LTC4054ES5-4.2#TR_技术文档

LTC4054-4.2/LTC4054X-4.2

Standalone Linear

Li-Ion Battery Charger with

Thermal Regulation in ThinSOT

U

FEATURES

DESCRIPTIO

■

Programmable Charge Current Up to 800mA

The LTC^®4054 is a complete constant-current/constant-

voltage linear charger for single cell lithium-ion batteries.

Its ThinSOT package and low external component count

make the LTC4054 ideally suited for portable applications.

Furthermore, theLTC4054isspecificallydesignedtowork

within USB power specifications.

■

No MOSFET, Sense Resistor or Blocking

Diode Required

Complete Linear Charger in ThinSOT^TMPackage for

Single Cell Lithium-Ion Batteries

Constant-Current/Constant-Voltage Operation with

Thermal Regulation* to Maximize Charge Rate

Without Risk of Overheating

Charges Single Cell Li-Ion Batteries Directly

from USB Port

■

No external sense resistor is needed, and no blocking

diode is required due to the internal MOSFET architecture.

Thermal feedback regulates the charge current to limit the

die temperature during high power operation or high

ambient temperature. The charge voltage is fixed at 4.2V,

andthechargecurrentcanbeprogrammedexternallywith

a single resistor. The LTC4054 automatically terminates

the charge cycle when the charge current drops to 1/10th

the programmed value after the final float voltage is

reached.

■

Preset 4.2V Charge Voltage with ±1% Accuracy

Charge Current Monitor Output for Gas

Gauging*

■

Automatic Recharge

Charge Status Output Pin

C/10 Charge Termination

25µA Supply Current in Shutdown

2.9V Trickle Charge Threshold (LTC4054)

Available Without Trickle Charge (LTC4054X)

Soft-Start Limits Inrush Current

Available in 5-Lead SOT-23 Package

U

When the input supply (wall adapter or USB supply) is

removed, the LTC4054 automatically enters a low current

state, dropping the battery drain current to less than 2µA.

The LTC4054 can be put into shutdown mode, reducing

the supply current to 25µA.

Otherfeaturesincludechargecurrentmonitor,undervoltage

lockout, automatic recharge and a status pin to indicate

charge termination and the presence of an input voltage.

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

ThinSOT is a trademark of Linear Technology Corporation.

*U.S.Patent No. 6,522,118

APPLICATIO S

■

Cellular Telephones, PDAs, MP3 Players

Charging Docks and Cradles

■

Bluetooth Applications

U

Complete Charge Cycle (750mAh Battery)

TYPICAL APPLICATIO

700

600

500

400

300

200

100

0

4.75

4.50

4.25

4.00

3.75

3.50

3.25

3.00

CONSTANT

CURRENT

600mA Single Cell Li-Ion Charger

CONSTANT

POWER

CONSTANT

VOLTAGE

V

IN

4.5V TO 6.5V

1µF

4

V

3

5

CC

BAT

600mA

LTC4054-4.2

V

= 5V

CC

JA

4.2V

Li-Ion

BATTERY

PROG

θ

= 130°C/W

CHARGE

TERMINATED

GND

2

R

= 1.65k

PROG

= 25°C

1.65k

T

A

0

0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0

TIME (HOURS)

405442 TA01a

405442 TAO1b

405442xf

1

LTC4054-4.2/LTC4054X-4.2

W W U W

ABSOLUTE AXI U RATI GS

(Note 1)

U W

U

PACKAGE/ORDER I FOR ATIO

Input Supply Voltage (V_CC) ....................... –0.3V to 10V

PROG............................................. –0.3V to V_CC+ 0.3V

BAT.............................................................. –0.3V to 7V

CHRG........................................................ –0.3V to 10V

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

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

PROG Pin Current................................................ 800µA

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

Operating Ambient Temperature Range

ORDER PART

TOP VIEW

NUMBER

CHRG 1

GND 2

BAT 3

5 PROG

LTC4054ES5-4.2

LTC4054XES5-4.2

4 V

CC

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

S5 PART MARKING

T_JMAX= 125°C, (θ_JA= 80°C/ W TO

150°C/W DEPENDING ON PC BOARD LAYOUT)

(N0TE 3)

LTH7

LTADY

(Note 2) .............................................. –40°C to 85°C

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

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

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

ELECTRICAL CHARACTERISTICS ^The● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_CC= 5V, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

Input Supply Voltage

Input Supply Current

●

4.25

6.5

V

CC

I

Charge Mode (Note 4), R

Standby Mode (Charge Terminated)

= 10k

●

300

200

25

2000

500

50

µA

CC

PROG

Shutdown Mode (R

Not Connected,

< V , or V < V )

BAT CC UV

PROG

V

CC

V

Regulated Output (Float) Voltage

BAT Pin Current

0°C ≤ T ≤ 85°C, I = 40mA

BAT

4.158

4.2

4.242

V

FLOAT

A

I

R

= 10k, Current Mode

= 2k, Current Mode

●

93

465

0

100

500

–2.5

±1

107

535

–6

±2

mA

µA

BAT

PROG

Standby Mode, V

= 4.2V

BAT

Shutdown Mode (R

Not Connected)

