LTC4054 4.2, LTC4054X 4.2 Datasheet. Www.s Manuals.com. Linear

User Manual: Marking of electronic components, SMD Codes LT, LT-***, LTADY, LTAFT, LTAGN, LTAGP, LTB2, LTB3, LTCWK, LTCWY, LTCXB, LTDDQ, LTDWF, LTDWH, LTDWK, LTDWM, LTG6, LTH2, LTH7, LTJ, LTKX, LTP, LTPG, LTRD, LTUK, LTYD, LTYN. Datasheets 1SMB18AT3, LT1713CMS8, LT1713IMS8, LT1716, LT1933ES6, LT1933HS6, LT1933IS6, LT1937ES5, LT3465, LT3465A, LT6106, LT6202CS5, LT6203CMS8, LT6203IMS8, LTC1986ES6, LTC3401, LTC4054ES5-4.2, LTC4054XES5-4.2, LTC4151, LTC4151-1, LTC6246, LTC6247, P6SMB33A, PZU6.8B2A, RT9819A-36PV, SMBJ18A, TP

Open the PDF directly: View PDF .
Page Count: 17

1

LTC4054-4.2/LTC4054X-4.2

405442xf

FEATURES

DESCRIPTIO

U

APPLICATIO S

U

TYPICAL APPLICATIO

U

Standalone Linear

Li-Ion Battery Charger with

Thermal Regulation in ThinSOT

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

■

Programmable Charge Current Up to 800mA

■

No MOSFET, Sense Resistor or Blocking

Diode Required

■

Complete Linear Charger in ThinSOT

TM

Package 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

■

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

■

Cellular Telephones, PDAs, MP3 Players

■

Charging Docks and Cradles

■

Bluetooth Applications ThinSOT is a trademark of Linear Technology Corporation.

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

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, the LTC4054 is specifically designed to work

within USB power specifications.

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,

and the charge current can be programmed externally with

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.

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.

Other features include charge current monitor, undervoltage

lockout, automatic recharge and a status pin to indicate

charge termination and the presence of an input voltage.

600mA Single Cell Li-Ion Charger

V

CC

1.65k

4.2V

Li-Ion

BATTERY

405442 TA01a

LTC4054-4.2

1µF

V

IN

4.5V TO 6.5V

BAT

4

3

5

2

PROG

GND

600mA

Complete Charge Cycle (750mAh Battery)

TIME (HOURS)

0

CHARGE CURRENT (mA)

1.5

405442 TAO1b

0.5 1.0 2.0

700

600

500

400

300

200

100

0

4.75

4.50

4.25

4.00

3.75

3.50

3.25

3.00

0.25 0.75 1.25 1.75

CONSTANT

POWER CONSTANT

VOLTAGE

CONSTANT

CURRENT

CHARGE

TERMINATED

BATTERY VOLTAGE (V)

V

CC

= 5V

θ

JA

= 130°C/W

R

PROG

= 1.65k

T

A

= 25°C

2

LTC4054-4.2/LTC4054X-4.2

405442xf

(Note 1)

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

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

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

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

T

JMAX

= 125°C, (θ

JA

= 80°C/ W TO

150°C/W DEPENDING ON PC BOARD LAYOUT)

(N0TE 3)

ORDER PART

NUMBER

S5 PART MARKING

LTH7

LTADY

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

Input Supply Voltage ●4.25 6.5 V

I

CC

Input Supply Current Charge Mode (Note 4), R

PROG

= 10k ●300 2000 µA

Standby Mode (Charge Terminated) ●200 500 µA

Shutdown Mode (R

PROG

Not Connected, ●25 50 µA

V

CC

< V

BAT

, or V

CC

< V

UV

)

