Datasheet LTC4054-4.2, LTC4054X-4.2 Datasheet (LINEAR TECHNOLOGY)

Final Electrical Specifications

查询LTC4054供应商

LTC4054-4.2/LTC4054X-4.2

Standalone Linear

Li-Ion Battery Charger with

Thermal Regulation in ThinSOT

FEATURES

■

Programmable Charge Current Up to 800mA

■

No External 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

U

APPLICATIO S

■

Cellular Telephones, PDAs

■

Portable MP3 Players

■

Charging Docks and Cradles

■

Bluetooth Applications

U

February 2003

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 especially well-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 input voltage.

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

ThinSOT is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

600mA Single Cell Li-Ion Charger

4.5V TO 5.25V

1µF

LTC4054-4.2

U

Complete Charge Cycle (750mAh Battery)

700

600

V

IN

4

V

GND

3

CC

BAT

5

PROG

2

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.

1.65k

600mA

4.2V
Li-Ion
BATTERY

405442 TA01a

CONSTANT

500

POWER

400

300

200

CHARGE CURRENT (mA)

VCC = 5V

θ

JA

100

R

PROG

= 25°C

T

A

0

0.25 0.75 1.25 1.75

0

CONSTANT

CURRENT

CONSTANT

VOLTAGE

= 130°C/W

= 1.65k

0.5 1.0 2.0

CHARGE

TERMINATED

TIME (HOURS)

1.5

4.75

4.50

BATTERY VOLTAGE (V)

4.25

4.00

3.75

3.50

3.25

3.00

405442 TAO1b

405442i

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) ......................... –0.3 to 10V

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

BAT, CHRG ................................................. –0.3V to 7V

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

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

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

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

Operating 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

= 150°C, (θJA = 100°C/ W TO

JMAX

150°C/W DEPENDING ON PC BOARD LAYOUT)

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

(N0TE 4)

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 3), 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 R
Trickle Charge Hysteresis R
VCC Undervoltage Lockout Threshold From VCC Low to High ● 3.7 3.8 3.92 V
VCC Undervoltage Lockout Hysteresis ● 150 250 300 mV
Manual Shutdown Threshold 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 V

Lockout Threshold 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

< 2.9V, R

BAT

= 2k, V

PROG

= 2k (Note 6) 60 80 110 mV

PROG

PROG Pin Falling

V

from High to Low 5 30 50 mV

CC

= 10k (Note 5) ● 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

= 2k (Note 6) ● 20 45 70 mA

PROG

Rising (Note 6) 2.8 2.9 3.0 V

BAT

= 2k ● 1200 2000 µA

PROG

Not Connected, ● 25 50 µA

= 40mA 4.158 4.2 4.242 V

Not Connected) ±1 ±2 µA

● 200 500 µA

● 0.9 1.0 1.1 V

100 150 200 mV

2

405442i

LTC4054-4.2/LTC4054X-4.2

ELECTRICAL CHARACTERISTICS

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

T

LIM

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.

Junction Temperature in Constant 120 °C
Temperature Mode

Power FET “ON” Resistance Current Mode 600 mΩ
(Between V

Soft-Start Time I
Recharge Comparator Filter Time V
Termination Comparator Filter Time I
PROG Pin Pull-Up Current 3 µA

U

and BAT)

CC

UU

BAT

BAT

BAT

The ● denotes specifications which apply over the full operating

= 0 to I

High to Low 0.75 2 ms

Falling 400 1000 µs

=1000V/R

BAT

PROG

Note 3: Supply current includes PROG pin current but does not include
any current delivered to the battery through the BAT pin.

Note 4: See Thermal Considerations.
Note 5: I

with indicated PROG resistor.
Note 6: This parameter is not applicable to the LTC4054X.

is expressed as a fraction of measured full charge current

TERM

100 µs

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 to a high impedance
state.

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 and 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

BAT

to less

than 2µA.
PROG (Pin 5): Charge Current Program, Charge Current

Monitor and Shutdown Pin. The charge current is pro­grammed by connecting a 1% resistor, R

, to ground.

PROG

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

BAT

= (V

PROG/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 R

to ground will return the charger to

PROG

normal operation.

405442i

3

LTC4054-4.2/LTC4054X-4.2

W

BLOCK DIAGRA

120°C

T

A

T

DIE

CA

+

–

4

V

CC

1× 1000×

–

+

MA

5µA

+

VA

–

REF

1.21V

–

BAT

3

R1

R2

SHDN

CHRG

1

STANDBY

TRICKLE CHARGE

DISABLED ON

LTC4054X

C3

–

2.9V TO BAT

C1

+

+

C2

R3

1V

R4

0.1V

R5

–

V

CC

3µA

+

PROG

5

R

PROG

GND

405442 BD

2

4

405442i

OPERATIO

LTC4054-4.2/LTC4054X-4.2

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 three 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. 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:

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

V

I

BAT

PROG

= •1000

R

PROG

Charge Termination

The charge cycle terminates when the charge current falls
to 1/10th the programmed current. An internal compara­tor senses when the PROG pin voltage falls below 100mV

1

and puts the LTC4054 into standby mode. In standby
mode, the LTC4054 ceases to provide charge current to
the battery and the input supply current drops to 200µA.
If the battery voltage drops below 4.05V, a recharge cycle
will begin. To manually restart the charge cycle, the input
voltage must be removed and reapplied, or the charger
must be shut down and restarted by momentarily floating
the PROG pin.