< V , R = 2k (Note 5)

TRIKL PROG

PROG

Sleep Mode, V = 0V

±1

CC

I

Trickle Charge Current

V

●

20

2.8

60

45

2.9

80

70

3.0

mA

V

TRIKL

BAT

V

Trickle Charge Threshold Voltage

Trickle Charge Hysteresis Voltage

R

PROG

R

PROG

= 10k, V

Rising (Note 5)

TRIKL

TRHYS

UV

BAT

= 10k (Note 5)

110

3.92

300

mV

V

Undervoltage Lockout Threshold

Undervoltage Lockout Hysteresis

From V Low to High

●

3.7

150

3.8

200

CC

mV

UVHYS

MSD

Manual Shutdown Threshold Voltage

PROG Pin Rising

PROG Pin Falling

●

1.15

0.9

1.21

1.0

1.30

1.1

V

– V Lockout Threshold Voltage

V

from Low to High

from High to Low

70

5

100

30

140

50

mV

ASD

CC

BAT

CC

I

C/10 Termination Current Threshold

R

PROG

R

PROG

= 10k (Note 6)

= 2k

●

0.085

0.10

0.115

mA/mA

TERM

V

PROG Pin Voltage

R

= 10k, Current Mode

●

0.93

8

1.0

20

1.07

35

V

µA

V

PROG

CHRG

I

CHRG Pin Weak Pull-Down Current

CHRG Pin Output Low Voltage

Recharge Battery Threshold Voltage

V

= 5V

CHRG

V

I

= 5mA

0.35

150

0.6

CHRG

∆V

V

- V

RECHRG

100

200

mV

RECHRG

FLOAT

405442xf

2

LTC4054-4.2/LTC4054X-4.2

ELECTRICAL CHARACTERISTICS ^The● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C. V_CC= 5V, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

T

Junction Temperature in Constant

Temperature Mode

120

°C

LIM

R

ON

Power FET “ON” Resistance

600

mΩ

(Between V and BAT)

CC

t

I

Soft-Start Time

I

= 0 to I

=1000V/R

PROG

100

2

µs

ms

µs

SS

BAT

Recharge Comparator Filter Time

Termination Comparator Filter Time

PROG Pin Pull-Up Current

V

High to Low

0.75

400

4.5

RECHARGE

TERM

BAT

I

Falling Below I /10

1000

3

2500

CHG

µA

PROG

Note 4: Supply current includes PROG pin current (approximately 100µA)

but does not include any current delivered to the battery through the BAT

pin (approximately 100mA).

Note 1: Absolute Maximum Ratings are those values beyond which the life

of the device may be impaired.

Note 2: The LTC4054E-4.2 and the LTC4054XE-4.2 are guaranteed to meet

performance specifications from 0°C to 70°C. Specifications over the

–40°C to 85°C operating temperature range are assured by design,

characterization and correlation with statistical process controls.

Note 5: This parameter is not applicable to the LTC4054X.

Note 6: I

is expressed as a fraction of measured full charge current

TERM

with indicated PROG resistor.

Note 3: See Thermal Considerations.

U W

TYPICAL PERFOR A CE CHARACTERISTICS

Charge Current vs

PROG Pin Voltage

PROG Pin Voltage vs Supply

Voltage(Constant Current Mode)

PROG Pin Voltage vs

Temperature

1.015

1.010

1.005

1.000

0.995

0.990

0.985

600

500

400

300

200

100

0

1.0100

1.0075

1.0050

1.0025

1.0000

0.9975

0.9950

0.9925

0.9900

V

A

R

= 5V

V

= 5V

V

= 5V

CC

T = 25°C

A

= 4V

BAT

PROG

T

= 25°C

R

= 10k

R

= 2k

PROG

= 10k

PROG

75

4.0

5.0

5.5

(V)

6.0

6.5

7.0

–50

–25

0

25

50

100

4.5

0

0.25

0.50

V

0.75

(V)

1.00

1.25

TEMPERATURE (°C)

V

CC

PROG

4054 G01

4054 G02

4054 G03

405442xf

3

LTC4054-4.2/LTC4054X-4.2

U W

TYPICAL PERFOR A CE CHARACTERISTICS

PROG Pin Current vs PROG Pin

Voltage (Clamp Current)

PROG Pin Pull-Up Current vs

Temperature and Supply Voltage

PROG Pin Current vs PROG Pin

Voltage (Pull-Up Current)

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

3.7

3.5

3.3

3.1

2.9

2.7

2.5

0

–50

V

= 4.3V

PROG

BAT

= 0V

V

= 4.2V

CC

–100

–150

–200

–250

–300

–350

–400

V

= 6.5V

CC

V

A

= 5V

BAT

= 25°C

V

= 5V

BAT

T = 25°C

A

CC

= 4.3V

T

50

100 125

2.5

3.0 3.5 4.0 4.5

(V)

5.5

–50 –25

0

25

75

2.0

5.0

2.0

2.2

2.3

2.4

2.5

2.6

2.1

V

(V)

TEMPERATURE (°C)

