LTC4080EDD#TRPBF_技术文档

LTC4080

500mA Standalone Li-Ion

Charger with Integrated

300mA Synchronous Buck

DESCRIPTION

The LTC^®4080 is a complete constant-current/constant-

voltage linear battery charger for a single-cell 4.2V

lithium-ionbatterywithanintegrated300mAsynchronous

buck converter. The small packages and low external

component count make the LTC4080 especially suitable

forportableapplications.Furthermore,LTC4080isspecifi-

cally designed to work within USB power specifications.

FEATURES

n

Complete Linear Battery Charger with Integrated

Buck Converter

Battery Charger:

n

Constant-Current/Constant-Voltage Operation

with Thermal Feedback to Maximize Charge Rate

without Risk of Overheating

n

Internal 4.5-Hour Safety Timer for Termination

n

Charge Current Programmable Up to 500mA with

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 LTC4080 battery charger also includes

trickle charge, automatic recharge and soft-start (to limit

inrush current).

5% Accuracy

n

C/10 Charge Current Detection Output

n

5µA Supply Current in Shutdown Mode

Switching Regulator:

n

High Efﬁciency Synchronous Buck Converter

n

300mA Output Current

The LTC4080 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.

n

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

n

0.8V to V Output Range

BAT

n

MODE Pin Selects Fixed (2.25MHz) Constant-Frequency

PWM Mode or Low I (23µA) Burst Mode^®Operation

CC

n

2µA BAT Current in Shutdown Mode

The LTC4080 is available in 10-lead, low profile (0.75mm)

3mm × 3mm DFN and MSOP Exposed Pad packages.

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

and ThinSOT and PowerPath are trademarks of Linear Technology Corporation. All other

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

6522118.

APPLICATIONS

n

Wireless Headsets

n

Bluetooth Applications

Portable MP3 Players

n

Multifunction Wristwatches

Buck Efficiency vs Load Current

(V_OUT= 1.8V)

TYPICAL APPLICATION

Li-Ion Battery Charger with 1.8V Buck Regulator

100

80

60

40

20

0

1000

100

10

500mA

EFFICIENCY

(Burst)

4.2V

V

CC

V

BAT

CC

EFFICIENCY

(PWM)

C

+

Li-Ion

BAT

(3.75V

to 5.5V)

POWER

LOSS

(PWM)

EN_BUCK

4.7μF

BATTERY

L1, 1OμH

EN_CHRG

MODE

SW

C

R1

1M

PL

LTC4080

0

10pF

V

POWER LOSS

(Burst)

OUT

(1.8V/300mA)

FB

C

IN

V

= 3.8V

= 1.8V

GND PROG

BAT

OUT

4.7μF

0.1

0.01

R2

806k

C

OUT

4.7μF

R

PROG

L = 10μH

C = 4.7μF

806Ω

4080 TA01a

0.01

0.1

1

10

100

1000

LOAD CURRENT (mA)

4080 TA01b

4080fc

1

For more information www.linear.com/LTC4080

LTC4080

(Note 1)

ABSOLUTE MAXIMUM RATINGS

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

CC

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

Lead Temperature (MSE, Soldering, 10 sec) .........300°C

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

BAT

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

+ 0.3V

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

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

PIN CONFIGURATION

TOP VIEW

BAT

1

2

3

4

5

10 SW

BAT

CC

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

EN_CHRG

PROG

11

MODE

FB

ACPR

CHRG

ACPR

CHRG

MSE PACKAGE

10-LEAD PLASTIC MSOP

DD PACKAGE

10-LEAD (3mm × 3mm) PLASTIC DFN

T

JMAX

= 125°C, θ = 40°C/W

JA

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

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

LTC4080EDD#PBF

LTC4080EMSE#PBF

TAPE AND REEL

PART MARKING

LBXD

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC4080EDD#TRPBF

LTC4080EMSE#TRPBF

10-Lead (3mm × 3mm) Plastic DFN

10-Lead Plastic MSOP

–40°C to 85°C

LTCQH

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/

The ldenotes specifications which apply over the full operating temperature

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, V_{EN_CHRG}= 0V, V_{EN_BUCK}= V_BAT, V_MODE= 0V. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

(Note 4)

MIN

3.75

2.7

TYP

5

MAX

5.5

UNITS

l

V

CC

Supply Voltage

V

BAT

Input Voltage for the Switching

Regulator

(Note 5)

3.8

4.5

l

I

Quiescent Supply Current (Charger On,

Switching Regulator Off)

V

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

PROG

110

300

10

5

µA

CC

BAT

= 0

EN_BUCK

Supply Current in Shutdown (Both Battery

Charger and Switching Regulator Off)

V

=5V, V

=4V, V

=0, V >V

BAT

5

2

µA

CC_SD

EN_CHRG

EN_BUCK

CC

V

=0, V (3.5V)<V (4V)

EN_CHRG

CC BAT

Battery Current in Shutdown (Both Battery

Charger and Switching Regulator Off)

