

AND DRIVE

V

C

OUT

EN_BUCK

ENABLE BUCK

C6

10

7

SW

MN1

0.82V

C

R7

R8

PL

–

+

–

OUT

2.25MHz

BUCK

OSCILLATOR

ERROR

MODE

FB

C7

AMP

+

0.8V

0.82V

11

4080X BD

GND

Figure 1. LTC4080X Block Diagram

4080Xf

10

LTC4080X

U

OPERATIO

The LTC4080X is a full-featured linear battery charger

with an integrated synchronous buck converter designed

primarily 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

aprogrammableoutputvoltageprovidingamaximumload

current of 300mA. The converter and the battery charger

can run simultaneously or independently of each other.

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

chargerwillautomaticallyreducethecurrentinworst-case

conditions.

An internal timer sets the total charge time, t

(typi-

TIMER

cally 4.5 hours). When this time elapses, the charge cycle

terminates and the CHRG 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

BATTERY CHARGER OPERATION

it or momentarily force the EN_CHRG pin above V . A

new charge cycle will automatically restart if the BAT pin

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 CHRG open-drain status

outputindicateswhenC/10hasbeenreached. Noblocking

diode or external sense resistor is required; thus, the basic

chargercircuitrequiresonlytwoexternalcomponents.The

IH

voltage falls below V

(typically 4.1V).

RECHRG

Constant-Current / Constant-Voltage /

Constant-Temperature

The LTC4080X 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 LTC4080X. Three of the

ampliﬁer feedback loops shown control the constant-cur-

rent,CA,constant-voltage,VA,andconstant-temperature,

TAmodes.Afourthampliﬁerfeedbackloop,MA,isusedto

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.

ACPR open-drain output indicates if the V input voltage,

CC

and the difference between V and BAT, are sufﬁcient for

CC

charging. An internal charge termination timer adheres to

battery manufacturer safety guidelines. Furthermore, the

LTC4080X battery charger is capable of operating from a

USB power source.

A charge cycle begins when the voltage at the V pin

CC

rises above 3.6V and approximately 82mV above the BAT

pin voltage, a 1% program resistor is connected from the

PROGpintoground, andtheEN_CHRGpinispulledbelow

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.Theoutputoftheotherampliﬁersaturateslowwhich

effectively removes its loop from the system. When in

constant-currentmode,CAservosthevoltageatthePROG

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.

the shutdown threshold (V ).

IL

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

internalcomparatorturnsofftheN-channelMOSFETdriving

the CHRG 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

presetvalueofapproximately115°C. Thisfeatureprotects

the LTC4080X 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

LTC4080X or external components. Another beneﬁt of the

4080Xf

11

LTC4080X

U

OPERATIO

If the die temperature starts to creep up above 115°C

due to internal power dissipation, the transconductance

ampliﬁer, TA, limits the die temperature to approximately

115°C by reducing the charge current. Diode D3 ensures

that TA does not affect the charge current when the die

temperature is below 115°C. In thermal regulation, the

PROG pin voltage continues to give an indication of the

charge current.

be restarted. To restart the charge cycle (i.e., when the

dead battery is replaced with a discharged battery less

than 2.9V), the charger must be reset by removing the

input voltage and reapplying it or temporarily pulling the

EN_CHRG pin above the shutdown threshold.

Battery Charger Shutdown Mode

TheLTC4080X’sbatterychargercanbedisabledbypulling

the EN_CHRG pin above the shutdown threshold (V ).

In typical operation, the charge cycle begins in constant-

currentmodewiththecurrentdeliveredtothebatteryequal

IH

In shutdown mode, the battery drain current is reduced

to about 2µA and the V supply current to about 5µA

to 400V/R . If the power dissipation of the LTC4080X

PROG

CC

provided the regulator is off. When the input voltage is

not present, the battery charger is in shutdown and the

battery drain current is less than 5µA.

resultsinthejunctiontemperatureapproaching115°C,the

ampliﬁer (TA) will begin decreasing the charge current to

limit the die temperature to approximately 115°C. As the

battery voltage rises, the LTC4080X either returns to full

constant-current mode or enters constant-voltage mode

straight from constant-temperature mode.

Power Supply Status Indicator (ACPR)

The power supply status output has two states: pulldown

andhighimpedance.ThepulldownstateindicatesthatV

CC

Battery Charger Undervoltage Lockout (UVLO)

is above the undervoltage lockout threshold and at least

82mV above the BAT voltage (see Undervoltage Lockout).

When these conditions are not met, the ACPR pin is high

impedance indicating that the LTC4080X is unable to

charge the battery.