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
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 within 100mV of
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.

R

PROG

V

1000 1000

==

I

CHRG

I

,

CHRG

R

PROG

V

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

from terminating a charge cycle.

405442i

5

LTC4054-4.2/LTC4054X-4.2

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 <30µA

POWER ON

PROG < 100mV

STANDBY MODE

NO CHARGE CURRENT

CHRG: WEAK

PULL-DOWN

2.9V < BAT < 4.05V

405442 F01

U

OPERATIO

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.

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.

Automatic Recharge

Once the charge cycle is terminated, the LTC4054 continu­ously monitors the voltage on the BAT pin. 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 conditon and eliminates the need for periodic
charge cycle initiations. CHRG output enters a strong pull­down state during recharge cycles.

Manual Shutdown

At any point in the charge cycle, the LTC4054 can be put
into shutdown mode by removing R

thus floating the

PROG

PROG pin. This reduces the battery drain current to less
than 2µA and the supply current to less than 50µA. A new
charge cycle can be initiated by reconnecting the program
resistor.

6

Figure 1. State Diagram of a Typical Charge Cycle

405442i

WUUU

R

C

PROG

PROG

≤

π1210

5

••

APPLICATIO S I FOR ATIO

LTC4054-4.2/LTC4054X-4.2

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,

R

10k

PROG

PROG

LTC4054

GND

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

:

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.

CHARGE
CURRENT
MONITOR
CIRCUITRY

C

FILTER

405442 F02

Figure 2. Isolating Capacitive Load on PROG Pin and Filtering

405442i

7

LTC4054-4.2/LTC4054X-4.2

WUUU

APPLICATIO S I FOR ATIO

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

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 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:

120 –

CT

°

I

BAT

=

–•θ

VV

()

CC BAT JA

A

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

I

=

BAT

=

ImA

BAT

120 60

5 3 75 150

–. • / . /

VV CWCCA

()

320

–

CC

°°

=

°

60

187 5

°

°

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 one ounce
copper.

Table 1. Measured Thermal Resistance

COPPER AREA BOARD THERMAL RESISTANCE

TOPSIDE* BACKSIDE AREA JUNCTION-TO-AMBIENT

2500mm22500mm22500mm
1000mm22500mm22500mm

225mm22500mm22500mm
100mm22500mm22500mm

2

50mm

*Device is mounted on topside

2500mm22500mm

2

2

2

2

2

125°C/W
125°C/W
130°C/W

135°C/W
150°C/W

405442i

8

WUUU

APPLICATIO S I FOR ATIO

LTC4054-4.2/LTC4054X-4.2

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–

Using RCC = 0.25Ω, VS = 5V, V

= 3.75V, TA = 25°C and

BAT

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.

1000

VS = 5V

800

600

400

THERMAL

MODE

CHARGE CURRENT (mA)

200

0

0

0.25

CONSTANT

CURRENT

VS = 5.25V

0.5

0.75

VS = 5.5V

RCC (Ω)

1.0

V

= 3.75V

BAT

= 25°C

T

A

= 125°C/W

θ

JA

R

PROG

1.25

DROPOUT

= 1.25kΩ

1.5

405442 F04

1.75

V

S

R

CC

V

CC

BAT

LTC4054-4.2

1µF

PROG

GND

Figure 3. A Circuit to Maximize Thermal Mode Charge Current

Solving for I

I

=

BAT

VV VV

(– )– (– )

S BAT S BAT

using the quadratic formula2.

BAT






2

2

R

CC

Li-Ion
CELL

R

PROG

405442 F03

4 120

RCT

CC A

°

(–)

θ

JA






Figure 4. Charge Current vs R

CC

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.

Note 2: Large values of RCC will result in no solution for I
will not generate enough heat to require thermal regulation.

. This indicates that the LTC4054

BAT

405442i

9

LTC4054-4.2/LTC4054X-4.2

WUUU

APPLICATIO S I FOR ATIO

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.

CHRG Status Output Pin

With no battery present, the CHRG pin can provide an
indication that the input voltage is present and it 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.

+

V

V

CC

LTC4054 µPROCESSOR

CHRG OUT

Figure 5. Using a Microprocessor to Determine CHRG State

800k

2k

V

DD

IN

405442 F05

10

405442i

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)

1.90 BSC

0.30 – 0.45 TYP
5 PLCS (NOTE 3)

0.01 – 0.10

S5 TSOT-23 0302

405442i

11

LTC4054-4.2/LTC4054X-4.2

U

TYPICAL APPLICATIO

Full Featured Single Cell

Li-Ion Charger

VIN = 5V

4

V

330Ω

LTC4054-4.2

1

CHRG

CC

GND

2

BAT

PROG

3

5

500mA

2k

1µF

SHDN

405442 TA02

800mA Li-Ion Charger with
External Power Dissipation

VIN = 5V

0.25Ω

4

V

1µF

+

CC

LTC4054-4.2

GND

2

BAT

PROG

1.25k

800mA

3

5

+

405442 TA03

Basic Li-Ion Battery 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

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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
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

12

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear.com

405442i

LT/TP 0203 1.5K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2003