Datasheet LTC4054XES5-4.2 Datasheet (Linear) [ru]

FEATURES

■

Programmable Charge Current Up to 800mA

■

No MOSFET, Sense Resistor or Blocking
Diode Required

■

Complete Linear Charger in ThinSOTTM 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

U

APPLICATIO S

■

Cellular Telephones, PDAs, MP3 Players

■

Charging Docks and Cradles

■

Bluetooth Applications

LTC4054-4.2/LTC4054X-4.2

Standalone Linear

Li-Ion Battery Charger with

Thermal Regulation in ThinSOT

U

DESCRIPTIO

The LTC®4054 is a complete constant-current/constant­voltage 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.

, 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

TYPICAL APPLICATIO

600mA Single Cell Li-Ion Charger

V

IN

4.5V TO 6.5V

1µF

4

V

CC

LTC4054-4.2

PROG

GND

2

BAT

3

5

1.65k

U

600mA

4.2V
Li-Ion
BATTERY

405442 TA01a

Complete Charge Cycle (750mAh Battery)

700

CONSTANT

CURRENT

600

CONSTANT
POWER

500

400

300

200

CHARGE CURRENT (mA)

VCC = 5V

= 130°C/W

θ

JA

100

R

= 1.65k

PROG

= 25°C

T

A

0

0.5 1.0 2.0

0.25 0.75 1.25 1.75

0

TIME (HOURS)

CHARGE

TERMINATED

CONSTANT

VOLTAGE

1.5

4.75

4.50

BATTERY VOLTAGE (V)

4.25

4.00

3.75

3.50

3.25

3.00

405442 TAO1b

405442xf

1

LTC4054-4.2/LTC4054X-4.2

PACKAGE/ORDER I FOR ATIO

UU

W

CHRG 1

GND 2

TOP VIEW

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

BAT 3

5 PROG

4 V

CC

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

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

PROG............................................. –0.3V to VCC + 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

ORDER PART

NUMBER

LTC4054ES5-4.2
LTC4054XES5-4.2

S5 PART MARKING

T

= 125°C, (θJA = 80°C/ W TO

JMAX

150°C/W DEPENDING ON PC BOARD LAYOUT)

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

(N0TE 3)

LTH7
LTADY

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

I

CC

V

FLOAT

I

BAT

I

TRIKL

V

TRIKL

V

TRHYS

V

UV

V

UVHYS

V

MSD

V

ASD

I

TERM

V

PROG

I

CHRG

V

CHRG

∆V

RECHRG

Input Supply Voltage ● 4.25 6.5 V
Input Supply Current Charge Mode (Note 4), R

Standby Mode (Charge Terminated)
Shutdown Mode (R

< V

V

CC

BAT

Regulated Output (Float) Voltage 0°C ≤ TA ≤ 85°C, I
BAT Pin Current R

Trickle Charge Current V
Trickle Charge Threshold Voltage R
Trickle Charge Hysteresis Voltage R
VCC Undervoltage Lockout Threshold From VCC Low to High ● 3.7 3.8 3.92 V
VCC Undervoltage Lockout Hysteresis ● 150 200 300 mV
Manual Shutdown Threshold Voltage PROG Pin Rising ● 1.15 1.21 1.30 V

VCC – V

C/10 Termination Current Threshold R

PROG Pin Voltage R
CHRG Pin Weak Pull-Down Current V
CHRG Pin Output Low Voltage I
Recharge Battery Threshold Voltage V

Lockout Threshold Voltage VCC from Low to High 70 100 140 mV

BAT

= 10k, Current Mode ● 93 100 107 mA

PROG

R

= 2k, Current Mode ● 465 500 535 mA

PROG

Standby Mode, V
Shutdown Mode (R
Sleep Mode, V

< V

BAT

TRIKL

= 10k, V

PROG

= 10k (Note 5) 60 80 110 mV

PROG

PROG Pin Falling

V

from High to Low 5 30 50 mV

CC

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

PROG

= 2k ● 0.085 0.10 0.115 mA/mA

R

PROG

= 10k, Current Mode ● 0.93 1.0 1.07 V

PROG

= 5V 8 20 35 µA

CHRG

= 5mA 0.35 0.6 V

CHRG

- V

FLOAT

RECHRG

PROG

, or VCC < VUV)

BAT

= 4.2V ● 0 –2.5 –6 µA

BAT

PROG

= 0V ±1 ±2 µA

CC

, R

PROG

Rising (Note 5) 2.8 2.9 3.0 V

BAT

= 10k ● 300 2000 µA

PROG

Not Connected, ● 25 50 µA

= 40mA 4.158 4.2 4.242 V

Not Connected) ±1 ±2 µA

= 2k (Note 5) ● 20 45 70 mA

● 200 500 µA

● 0.9 1.0 1.1 V

100 150 200 mV

2

405442xf

LTC4054-4.2/LTC4054X-4.2

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

T

LIM

Junction Temperature in Constant 120 °C
Temperature Mode

R

ON

t

SS

t

RECHARGE

t

TERM

I

PROG

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.