An internal undervoltage lockout circuit monitors the V

CC

input voltage and keeps the battery charger off until V

CC

rises above 3.6V and approximately 82mV above the BAT

pin voltage. The 3.6V UVLO circuit has a built-in hysteresis

of approximately 0.6V, and the 82mV automatic shutdown

threshold has a built-in hysteresis of approximately 50mV.

During undervoltage lockout conditions, maximum battery

CHRG Status Output Pin

Thechargestatusindicatorpinhasthreestates:pulldown,

pulsing at 2Hz (see Defective Battery Detection) and high

impedance. The pulldown state indicates that the battery

charger is in a charge cycle. A high impedance state indi-

cates that the charge current has dropped below 10% of

the full-scale current or the battery charger is disabled.

When the timer runs out (4.5 hrs), the CHRG pin is also

forced to the high impedance state. If the battery charger

is not in constant-voltage mode when the charge current

is forced to drop below 10% of the full-scale current by

UVCL, CHRG will stay in the strong pulldown state.

drain current is 5µA and maximum supply current is 10µA.

Undervoltage Charge Current Limiting (UVCL)

ThebatterychargerintheLTC4080Xincludesundervoltage

charge current limiting that prevents full charge current

untiltheinputsupplyvoltagereachesapproximately300mV

abovethebatteryvoltage(ΔV ).Thisfeatureisparticu-

UVCL1

larly useful if the LTC4080X is powered from a supply with

long leads (or any relatively high output impedance). See

Applications Information section for further details.

Defective Battery Detection

Charge Current Soft-Start

At the beginning of a charge cycle, if the battery voltage

is below 2.9V for one quarter of the total charge time

(1.125 hr), the battery is assumed to be defective, the

charge cycle terminates and the CHRG output pulses at a

frequency of 2Hz with a 75% duty cycle. If, for any reason,

the battery voltage rises above 2.9V, the charge cycle will

TheLTC4080X’sbatterychargerincludesasoft-startcircuit

tominimizetheinrushcurrentatthestartofachargecycle.

When a charge cycle is initiated, the charge current ramps

fromzerotofull-scalecurrentoveraperiodofapproximate-

ly 180µs. This has the effect of minimizing the transient

current load on the power supply during start-up.

4080Xf

12

LTC4080X

U

OPERATIO

Timer and Recharge

peak current demanded by the error amp. At this point,

the main switch turns off and the synchronous switch

MN1 (N-channel MOSFET) turns on allowing the inductor

current to ﬂow from ground to the load until either the

next clock cycle begins or the current reduces to the zero

The LTC4080X’s battery charger has an internal charge

termination timer that starts when the input voltage is

greater than the undervoltage lockout threshold and at

least 82mV above BAT, and the battery charger is leaving

shutdown.

current (I

) level.

ZERO

Oscillator: In constant-frequency mode, the switching

regulator uses a dedicated oscillator which runs at a

ﬁxed frequency of 2.25MHz. This frequency is chosen to

minimize possible interference with the AM radio band.

At power-up or when exiting shutdown, the charge time

is set to 4.5 hours. Once the charge cycle terminates, the

batterychargercontinuouslymonitorstheBATpinvoltage

using a comparator with a 2ms ﬁlter time. When the aver-

age battery voltage falls below 4.1V (which corresponds

to 80%-90% battery capacity), a new charge cycle is initi-

ated and a 2.25 hour timer begins. This ensures that the

battery is kept at, or near, a fully charged condition and

eliminates the need for periodic charge cycle initiations.

The CHRG output assumes a strong pulldown state dur-

ing recharge cycles until C/10 is reached or the recharge

cycle terminates.

Error Ampliﬁer: The error ampliﬁer is an internally com-

pensated transconductance (g ) ampliﬁer with a g

m

of 65 µmhos. The internal 0.8V reference voltage is

compared to the voltage at the FB pin to generate a

current signal at the output of the error ampliﬁer. This cur-

rent signal represents the peak inductor current required

to achieve regulation.

PWM Comparator: Lossless current sensing converts

the PMOS switch current signal to a voltage which is

summed with the internal slope compensation signal.

The PWM comparator compares this summed signal to

determine when to turn off the main switch. The switch

current sensing is blanked for ~12ns at the beginning of

each clock cycle to prevent false switch turn-off.

