LTC4050EMS-4.2#TRPBF - Linear Technology

LTC4050

4050f

Lithium-Ion Linear Battery

Charger with Thermistor Interface

The LTC

4050-4.1/LTC4050-4.2 are complete standalone

constant-current/constant-voltage linear charge control-

lers for lithium-ion (Li-Ion) batteries. Charge current is

programmable and final float voltage has ±1% accuracy.

When the input supply is removed, the LTC4050 automati-

cally enters a low quiescent current sleep mode, dropping

the battery drain current to 5µA. An internal comparator

detects the near-end-of-charge (C/10) condition while a

programmable timer, using an external capacitor, sets the

total charge time. Fully discharged cells are automatically

trickle charged at 10% of the programmed current until

cell voltage exceeds 2.49V. The thermistor interface

suspends charging if the cell temperature is outside of a

0°C to 50°C temperature window.

The LTC4050 begins a new charge cycle when a discharged

battery is connected to the charger or when the input power

is applied. In addition, a new charge cycle is automatically

started if the battery remains connected to the charger and

the cell voltage drops below 3.88V for 4.1V cells or below

3.98V for 4.2V cells.

The LTC4050 is available in the 10-pin MSOP package.

■

Complete Standalone Linear Charger Controller

for 1-Cell Lithium-Ion Batteries

■

Thermistor Interface for Battery Temperature

Sensing

■

Preset Charge Voltage with ±1% Accuracy

■

Programmable Charge Current

■

C/10 Charge Current Detection Output

■

Programmable Charge Termination Timer

■

Input Supply (Wall Adapter) Detection Output

■

4.5V to 10V Input Voltage Range

■

Automatic Sleep Mode When Input Supply

is Removed (Only 5µA Battery Drain)

■

Automatic Trickle Charging of Low Voltage Cells

■

Automatic Battery Recharge

■

Battery Insertion Detection

■

Space Saving 10-Pin MSOP Package

■

Cellular Phones

■

Handheld Computers

■

Charging Docks and Cradles

APPLICATIO S

TYPICAL APPLICATIO

Single Cell 4.2V 500mA Li-Ion Battery Charger

FEATURES DESCRIPTIO

SENSE

DRV

0.2Ω

19.6k 4.2V

Li-Ion

CELL

LTC4050-4.2

*SHUTDOWN INVOKED BY FLOATING THE PROG PIN

BAT

CHRG

MBRM120T3

10µF

4050 TA01

1µF

BAT

= 500mA

0.1µF

Si9430DY

4ACPR

TIMER PROG

NTCGND 10k NTC

DALE NTHS-1206N02

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

Charge Current vs

Thermistor Temperature

THERMISTOR TEMPERATURE (°C)

–50

CHARGE CURRENT (mA)