V

FLOAT

Regulated Output (Float) Voltage 0°C ≤ T

A

≤ 85°C, I

BAT

= 40mA 4.158 4.2 4.242 V

I

BAT

BAT Pin Current R

PROG

= 10k, Current Mode ●93 100 107 mA

R

PROG

= 2k, Current Mode ●465 500 535 mA

Standby Mode, V

BAT

= 4.2V ●0 –2.5 –6 µA

Shutdown Mode (R

PROG

Not Connected) ±1±2µA

Sleep Mode, V

CC

= 0V ±1±2µA

I

TRIKL

Trickle Charge Current V

BAT

< V

TRIKL

, R

PROG

= 2k (Note 5) ●20 45 70 mA

V

TRIKL

Trickle Charge Threshold Voltage R

PROG

= 10k, V

BAT

Rising (Note 5) 2.8 2.9 3.0 V

V

TRHYS

Trickle Charge Hysteresis Voltage R

PROG

= 10k (Note 5) 60 80 110 mV

V

UV

V

CC

Undervoltage Lockout Threshold From V

CC

Low to High ●3.7 3.8 3.92 V

V

UVHYS

V

CC

Undervoltage Lockout Hysteresis ●150 200 300 mV

V

MSD

Manual Shutdown Threshold Voltage PROG Pin Rising ●1.15 1.21 1.30 V

PROG Pin Falling ●0.9 1.0 1.1 V

V

ASD

V

CC

– V

BAT

Lockout Threshold Voltage V

CC

from Low to High 70 100 140 mV

V

CC

from High to Low 5 30 50 mV

I

TERM

C/10 Termination Current Threshold R

PROG

= 10k (Note 6) ●0.085 0.10 0.115 mA/mA

R

PROG

= 2k ●0.085 0.10 0.115 mA/mA

V

PROG

PROG Pin Voltage R

PROG

= 10k, Current Mode ●0.93 1.0 1.07 V

I

CHRG

CHRG Pin Weak Pull-Down Current V

CHRG

= 5V 8 20 35 µA

V

CHRG

CHRG Pin Output Low Voltage I

CHRG

= 5mA 0.35 0.6 V

∆V

RECHRG

Recharge Battery Threshold Voltage V

FLOAT

- V

RECHRG

100 150 200 mV

The ● denotes specifications which apply over the full operating

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

ABSOLUTE AXI U RATI GS

WWWU

PACKAGE/ORDER I FOR ATIO

UU

W

ELECTRICAL CHARACTERISTICS

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

CHRG 1

GND 2

TOP VIEW

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

BAT 3

5 PROG

4 V

CC

LTC4054ES5-4.2

LTC4054XES5-4.2

3

LTC4054-4.2/LTC4054X-4.2

405442xf

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 3: See Thermal Considerations.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

T

LIM

Junction Temperature in Constant 120 °C

Temperature Mode

R

ON

Power FET “ON” Resistance 600 mΩ

(Between V

CC

and BAT)

t

SS

Soft-Start Time I

BAT

= 0 to I

BAT

=1000V/R

PROG

100 µs

t

RECHARGE

Recharge Comparator Filter Time V

BAT

High to Low 0.75 2 4.5 ms

t

TERM

Termination Comparator Filter Time I

BAT

Falling Below I

CHG

/10 400 1000 2500 µs

I

PROG

PROG Pin Pull-Up Current 3 µA

The ● denotes specifications which apply over the full operating

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

ELECTRICAL CHARACTERISTICS

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 5: This parameter is not applicable to the LTC4054X.

Note 6: I

TERM

is expressed as a fraction of measured full charge current

with indicated PROG resistor.

TYPICAL PERFOR A CE CHARACTERISTICS

UW

PROG Pin Voltage vs Supply

Voltage(Constant Current Mode) PROG Pin Voltage vs

Temperature

Charge Current vs

PROG Pin Voltage

V

PROG

(V)

V

CC

(V)

4.0

V

PROG

(V)

1.015

1.010

1.005

1.000

0.995

0.990

0.985 4.5 5.0 5.5 6.0

4054 G01

6.5 7.0

TEMPERATURE (°C)

–50 –25 0 5025 75 100

4054 G02

1.0100

1.0075

1.0050

1.0025

1.0000

0.9975

0.9950

0.9925

0.9900

V

PROG

(V)

0

I

BAT

(mA)