V

=5V, V

=4V, V

=0, V >V

BAT

=0, V (3.5V)<V (4V)

EN_BUCK CC BAT

0.6

2

µA

BAT_SD

EN_CHRG

EN_BUCK

CC

V

EN_CHRG

4080fc

2

For more information www.linear.com/LTC4080

LTC4080

The ldenotes specifications which apply over the full operating temperature

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, V_{EN_CHRG}= 0V, V_{EN_BUCK}= V_BAT, V_MODE= 0V. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Battery Charger

V

FLOAT

V

Regulated Output Voltage

I

= 2mA

= 2mA, 4.3V < V < 5.5V

4.179

4.158

4.2

4.221

4.242

V

BAT

l

CC

l

I

Current Mode Charge Current

Undervoltage Lockout Voltage

R

= 4k; Current Mode; V

= 0.8k; Current Mode; V

= 0

90

475

100

500

110

525

mA

BAT

PROG

EN_BUCK

= 0

EN_BUCK

l

V

Rising

Falling

3.5

2.8

3.6

3.0

3.7

3.2

V

UVLO_CHRG

CC

l

V

PROG Pin Servo Voltage

0.8k ≤ R

≤ 4k

0.98

1.0

1.02

V

PROG

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

60

15

82

32

100

45

mV

ASD

CC

BAT

CC

(V – V ), V High to Low

CC

BAT

CC

t

I

Battery Charger Soft-Start Time

Trickle Charge Current

180

50

µs

mA

V

SS_CHRG

V

= 2V, R

Rising

= 0.8k

35

65

TRKL

BAT

PROG

l

V

Trickle Charge Threshold Voltage

2.75

100

2.9

150

3.05

350

TRKL

BAT

V

Trickle Charge Threshold Voltage

Hysteresis

mV

TRHYS

DV

RECHRG

Recharge Battery Threshold Voltage

V

FLOAT

– V , 0°C < T < 85°C

70

100

130

mV

BAT

A

DV

UVCL1,

DV

UVCL2

(V – V ) Undervoltage Current

I

= 0.9 I

180

90

300

130

mV

CC

BAT

CHG

= 0.1 I

Limit Threshold Voltage

CHG

l

t

Termination Timer

3

4.5

2.25

1.125

0.1

6

3

hrs

TIMER

Recharge Time

1.5

Low-Battery Charge Time

End of Charge Indication Current Level

V

= 2.5V

0.75

0.085

1.5

0.115

hrs

BAT

I

R

= 2k (Note 6)

mA/mA

°C

C/10

PROG

T

Junction Temperature in Constant-

Temperature Mode

115

LIM

R

Power FET On-Resistance (Between

CC

I

= 350mA, V = 4V

750

2

mW

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

l

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,

BAT_NL_CF

EN_CHRG

I

No-Load Battery Current (Burst Mode

Operation)

No-Load for Regulator, V

23

15

µA

BAT_NL_BM

BAT_SLP

EN_CHRG

MODE = V , L = 10µH, C = 4.7µF

BAT

l

Battery Current in SLEEP Mode

Buck Undervoltage Lockout

PMOS Switch On-Resistance

V

= 5V, MODE = V

,

10

20

EN_CHRG

BAT

> Regulation Voltage

OUT

l

V

BAT

V

BAT

Rising

Falling

2.6

2.4

2.7

2.5

2.8

2.6

V

UVLO_BUCK

W

R

0.95

ON_P

4080fc

3

For more information www.linear.com/LTC4080

LTC4080

The ldenotes specifications which apply over the full operating temperature

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, V_{EN_CHRG}= 0V, V_{EN_BUCK}= V_BAT, V_MODE= 0V. (Note 2)

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

0.85

520

700

15

MAX

UNITS

W

R

ON_N

NMOS Switch On-Resistance

PMOS Switch Current Limit

NMOS Switch Current Limit

NMOS Zero Current in Normal Mode

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

l

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

MW

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

EN_CHRG

1.7

3.3

1

EN_CHRG

CHRG

l

I

= 4.5V, V

= 5V

BAT

EN_CHRG

= 3V, V = 5V

EN_CHRG

1

ACPR

CC

Note 4: Although the LTC4080 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 ∆

specification.

VUVCL1

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 LTC4080 is guaranteed to meet performance specifications

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

BAT

temperature range are assured by design, characterization and correlation

with statistical process controls.

Note 6: IC/10 is expressed as a fraction of measured full charge current

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.