400

500

600

25 75

4050 TA05

300

200

–25 0 50 100 125

100

VBAT = 3.7V

LTC4050

4050f

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Voltage ●4.5 10 V

Input Supply Current Charger On, Current Mode ●1.3 3 mA

Shutdown Mode ●1.3 3 mA

Sleep Mode (Battery Drain Current) 5 15 µA

BAT

Regulated Output (Float) Voltage in LTC4050-4.1; 5V ≤ V

≤ 10V, 0°C ≤ T

≤ 85°C 4.059 4.1 4.141 V

Constant Voltage Mode LTC4050-4.2; 5V ≤ V

≤ 10V, 0°C ≤ T

≤ 85°C 4.158 4.2 4.242 V

LTC4050-4.1; 5V ≤ V

≤ 10V ●4.039 4.1 4.141 V

LTC4050-4.2; 5V ≤ V

≤ 10V ●4.137 4.2 4.242 V

BAT

Current Mode Charge Current R

PROG

= 19.6k, R

SENSE

= 0.2Ω440 500 535 mA

PROG

= 19.6k, R

SENSE

= 0.2Ω●415 585 mA

PROG

= 97.6k, R

SENSE

= 0.2Ω60 100 140 mA

TRIKL

Trickle Charge Current V

BAT

= 2V, R

PROG

= 19.6k, I

TRIKL

= (V

– V

SENSE

)/0.2Ω●20 55 90 mA

TRIKL

Trickle Charge Threshold Voltage ●2.41 2.49 2.58 V

Undervoltage Lockout Voltage ●44.5 V

∆V

Undervoltage Lockout Hysteresis 130 mV

MSD

PROG Pin Manual Shutdown 3.6 V

Threshold Voltage

ASD

Automatic Shutdown Threshold Voltage (V

– V

BAT

) High to Low 25 54 85 mV

– V

BAT

) Low to High 40 69 100 mV

PROG

PROG Pin Current Internal Pull-Up Current, No R

PROG

2.3 µA

PROG Pin Source Current, ∆V

PROG

≤ 5mV ●300 µA

PROG

PROG Pin Voltage R

PROG

=19.6k 2.47 V

ACPR

ACPR Pin Output Low Voltage I

ACPR

= 5mA 0.525 V

CHRG

CHRG Pin Weak Pull-Down Current V

CHRG

= 1V 32 µA

CHRG

CHRG Pin Output Low Voltage I

CHRG

= 5mA 0.525 V

HOT

Thermistor Resistance for Hot Fault 3.7 4.1 4.4 kΩ

COLD

Thermistor Resistance for Cold Fault 25 28.5 31 kΩ

ORDER PART

NUMBER

(Note 1)

Input Supply Voltage (V

) ...................................... 12V

SENSE, DRV, BAT, SEL,

TIMER, PROG, CHRG, ACPR .................–0.3V to 12V

Operating Temperature Range (Note 2) . –40°C to 85°C

Storage Temperature Range ................. –65°C to 150°C

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

LTC4050EMS-4.1

LTC4050EMS-4.2

JMAX

= 140°C, θ

= 180°C/W

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

ABSOLUTE MAXIMUM RATINGS

PACKAGE/ORDER INFORMATION

MS PART MARKING

LTTW

LTTX

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.

ELECTRICAL CHARACTERISTICS

BAT

NTC

CHRG

TIMER

GND

ACPR

SENSE

VCC

DRV

PROG

TOP VIEW

MS PACKAGE

10-LEAD PLASTIC MSOP

LTC4050

TYPICAL PERFOR A CE CHARACTERISTICS

TEMPERATURE (°C)

–50

460

IBAT (mA)

480

500

520

540

–25 0 25 50

LTC4050 G01

75 100 125

RPROG = 19.6k

RSEN = 0.2Ω

VBAT = 3V

VCC = 6V

VCC (V)

IBAT (mA)

500

505

510

LC4050 G02

495

490

480 6810

485

520

515

RPROG = 19.6k

RSEN = 0.2Ω

VBAT = 3V

TA = 25°C

TEMPERATURE (°C)

–50

ITRKL (mA)

25 75

LTC4050 G03

–25 0 50 100 125

RPROG = 19.6k

RSEN = 0.2Ω

VBAT = 2V

VCC = 6V

VCC (V)

ITRKL (mA)

6810

LTC4050 G04

RPROG = 19.6k

RSEN = 0.2Ω

VBAT = 2V

TA = 25°C

TEMPERATURE (°C)

–50 –25

2.46

TRKL

(V)

2.48

2.51

050 75

LTC4050 G05

2.47

2.50

2.49

25 100 125

= 6V

PROG

= 19.6k

VCC (V)

2.45

VTRKL (V)

2.47

2.48

2.49

2.50

2.51

2.52

LTC4050 G06

2.53

2.54

2.55

2.46

RPROG = 19.6k

TA = 25°C

Charge Current vs Temperature Charge Current vs VCC

Trickle Charge Current

vs Temperature

Trickle Charge Current vs VCC

Trickle Charge Threshold Voltage

vs Temperature Trickle Charge Threshold Voltage

vs VCC

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

C/10

10% Charge Current Indication Level R

PROG

= 19.6k, R

SENSE

= 0.2Ω●25 50 100 mA

TIMER

TIMER Accuracy C

TIMER

= 0.1µF10%

RECHRG

Recharge Threshold Voltage V

BAT

from High to Low (LTC4050-4.1) 3.83 3.88 V

BAT

from High to Low (LTC4050-4.2) 3.93 3.98 V

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

of a device may be impaired. Note 2: The LTC4050E is 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.

The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 6V unless otherwise noted.

ELECTRICAL CHARACTERISTICS

LTC4050

TYPICAL PERFOR A CE CHARACTERISTICS

TEMPERATURE (°C)

–50

28.1

COLD

(kΩ)

28.2

28.4

28.5

28.6

29.0

LTC4050 G13

28.3

–25 75 100

25 125

28.7

28.8

28.9

= 6V

VCC (V)

RHOT (kΩ)

4.100

4.125

LT4050 G14

4.075

4.050 68

4.150 TA = 25°C

VCC (V)

RCOLD (kΩ)

28.50

28.55

LTC4050 G15

28.45

28.40 68

28.60 TA = 25°C

TEMPERATURE (°C)

–50

TIMER (%)