600

500

400

300

200

100

00.25 0.50 0.75 1.00

4054 G03

1.25

V

CC

= 5V

V

BAT

= 4V

T

A

= 25°C

R

PROG

= 10k

V

CC

= 5V

V

BAT

= 4V

R

PROG

= 10k

V

CC

= 5V

T

A

= 25°C

R

PROG

= 2k

4

LTC4054-4.2/LTC4054X-4.2

405442xf

TEMPERATURE (°C)

–50

I

PROG

(µA)

3.7

3.5

3.3

3.1

2.9

2.7

2.5 25 75

4054 G04

–25 0 50 100 125

V

PROG

(V)

I

PROG

(µA)

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

4054 G05

2.0 2.1 2.2 2.3 2.4 2.5 2.6

V

PROG

(V)

2.0

I

PROG

(µA)

5.0

4054 G06

3.0 4.0

0

–50

–100

–150

–200

–250

–300

–350

–400 2.5 3.5 4.5 5.5

TEMPERATURE (°C)

–50

V

FLOAT

(V)

V

FLOAT

(V)

V

FLOAT

(V)

100

4054 G07

050

4.26

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10 –25 25 75

4.215

4.210

4.205

4.200

4.195

4.190

4.185

4054 G08

I

BAT

(mA)

0100 200 300 400 500 700600

V

CC

(V)

4.0

4.215

4.210

4.205

4.200

4.195

4.190

4.185 4.5 5.0 5.5 6.0

4054 G09

6.5 7.0

TEMPERATURE (°C)

–50

I

CHRG

(mA)

100

4054 G11

050

20

18

16

14

12

10

8

6

4–25 25 75 125 0

22

20

18

16

14

12

10

835

4054 G12

12 467

V

CHRG

(V)

0

I

CHRG

(mA)

25

20

15

10

5

0245

4054 G10

1367

V

BAT

= 4.3V

V

PROG

= 0V

V

CC

= 5V

V

BAT

= 4.3V

T

A

= 25°C

V

CC

= 5V

V

BAT

= 4.3V

T

A

= 25°C

V

CC

= 6.5V

V

CC

= 4.2V

V

CC

= 5V

T

A

= 25°C

R

PROG

= 1.25k

V

CC

= 5V

R

PROG

= 10k T

A

= 25°C

R

PROG

= 10k

V

CC

= 5V

V

BAT

= 4V

T

A

= 25°C

V

CC

= 5V

V

BAT

= 4.3V

T

A

= 25°C

V

CC

= 5V

V

BAT

= 4V

V

CHRG

= 1V

V

CHRG

(V)

I

CHRG

(µA)

TYPICAL PERFOR A CE CHARACTERISTICS

UW

PROG Pin Pull-Up Current vs

Temperature and Supply Voltage PROG Pin Current vs PROG Pin

Voltage (Pull-Up Current)

PROG Pin Current vs PROG Pin

Voltage (Clamp Current)

Regulated Output (Float) Voltage

vs Charge Current Regulated Output (Float) Voltage

vs Temperature

Regulated Output (Float) Voltage

vs Supply Voltage

CHRG Pin I-V Curve

(Strong Pull-Down State) CHRG Pin Current vs Temperature

(Strong Pull-Down State)

CHRG Pin I-V Curve

(Weak Pull-Down State)

5

LTC4054-4.2/LTC4054X-4.2

405442xf

TEMPERATURE (°C)

–50 –25 0 25 50 75 100

TEMPERATURE (°C)

–50

I

CHRG

(µA)

28

25

23

19

16

13

10 –25 02550

4054 G13

75 100

TEMPERATURE (°C)

–50 –25 0 25 50 75 100

I

TRIKL

(mA)

I

TRIKL

(mA)

50

40

30

20

10

0

4054 G14

V

CC

(V)

4.0

50

40

30

20

10

04.5 5.0 5.5 6.0

4054 G15

6.5 7.0

V

TRIKL

(V)

4054 G16

3.000

2.975

2.950

2.925

2.900

2.875

2.850

2.825

2.800

V

BAT

(V)

2.7 3.0

I

BAT

(mA)

I

BAT

(mA)