V

PROG

4054 G05

4054 G04

4054 G06

Regulated Output (Float) Voltage

vs Supply Voltage

Regulated Output (Float) Voltage

vs Charge Current

Regulated Output (Float) Voltage

vs Temperature

4.26

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4.215

4.210

4.205

4.200

4.195

4.190

4.185

4.215

4.210

4.205

4.200

4.195

4.190

4.185

V

A

R

= 5V

V

= 5V

PROG

T = 25°C

A

CC

= 25°C

CC

T

R

= 10k

R

= 10k

PROG

= 1.25k

PROG

–25

0

25

50

75

100

–50

0

200 300 400 500 600 700

(mA)

4.0

5.0

5.5

(V)

6.0

6.5

7.0

100

4.5

I

V

TEMPERATURE (°C)

BAT

CC

4054 G07

4054 G08

4054 G09

CHRG Pin I-V Curve

(Weak Pull-Down State)

CHRG Pin I-V Curve

(Strong Pull-Down State)

CHRG Pin Current vs Temperature

(Strong Pull-Down State)

25

20

15

10

5

20

18

16

14

12

10

8

22

20

18

16

14

12

10

8

V

= 5V

= 4V

CHRG

CC

BAT

= 1V

V

T

= 5V

= 4V

V

T

= 5V

BAT

= 25°C

CC

BAT

CC

6

= 4.3V

= 25°C

A

0

4

–50

0

2

3

4

5

6

7

–25

0

25

50

75

100

125

1

4

6

7

0

1

2

3

5

V

(V)

V

(V)

TEMPERATURE (°C)

CHRG

4054 G10

4054 G11

4054 G12

405442xf

4

LTC4054-4.2/LTC4054X-4.2

U W

TYPICAL PERFOR A CE CHARACTERISTICS

Trickle Charge Current vs

CHRG Pin Current vs Temperature

(Weak Pull-Down State)

Trickle Charge Current

vs Temperature

Supply Voltage

28

25

23

19

16

13

10

50

40

30

20

10

0

50

V

= 5V

CC

R = 2k

PROG

R

= 2k

= 4.3V

PROG

BAT

CHRG

= 5V

40

30

20

10

0

V

= 5V

BAT

V

T

= 2.5V

CC

BAT

= 25°C

= 2.5V

A

R = 10k

PROG

R

= 10k

PROG

25

–50

0

25

50

75

100

–50

0

50

75

100

–25

4.0

4.5

5.0

5.5

(V)

6.0

6.5

7.0

TEMPERATURE (°C)

V

CC

4054 G13

4054 G14

4054 G15

Trickle Charge Threshold vs

Temperature

Charge Current vs Supply Voltage

Charge Current vs Battery Voltage

600

500

400

300

200

100

0

3.000

2.975

2.950

2.925

2.900

2.875

2.850

2.825

2.800

600

500

400

300

200

100

0

V

= 5V

PROG

CC

R = 2k

PROG

T

= 0°C

R

= 10k

A

T

= 40°C

ONSET OF

A

THERMAL

REGULATION

V

T

JA

= 4V

T

= 25°C

BAT

= 25°C

A

θ

= 80°C/W

R

= 10k

PROG

V

= 5V

CC

JA

θ

= 125°C/W

R

= 2k

PROG

4.0

5.0

5.5

6.0

6.5

7.0

–50

0

25

50

75

100

4.2

4.5

–25

2.7

3.0

3.3

3.6

3.9

4.5

TEMPERATURE (°C)

V

(V)

V

(V)

BAT

CC

4054 G18

4054 G16

4054 G17

Power FET “ON” Resistance

vs Temperature

Charge Current vs Ambient

Temperature

Recharge Voltage Threshold

vs Temperature

4.11

4.09

4.07

4.05

4.03

4.01

3.99

600

500

400

300

200

100

0

700

650

600

550

500

450

400

350

V

I

= 4.2V

CC

BAT

R

V

= 5V

PROG

CC

R

= 2k

= 100mA

PROG

R

= 10k

= 2k

PROG

ONSET OF

THERMAL

REGULATION

V

θ

= 5V

BAT

= 80°C/W

CC

= 4V

JA

R

= 10k

PROG

50

100 125

50

TEMPERATURE (°C)

100

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

–50 –25

0

25

75

–50 –25

0

25

75

TEMPERATURE (°C)

4054 G20

4054 G19

4054 G21

405442xf

5

LTC4054-4.2/LTC4054X-4.2

U

PI FU CTIO S

PROG (Pin 5): Charge Current Program, Charge Current

Monitor and Shutdown Pin. The charge current is pro-

grammedbyconnectinga1%resistor, R_PROG, toground.

When charging in constant-current mode, this pin servos

to 1V. In all modes, the voltage on this pin can be used to

measure the charge current using the following formula:

CHRG (Pin 1): Open-Drain Charge Status Output. When

the battery is charging, the CHRG pin is pulled low by an

internal N-channel MOSFET. When the charge cycle is

completed, a weak pull-down of approximately 20µA is

connected to the CHRG pin, indicating an “AC present”

condition. When the LTC4054 detects an undervoltage

lockout condition, CHRG is forced high impedance.

I_BAT= (V_PROG/R_PROG) • 1000

GND (Pin 2): Ground.