Power FET “ON” Resistance 600 mΩ
(Between V

Soft-Start Time I
Recharge Comparator Filter Time V
Termination Comparator Filter Time I

and BAT)

CC

= 0 to I

BAT

High to Low 0.75 2 4.5 ms

BAT

Falling Below I

BAT

=1000V/R

BAT

PROG

/10 400 1000 2500 µs

CHG

100 µs

PROG Pin Pull-Up Current 3 µA

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

is expressed as a fraction of measured full charge current

TERM

with indicated PROG resistor.

Note 3: See Thermal Considerations.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

PROG Pin Voltage vs Supply
Voltage(Constant Current Mode)

1.015
VCC = 5V

= 4V

V

BAT

1.010

T

= 25°C

A

= 10k

R

PROG

1.005

(V)

1.000

PROG

V

0.995

0.990

0.985

4.0

5.0 5.5 6.0

4.5
VCC (V)

6.5 7.0

4054 G01

PROG Pin Voltage vs
Temperature

1.0100
VCC = 5V

= 4V

V

1.0075

1.0050

1.0025

(V)

1.0000

PROG

V

0.9975

0.9950

0.9925

0.9900

BAT

R

= 10k

PROG

–50 –25 0 5025

TEMPERATURE (°C)

Charge Current vs
PROG Pin Voltage

600

VCC = 5V

= 25°C

T

A

500

R

= 2k

PROG

400

(mA)

300

BAT

I

200

100

75

100

4054 G02

0

0.25 0.50 0.75 1.00

0

V

PROG

(V)

1.25

4054 G03

405442xf

3

LTC4054-4.2/LTC4054X-4.2

UW

TYPICAL PERFOR A CE CHARACTERISTICS

PROG Pin Pull-Up Current vs
Temperature and Supply Voltage

3.7
V

= 4.3V

BAT

= 0V

V

PROG

3.5

3.3

(µA)

3.1

2.9

2.7

2.5

–50

VCC = 6.5V

–25 0

50 100 125

25 75

TEMPERATURE (°C)

PROG

I

Regulated Output (Float) Voltage
vs Charge Current

4.26
VCC = 5V

4.24

= 25°C

T

A

= 1.25k

R

PROG

4.22

4.20

(V)

4.18

FLOAT

V

4.16

4.14

4.12

4.10

0

200 300 400 500 700600

100

I

(mA)

BAT

VCC = 4.2V

4054 G04

4054 G07

PROG Pin Current vs PROG Pin
Voltage (Pull-Up Current)

3.5

3.0

2.5

2.0

(µA)

1.5

PROG

I

1.0

VCC = 5V

0.5
= 4.3V

V

BAT

= 25°C

T

A

0

2.0

2.2 2.3 2.4 2.5 2.6

2.1

V

PROG

(V)

Regulated Output (Float) Voltage
vs Temperature

4.215
VCC = 5V

= 10k

R

PROG

4.210

4.205

(V)

4.200

FLOAT

V

4.195

4.190

4.185

–50

050

–25 25 75

TEMPERATURE (°C)

4054 G05

4054 G08

100

PROG Pin Current vs PROG Pin
Voltage (Clamp Current)

0

–50

–100

–150

(µA)

–200

PROG

I

–250

–300

VCC = 5V

–350

–400

= 4.3V

V

BAT

= 25°C

T

A

3.0 4.0

2.5 3.5 4.5 5.5

2.0
(V)

V

PROG

Regulated Output (Float) Voltage
vs Supply Voltage

4.215
TA = 25°C

= 10k

R

PROG

4.210

4.205

(V)

4.200

FLOAT

V

4.195

4.190

4.185

4.0

5.0 5.5 6.0

4.5
VCC (V)

5.0

4054 G06

6.5 7.0

4054 G09

CHRG Pin I-V Curve
(Strong Pull-Down State)

25

20

15

(mA)

CHRG

10

I

5

0

0

2

1

4

V

3

CHRG

4

(V)

VCC = 5V
V

BAT

T

A

5

= 4V

= 25°C

6

4054 G10

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

20

VCC = 5V

= 4V

V

18

BAT

= 1V

V

CHRG

16

14

(mA)