3.3 3.93.6 4.2 4.5

4054 G17

600

500

400

300

200

100

0

I

BAT

(mA)

600

500

400

300

200

100

0

V

CC

(V)

4.0

600

500

400

300

200

100

04.5 5.0 5.5 6.0

4054 G18

6.5 7.0

V

RECHRG

(V)

4.11

4.09

4.07

4.05

4.03

4.01

3.99

4054 G20

TEMPERATURE (°C)

–50 25 75

4054 G19

–25 0 50 100 125

TEMPERATURE (°C)

–50 25 75

–25 0 50 100 –50 25 75

–25 0 50 100 125

TEMPERATURE (°C)

R

DS(ON)

(mΩ)

700

650

600

550

500

450

400

350

4054 G21

V

CC

= 5V

V

BAT

= 4.3V

V

CHRG

= 5V

V

CC

= 5V

V

BAT

= 2.5V V

BAT

= 2.5V

T

A

= 25°C

V

BAT

= 4V

T

A

= 25°C

θ

JA

= 80°C/W

ONSET OF

THERMAL

REGULATION

V

CC

= 5V

θ

JA

= 125°C/W

R

PROG

= 2k

V

CC

= 5V

R

PROG

= 10k

V

CC

= 5V

V

BAT

= 4V

θ

JA

= 80°C/W

V

CC

= 5V

R

PROG

= 10k

V

CC

= 4.2V

I

BAT

= 100mA

R

PROG

= 2k

R

PROG

= 2k

R

PROG

= 10k R

PROG

= 10k

R

PROG

= 2k

R

PROG

= 10k

R

PROG

= 2k

R

PROG

= 10k

R

PROG

= 2k

T

A

= 40°C

T

A

= 25°C

T

A

= 0°C

ONSET OF

THERMAL

REGULATION

TYPICAL PERFOR A CE CHARACTERISTICS

UW

CHRG Pin Current vs Temperature

(Weak Pull-Down State) Trickle Charge Current

vs Temperature

Trickle Charge Current vs

Supply Voltage

Trickle Charge Threshold vs

Temperature Charge Current vs Battery Voltage Charge Current vs Supply Voltage

Charge Current vs Ambient

Temperature Recharge Voltage Threshold

vs Temperature

Power FET “ON” Resistance

vs Temperature

6

LTC4054-4.2/LTC4054X-4.2

405442xf

UU

U

PI FU CTIO S

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.

GND (Pin 2): Ground.

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

CC

can range from 4.25V to 6.5V

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

When V

CC

drops to within 30mV of the BAT pin voltage, the

LTC4054 enters shutdown mode, dropping I

BAT

to less

than 2µA.

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

Monitor and Shutdown Pin. The charge current is pro-

grammed by connecting a 1% resistor, RPROG, to ground.

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:

IBAT = (VPROG/RPROG) • 1000

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

the 1.21V shutdown threshold voltage, the charger enters

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 RPROG to ground will return the charger to

normal operation.

7

LTC4054-4.2/LTC4054X-4.2

405442xf

BLOCK DIAGRA

W

–

+

–

+

–

+

–

+

–

+

3

4

–

+

120°C

T

DIE

T

A

MA

CA

C1

C2

1×1000×

VA

R1

BAT

R2

R3

1V

0.1V

R4

R5

PROG

3µA

5µA

V

CC

R

PROG

REF

1.21V

SHDN

V

CC

STANDBY

CHRG

1

5GND

405442 BD

2

C3

2.9V

TO

BAT

TRICKLE CHARGE

DISABLED ON

LTC4054X

8

LTC4054-4.2/LTC4054X-4.2

405442xf

OPERATIO

U

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.

Normal Charge Cycle

A charge cycle begins when the voltage at the V

CC

pin rises

above the UVLO threshold level and a 1% program resistor

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 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

pin approaches the final float voltage (4.2V), the LTC4054

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.