The PROG pin can also be used to shut down the charger.

Disconnecting the program resistor from ground allows

a 3µA current to pull the PROG pin high. When it reaches

the1.21Vshutdownthresholdvoltage, thechargerenters

shutdown mode, charging stops and the input supply

current drops to 25µA. This pin is also clamped to

approximately 2.4V. Driving this pin to voltages beyond

the clamp voltage will draw currents as high as 1.5mA.

Reconnecting R_PROGto ground will return the charger to

normal operation.

BAT (Pin 3): Charge Current Output. Provides charge

current to the battery and regulates the final float voltage

to 4.2V. An internal precision resistor divider from this pin

sets the float voltage which is disconnected in shutdown

mode.

V_CC(Pin 4): Positive Input Supply Voltage. Provides

power to the charger. V_CCcan range from 4.25V to 6.5V

and should be bypassed with at least a 1µF capacitor.

WhenV_CCdropstowithin30mVoftheBATpinvoltage,the

LTC4054 enters shutdown mode, dropping I_BATto less

than 2µA.

405442xf

6

LTC4054-4.2/LTC4054X-4.2

W

BLOCK DIAGRA

4

V

CC

120°C

1×

T

A

1000×

T

DIE

–

+

BAT

5µA

3

MA

R1

R2

+

–

VA

CA

+

–

+

REF

1.21V

SHDN

C1

R3

1V

R4

0.1V

R5

+

–

C2

CHRG

1

STANDBY

3µA

TRICKLE CHARGE

DISABLED ON

LTC4054X

TO

V

+

–

CC

BAT

C3

2.9V

PROG

GND

5

2

405442 BD

R

PROG

405442xf

7

LTC4054-4.2/LTC4054X-4.2

U

OPERATIO

V_PROG

R_PROG

The LTC4054 is a single cell lithium-ion battery charger

using a constant-current/constant-voltage algorithm. It

can deliver up to 800mA of charge current (using a good

thermal PCB layout) with a final float voltage accuracy of

±1%. The LTC4054 includes an internal P-channel power

MOSFET and thermal regulation circuitry. No blocking

diode or external current sense resistor is required; thus,

the basic charger circuit requires only two external com-

ponents. Furthermore, the LTC4054 is capable of operat-

ing from a USB power source.

I_BAT

=

•1000

Charge Termination

A charge cycle is terminated when the charge current falls

to1/10ththeprogrammedvalueafterthefinalfloatvoltage

is reached. This condition is detected by using an internal,

filtered comparator to monitor the PROG pin. When the

PROG pin voltage falls below 100mV¹for longer than

t_TERM(typically 1ms), charging is terminated. The charge

current is latched off and the LTC4054 enters standby

mode, where the input supply current drops to 200µA.

(Note: C/10 termination is disabled in trickle charging and

thermal limiting modes).

Normal Charge Cycle

AchargecyclebeginswhenthevoltageattheV_CCpinrises

abovetheUVLOthresholdlevelanda1%programresistor

is connected from the PROG pin to ground or when a

battery is connected to the charger output. If the BAT pin

is less than 2.9V, the charger enters trickle charge mode.

In this mode, the LTC4054 supplies approximately 1/10

the programmed charge current to bring the battery volt-

age up to a safe level for full current charging. (Note: The

LTC4054X does not include this trickle charge feature).

When charging, transient loads on the BAT pin can cause

thePROGpintofallbelow100mVforshortperiodsoftime

before the DC charge current has dropped to 1/10th the

programmed value. The 1ms filter time (t_TERM) on the

termination comparator ensures that transient loads of

this nature do not result in premature charge cycle termi-

nation. Once the average charge current drops below

1/10th the programmed value, the LTC4054 terminates

thechargecycleandceasestoprovideanycurrentthrough

the BAT pin. In this state, all loads on the BAT pin must be

supplied by the battery.

When the BAT pin voltage rises above 2.9V, the charger

enters constant-current mode, where the programmed

charge current is supplied to the battery. When the BAT

pinapproachesthefinalfloatvoltage(4.2V), theLTC4054

enters constant-voltage mode and the charge current

begins to decrease. When the charge current drops to

1/10 of the programmed value, the charge cycle ends.

The LTC4054 constantly monitors the BAT pin voltage in

standby mode. If this voltage drops below the 4.05V

recharge threshold (V_RECHRG), another charge cycle be-

gins and current is once again supplied to the battery. To

manuallyrestartachargecyclewheninstandbymode, the

input voltage must be removed and reapplied, or the

charger must be shut down and restarted using the PROG

pin. Figure 1 shows the state diagram of a typical charge

cycle.

Programming Charge Current

The charge current is programmed using a single resistor

from the PROG pin to ground. The battery charge current

is 1000 times the current out of the PROG pin. The

program resistor and the charge current are calculated

using the following equations:

Charge Status Indicator (CHRG)

1000V

I_CHG

1000V

R_PROG

=

, I_CHG=

The charge status output has three different states: strong

pull-down (~10mA), weak pull-down (~20µA) and high

impedance. The strong pull-down state indicates that the

LTC4054 is in a charge cycle. Once the charge cycle has

terminated, the pin state is determined by undervoltage

The charge current out of the BAT pin can be determined

at any time by monitoring the PROG pin voltage using the

following equation:

Note 1: Any external sources that hold the PROG pin above 100mV will prevent the LTC4054

from terminating a charge cycle.