12

CHRG

I

10

8

6

7

4

–50

050

–25 25 75 125

TEMPERATURE (°C)

100

4054 G11

CHRG Pin I-V Curve
(Weak Pull-Down State)

22

20

18

16

(µA)

14

CHRG

I

12

10

8

0

12

V

VCC = 5V

= 4.3V

V

BAT

= 25°C

T

A

467

35

(V)

CHRG

4054 G12

405442xf

LTC4054-4.2/LTC4054X-4.2

UW

TYPICAL PERFOR A CE CHARACTERISTICS

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

28

VCC = 5V

= 4.3V

V

BAT

(µA)

CHRG

I

25

23

19

16

13

10

–50

V

CHRG

= 5V

–25

02550

TEMPERATURE (°C)

Trickle Charge Threshold vs
Temperature

3.000
VCC = 5V

= 10k

R

2.975

PROG

2.950

2.925

(V)

2.900

TRIKL

V

2.875

2.850

2.825

2.800

–50

0 25 50 75 100

–25

TEMPERATURE (°C)

75 100

4054 G13

4054 G16

Trickle Charge Current
vs Temperature

50

R

= 2k

PROG

40

30

(mA)

TRIKL

20

I

10

0

–50

R

PROG

0 25 50 75 100

–25

TEMPERATURE (°C)

= 10k

VCC = 5V
V

Charge Current vs Battery Voltage

600

500

400

(mA)

300

BAT

I

200

100

0

2.7 3.0

TA = 0°C

3.3 3.93.6

TA = 40°C

TA = 25°C

VCC = 5V

= 125°C/W

θ

JA

R

PROG

V

(V)

BAT

= 2k

BAT

= 2.5V

4054 G14

4.2

4054 G17

4.5

Trickle Charge Current vs
Supply Voltage

50

R

= 2k

PROG

40

30

(mA)

TRIKL

20

I

10

0

4.5 5.0 5.5 6.0

4.0

R

PROG

= 10k

VCC (V)

Charge Current vs Supply Voltage

600

R

= 2k

500

400

(mA)

300

BAT

I

200

100

V

= 4V

BAT

= 25°C

T

A

= 80°C/W

θ

JA

0

4.0

4.5

PROG

R

= 10k

PROG

5.0 5.5 6.0
VCC (V)

ONSET OF
THERMAL
REGULATION

V

BAT

T

A

= 25°C

= 2.5V

6.5 7.0

4054 G15

6.5 7.0

4054 G18

Charge Current vs Ambient
Temperature

600

R

= 2k

= 4V

BAT

= 80°C/W

JA

–25 0

PROG

REGULATION

R

= 10k

PROG

TEMPERATURE (°C)

500

400

VCC = 5V

(mA)

V

300

θ

BAT

I

200

100

0

–50 25 75

ONSET OF
THERMAL

50 100 125

4054 G19

Recharge Voltage Threshold
vs Temperature

4.11
VCC = 5V

= 10k

R

PROG

4.09

4.07

(V)

4.05

RECHRG

V

4.03

4.01

3.99

–50 25 75

–25 0

TEMPERATURE (°C)

50 100

4054 G20

Power FET “ON” Resistance
vs Temperature

700

VCC = 4.2V

= 100mA

I

BAT

650

600

550

(mΩ)

500

DS(ON)

R

450

400

350

= 2k

R

PROG

–50 25 75

–25 0

TEMPERATURE (°C)

50 100 125

4054 G21

405442xf

5

LTC4054-4.2/LTC4054X-4.2

U

UU

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.

VCC (Pin 4): Positive Input Supply Voltage. Provides
power to the charger. VCC can range from 4.25V to 6.5V
and should be bypassed with at least a 1µF capacitor.
When VCC drops to within 30mV of the BAT pin voltage, the
LTC4054 enters shutdown mode, dropping I
than 2µA.

BAT

to less

PROG (Pin 5): Charge Current Program, Charge Current
Monitor and Shutdown Pin. The charge current is pro­grammed by connecting a 1% resistor, R
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:

I

= (V

BAT

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 R
normal operation.

PROG/RPROG

PROG

) • 1000

to ground will return the charger to

, to ground.

PROG

6

405442xf

BLOCK DIAGRA

120°C

T

DIE

W

T

A

SHDN

LTC4054-4.2/LTC4054X-4.2

4

V

CC

1×

–

+

MA

+

CA

+

–

VA

–

–

C1

+

R3

1V

R4

REF

1.21V

5µA

1000×

BAT

R1

R2

3

3µA

0.1V

R5

V

CC

GND

2

R

PROG

405442 BD

+

CHRG

1

STANDBY

TRICKLE CHARGE

DISABLED ON

LTC4054X

C2

–

TO

+

C3

BAT

2.9V

–

PROG

5

405442xf

7

LTC4054-4.2/LTC4054X-4.2

U

OPERATIO

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 com­ponents. Furthermore, the LTC4054 is capable of operat­ing from a USB power source.