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:

RV

IIV

R

PROG CHG CHG PROG

==

1000 1000

,

The charge current out of the BAT pin can be determined

at any time by monitoring the PROG pin voltage using the

following equation:

IV

R

BAT PROG

PROG

=•1000

Charge Termination

A charge cycle is terminated when the charge current falls

to 1/10th the programmed value after the final float voltage

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

filtered comparator to monitor the PROG pin. When the

PROG pin voltage falls below 100mV

1

for 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).

When charging, transient loads on the BAT pin can cause

the PROG pin to fall below 100mV for short periods of time

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

the charge cycle and ceases to provide any current through

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

supplied by the battery.

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

manually restart a charge cycle when in standby mode, 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.

Charge Status Indicator (CHRG)

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

Note 1:

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

from terminating a charge cycle.

9

LTC4054-4.2/LTC4054X-4.2

405442xf

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

CC

is 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

is within 100mV of the BAT pin voltage or insufficient voltage

is applied to the V

CC

pin.

Automatic Recharge

Once the charge cycle is terminated, the LTC4054 continu-

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 a strong pull-

down state during recharge cycles.

OPERATIO

U

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

undervoltage lockout mode: either V

CC

is less than 100mV

above the BAT pin voltage or insufficient voltage is applied

to the V

CC

pin. A microprocessor can be used to distin-

guish between these three states—this method is dis-

cussed in the Applications Information section.

Thermal Limiting

An internal thermal feedback loop reduces the programmed

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

capability of a given circuit board without risk of damaging

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-

erations are discussed further in the Applications Informa-

tion section.

Undervoltage Lockout (UVLO)

An internal undervoltage lockout circuit monitors the input

voltage and keeps the charger in shutdown mode until V

CC

rises above the undervoltage lockout threshold. The UVLO

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

CC

rises 100mV above the battery

voltage.

Manual Shutdown

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

into shutdown mode by removing R

PROG

thus floating the

PROG pin. This reduces the battery drain current to less

TRICKLE CHARGE

MODE

1/10TH FULL CURRENT

BAT > 2.9V

BAT < 2.9V

BAT > 2.9V

CHRG: STRONG

PULL-DOWN

CHARGE MODE

FULL CURRENT

CHRG: STRONG

PULL-DOWN

SHUTDOWN MODE

CHRG: Hi-Z IN UVLO

WEAK PULL-DOWN

OTHERWISE

PROG

RECONNECTED

OR

UVLO CONDITION

STOPS

PROG FLOATED

OR

UVLO CONDITION

I

CC

DROPS TO <25µA

POWER ON

PROG < 100mV

STANDBY MODE

NO CHARGE CURRENT

CHRG: WEAK

PULL-DOWN

2.9V < BAT < 4.05V

405442 F01

Figure 1. State Diagram of a Typical Charge Cycle

10

LTC4054-4.2/LTC4054X-4.2

405442xf

APPLICATIO S I FOR ATIO

WUUU

Stability Considerations

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.

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

resistance value for R

PROG

:

RC

PROG PROG

≤π

1

210

5

••

Average, rather than instantaneous, charge current may

be of interest to the user. For example, if a switching power

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.

Power Dissipation

The conditions that cause the LTC4054 to reduce charge

current through thermal feedback can be approximated by

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:

P

D

= (V

CC

– V

BAT

) • I

BAT

where P

D

is the power dissipated, V

CC

is the input supply

voltage, V

BAT

is the battery voltage and I

BAT

is the charge

current. The approximate ambient temperature at which

the thermal feedback begins to protect the IC is:

T

A

= 120°C – P

D

θ

JA

T

A

= 120°C – (V

CC

– V

BAT

) • I

BAT

• θ

JA

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-

ing θ

JA

is 150°C/W (see Board Layout Considerations), the

ambient temperature at which the LTC4054 will begin to

reduce the charge current is approximately:

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

PROG

10k

R

PROG

C

FILTER

405442 F02

CHARGE

CURRENT

MONITOR

CIRCUITRY

LTC4054

GND

Figure 2. Isolating Capacitive Load on PROG Pin and Filtering

11

LTC4054-4.2/LTC4054X-4.2

405442xf

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*)