405442xf

8

LTC4054-4.2/LTC4054X-4.2

U

OPERATIO

lockout conditions. A weak pull-down indicates that V_CC

meets the UVLO conditions and the LTC4054 is ready to

charge. High impedance indicates that the LTC4054 is in

undervoltagelockoutmode:eitherV_CCis less than 100mV

above theBATpinvoltageorinsufficientvoltageisapplied

to the V_CCpin. A microprocessor can be used to distin-

guish between these three states—this method is dis-

cussed in the Applications Information section.

than 2µA and the supply current to less than 50µA. A new

charge cycle can be initiated by reconnecting the program

resistor.

In manual shutdown, the CHRG pin is in a weak pull-down

state as long as V_CCis high enough to exceed the UVLO

conditions. The CHRG pin is in a high impedance state if

the LTC4054 is in undervoltage lockout mode: either V_CC

iswithin100mVoftheBATpinvoltageorinsufficientvoltage

is applied to the V_CCpin.

Thermal Limiting

Aninternalthermalfeedbackloopreducestheprogrammed

charge current if the die temperature attempts to rise

above a preset value of approximately 120°C. This feature

protects the LTC4054 from excessive temperature and

allows the user to push the limits of the power handling

capabilityofagivencircuitboardwithoutriskofdamaging

the LTC4054. The charge current can be set according to

typical (not worst-case) ambient temperature with the

assurance that the charger will automatically reduce the

current in worst-case conditions. ThinSOT power consid-

erationsarediscussedfurtherintheApplicationsInforma-

tion section.

Automatic Recharge

Oncethechargecycleisterminated,theLTC4054continu-

ously monitors the voltage on the BAT pin using a com-

parator with a 2ms filter time (t_RECHARGE). A charge cycle

restarts when the battery voltage falls below 4.05V (which

corresponds to approximately 80% to 90% battery capac-

ity). This ensures that the battery is kept at or near a fully

charged condition and eliminates the need for periodic

charge cycle initiations. CHRG output enters astrong pull-

down state during recharge cycles.

POWER ON

BAT < 2.9V

Undervoltage Lockout (UVLO)

TRICKLE CHARGE

MODE

PROG

RECONNECTED

OR

UVLO CONDITION

STOPS

Aninternalundervoltagelockoutcircuitmonitorstheinput

voltageandkeepsthechargerinshutdownmodeuntilV_CC

risesabovetheundervoltagelockoutthreshold. TheUVLO

circuit has a built-in hysteresis of 200mV. Furthermore, to

protect against reverse current in the power MOSFET, the

UVLO circuit keeps the charger in shutdown mode if V_CC

falls to within 30mV of the battery voltage. If the UVLO

comparator is tripped, the charger will not come out of

shutdown mode until V_CCrises 100mV above the battery

voltage.

1/10TH FULL CURRENT

CHRG: STRONG

PULL-DOWN

BAT > 2.9V

SHUTDOWN MODE

DROPS TO <25µA

CHARGE MODE

I

CC

FULL CURRENT

CHRG: Hi-Z IN UVLO

WEAK PULL-DOWN

OTHERWISE

CHRG: STRONG

PULL-DOWN

PROG < 100mV

STANDBY MODE

NO CHARGE CURRENT

PROG FLOATED

OR

UVLO CONDITION

CHRG: WEAK

PULL-DOWN

Manual Shutdown

2.9V < BAT < 4.05V

At any point in the charge cycle, the LTC4054 can be put

into shutdown mode by removing R_PROGthus floating the

PROG pin. This reduces the battery drain current to less

405442 F01

Figure 1. State Diagram of a Typical Charge Cycle

405442xf

9

LTC4054-4.2/LTC4054X-4.2

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APPLICATIO S I FOR ATIO

CHARGE

Stability Considerations

10k

CURRENT

MONITOR

CIRCUITRY

PROG

LTC4054

GND

The constant-voltage mode feedback loop is stable with-

out an output capacitor provided a battery is connected to

the charger output. With no battery present, an output

capacitor is recommended to reduce ripple voltage. When

using high value, low ESR ceramic capacitors, it is recom-

mended to add a 1Ω resistor in series with the capacitor.

No series resistor is needed if tantalum capacitors are

used.