Normal Charge Cycle

A charge cycle begins when the voltage at the VCC 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 volt­age 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:

V

I

BAT

PROG

= •1000

R

PROG

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 100mV1 for longer than
t

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

TERM

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 termi­nation. 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 be­gins 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.

R

V

PROG

I

CHG

1000 1000

==

I

,

CHG

R

PROG

V

The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage using the
following equation:

8

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.

405442xf

OPERATIO

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

LTC4054-4.2/LTC4054X-4.2

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 VCC is less than 100mV
above the BAT pin voltage or insufficient voltage is applied
to the VCC pin. A microprocessor can be used to distin­guish between these three states—this method is dis­cussed 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 consid­erations are discussed further 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 VCC 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 VCC pin.

Automatic Recharge

Once the charge cycle is terminated, the LTC4054 continu­ously monitors the voltage on the BAT pin using a com­parator 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 capac­ity). 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 pull­down state during recharge cycles.

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 VCC 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 pin. This reduces the battery drain current to less

thus floating the

PROG

Figure 1. State Diagram of a Typical Charge Cycle

405442xf

9

LTC4054-4.2/LTC4054X-4.2

WUUU

APPLICATIO S I FOR ATIO

Stability Considerations

The constant-voltage mode feedback loop is stable with­out 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 recom­mended 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. 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, C

PROG

, the
following equation can be used to calculate the maximum
resistance value for R

R

PROG

≤

π1210

5

••

PROG

C

PROG

:

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.

R

10k

PROG

405442 F02

PROG

LTC4054

GND

Figure 2. Isolating Capacitive Load on PROG Pin and Filtering

C

FILTER

CHARGE
CURRENT
MONITOR
CIRCUITRY

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:

PD = (VCC – V

BAT

) • I

BAT

where PD is the power dissipated, VCC is the input supply
voltage, V

is the battery voltage and I

BAT

is the charge

BAT

current. The approximate ambient temperature at which
the thermal feedback begins to protect the IC is:

TA = 120°C – PDθ
TA = 120°C – (VCC – V

JA

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. Assum­ing θJA is 150°C/W (see Board Layout Considerations), the
ambient temperature at which the LTC4054 will begin to
reduce the charge current is approximately:

TA = 120°C – (5V – 3.75V) • (400mA) • 150°C/W
TA = 120°C – 0.5W • 150°C/W = 120°C – 75°C
TA = 45°C

10

405442xf

WUUU

APPLICATIO S I FOR ATIO

LTC4054-4.2/LTC4054X-4.2

The LTC4054 can be used above 45°C ambient, but the
charge current will be reduced from 400mA. The approxi­mate current at a given ambient temperature can be
approximated by:

I

BAT

120 –

=

VV

–•θ

CC BAT JA

()

A

CT

°

Using the previous example with an ambient temperature
of 60°C, the charge current will be reduced to approxi­mately:

CC

°°

I

=

BAT

=

ImA

BAT

120 60

VV CW

5 3 75 150

–. • /

()

320

–

=

°

60

187 5

./

°

°

C

CA

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.

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

2

2

2

2

2

125°C/W
125°C/W
130°C/W
135°C/W
150°C/W

80°C/W

2500mm22500mm22500mm
1000mm22500mm22500mm

225mm22500mm22500mm
100mm22500mm22500mm

2

50mm

*Each layer uses one ounce copper

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

COPPER AREA BOARD THERMAL RESISTANCE

*Top and bottom layers use two ounce copper, inner layers use one ounce copper.
**10,000mm

2500mm22500mm

(EACH SIDE) AREA JUNCTION-TO-AMBIENT

2500mm

2***

2

total copper area

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 compo­nent, 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. Assum­ing θJA is 125°C/W, the approximate charge current at an
ambient temperature of 25°C is:

I

BAT

=

120 25

VVCW

5 3 75 125

(–. )• /

–

=

608

mA

°

CC

°°

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 ther­mally regulated charge current

CC

I

BAT

=

VIR V

(– – )•θ

S BAT CC BAT JA

°°120 25–

405442xf

11

LTC4054-4.2/LTC4054X-4.2

WUUU

APPLICATIO S I FOR ATIO

V

S

R

CC

V

CC

BAT

LTC4054-4.2

1µF

GND

PROG

R

PROG

405442 F03

Li-Ion
CELL

Figure 3. A Circuit to Maximize Thermal Mode Charge Current

Solving for I

I

=

BAT

VV VV

(– )– (– )

S BAT S BAT

Using RCC = 0.25Ω, VS = 5V, V

using the quadratic formula2.