COPPER AREA BOARD THERMAL RESISTANCE

TOPSIDE BACKSIDE AREA JUNCTION-TO-AMBIENT

2500mm

2

2500mm

2

2500mm

2

125°C/W

1000mm

2

2500mm

2

2500mm

2

125°C/W

225mm

2

2500mm

2

2500mm

2

130°C/W

100mm

2

2500mm

2

2500mm

2

135°C/W

50mm

2

2500mm

2

2500mm

2

150°C/W

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

COPPER AREA BOARD THERMAL RESISTANCE

(EACH SIDE) AREA JUNCTION-TO-AMBIENT

2500mm

2***

2500mm

2

80°C/W

Increasing Thermal Regulation Current

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

dissipating some of the power through an external compo-

nent, such as a resistor or diode.

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

JA

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

ambient temperature of 25°C is:

ICC

VVCWmA

BAT =°°

°=

120 25

5 3 75 125 608

–

(–. )• /

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

ICC

VIR V

BAT S BAT CC BAT JA

=°°120 25–

(– – )•θ

APPLICATIO S I FOR ATIO

WUUU

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:

ICT

VV

BAT A

CC BAT JA

=°

()

120 –

–•θ

Using the previous example with an ambient temperature

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

mately:

ICC

VV CW

C

CA

ImA

BAT

BAT

=°°

()

°=°

°

=

120 60

5 3 75 150

60

187 5

320

–

–. • / ./

Moreover, when thermal feedback reduces the charge

current, the voltage at the PROG pin is also reduced

proportionally as discussed in the Operation section.

It is important to remember that LTC4054 applications do

not need to be designed for worst-case thermal conditions

since the IC will automatically reduce power dissipation

when the junction temperature reaches approximately

120°C.

Thermal Considerations

Because of the small size of the ThinSOT package, it is very

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

overall temperature rise and the maximum charge current.

*Each layer uses one ounce copper

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

**10,000mm

2

total copper area

12

LTC4054-4.2/LTC4054X-4.2

405442xf

APPLICATIO S I FOR ATIO

WUUU

Solving for I

BAT

using the quadratic formula

2

.

I

VV VV RCT

R

BAT

S BAT S BAT CC A

JA

CC

=

°











(– )– (– ) (–)

24 120

2

θ

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:

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

CC

becomes low

R

CC

(Ω)

0

CHARGE CURRENT (mA)

1000

800

600

400

200

00.5 1.0 1.25

405442 F04

0.25 0.75 1.5 1.75

CONSTANT

CURRENT

V

BAT

= 3.75V

T

A

= 25°C

θ

JA

= 125°C/W

R

PROG

= 1.25kΩ

THERMAL

MODE

DROPOUT

V

S

= 5.25V

V

S

= 5.5V

V

S

= 5V

Figure 4. Charge Current vs RCC

enough to put the LTC4054 into dropout. Figure 4 shows

how this circuit can result in dropout as R

CC

becomes

large.

This technique works best when R

CC

values are minimized

to keep component size small and avoid dropout. Remem-

ber to choose a resistor with adequate power handling

capability.

V

CC

Bypass Capacitor

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 capaci-

tors, high voltage transients 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.

Charge Current Soft-Start

The LTC4054 includes a soft-start circuit to minimize the

inrush current at the start of a charge cycle. When a charge

cycle is initiated, the charge current ramps from zero to the

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.

Note 2: Large values of R

CC

will result in no solution for I

BAT

. This indicates that the LTC4054

will not generate enough heat to require thermal regulation.

Figure 3. A Circuit to Maximize Thermal Mode Charge Current

V

CC

R

PROG

R

CC

Li-Ion

CELL

405442 F03

LTC4054-4.2

1µF

V

S

BAT

PROG

GND

13

LTC4054-4.2/LTC4054X-4.2

405442xf

Figure 5. Using a Microprocessor to Determine CHRG State

CHRG Status Output Pin

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

CC

to 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.

APPLICATIO S I FOR ATIO

WUUU

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-

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

Figure 6. Low Loss Input Reverse Polarity Protection

V

IN

V

CC

LTC4054

DRAIN-BULK

DIODE OF FET

4054 F06

CHRG OUT

IN

2k

800k

405442 F05

LTC4054 µPROCESSOR

V

+

V

DD

V

CC

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. To determine if there is a weak pull-down current,

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.