R

C

FILTER

PROG

405442 F02

Figure 2. Isolating Capacitive Load on PROG Pin and Filtering

Power Dissipation

The conditions that cause the LTC4054 to reduce charge

current through thermalfeedback can be approximatedby

considering the power dissipated in the IC. Nearly all of

this power dissipation is generated by the internal

MOSFET—this is calculated to be approximately:

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

loop, not the battery. The constant-current mode stability

is affected by the impedance at the PROG pin. With no

additional capacitance on the PROG pin, the charger is

stable with program resistor values as high as 20k. How-

ever, 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, C_PROG, the

following equation can be used to calculate the maximum

P_D= (V_CC– V_BAT) • I_BAT

where P_Dis the power dissipated, V_CCis the input supply

voltage, V_BATis the battery voltage and I_BATis the charge

current. The approximate ambient temperature at which

the thermal feedback begins to protect the IC is:

resistance value for R_PROG

:

T_A= 120°C – P_Dθ_JA

1

R_PROG

≤

T_A= 120°C – (V_CC– V_BAT) • I_BAT• θ_JA

2π •10⁵•C_PROG

Example: An LTC4054 operating from a 5V USB supply is

programmed to supply 400mA full-scale current to a

discharged Li-Ion battery with a voltage of 3.75V. Assum-

ingθ_JAis150°C/W(seeBoardLayoutConsiderations),the

ambient temperature at which the LTC4054 will begin to

reduce the charge current is approximately:

Average, rather than instantaneous, charge current may

beofinteresttotheuser.Forexample,ifaswitchingpower

supply 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.

T_A= 120°C – (5V – 3.75V) • (400mA) • 150°C/W

T_A= 120°C – 0.5W • 150°C/W = 120°C – 75°C

T_A= 45°C

405442xf

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LTC4054-4.2/LTC4054X-4.2

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APPLICATIO S I FOR ATIO

The LTC4054 can be used above 45°C ambient, but the

charge current will be reduced from 400mA. The approxi-

mate current at a given ambient temperature can be

approximated by:

The following table lists thermal resistance for several

different board sizes and copper areas. All measurements

were taken in still air on 3/32" FR-4 board with the device

mounted on topside.

Table 1. Measured Thermal Resistance (2-Layer Board*)

120°C – T_A

COPPER AREA

TOPSIDE BACKSIDE

BOARD

AREA

THERMAL RESISTANCE

JUNCTION-TO-AMBIENT

I_BAT

=

V

_CC– V_BAT•θ_JA

(

)

2

2500mm

125°C/W

130°C/W

135°C/W

150°C/W

2

1000mm

Usingthepreviousexamplewithanambient temperature

of 60°C, the charge current will be reduced to approxi-

mately:

2

225mm

100mm

2

50mm

*Each layer uses one ounce copper

120°C – 60°C

60°C

187.5°C/A

I_BAT

=

Table 2. Measured Thermal Resistance (4-Layer Board**)

5V – 3.75V •150°C/W

(

)

COPPER AREA

(EACH SIDE)

BOARD

AREA

THERMAL RESISTANCE

JUNCTION-TO-AMBIENT

I_BAT= 320mA

2***

2

2500mm

80°C/W

Moreover, when thermal feedback reduces the charge

current, the voltage at the PROG pin is also reduced

proportionally as discussed in the Operation section.

*Top and bottom layers use two ounce copper, inner layers use one ounce copper.

**10,000mm²total copper area

Increasing Thermal Regulation Current

It is important to remember that LTC4054 applications do

notneedtobedesignedforworst-casethermalconditions

since the IC will automatically reduce power dissipation

when the junction temperature reaches approximately

120°C.

Reducing the voltage drop across the internal MOSFET

can significantly decrease the power dissipation in the IC.

This has the effect of increasing the current delivered to

the battery during thermal regulation. One method is by

dissipatingsomeofthepowerthroughanexternalcompo-

nent, such as a resistor or diode.

Thermal Considerations

Example: An LTC4054 operating from a 5V wall adapter is

programmed to supply 800mA full-scale current to a

discharged Li-Ion battery with a voltage of 3.75V. Assum-

ing θ_JAis 125°C/W, the approximate charge current at an

ambient temperature of 25°C is:

BecauseofthesmallsizeoftheThinSOTpackage, itisvery

important to use a good thermal PC board layout to

maximize the available charge current. The thermal path

for the heat generated by the IC is from the die to the

copper lead frame, through the package leads, (especially

the ground lead) to the PC board copper. The PC board

copper is the heat sink. The footprint copper pads should

be as wide as possible and expand out to larger copper

areas to spread and dissipate the heat to the surrounding

ambient. Feedthrough vias to inner or backside copper

layers are also useful in improving the overall thermal

performance of the charger. Other heat sources on the

board, not related to the charger, must also be considered

when designing a PC board layout because they will affect

overalltemperatureriseandthemaximumchargecurrent.

120°C – 25°C

(5V – 3.75V)•125°C / W

I_BAT

=

= 608mA

By dropping voltage across a resistor in series with a 5V

wall adapter (shown in Figure 3), the on-chip power

dissipation can be decreased, thus increasing the ther-

mally regulated charge current

120°C – 25°C

I_BAT

=

(V_S– I_{BAT CC}– V_BAT)•θ_JA

R

405442xf

11

LTC4054-4.2/LTC4054X-4.2

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APPLICATIO S I FOR ATIO

V

S

enough to put the LTC4054 into dropout. Figure 4 shows

how this circuit can result in dropout as R_CCbecomes

large.

R

CC

ThistechniqueworksbestwhenR_CCvaluesareminimized

tokeepcomponentsizesmallandavoiddropout. Remem-

ber to choose a resistor with adequate power handling

capability.