SWITCHING REGULATOR OPERATION:

TheswitchingbuckregulatorintheLTC4080Xcanbeturned

on by pulling the EN_BUCK pin above V . It has two user-

IH

selectablemodesofoperation:constant-frequency(PWM)

mode and Burst Mode Operation. The constant-frequency

modeoperationofferslownoiseattheexpenseofefﬁciency

whereas the Burst Mode operation offers higher efﬁciency

at light loads at the cost of increased noise, higher output

voltage ripple, and less output current. A detailed descrip-

tion of different operating modes and different aspects of

operation follow. Operations can best be understood by

referring to the Block Diagram.

Burst Mode Operation

Burst Mode operation can be selected by pulling the

MODE pin above V . In this mode, the internal oscil-

IH

lator is disabled, the error ampliﬁer is converted into a

comparator monitoring the FB voltage, and the inductor

current swings between a ﬁxed I

(~100mA) and I

PEAK

ZERO

(35mA) irrespective of the load current as long as the FB

pin voltage is less than or equal to the reference voltage

Constant-Frequency (PWM) Mode Operation

of 0.8V. Once V is greater than 0.8V, the control logic

FB

The switching regulator operates in constant-frequency

shuts off both switches along with most of the circuitry

and the regulator is said to enter into SLEEP mode. In

(PWM) mode when the MODE pin is pulled below V . In

IL

this mode, it uses a current mode architecture including

an oscillator, an error ampliﬁer, and a PWM comparator

for excellent line and load regulation. The main switch

MP2 (P-channel MOSFET) turns on to charge the inductor

at the beginning of each clock cycle if the FB pin voltage

is less than the 0.8V reference voltage. The current into

the inductor (and the load) increases until it reaches the

SLEEP mode, the regulator only draws about 20µA from

the BAT pin provided that the battery charger is turned

off. When the output voltage droops about 1% from its

nominal value, the regulator wakes up and the inductor

current resumes swinging between I

and I

. The

PEAK

ZERO

output capacitor recharges and causes the regulator to

re-enter the SLEEP state if the output load remains light

4080Xf

13

LTC4080X

U

OPERATIO

enough. Thefrequencyofthisintermittentburstoperation

depends on the load current. That is, as the load current

drops further, the regulator turns on less frequently. Thus

BurstModeoperationincreasestheefﬁciencyatlightloads

byminimizingtheswitchingandquiescentlosses.However,

the output voltage ripple increases to about 2%.

However, in Burst Mode operation, I

is set to positive

ZERO

35mA meaning that the synchronous switch is turned off

as soon as the current through the inductor to the output

decreases to 35mA in the discharge cycle. This preserves

thechargeontheoutputcapacitorandincreasestheoverall

efﬁciency at light loads.

To minimize ripple in the output voltage, the current limits

for both switches in Burst Mode operation are reduced

to about 20% of their values in the constant-frequency

mode. Also the zero current of the synchronous switch

is changed to about 35mA thereby preventing reverse

conduction through the inductor. Consequently, the regu-

lator can only deliver approximately 67mA of load current

while in Burst Mode operation. Any attempt to draw more

load current will cause the output voltage to drop out of

regulation.

Soft-Start

The LTC4080X switching regulator provides soft-start in

both modes of operation by slowly charging an internal

capacitor. The voltage on this capacitor, in turn, slowly

ramps the current limits of both switches from a low value

to their respective maximum values over a period of about

400µs. The soft-start capacitor is discharged completely

whenever the regulator is disabled.

Short-Circuit Protection

Current Limit

In the event of a short circuit at the output or during

start-up, V

will be near zero volts. Since the downward

To prevent inductor current runaway, there are absolute

current limits (I ) on both the PMOS main switch and

OUT

slope of the inductor current is ~V /L, the inductor

OUT

LIM

current may not get a chance to discharge enough to

avoid a runaway situation. Because the current sensing

is blanked for ~12ns at the beginning of each clock cycle,

inductor current can build up to a dangerously high level

over a number of cycles even if there is a hard current

limit on the main PMOS switch. This is why the switching

regulator in the LTC4080X also monitors current through

the synchronous NMOS switch and imposes a hard limit

on it. If the inductor current through the NMOS switch at

the end of a discharge cycle is not below this limit, the

regulator skips the next charging cycle thereby preventing

inductor current runaway.

the NMOS synchronous switch. These limits are internally

set at 520mA and 700mA respectively for PWM mode. If

the peak inductor current demanded by the error ampliﬁer

ever exceeds the PMOS I , the error ampliﬁer will be

LIM

ignored and the inductor current will be limited to PMOS

I

. In Burst Mode operation, the PMOS current limit is

LIM

reduced to 100mA to minimize output voltage ripple.