4080fc

4

For more information www.linear.com/LTC4080

LTC4080

TYPICAL PERFORMANCE CHARACTERISTICS

(T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, unless otherwise specified)

Battery Regulation (Float) Voltage

vs Charge Current

Battery Regulation (Float) Voltage

vs Temperature

Charge Current

₂₅₀vs Battery Voltage

4.210

4.205

4.200

4.195

4.190

4.185

4.180

4.175

4.170

4.165

4.160

4.21

4.20

4.19

4.18

4.17

4.16

4.15

4.14

4.13

R

PROG

= 2k

R

PROG

= 2k

V

RISING

BAT

200

150

100

50

TRICKLE CHARGE

0

1

2

3

4

5

–30 –10

30

50

70

90

–50

10

200

CHARGE CURRENT (mA)

250

0

50

100

150

BATTERY VOLTAGE (V)

TEMPERATURE (°C)

4080 G01

4080 G03

4080 G02

Charge Current vs Temperature

with Thermal Regulation

(Constant-Current Mode)

Battery Regulation (Float) Voltage

vs Supply Voltage

PROG Pin Voltage

vs Charge Current

4.25

1.0

0.8

0.6

0.4

0.2

0

250

200

150

100

50

V

= 6V

CC

R

PROG

= 2k

= 3V

BAT

4.20

4.15

R

= 2k

PROG

4.10

4.05

4.00

3.95

3.90

THERMAL CONTROL

LOOP IN OPERATION

0

3.85

0

25 50 75 100 125 150 175 200

–25

0

25

50

75

–50

100 125

4.5

5

6

4

5.5

CHARGE CURRENT (mA)

TEMPERATURE (°C)

INPUT VOLTAGE (V)

4080 G06

4080 G05

4080 G04

EN_CHRG, BUCK and

MODE Pin Threshold Voltage

vs Temperature

Charger FET On-Resistance

vs Temperature

EN_CHRG Pin Pull-Down

Resistance vs Temperature

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

V

I

= 4V

CC

BAT

= 350mA

RISING

FALLING

0.50

–50 –30 –10 10

TEMPERATURE (°C)

90

–50 –30 –10 10

TEMPERATURE (°C)

90

30

50

70

30

50

70

–30 –10

30

50

70

90

–50

10

TEMPERATURE (°C)

4080 G08

4080 G09

4080 G07

4080fc

5

For more information www.linear.com/LTC4080

LTC4080

TYPICAL PERFORMANCE CHARACTERISTICS

(T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, unless otherwise specified)

CHRG and ACPR Pin Output

Normalized Charger Timer

Period vs Temperature

Buck Oscillator Frequency

vs Battery Voltage

Low Voltage vs Temperature

80

2.28

2.27

2.26

2.25

2.24

1.05

1.00

0.95

0.90

0.85

0.80

I

, I

= 5mA

CHRG ACPR

70

60

50

40

30

20

10

2.23

2.22

0

–50 –30 –10 10

TEMPERATURE (°C)

90

30

50

70

3.0

3.5

4.5

2.5

4.0

–50 –30 –10 10

90

30

50

70

TEMPERATURE (°C)

BATTERY VOLTAGE (V)

4080 G11

4080 G10

4080 G12

Buck Oscillator Frequency

vs Temperature

Buck Efficiency vs Load Current

(V_OUT= 1.8V)

Buck Efficiency vs Load Current

(V_OUT= 1.5V)

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

V

= 4.5V

EFFICIENCY

(Burst)

BAT

EFFICIENCY

(Burst)

EFFICIENCY

(PWM)

EFFICIENCY

(PWM)

POWER

V

BAT

= 2.7V

LOSS

(PWM)

0

POWER LOSS

(Burst)

POWER LOSS

(Burst)

V

= 3.8V

= 1.8V

V

= 3.8V

= 1.5V

BAT

OUT

L = 10μH

C = 4.7μF

BAT

OUT

0.1

0.01

0.1

0.01

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)

4080 G13

4080 G15

4080 G14

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

1.800

1.795

1.810

1.805

I

= 1mA

OUT

I

= 1μA

OUT

Burst Mode

OPERATION

OUT

I

= 1mA

OUT

V

SET FOR 1.8V

V

= 1.8V

Burst Mode

V

SET FOR 1.8V

L = 10μH

OPERATION

PWM MODE

1.800

1.795

20

15

10

5

1.790

1.785

1.780

1.790

1.785

1.780

0

2.5

3.0

3.5

4.0

4.5

30

–50 –30 –10 10

TEMPERATURE (°C)

70

90

50

3.5

BATTERY VOLTAGE (V)

2.5

3.0

4.0

4.5

BATTERY VOLTAGE (V)

4080 G16

4080 G17

4080 G18

4080fc

6

For more information www.linear.com/LTC4080

LTC4080

TYPICAL PERFORMANCE CHARACTERISTICS

(T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, unless otherwise 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

35

30

1.2

1.0

0.8

0.6

0.4

0.2

0

L = 10μH

1.2

1.0

0.8

0.6

0.4

0.2

0

V

= 4.2V

= 3.8V

BAT

C = 4.7μF

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

30

TEMPERATURE (°C)

70

90

3.5

BATTERY VOLTAGE (V)

–50 –30 –10 10

50

2.5

3.0

4.0

4.5

5.0

4080 G21

4080 G19

4080 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

70

90

–50 –30 –10 10

50

TEMPERATURE (°C)

4080 G22

4080 G23

Maximum Output Current

(PWM Mode)

Maximum Output Current

(Burst Mode Operation)