V

CC

BAT

LTC4054-4.2

PROG

1µF

Li-Ion

CELL

GND

R

PROG

V

_CCBypass Capacitor

405442 F03

Many types of capacitors can be used for input bypassing,

however, caution must be exercised when using multi-

layerceramiccapacitors.Becauseoftheself-resonantand

high Q characteristics of some types of ceramic capaci-

tors, high voltagetransients can be generated under some

start-up conditions, such as connecting the charger input

to a live power source. Adding a 1.5Ω resistor in series

with an X5R ceramic capacitor will minimize start-up

voltage transients. For more information, refer to Applica-

tion Note 88.

Figure 3. A Circuit to Maximize Thermal Mode Charge Current

Solving for I_BATusing the quadratic formula².

I_BAT

=

₂4R_CC(120°C – T_A)

(V_S– V_BAT)– (V_S– V_BAT

2R_CC

)

θ_JA

Using R_CC= 0.25Ω, V_S= 5V, V_BAT= 3.75V, T_A= 25°C and

θ_JA= 125°C/W we can calculate the thermally regulated

charge current to be:

Charge Current Soft-Start

The LTC4054 includes a soft-start circuit to minimize the

inrushcurrentatthestartofachargecycle. Whenacharge

cycleisinitiated,thechargecurrentrampsfromzerotothe

full-scale current over a period of approximately 100µs.

This has the effect of minimizing the transient current load

on the power supply during start-up.

I_BAT= 708.4mA

While this application delivers more energy to the battery

and reduces charge time in thermal mode, it may actually

lengthen charge time in voltage mode if V_CCbecomes low

1000

V

= 5V

CONSTANT

CURRENT

S

800

600

400

200

0

V

= 5.5V

S

DROPOUT

V

= 5.25V

S

THERMAL

MODE

V

= 3.75V

BAT

T

= 25°C

A

JA

θ

= 125°C/W

R

= 1.25kΩ

PROG

0

0.5 0.75 1.0 1.25 1.5 1.75

(Ω)

0.25

R

CC

405442 F04

Figure 4. Charge Current vs R_CC

Note 2: Large values of R_CCwill result in no solution for I_BAT. This indicates that the LTC4054

will not generate enough heat to require thermal regulation.

405442xf

12

LTC4054-4.2/LTC4054X-4.2

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APPLICATIO S I FOR ATIO

CHRG Status Output Pin

To detect when the LTC4054 is in charge mode, force the

digital output pin (OUT) high and measure the voltage at

the CHRG pin. The N-channel MOSFET will pull the pin

voltage low even with the 2k pull-up resistor. Once the

charge cycle terminates, the N-channel MOSFET is turned

off and a 20µA current source is connected to the CHRG

pin. The IN pin will then be pulled high by the 2k pull-up

resistor. Todetermineifthereisaweakpull-downcurrent,

the OUT pin should be forced to a high impedance state.

The weak current source will pull the IN pin low through

the 800k resistor; if CHRG is high impedance, the IN pin

will be pulled high, indicating that the part is in a UVLO

state.

The CHRG pin can provide an indication that the input

voltage is greater than the undervoltage lockout threshold

level. A weak pull-down current of approximately 20µA

indicates that sufficient voltage is applied to V_CCto begin

charging. When a discharged battery is connected to the

charger, the constant current portion of the charge cycle

begins and the CHRG pin pulls to ground. The CHRG pin

can sink up to 10mA to drive an LED that indicates that a

charge cycle is in progress.

When the battery is nearing full charge, the charger enters

the constant-voltage portion of the charge cycle and the

charge current begins to drop. When the charge current

drops below 1/10 of the programmed current, the charge

cycle ends and the strong pull-down is replaced by the

20µA pull-down, indicating that the charge cycle has

ended. If the input voltage is removed or drops below the

undervoltage lockout threshold, the CHRG pin becomes

high impedance. Figure 5 shows that by using two

different value pull-up resistors, a microprocessor can

detect all three states from this pin.

Reverse Polarity Input Voltage Protection

In some applications, protection from reverse polarity

voltage on V_CCis desired. If the supply voltage is high

enough, a series blocking diode can be used. In other

cases, where the voltage drop must be kept low a P-

channel MOSFET can be used (as shown in Figure 6).

+

V

DD

DRAIN-BULK

DIODE OF FET

LTC4054

CC

V

IN

V

CC

800k

LTC4054

CHRG

µPROCESSOR

4054 F06

2k

OUT

IN

405442 F05

Figure 5. Using a Microprocessor to Determine CHRG State

Figure 6. Low Loss Input Reverse Polarity Protection

405442xf

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

13

LTC4054-4.2/LTC4054X-4.2

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APPLICATIO S I FOR ATIO

USB and Wall Adapter Power

5V WALL

ADAPTER

The LTC4054 allows charging from both a wall adapter

and a USB port. Figure 7 shows an example of how to

combine wall adapter and USB power inputs. A P-channel

MOSFET,MP1,isusedtopreventbackconductingintothe

USB port when a wall adapter is present and a Schottky

diode, D1, is used to prevent USB power loss through the

1k pull-down resistor.