Zero Current Comparator

Thezeroorreversecurrentcomparatormonitorstheinduc-

tor current to the output and shuts off the synchronous

rectiﬁer when this current reduces to a predetermined

value (I

). In ﬁxed frequency mode, this is set to nega-

ZERO

Switching Regulator Undervoltage Lockout

tive 15mA meaning that the regulator allows the inductor

current to ﬂow in the reverse direction (from the output to

ground through the synchronous rectiﬁer) to a maximum

value of 15mA. This is done to ensure that the regulator

is able to regulate at very light loads without skipping any

cyclestherebykeepingoutputvoltagerippleandnoiselow

at the cost of efﬁciency.

Whenever V

is less than 2.7V, an undervoltage lock-

BAT

out circuit keeps the regulator off, preventing unreliable

operation. However, if the regulator is already running

and the battery voltage is dropping, the undervoltage

comparator does not shut down the regulator until V

drops below 2.5V.

BAT

4080Xf

14

LTC4080X

U

OPERATIO

Dropout Operation

Global Thermal Shutdown

When the BAT pin voltage approaches V , the duty cycle

The LTC4080X includes a global thermal shutdown which

shuts off the entire device (battery charger and switch-

ing regulator) if the die temperature exceeds 160°C. The

LTC4080X resumes normal operation once the temperature

drops approximately 14°C.

OUT

of the switching regulator approaches 100%. When V

BAT

is approximately equal to V , the regulator is said to be

OUT

in dropout. In dropout, the main switch (MP2) stays on

continuously with the output voltage being equal to the

battery voltage minus the voltage drops across the main

switch and the inductor.

U

W U U

APPLICATIO S I FOR ATIO

BATTERY CHARGER

the additional pole created by PROG pin capacitance,

capacitance on this pin must be kept to a minimum. With

no additional capacitance on the PROG pin, the battery

charger is stable with program resistor values as high

as 25k. However, additional capacitance on this node

reduces the maximum allowed program resistor. The pole

frequency at the PROG pin should be kept above 100kHz.

Therefore, if the PROG pin is loaded with a capacitance,

Programming Charge Current

The battery charge current is programmed using a single

resistor from the PROG pin to ground. The charge current

is400timesthecurrentoutofthePROGpin. Theprogram

resistor and the charge current are calculated using the

following equations:

C

, the following equation should be used to calculate

PROG

1V

I_BAT

1V

R_PROG

the maximum resistance value for R

:

PROG

R_PROG= 400 •

, I_BAT= 400 •

1

R_PROG

≤

The charge current out of the BAT pin can be determined

at any time by monitoring the PROG pin voltage and using

the following equation:

2π • 100kHz • C_PROG

Average,ratherthaninstantaneous,batterycurrentmaybe

of interest to the user. For example, when the switching

regulator operating in low-current mode is connected in

parallel with the battery, the average current being pulled

out of the BAT pin is typically of more interest than the

instantaneous current pulses. In such a case, a simple RC

ﬁlter can be used on the PROG pin to measure the average

battery current as shown in Figure 2. A 10k resistor has

been added between the PROG pin and the ﬁlter capacitor

to ensure stability.

V_PROG

R_PROG

I_BAT

=

•400

Stability Considerations

TheLTC4080Xbatterychargercontainstwocontrolloops:

constant-voltage and constant-current. The constant-

voltage loop is stable without any compensation when a

battery is connected with low impedance leads. Excessive

lead length, however, may add enough series inductance

to require a bypass capacitor of at least 1µF from BAT to

LTC4080X

PROG

CHARGE

10k

CURRENT

MONITOR

CIRCUITRY

GND. Furthermore, a 4.7µF capacitor with a 0.2Ω to 1Ω

series resistor from BAT to GND is required to keep ripple

voltage low when the battery is disconnected.

GND

R

C

FILTER

PROG

4080X F02

In constant-current mode, the PROG pin voltage is in

the feedback loop, not the battery voltage. Because of

Figure 2. Isolating Capacitive Load

on PROG Pin and Filtering

4080Xf

15

LTC4080X

U

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APPLICATIO S I FOR ATIO

Undervoltage Charge Current Limiting (UVCL)

times improvement over the non-current limited supply

power dissipation.

USB powered systems tend to have highly variable source

impedances (due primarily to cable quality and length). A

transientloadcombinedwithsuchimpedancecaneasilytrip

theUVLOthresholdandturnthebatterychargeroffunless

undervoltage charge current limiting is implemented.

USB and Wall Adapter Power

Although the LTC4080X allows charging from a USB port,

a wall adapter can also be used to charge Li-Ion batter-

ies. Figure 3 shows an example of how to combine wall

adapter and USB power inputs. A P-channel MOSFET,

MP1, is used to prevent back conducting into the USB

port when a wall adapter is present and Schottky diode,

D1, is used to prevent USB power loss through the 1k

pulldown resistor.