500

400

300

200

100

L = 10μH

80

70

60

50

40

30

20

10

0

L = 10μH

V

SET FOR 1.8V

OUT

V

OUT

SET FOR 1.8V

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)

4080 G25

4080 G24

4080fc

7

For more information www.linear.com/LTC4080

LTC4080

TYPICAL PERFORMANCE CHARACTERISTICS

(T_A= 25°C, V_CC= 5V, V_BAT= 3.8V, unless otherwise specified)

Output Voltage Waveform

when Switching Between Burst

and PWM Mode (I_LOAD= 10mA)

Output Voltage Transient

Step Response (PWM Mode)

Output Voltage Transient

Step Response (Burst Mode)

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

4080 G26

4080 G27

4080 G28

50μs/DIV

Buck V_OUTSoft-Start

(I_LOAD= 50mA)

Charger V_PROGSoft-Start

V

OUT

1V/DIV

0V

V

PROG

200mV/DIV

V

_

EN BUCK

V = 0

5V/DIV

0V

4080 G29

4080 G30

50μs/DIV

200μs/DIV

4080fc

8

For more information www.linear.com/LTC4080

LTC4080

PIN FUNCTIONS

BAT (Pin 1): Charge Current Output and Buck Regulator CHRG (Pin 6): Open-Drain Charge Status Output. The

Input. Provides charge current to the battery and regu- charge status indicator pin has three states: pull-down,

lates the final float voltage to 4.2V. An internal precision high impedance state, and pulse at 2Hz. This output can

resistor divider from this pin sets the float voltage and is be used as a logic interface or as an LED driver. When the

disconnected in charger shutdown mode. This pin should battery is being charged, the CHRG pin is pulled low by

be decoupled with a low ESR capacitor for low noise buck an internal N-channel MOSFET. When the charge current

operation.

drops to 10% of the full-scale current, the CHRG pin is

forced to a high impedance state. When the battery volt-

age remains 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.

V

(Pin 2): Positive Input Supply Voltage. This pin pro-

CC

vides power to the battery charger. V can range from

CC

3.75V to 5.5V. This pin should be bypassed with at least a

1µF capacitor. When V is less than 32mV above the B

CC

AT

pin voltage, the battery charger enters shutdown mode.

FB(Pin7):FeedbackPinfortheBuckRegulator. Aresistor

divider from the regulator’s output to the FB pin programs

the output voltage. Servo value for this pin is 0.8V.

EN_CHRG (Pin 3): Enable Input Pin for the Battery Char-

ger. Pullingthispinabovethemanualshutdownthreshold

(V ) puts the LTC4080 charger in shutdown mode, thus MODE (Pin 8): Burst Mode Enable Pin. Tie this pin high

IH

stopping the charge cycle. In battery charger shutdown to force the LTC4080 regulator into Burst Mode operation

mode, the LTC4080 has less than 10µA supply current for all load conditions. Tie this pin low to force constant-

and less than 5µA battery drain current if the regulator is frequency mode operation for all load conditions. Do not

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

be tied to GND if unused.

EN_BUCK (Pin 9): Enable Input Pin for the Switching

PROG (Pin 4): Charge Current Program and Charge Cur- Regulator. Pull this pin high to enable the regulator, pull

rent Monitor Pin. Connecting a 1% resistor, RPROG, to low to shut down. Do not float this pin.

ground programs the charge current. When charging in

constant-currentmode,thispinservosto1V.Inallmodes,

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

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

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

the inductor as close to this pin as possible.

current using the following formula:

GND (Pin 11): Ground. This pin is the back of the Exposed

PadpackageandmustbesolderedtothePCBforelectrical

connection and rated thermal performance.

V_PROG

R_PROG

I_BAT

=

•400

ACPR (Pin 5): Open-Drain Power Supply Status Output.

WhenV isgreaterthantheundervoltagelockoutthresh-

CC

old(3.6V)andgreaterthanV +80mV,theACPRpinwill

BAT

be pulled to ground; otherwise the pin is high impedance.

4080fc

9

For more information www.linear.com/LTC4080

LTC4080

BLOCK DIAGRAM

2

V

CC

+

3

CHARGER

SHUTDOWN

EN_CHRG

C3

MP3

X1

MP1

115C

–

+

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

CHRG

1V

0.1V

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

BAT

+ 80mV

LINEAR BATTERY CHARGER

MP2

+

–

SYNCHRONOUS BUCK CONVERTER

9

8

L1

PWM

V

C

OUT

EN_BUCK

ENABLE BUCK

C6

10

7

CONTROL

AND DRIVE

SW

MN1

0.82V

C

R7

R8

PL

–

+

–

OUT

2.25MHz

BUCK

OSCILLATOR

ERROR

MODE

FB

C7

AMP

+

0.8V

0.82V

11

4080 BD

GND

4080fc

10

For more information www.linear.com/LTC4080

LTC4080

OPERATION

The LTC4080 is a full-featured linear battery charger with

an integrated synchronous buck converter designed pri-

marily 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 a

programmable output voltage providing a maximum load

current of 300mA. The converter and the battery charger

can run simultaneously or independently of each other.

user to push the limits of the power handling capability of a

givencircuitboardwithouttheriskofdamagingtheLTC4080

or external components. Another benefit of the 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 charger will

automatically reduce the current in worst-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

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 output indicates when C/10 has been reached.