I

CHG

600mA I

LTC4054-4.2

BAT

CHG

3

5

SYSTEM

LOAD

D1

USB POWER

4

V

CC

500mA I

CHG

MP1

+

PROG

10k

Li-Ion

BATTERY

1k

2k

MN1

405442 F07

Typically a wall adapter can supply more current than the

500mA-limitedUSBport.Therefore,anN-channelMOSFET,

MN1, and an extra 10k program resistor are used to

increase the charge current to 600mA when the wall

adapter is present.

Figure 7. Combining Wall Adapter and USB Power

405442xf

14

LTC4054-4.2/LTC4054X-4.2

U

PACKAGE DESCRIPTIO

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

0.62

MAX

0.95

REF

2.90 BSC

(NOTE 4)

1.22 REF

1.50 – 1.75

(NOTE 4)

2.80 BSC

1.4 MIN

3.85 MAX 2.62 REF

PIN ONE

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.30 – 0.45 TYP

5 PLCS (NOTE 3)

0.95 BSC

0.80 – 0.90

0.20 BSC

DATUM ‘A’

0.01 – 0.10

1.00 MAX

0.30 – 0.50 REF

1.90 BSC

0.09 – 0.20

(NOTE 3)

NOTE:

S5 TSOT-23 0302

1. DIMENSIONS ARE IN MILLIMETERS

2. DRAWING NOT TO SCALE

3. DIMENSIONS ARE INCLUSIVE OF PLATING

4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

5. MOLD FLASH SHALL NOT EXCEED 0.254mm

6. JEDEC PACKAGE REFERENCE IS MO-193

405442xf

15

LTC4054-4.2/LTC4054X-4.2

U

TYPICAL APPLICATIO S

USB/Wall Adapter Power Li-Ion Charger

Full Featured Single Cell Li-Ion Charger

V

= 5V

I

IN

BAT

5V WALL

ADAPTER

3

BAT

+

LTC4054-4.2

Li-Ion

CELL

1µF

500mA

4

USB

POWER

V

CC

2.5k

5

V

3

5

CC

1µF

PROG

GND

BAT

330Ω

100mA/

500mA

LTC4054-4.2

2

1k

10k

1

+

CHRG

PROG

µC

GND

2

2k

405442 TA05

SHDN

800mA Li-Ion Charger with External Power Dissipation

405442 TA02

V

= 5V

IN

Basic Li-Ion Charger with Reverse Polarity Input Protection

0.25Ω

800mA

4

3

5

V

BAT

LTC4054-4.2

CC

500mA

4

3

5

5V WALL

ADAPTER

1µF

V

CC

BAT

LTC4054-4.2

PROG

GND

2

+

PROG

1µF

1.25k

GND

2

2k

405442 TA03

405442 TA04

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LTC1732

Lithium-Ion Linear Battery Charger Controller

Simple Charger uses External FET, Features Preset Voltages, C/10

Charger Detection and Programmable Timer, Input Power Good Indication

LTC1733

LTC1734

LTC1734L

LTC1998

LTC4050

Monolithic Lithium-Ion Linear Battery Charger

Lithium-Ion Linear Battery Charger in ThinSOT

Lithium-Ion Low Battery Detector

Standalone Charger with Programmable Timer, Up to 1.5A Charge Current

Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed

Low Current Version of LTC1734

1% Accurate 2.5µA Quiescent Current, SOT-23

Lithium-Ion Linear Battery Charger Controller

Simple Charger uses External FET, Features Preset Voltages, C/10

Charger Detection and Programmable Timer, Input Power Good Indication,

Thermistor Interface

LTC4052

LTC4053

LTC4054L

Monolithic Lithium-Ion Battery Pulse Charger

No Blocking Diode or External Power FET Required

USB Compatible Monolithic Li-Ion Battery Charger

Standalone Charger with Programmable Timer, Up to 1.25A Charge Current

10mA to 150mA Standalone Monolithic Lithium-Ion Low Current Version of LTC4054

Linear Battery Charger in ThinSOT

LTC4056

LTC4057

LTC4410

Standalone Lithium-Ion Linear Battery Charger

in ThinSOT

Standalone Charger with Programmable Timer, No Blocking Diode,

No Sense Resistor Needed

Monolithic Lithium-Ion Linear Battery Charger

with Thermal Regulation in ThinSOT

No External MOSFET, Sense Resistor or Blocking Diode Required,

Charge Current Monitor for Gas Gauging

USB Power Manager

For Simultaneous Operation of USB Peripheral and Battery Charging from USB

Port, Keeps Current Drawn from USB Port Constant, Keeps Battery Fresh, Use

with the LTC4053, LTC1733, or LTC4054

405442xf

LT/TP 0903 1K • PRINTED IN USA

16 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

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

LINEAR TECHNOLOGY CORPORATION 2003


型号：	LTC4054ES5-4.2#TR
厂家：	Linear
描述：	LTC4054-4.2 - Standalone Linear Li-Ion Battery Charger with Thermal Regulation in ThinSOT; Package: SOT; Pins: 5; Temperature Range: -40°C to 85°C 电池
文件：	总16页 (文件大小：188K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC4054ES5-4.2#TR [Linear]

相关型号：

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