ConsiderasituationwheretheLTC4080Xisoperatingunder

normal conditions and the input supply voltage begins to

sag (e.g. an external load drags the input supply down).

If the input voltage reaches V

(approximately 300mV

), undervoltage charge

UVCL

above the battery voltage, ΔV

UVCL

current limiting will begin to reduce the charge current in

an attempt to maintain ΔV between V and BAT. The

Typically a wall adapter can supply signiﬁcantly more

current than the current-limited USB port. Therefore, an

N-channel MOSFET, MN1, and an extra program resistor

can be used to increase the charge current when the wall

adapter is present.

UVCL

CC

LTC4080X will continue to operate at the reduced charge

current until the input supply voltage is increased or volt-

age mode reduces the charge current further.

Operation from Current Limited Wall Adapter

I

5V WALL

ADAPTER

(300mA)

CHG

1

SYSTEM

LOAD

BAT

LTC4080X

By using a current limited wall adapter as the input sup-

ply, the LTC4080X can dissipate signiﬁcantly less power

when programmed for a current higher than the limit of

the wall adapter.

D1

2

USB

POWER

(200mA)

V

CC

4

+

Li-Ion

BATTERY

MP1

PROG

1.33k

MN1

Considerasituationwhereanapplicationrequiresa200mA

charge current for a discharged 800mAh Li-Ion battery.

If a typical 5V (non-current limited) input supply is avail-

able then the peak power dissipation inside the part can

exceed 300mW.

2k

1k

4080X F03

Figure 3. Combining Wall Adapter and USB Power

Now consider the same scenario, but with a 5V input

supply with a 200mA current limit. To take advantage

of the supply, it is necessary to program the LTC4080X

to charge at a current greater than 200mA. Assume that

the LTC4080X charger is programmed for 300mA (i.e.,

Power Dissipation

The conditions that cause the LTC4080X battery charger

to reduce charge current through thermal feedback can be

approximated by considering the total power dissipated

in the IC. For high charge currents, the LTC4080X power

dissipation is approximately:

R

= 1.33kΩ) to ensure that part tolerances maintain

PROG

a programmed current higher than 200mA. Since the

battery charger will demand a charge current higher than

the current limit of the input supply, the supply voltage

will collapse to the battery voltage plus 200mA times the

on-resistance of the internal PFET. The on-resistance of

the battery charger power device is approximately 0.75Ω

with a 5V supply. The actual on-resistance will be slightly

higher due to the fact that the input supply will have col-

lapsed to less than 5V. The power dissipated during this

phase of charging is approximately 30mW. That is a ten

P = V_CC− V_BAT•I_BAT+ P_{D_BUCK}

(

)

D

Where P is the total power dissipated within the IC, V

D

CC

BAT

istheinputsupplyvoltage, V isthebatteryvoltage, I

BAT

D_BUCK

is the charge current and P

due to the regulator. P

is the power dissipation

can be calculated as:

D_BUCK

⎛

⎝ η

⎞

⎠

1

P_{D_BUCK}= V_OUT•I_OUT

− 1

⎜

⎟

4080Xf

16

LTC4080X

U

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APPLICATIO S I FOR ATIO

Where V

is the regulated output of the switching

OUT

V

Bypass Capacitor

OUT

regulator, I

CC

is the regulator load and η is the regulator

Many types of capacitors can be used for input bypassing;

however, caution must be exercised when using multi-layer

ceramic capacitors. Because of the self-resonant and high

Q characteristics of some types of ceramic capacitors, high

voltage transients can be generated under some start-up con-

ditions, such as connecting the battery charger input to a live

power source. Adding a 1

X5Rceramiccapacitorwillminimizestart-upvoltagetransients.

For more information, refer to Application Note 88.

efﬁciency at that particular load.

It is not necessary to perform worst-case power dissipa-

tion scenarios because the LTC4080X will automatically

reduce the charge current to maintain the die temperature

at approximately 115°C. However, the approximate ambi-

ent temperature at which the thermal feedback begins to

protect the IC is:

Ω series resistor in series with an

T = 115°C – P_Dθ_JA

A

T = 115°C – (V – V ) • I

• θ_JAif the regulator

A

CC

BAT

SWITCHING REGULATOR

is off.