No blocking diode or external sense resistor is required;

thus, the basic charger circuit requires only two external

components. The ACPR open-drain output indicates if the

it or momentarily force the EN_ CHRG pin above V . A

IH

new charge cycle will automatically restart if the BAT pin

voltage falls below V

(typically 4.1V).

RECHRG

Constant-Current/Constant-Voltage/Constant-Temperature

The LTC4080 battery charger uses a unique architecture

tochargeabatteryinaconstant-current,constant-voltage

and constant-temperature fashion. Three of the amplifier

feedback loops shown control the constant-current, CA,

constant-voltage,VA,andconstant-temperature,TAmodes

(seeBlockDiagram). Afourthamplifierfeedbackloop,MA,

is used to 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 cur-

rent of MP1 is exactly 400 times the drain current of MP3.

V

CC

input voltage, and the difference between V and

CC

BAT, are sufficient for charging. An internal termination

timer adheres to battery manufacturer safety guidelines.

Furthermore, the LTC4080 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 80mV 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. The output of the other amplifier saturates low

which effectively removes its loop from the system. When

in constant-current mode, CA servos the voltage at the

PROG 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 voltage gives an indication of the charge current any-

time in the charge cycle, as discussed in “Programming

Charge Current” in the Applications Information section.

the shutdown threshold (V ). If the battery voltage is less

IL

than 2.9V, the battery charger begins trickle charging at

10% of the programmed charge current.

When the BAT pin approaches the final float voltage of

4.2V,thebatterychargerentersconstant-voltagemodeand

the charge current begins to decrease. When the current

drops to 10% of the full-scale charge current, an internal

comparator turns off the N-channel MOSFET driving 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

preset value of approximately 115°C. This feature protects

the LTC4080 from excessive temperature and allows the

4080fc

11

For more information www.linear.com/LTC4080

LTC4080

OPERATION

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

tointernalpowerdissipation,thetransconductanceampli-

fier, TA, limits the die temperature to approximately 115°C

by reducing the charge current. Diode D3 ensures that TA

doesnotaffectthechargecurrentwhenthedietemperature

is below 115°C. In thermal regulation, the PROG pin voltage

continues to give an indication of the charge current.

the CHRG pin 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 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

reapplyingitortemporarilypullingtheEN_CHRGpinabove

the shutdown threshold.

In typical operation, the charge cycle begins in constant-

currentmodewiththecurrentdeliveredtothebatteryequal

Battery Charger Shutdown Mode

to 400V/R . If the power dissipation of the LTC4080

PROG

The LTC4080’s battery charger can be disabled by pulling

results in the junction temperature approaching 115°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 LTC4080 either returns to

constant-current mode or enters constant-voltage mode

straight from constant-temperature mode.

the EN_CHRG pin above the shutdown threshold (V ).

IH

In shutdown mode, the battery drain current is reduced

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

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.

Battery Charger Undervoltage Lockout (UVLO)

Power Supply Status Indicator ACPR

An internal undervoltage lockout circuit monitors the

input voltage and keeps the battery charger off until V_CC

rises above 3.6V and approximately 80mV above the BAT

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

of approximately 0.6V, and the 80mV automatic shutdown

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

During undervoltage lockout conditions, maximum battery

The power supply status output has two states: pull-down

and high impedance. The pull-down state indicates that V

CC

isabovetheundervoltagelockoutthresholdandatleast82mV

above the BAT voltage (see Undervoltage Lockout). When

theseconditionsarenotmet,theACPRpinishighimpedance

indicating that the LTC4080 is unable to charge the battery.

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

CHRG Status Output Pin

Undervoltage Charge Current Limiting (UVCL)

Thechargestatusindicatorpinhasthreestates:pull-down,

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

impedance. The pull-down state indicates that the bat-

tery charger is in a charge cycle. A high impedance state

indicates 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 pull-down state.

ThebatterychargerintheLTC4080includesundervoltage

charge current limiting that prevents full charge current

untiltheinputsupplyvoltagereachesapproximately300mV

abovethebatteryvoltage(DV ).Thisfeatureisparticu-

UVCL1

larly useful if the LTC4080 is powered from a supply with

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

Applications Information section for further details.

Trickle Charge and Defective Battery Detection

At the beginning of a charge cycle, if the battery volt-

age is below 2.9V, the battery charger goes into trickle

charge mode, reducing the charge current to 10% of the

programmed current. If the low battery voltage persists

for one quarter of the total time (1.125 hr), the battery is

assumed to be defective, the charge cycle terminates and

Charge Current Soft-Start

TheLTC4080’sbatterychargerincludesasoft-startcircuit

to minimize the inrush current at the start of a charge

cycle. When a charge cycle is initiated, the charge current

4080fc

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For more information www.linear.com/LTC4080

LTC4080

OPERATION

ramps from zero to full-scale current over a period of ap-

proximately 180µs. This has the effect of minimizing the

transientcurrentloadonthepowersupplyduringstart-up.