Reverse Polarity Input Voltage Protection

In some applications, protection from reverse polarity

voltage on V

CC

is 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).

14

LTC4054-4.2/LTC4054X-4.2

405442xf

USB and Wall Adapter Power

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, is used to prevent back conducting into the

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.

Typically a wall adapter can supply more current than the

500mA-limited USB port. Therefore, an N-channel MOSFET,

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

+

LTC4054-4.2

BAT

PROG

VCC

D1

5V WALL

ADAPTER

600mA ICHG

USB POWER

500mA ICHG

ICHG SYSTEM

LOAD

Li-Ion

BATTERY

MP1

1k 10k 2k

MN1

4

3

5

405442 F07

APPLICATIO S I FOR ATIO

WUUU

15

LTC4054-4.2/LTC4054X-4.2

405442xf

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

1.50 – 1.75

(NOTE 4)

2.80 BSC

0.30 – 0.45 TYP

5 PLCS (NOTE 3)

DATUM ‘A’

0.09 – 0.20

(NOTE 3)

S5 TSOT-23 0302

PIN ONE

2.90 BSC

(NOTE 4)

0.95 BSC

1.90 BSC

0.80 – 0.90

1.00 MAX 0.01 – 0.10

0.20 BSC

0.30 – 0.50 REF

NOTE:

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

3.85 MAX

0.62

MAX 0.95

REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

1.4 MIN

2.62 REF

1.22 REF

U

PACKAGE DESCRIPTIO

16

LTC4054-4.2/LTC4054X-4.2

405442xf

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 Monolithic Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, Up to 1.5A Charge Current

LTC1734 Lithium-Ion Linear Battery Charger in ThinSOT Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed

LTC1734L Lithium-Ion Linear Battery Charger in ThinSOT Low Current Version of LTC1734

LTC1998 Lithium-Ion Low Battery Detector 1% Accurate 2.5µA Quiescent Current, SOT-23

LTC4050 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 Monolithic Lithium-Ion Battery Pulse Charger No Blocking Diode or External Power FET Required

LTC4053 USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current

LTC4054L 10mA to 150mA Standalone Monolithic Lithium-Ion Low Current Version of LTC4054

Linear Battery Charger in ThinSOT

LTC4056 Standalone Lithium-Ion Linear Battery Charger Standalone Charger with Programmable Timer, No Blocking Diode,

in ThinSOT No Sense Resistor Needed

LTC4057 Monolithic Lithium-Ion Linear Battery Charger No External MOSFET, Sense Resistor or Blocking Diode Required,

with Thermal Regulation in ThinSOT Charge Current Monitor for Gas Gauging

LTC4410 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

LT/TP 0903 1K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2003

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

●

FAX: (408) 434-0507

●

www.linear.com

RELATED PARTS

+

LTC4054-4.2

PROG

V

CC

5V WALL

ADAPTER

USB

POWER

Li-Ion

CELL

1k 10k

2.5k

4

3

5

2

405442 TA05

GND

1µF

100mA/

500mA

µC

BAT

I

BAT

USB/Wall Adapter Power Li-Ion Charger

800mA Li-Ion Charger with External Power Dissipation

V

CC

0.25Ω

1µFLTC4054-4.2

BAT

800mA

405442 TA03

PROG

1.25k

V

IN

= 5V

GND

+

43

2

5

V

CC

1µF

LTC4054-4.2

BAT

405442 TA04

PROG

2k

5V WALL

ADAPTER

GND

43

2

5

+

500mA

Basic Li-Ion Charger with Reverse Polarity Input Protection

VCC

330Ω

1µF

LTC4054-4.2

BAT

405442 TA02

PROG

2k

VIN = 5V

GND +

4

3

2

5

CHRG

SHDN

1

500mA

Full Featured Single Cell Li-Ion Charger

TYPICAL APPLICATIO S

U

www.s-manuals.com