Example: Consider the extreme case when an LTC4080X

is operating from a 6V supply providing 250mA to a 3V

Li-Ion battery and the regulator is off. The ambient tem-

perature above which the LTC4080X will begin to reduce

the 250mA charge current is approximately:

Setting the Buck Converter Output Voltage

The LTC4080X regulator compares the FB pin voltage with

aninternal0.8Vreferencetogenerateanerrorsignalatthe

output of the error ampliﬁer. A voltage divider from V

to ground (as shown in the Block Diagram) programs the

output voltage via FB using the formula:

OUT

T = 115°C – (6V – 3V) • (250mA) • 43°C/W

A

T = 115°C – 0.75W • 43°C/W = 115°C – 32.25°C

R7

R8

⎡

⎣

⎤

A

V_OUT= 0.8V • 1+

⎢

⎥

⎦

T = 82.75°C

A

If there is more power dissipation due to the regulator,

the thermal regulation will begin at a somewhat lower

temperature. In the above circumstances, the LTC4080X

can be used above 82.75°C, but the charge current will be

reduced from 250mA. The approximate current at a given

ambient temperature can be calculated:

Keeping the current low (<5µA) in these resistors maxi-

mizes efﬁciency, but making them too low may allow stray

capacitancetocausenoiseproblemsandreducethephase

margin of the error amp loop. To improve the frequency

response, a phase-lead capacitor (C ) of approximately

PL

10pF can be used. Great care should be taken to route the

FB line away from noise sources, such as the inductor or

the SW line.

115°C − T_A

I_BAT

=

V

_CC− V_BAT• θ

(

)

JA

Inductor Selection

Using the previous example with an ambient temperature

of 85°C, the charge current will be reduced to approxi-

mately:

The value of the inductor primarily determines the cur-

rent ripple in the inductor. The inductor ripple

115°C − 85°C

30°C

current ΔI decreases with higher inductance and

I_BAT

=

= 232.6mA

L

6V − 3V • 43°C /W 129°C /A

(

)

increases with higher V or V

:

IN

OUT

Furthermore, the voltage at the PROG pin will change

proportionally with the charge current as discussed in

the Programming Charge Current section.

⎛

⎞

V_OUT

f₀•L

V_OUT

∆I_L=

• 1−

⎜

⎝

⎟

⎠

V

IN

Accepting larger values of ΔI allows the use of low

L

inductances, but results in higher output voltage ripple,

greater core losses, and lower output current capability. A

4080Xf

17

LTC4080X

U

W U U

APPLICATIO S I FOR ATIO

reasonable starting point for setting ripple current is ΔI

To prevent large V

load conditions, it is also recommended that a ceramic

voltage steps during transient

OUT

L

=0.3 • I , where I

is the peak switch current limit.

LIM

The largest ripple current occurs at the maximum input

voltage. To guarantee that the ripple current stays below a

speciﬁed maximum, the inductor value should be chosen

according to the following equation:

capacitor be used to bypass V . A typical value for this

capacitor is 4.7µF.

OUT

Multilayer Ceramic Chip Capacitors (MLCC) typically have

exceptional ESR performance. MLCCs combined with a

carefullylaidoutboardwithanunbrokengroundplanewill

yield very good performance and low EMI emissions.

⎛

⎞

⎟

V_OUT

L ≥

• 1−

⎜

⎝

⎟

⎠

f₀• ∆I_L

V

IN

MAX

(

)

Thereareseveraltypesofceramiccapacitorswithconsider-

ablydifferentcharacteristics.Y5Vceramiccapacitorshave

apparently higher packing density but poor performance

over their rated voltage or temperature ranges. Under

given voltage and temperature conditions, X5R and X7R

ceramic capacitors should be compared directly by case

size rather than speciﬁed value for a desired minimum

capacitance. Some manufacturers provide excellent data

on their websites about achievable capacitance. Table 2

shows a list of several ceramic capacitor manufacturers.

For applications with V

suggests that an inductor of at least 6.8µH should be used

for proper operation.

= 1.8V, the above equation

OUT

Many different sizes and shapes of inductors are

available from numerous manufacturers. To maximize

efﬁciency, choose an inductor with a low DC resistance.

Keep in mind that most inductors that are very thin or

have a very small volume typically have much higher

core and DCR losses and will not give the best efﬁciency.

Also choose an inductor with a DC current rating at least

1.5 times larger than the peak inductor current limit to

ensure that the inductor does not saturate during nor-

mal operation. To minimize radiated noise, use a toroid,

or shielded pot core inductors in ferrite or permalloy

materials. Table 1 shows a list of several inductor manu-

facturers.