BAT






2

4 120

RCT

CC A

2

R

CC

= 3.75V, TA = 25°C and

BAT

°

(–)

θ

JA






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

charge current to be:

I

= 708.4mA

BAT

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 VCC becomes low

enough to put the LTC4054 into dropout. Figure 4 shows
how this circuit can result in dropout as RCC becomes
large.

This technique works best when RCC values are minimized
to keep component size small and avoid dropout. Remem­ber to choose a resistor with adequate power handling
capability.

VCC Bypass Capacitor

Many types of capacitors can be used for input bypassing,
however, caution must be exercised when using multi­layer 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 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 Applica­tion 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 RCC will result in no solution for I
will not generate enough heat to require thermal regulation.

BAT

12

1000

VS = 5V

800

600

THERMAL

MODE

0.25

VS = 5.25V

0.5

400

CHARGE CURRENT (mA)

200

0

0

Figure 4. Charge Current vs R

. This indicates that the LTC4054

CONSTANT

CURRENT

VS = 5.5V

1.0

0.75
RCC (Ω)

V

= 3.75V

BAT

= 25°C

T

A

= 125°C/W

θ

JA

R

PROG

1.25

DROPOUT

= 1.25kΩ

1.5

405442 F04

CC

1.75

405442xf

WUUU

V

IN

V

CC

LTC4054

DRAIN-BULK

DIODE OF FET

4054 F06

APPLICATIO S I FOR ATIO

LTC4054-4.2/LTC4054X-4.2

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 VCC 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.

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

+

V

V

CC

LTC4054 µPROCESSOR

CHRG OUT

Figure 5. Using a Microprocessor to Determine CHRG State

800k

2k

V

DD

IN

405442 F05

Figure 6. Low Loss Input Reverse Polarity Protection

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

405442xf

13

LTC4054-4.2/LTC4054X-4.2

+

LTC4054-4.2

BAT

PROG

V

CC

D1

5V WALL

ADAPTER

600mA I

CHG

USB POWER

500mA I

CHG

I

CHG

SYSTEM
LOAD

Li-Ion
BATTERY

MP1

1k

10k

2k

MN1

4

3

5

405442 F07

WUUU

APPLICATIO S I FOR ATIO

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

14

405442xf

PACKAGE DESCRIPTIO

LTC4054-4.2/LTC4054X-4.2

U

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

0.62

MAX

3.85 MAX

0.20 BSC

DATUM ‘A’

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

2.62 REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.30 – 0.50 REF

0.95
REF

1.22 REF

1.4 MIN

0.09 – 0.20
(NOTE 3)

2.80 BSC

1.50 – 1.75
(NOTE 4)

1.00 MAX

PIN ONE

0.95 BSC

0.80 – 0.90

2.90 BSC
(NOTE 4)

0.30 – 0.45 TYP
5 PLCS (NOTE 3)

0.01 – 0.10

1.90 BSC

S5 TSOT-23 0302

405442xf

15

LTC4054-4.2/LTC4054X-4.2

U

TYPICAL APPLICATIO S

USB/Wall Adapter Power Li-Ion Charger

I

5V WALL

ADAPTER

USB

POWER

BAT

LTC4054-4.2

4

V

CC

1µF

1k 10k

GND

PROG

2

BAT

3

+

Li-Ion
CELL

2.5k

5

800mA Li-Ion Charger with External Power Dissipation

VIN = 5V

1µF

0.25Ω

4

V

CC

LTC4054-4.2

GND

2

BAT

PROG

1.25k

800mA

3

5

+

405442 TA03

100mA/
500mA

µC

405442 TA05

Full Featured Single Cell Li-Ion Charger

VIN = 5V

3

5

1µF

500mA

+

2k

SHDN

405442 TA02

330Ω

LTC4054-4.2

1

CHRG

V

CC

GND

4

BAT

PROG

2

Basic Li-Ion Charger with Reverse Polarity Input Protection

5V WALL

ADAPTER

1µF

4

V

CC

LTC4054-4.2

GND

2

BAT

PROG

3

5

2k

500mA

+

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 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

405442xf

LT/TP 0903 1K • PRINTED IN USA

16

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear.com

 LINEAR TECHNOLOGY CORP ORATION 2003