(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 peak

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

switchturnsoffandthesynchronousswitchMN1(N-channel

MOSFET)turnsonallowingtheinductorcurrenttoflowfrom

ground to the load until either the next clock cycle begins

Timer and Recharge

The LTC4080’s battery charger has an internal termina-

tion timer that starts when the input voltage is greater

than the undervoltage lockout threshold and at least

80mV above BAT, and the battery charger is leaving

shutdown.

or the current reduces to the zero 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 band.

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

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

battery charger continuously monitors the BAT pin voltage

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

initiated 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 pull-down 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 current

signal is then converted into a voltage signal (I ), and repre-

TH

sentsthepeakinductorcurrentrequiredtoachieveregulation.

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

SWITCHING REGULATOR OPERATION:

comparator compares this summed signal to I and

TH

The switching regulator in the LTC4080 can be turned on

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

determines 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.

IH

selectablemodesofoperation:constant-frequency(PWM)

mode and Burst Mode Operation. The constant-frequency

mode operation offers low noise at the expense of effi-

ciencywhereastheBurstModeoperationoffersincreased

efficiency at light loads at the cost of increased noise and

output voltage ripple. A detailed description of different

operating modes and different aspects of operation fol-

low. 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

(~80mA) and I

ZERO

PEAK

(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

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

shuts off both switches along with most of the circuitry

and the regulator is said to enter into SLEEP mode. 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

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

4080fc

13

For more information www.linear.com/LTC4080

LTC4080

OPERATION

nominal value, the regulator wakes up and the inductor

current resumes swinging between I

cyclestherebykeepingoutputvoltagerippleandnoiselow

at the cost of efficiency.

and I

. The

ZERO

PEAK

output capacitor recharges and causes the regulator to

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

enough. Thefrequencyofthisintermittentburstoperation

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

drops further, the regulator turns on less frequently. Thus

Burst Mode operation increases the efficiency at light

loads by minimizing the switching and quiescent losses.

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.

Soft-Start

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

regulator can only deliver approximately 55mA 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.

The LTC4080 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

400

µs. The soft-start capacitor is discharged completely

whenever the regulator is disabled.

Short-Circuit Protection

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

Current Limit

start-up, V

will be near zero volts. Since the downward

OUT

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

OUT

To prevent inductor current runaway, there are absolute

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 LTC4080 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.

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

LIM

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 80mA 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

Switching Regulator Undervoltage Lockout

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

ZERO

Whenever V

is less than 2.7V, an undervoltage lock-

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

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

BAT

drops below 2.5V.

4080fc

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For more information www.linear.com/LTC4080

LTC4080

OPERATION

Dropout Operation

Global Thermal Shutdown

WhentheBATpinvoltageapproachesV , thedutycycle

The LTC4080 includes a global thermal shutdown which

shuts off the entire part (both battery charger and switch-

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

LTC4080 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.

APPLICATIONS INFORMATION

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

≤

2π •10⁵•C_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:

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 1. 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

The LTC4080 battery charger contains two control loops:

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

LTC4080

PROG

GND

CHARGE

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

series resistor from BAT to GND is required to keep ripple

voltage low when the battery is disconnected.

10k

CURRENT

MONITOR

CIRCUITRY

R

C

FILTER

PROG

4080 F01

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

the feedback loop, not the battery voltage. Because of

Figure 1. Isolating Capacitive Load

on PROG Pin and Filtering

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For more information www.linear.com/LTC4080

LTC4080

APPLICATIONS INFORMATION

Undervoltage Charge Current Limiting (UVCL)

is approximately 30mW. That is a ten 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

transient load combined with such impedance can easily

triptheUVLOthresholdandturnthebatterychargeroffun-

less undervoltage charge current limiting is implemented.

USB and Wall Adapter Power

Although the LTC4080 allows charging from a USB port,

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

ies. Figure 2 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

pull-down resistor.

ConsiderasituationwheretheLTC4080isoperatingunder

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

above the battery voltage, DV

(approximately 300mV

), undervoltage charge

UVCL

current limiting will begin to reduce the charge current in

an attempt to maintain DV 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

LTC4080 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

4

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

ply, the LTC4080 can dissipate significantly less power

when programmed for a current higher than the limit of

the supply.

SYSTEM

LOAD

BAT

LTC4080

D1

2

USB

POWER

(200mA)

V

CC

+

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

4080 F02

Figure 2. Combining Wall Adapter and USB Power

Power Dissipation

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

ply with a 200mA current limit. To take advantage of the

supply, it is necessary to program the LTC4080 to charge

atacurrentgreaterthan200mA.AssumethattheLTC4080

The conditions that cause the LTC4080 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 LTC4080 power

dissipation is approximately:

charger is programmed for 300mA (i.e., R

= 1.33kW)

PROG

to ensure that part tolerances maintain 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 0.75W with a 5V supply.