Table 2. Recommended Ceramic Capacitor Manufacturers

Taiyo Yuden

AVX

www.t-yuden.com

www.avxcorp.com

www.murata.com

www.tdk.com

Murata

TDK

Board Layout Considerations

Table 1. Recommended Surface Mount Inductor Manufacturers

Coilcraft

Sumida

Murata

Toko

www.coilcraft.com

www.sumida.com

www.murata.com

www.tokoam.com

To be able to deliver maximum charge current under all

conditions, it is critical that the exposed metal pad on the

backside of the LTC4080X’s package has a good thermal

contact to the PC board ground. Correctly soldered to a

2

2500mm double-sided1oz.copperboard,theLTC4080X

Input and Output Capacitor Selection

has a thermal resistance of approximately 43°C/W. Failure

to make thermal contact between the exposed pad on the

backside of the package and the copper board will result

in thermal resistances far greater than 43°C/W.

Since the input current waveform to a buck converter is a

squarewave,itcontainsveryhighfrequencycomponents.

It is strongly recommended that a low equivalent series

resistance (ESR) multilayer ceramic capacitor be used to

bypass the BAT pin which is the input for the converter.

Tantalum and aluminum capacitors are not recommended

because of their high ESR. The value of the capacitor on

BATdirectlycontrolstheamountofinputvoltageripplefor

a given load current. Increasing the size of this capacitor

will reduce the input ripple.

Furthermore due to its high frequency switching circuitry,

it is imperative that the input capacitor, BAT pin capaci-

tor, inductor, and the output capacitor be as close to the

LTC4080Xaspossibleandthatthereisanunbrokenground

plane under the LTC4080X and all of its high frequency

components.

4080Xf

18

LTC4080X

U

PACKAGE DESCRIPTIO

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1699)

R = 0.115

0.38 0.10

TYP

6

10

0.675 0.05

3.50 0.05

2.15 0.05 (2 SIDES)

1.65 0.05

3.00 0.10

(4 SIDES)

1.65 0.10

(2 SIDES)

PIN 1

TOP MARK

(SEE NOTE 6)

PACKAGE

OUTLINE

(DD10) DFN 1103

5

1

0.75 0.05

0.200 REF

0.25 0.05

0.50 BSC

0.25 0.05

0.50

BSC

2.38 0.10

(2 SIDES)

2.38 0.05

(2 SIDES)

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

NOTE:

1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229

VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA

SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT

2. DRAWING NOT TO SCALE

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

3. ALL DIMENSIONS ARE IN MILLIMETERS

MSE Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1664)

BOTTOM VIEW OF

EXPOSED PAD OPTION

3.00 0.102

(.118 .004)

(NOTE 3)

0.497 0.076

(.0196 .003)

REF

2.06 0.102

(.081 .004)

2.794 0.102

(.110 .004)

0.889 0.127

(.035 .005)

1

10 9

8

7 6

1.83 0.102

(.072 .004)

3.00 0.102

(.118 .004)

(NOTE 4)

4.90 0.152

(.193 .006)

5.23

(.206)

MIN

2.083 0.102 3.20 – 3.45

(.082 .004) (.126 – .136)

10

4 5

1

2

3

0.50

(.0197) BSC

0.305 0.038

(.0120 .0015) TYP

0.86

(.034)

REF

RECOMMENDED SOLDER PAD LAYOUT

1.10

(.043)

MAX

DETAIL “A”

0° – 6° TYP

DETAIL “A”

0.254

(.010)

0.18

(.007)

SEATING

PLANE

GAUGE PLANE

NOTE:

0.17 – 0.27

(.007 – .011)

TYP

0.127 0.076

(.005 .003)

MSOP (MSE) 0603

0.53 0.152

(.021 .006)

0.50

(.0197) BSC

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm

(.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE

0.102mm (.004") MAX

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR

GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL

NOT EXCEED 0.152mm (.006") PER SIDE

4080Xf

InformationfurnishedbyLinearTechnologyCorporationisbelievedtobeaccurateandreliable.However,

no responsibility is assumed for its use. Linear Technology Corporation makes no representation that

the interconnection of its circuits as described herein will not infringe on existing patent rights.