The actual on-resistance will be slightly higher due to the

fact that the input supply will have collapsed to less than

5V. The power dissipated during this phase of charging

P = V − V

•I_BAT+P

D_BUCK

(

)

D

BAT

CC

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









1

h



−1

P_D

=V_OUT•I_OUT

_BUCK





4080fc

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For more information www.linear.com/LTC4080

LTC4080

APPLICATIONS INFORMATION

Where V

is the regulated output of the switching

OUT

V

Bypass Capacitor

OUT

regulator, I

CC

h

is the regulator load and 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

conditions, such as connecting the battery charger input to

a live power source. Adding a 1

with an X5R ceramic capacitor will minimize start-up voltage

transients. 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 LTC4080 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:

W series resistor in series

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 LTC4080 is

operatingfroma6Vsupplyproviding250mAtoa3VLi-Ion

battery and the regulator is off. The ambient temperature

above which the LTC4080 will begin to reduce the 250mA

charge current is approximately:

Setting the Buck Converter Output Voltage

The LTC4080 regulator compares the FB pin voltage with

an internal 0.8V reference to generate an error signal at

the output of the error amplifier. A voltage divider from

V

OUT

toground(asshownintheBlockDiagram)programs

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

A

the output voltage via FB using the formula:









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 kick in at a somewhat lower

temperature than this. In the above circumstances, the

LTC4080 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 − V

•θ

JA

(

)

BAT

CC

Inductor Selection

Usingthepreviousexamplewithanambienttemperatureof

85°C, thechargecurrentwillbereducedtoapproximately:

The value of the inductor primarily determines the cur-

rent ripple in the inductor. The inductor ripple cur-

115°C−85°C

30°C

I_BAT

=

=232.6mA

6V−3V •43°C/W 129°C/A

(

)

rent DI decreases with higher inductance and

L

increases with higher V or V

:

IN

OUT

Note: 1V = 1J/C = 1W/A





V_{OUT }V_{OUT }

Furthermore, the voltage at the PROG pin will change

proportionally with the charge current as discussed in

the Programming Charge Current section.

DI_L=

• 1−









f₀•L

V

IN





Accepting larger values of DI allows the use of low

L

inductances, but results in higher output voltage ripple,

4080fc

17

For more information www.linear.com/LTC4080

LTC4080

APPLICATIONS INFORMATION

greater core losses, and lower output current capability.

To prevent large V

voltage steps during transient

OUT

A reasonable starting point for setting ripple current is DI

load conditions, it is also recommended that a ceramic

L

=0.3 • I , where I

is the peak switch current limit.

capacitor be used to bypass V . The typical value for

LIM

OUT

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:

this capacitor is 4.7µF.

Multilayer Ceramic Chip Capacitors (MLCC) typically have

exceptional ESR performance. MLCCs combined with a

carefully laid out board with an unbroken ground plane

will yield very good performance and low EMI emissions.









V_OUT

f₀•DI_L

V_OUT

V

IN

MAX

(



L≥

• 1−







There are several types of ceramic capacitors with con-

siderably different characteristics. Y5V and X5R ceramic

capacitors have apparently higher packing density but

poor performance over their rated voltage or temperature

ranges. Under given voltage and temperature conditions,

Y5V, X5R and X7R ceramic capacitors should be com-

pared directly by case size rather than specified value for

a desired minimum capacitance. Some manufacturers

provide excellent data on their websites about achiev-

able capacitance. Table 2 shows a list of several ceramic

capacitor manufacturers.



⁾



For applications with V

= 1.8V, the above equation

OUT

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

for proper operation.

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 LTC4080’s package has a good thermal

contact to the PC board ground. Correctly soldered to a

2

2500mm double-sided 1 oz. copper board, the LTC4080

Input and Output Capacitor Selection

hasathermalresistanceofapproximately43°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

LTC4080aspossibleandthatthereisanunbrokenground

plane under the LTC4080 and all of its high frequency

components.

4080fc

18

For more information www.linear.com/LTC4080

LTC4080

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1699 Rev C)

0.70 ±0.05

3.55 ±0.05

2.15 ±0.05 (2 SIDES)

1.65 ±0.05

PACKAGE

OUTLINE

0.25 ±0.05

0.50

BSC

2.38 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

R = 0.125

0.40 ±0.10

TYP

6

10

3.00 ±0.10

(4 SIDES)

1.65 ±0.10

(2 SIDES)

PIN 1 NOTCH

R = 0.20 OR

PIN 1

TOP MARK

(SEE NOTE 6)

0.35 × 45°

CHAMFER

(DD) DFN REV C 0310

5

1

0.25 ±0.05

0.50 BSC

0.75 ±0.05

0.200 REF

2.38 ±0.10

(2 SIDES)

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

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

3. ALL DIMENSIONS ARE IN MILLIMETERS

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

4080fc

19

For more information www.linear.com/LTC4080

LTC4080

PACKAGE DESCRIPTION

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

MSE Package

10-Lead Plastic MSOP, Exposed Die Pad

(Reference LTC DWG # 05-08-1664 Rev I)

BOTTOM VIEW OF

EXPOSED PAD OPTION

1.88

(.074)

1.88 ±0.102

(.074 ±.004)

0.889 ±0.127

(.035 ±.005)

1

0.29

REF

1.68

(.066)

0.05 REF

5.10

(.201)

MIN

1.68 ±0.102

3.20 – 3.45

DETAIL “B”

(.066 ±.004) (.126 – .136)

CORNER TAIL IS PART OF

THE LEADFRAME FEATURE.