19

LTC4080X

U

TYPICAL APPLICATIO

Li-Ion Battery Charger with 1.5V Buck Regulator

Buck Efﬁciency vs Load Current

(V = 1.5V)

OUT

R3

100

80

60

40

20

0

1000

100

10

510Ω

500mA

EFFICIENCY

(Burst)

D1

V

CC

V

BAT

CHRG

SW

CC

EFFICIENCY

(PWM)

4.2V

(3.75V

to 5.5V)

+

R4, 510Ω

C

POWER

LOSS

(PWM)

BAT

Li-Ion

ACPR

4.7µF

BATTERY

LTC4080X

L1, 1OµH*

D2

EN_CHRG

EN_BUCK

C

10pF

PL

C

IN

1

POWER LOSS

(Burst)

4.7µF

FB

V

R1

715k

OUT

(1.5V/300mA)

V

= 3.8V

= 1.5V

MODE GND PROG

BAT

OUT

0.1

0.01

R

R2

806k

C

OUT

4.7µF

PROG

L = 10µH

C = 4.7µF

806Ω

4080X TA02

0.01

0.1

1

10

100

1000

*COILCRAFT LPO1704-103M

LOAD CURRENT (mA)

4080X G13

RELATED PARTS

PART NUMBER

Battery Chargers

LTC3550

DESCRIPTION

COMMENTS

Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efﬁciency: 93%, Adjustable Output: 600mA,

with Adjustable Output 600mA Buck Converter

Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power

Detection and Selection

LTC3550-1

Dual Input USB/AC Adapter Li-Ion Battery Charger Synchronous Buck Converter, Efﬁciency: 93%, Output: 1.875V at 600mA,

with 600mA Buck Converter

Charge Current: 950mA Programmable, USB Compatible, Automatic Input Power

Detection and Selection

LTC4054

Standalone Linear Li-Ion Battery Charger with

Integrated Pass Transistor in ThinSOT^TM

Thermal Regulation Prevents Overheating, C/10 Termination

LTC4061

Standalone Li-Ion Charger with Thermistor

Interface

4.2V, 0.35% Float Voltage, Up to 1A Charge Current, 3mm × 3mm

DFN Package

LTC4061-4.4

LTC4062

Standalone Li-Ion Charger with Thermistor

Interface

4.4V (Max), 0.4% Float Voltage, Up to 1A Charge Current, 3mm × 3mm

DFN Package

Standalone Linear Li-Ion Battery Charger with

Micropower Comparator

Up to 1A Charge Current, Charges from USB Port, Thermal Regulation

3mm × 3mm DFN Package

LTC4063

LTC4080

Li-Ion Charger with Linear Regulator

Up to 1A Charge Current, 100mA, 125mV LDO, 3mm × 3mm DFN Package

Standalone 500mA Charger with 300mA

Synchronous Buck

For 1-Cell Li-Ion/Polymer Batteries; Trickle Charge; Timer Termination +C/10;

Thermal Regulation, Buck Output: 0.8V to V , Buck Input: 2.7V to 5.5V, 3mm ×

BAT

3mm DFN-10 Package

Power Management

LTC3405/LTC3405A 300mA (I ), 1.5MHz, Synchronous Step-Down 95% Efﬁciency, V : 2.7V to 6V, V

= 0.8V, I = 20µA, I < 1µA,

Q SD

OUT

IN

OUT

DC/DC Converter

ThinSOT Package

LTC3406/LTC3406A 600mA (I ), 1.5MHz, Synchronous Step-Down 95% Efﬁciency, V : 2.5V to 5.5V, V

= 0.6V, I = 20µA, I < 1µA,

Q SD

OUT

IN

OUT

DC/DC Converter

ThinSOT Package

LTC3411

LTC3440

1.25A (I ), 4MHz, Synchronous Step-Down

95% Efﬁciency, V : 2.5V to 5.5V, V

= 0.8V, I = 60µA, I < 1µA,

Q SD

OUT

IN

DC/DC Converter

MS Package

600mA (I ), 2MHz, Synchronous Buck-Boost 95% Efﬁciency, V : 2.5V to 5.5V, V

= 2.5V, I = 25µA, I < 1µA,

Q SD

OUT

IN

DC/DC Converter

MS Package

LTC4411/LTC4412 Low Loss PowerPath^TMController in ThinSOT

Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes

LTC4413

Dual Ideal Diode in DFN

2-Channel Ideal Diode ORing, Low Forward On-Resistance, Low Regulated

Forward Voltage, 2.5V ≤ V ≤ 5.5V

IN

ThinSOT and PowerPath are trademarks of Linear Technology Corporation.

4080Xf

LT 0307 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

20

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LTC4080X
厂家：	Linear
描述：	500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck in 3mm × 3mm DFN 500毫安独立锂离子电池充电器，带有集成300毫安同步降压型采用3mm × 3mm DFN封装电池
文件：	总20页 (文件大小：300K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC4080X [Linear]

相关型号：

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LTC4080XEDD#TRPBF

LTC4080XEDD-PBF

LTC4080XEDD-TRPBF

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LTC4080XEMSE#TRPBF

LTC4080XEMSE-PBF

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