FOR REFERENCE ONLY

DETAIL “B”

10

NO MEASUREMENT PURPOSE

0.50

(.0197)

BSC

0.305 ± 0.038

(.0120 ±.0015)

TYP

3.00 ±0.102

(.118 ±.004)

(NOTE 3)

0.497 ±0.076

(.0196 ±.003)

10 9

8

7 6

RECOMMENDED SOLDER PAD LAYOUT

REF

3.00 ±0.102

(.118 ±.004)

(NOTE 4)

4.90 ±0.152

(.193 ±.006)

DETAIL “A”

0.254

(.010)

0° – 6° TYP

1

2

3

4 5

GAUGE PLANE

0.53 ±0.152

(.021 ±.006)

0.86

(.034)

REF

1.10

(.043)

MAX

DETAIL “A”

0.18

(.007)

SEATING

PLANE

0.17 – 0.27

(.007 – .011)

TYP

0.1016 ±0.0508

(.004 ±.002)

0.50

(.0197)

BSC

MSOP (MSE) 0213 REV I

NOTE:

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

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

6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD

SHALL NOT EXCEED 0.254mm (.010") PER SIDE.

4080fc

20

For more information www.linear.com/LTC4080

LTC4080

REVISION HISTORY ^{(Revision history begins at Rev C)}

REV

DATE

DESCRIPTION

PAGE NUMBER

C

07/15 Modified Typical Application diagrams

1, 22

4080fc

21

For more information www.linear.com/LTC4080

LTC4080

TYPICAL APPLICATION

Li-Ion Battery Charger with 1.5V Buck Regulator

Buck Efficiency vs Load Current

(V_OUT= 1.5V)

100

80

60

40

20

0

1000

R3

510Ω

EFFICIENCY

(Burst)

D1

100

10

V

CC

V

CHRG

CC

500mA

EFFICIENCY

(PWM)

(3.75V

to 5.5V)

POWER

LOSS

LTC4080

R4

BAT

4.2V

+

510Ω

C

BAT

Li-Ion

(PWM)

EN_BUCK

SW

ACPR

4.7μF

BATTERY

L1, 1OμH*

D2

0

POWER LOSS

(Burst)

EN_CHRG

C

IN

4.7μF

PL

10pF

R1

715k

V

= 3.8V

= 1.5V

OUT

BAT

OUT

0.1

0.01

MODE

FB

(1.5V/300mA)

L = 10μH

C = 4.7μF

GND PROG

R2

806k

C

OUT

4.7μF

R

PROG

0.01

0.1

1

10

100

1000

806Ω

LOAD CURRENT (mA)

4080 TA02

4080 G13

*COILCRAFT LPO1704-103M

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

LTC4053-4.2

LTC4054-4.2

USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current

Standalone Linear Li-Ion Battery Charger with

Thermal Regulation Prevents Overheating, C/10 Termination,

TM

Integrated Pass Transistor in ThinSOT

LTC4061

Standalone Li-Ion Charger with Thermistor

Interface

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

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

LTC4061-4.4

LTC4062

Standalone Li-Ion Charger with Thermistor

Interface

Standalone Linear Li-Ion Battery Charger with

Micropower Comparator

Up to 1A Charge Current, Charges from USB Port, Thermal Regulation 3mm x

3mm DFN

LTC4063

Li-Ion Charger with Linear Regulator

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

Power Management

LTC3405/

LTC3405A

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

= 0.8V, IQ = 20µA, I < 1µA, ThinSOT

OUT SD

OUT

IN

DC/DC Converter

Package

LTC3406/

LTC3406A

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

= 0.6V, IQ = 20µA, I < 1µA, ThinSOT

SD

OUT

IN

OUT

DC/DC Converter

Package

LTC3411

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

DC/DC Converter

95% Efficiency, V : 2.5V to 5.5V, V

Package

= 0.8V, IQ = 60µA, I < 1µA, MS

SD

OUT

IN

LTC3440

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

= 2.5V, IQ = 25µA, I < 1µA, MS

SD

OUT

IN

DC/DC Converter

Package

TM

LTC4411/LTC4412 Low Loss PowerPath Controller 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

4080fc

LT 0715 REV C • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

22

For more information www.linear.com/LTC4080

●

 LINEAR TECHNOLOGY CORPORATION 2006

(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4080


型号：	LTC4080EDD#TRPBF
厂家：	Linear
描述：	LTC4080 - 500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C 光电二极管
文件：	总22页 (文件大小：448K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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