100

105

110

–25 0 25 50

LTC4050 G10

75 100 125

VCC = 6V

VBAT = 3V

CTIMER = 0.1µF

VCC (V)

TIMER (%)

100

105

110

5678

LTC4050 G11

910

VBAT = 3V

CTIMER = 0.1µF

TA = 25°C

TEMPERATURE (°C)

–50

RHOT (kΩ)

4.12

4.14

4.16

25 75

LTC4050 G12

4.10

4.08

–25 0 50 100 125

4.06

4.04

VCC = 6V

Timer Accuracy vs Temperature Timer Accuracy vs VCC

NTC RHOT Threshold Voltage

vs Temperature

NTC RCOLD Threshold Voltage

vs Temperature NTC RHOT Threshold Voltage

vs VCC

NTC RCOLD Threshold Voltage

vs VCC

TEMPERATURE (°C)

–50

3.7

VRECHRG (V)

3.8

3.9

4.0

4.1

–25 0 25 50

LTC4050 G07

75 100 125

LTC4050-4.1

LTC4050-4.2

VCC = 6V

TEMPERATURE (°C)

–50

VPROG (V)

2.470

2.475

2.480

25 75

LTC4050 G08

2.465

2.460

–25 0 50 100 125

2.455

2.450

VCC = 6V

RPROG = 19.6k

VCC (V)

VPROG (V)

2.47

2.48

LTC4050 G09

2.46

2.45 6810

2.50

2.49

RPROG = 19.6k

TA = 25°C

Recharge Threshold Voltage

vs Temperature PROG Pin Voltage vs Temperature PROG Pin Voltage vs VCC

LTC4050

4050f

PIN FUNCTIONS

UUU

BAT (Pin 1): Battery Sense Input. A precision internal

resistor divider on this pin sets the final float voltage. The

resistor divider is disconnected in sleep mode to reduce

the current drain on the battery. A bypass capacitor of

10µF or more is required to keep the loop stable when the

battery is not connected.

NTC (Pin 2): Thermistor Interface Input. A 10kΩ Dale

Curve 2 NTC thermistor (or other 10kΩ NTC thermistor

with a room temperature beta of around 3400) is con-

nected from this pin to ground. The charge cycle will be

disabled and the timer will be placed on hold if the

thermistor temperature is above 50°C or below 0°C.

CHRG (Pin 3): Charge Status Open-Drain Output. When

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

internal N-channel MOSFET. When the charge current

drops to 10% of the full-scale current for more than 15ms,

the N-channel MOSFET turns off and a 32µA current

source is connected from the CHRG pin to GND. When the

timer runs out or the input supply is removed, the current

source is disconnected and the CHRG pin becomes high

impedance.

TIMER (Pin 4): Timer Capacitor and Constant-Voltage

Mode Disable Input Pin. The timer period is set by placing

a capacitor, CTIMER, to GND. The timer period is tTIMER =

(CTIMER • 3 hours)/(0.1µF). Shorting the TIMER pin to

GND will disable the internal timer function and the

C/10

function.

GND (Pin 5): Ground.

PROG (Pin 6): Charge Current Program and Shutdown

Input Pin. The charge current is programmed by connect-

ing a resistor, R

PROG

to ground. The charge current is I

BAT

= (V

PROG

• 800Ω)/(R

PROG

• R

SENSE

). The IC can be forced

into shutdown by floating the PROG pin and allowing the

internal 2.3µA current source to pull the pin above the 3.6V

shutdown threshold voltage.

DRV (Pin 7): Drive Output Pin for the P-Channel MOSFET

or PNP Transistor. The impedance is high at this pin,

therefore, if a PNP pass transistor is used, it must have

high gain.

(Pin 8): Positive Input Supply Voltage. V

can range

from 4.5V to 10V. Bypass this pin with a 1µF capacitor.

When V

BAT

is within 54mV of V

, the LTC4050 is forced

into sleep mode, dropping I

to 5µA.

SENSE (Pin 9): Current Sense Input. A sense resistor,

SENSE

, must be connected from V

to the SENSE pin.

Select a resistor value that will develop approximately

100mV at the programmed full-scale charge current.

This resistor is chosen using the following equation:

SENSE

= (V

PROG

• 800Ω)/(R

PROG

• I

BAT

)

ACPR (Pin 10): Wall Adapter Present Output. When the

input voltage (wall adaptor) is applied to the LTC4050, this

pin is pulled to ground by an internal N-channel MOSFET

that is capable of sinking 5mA suitable for driving an

external LED.

LTC4050

4050f

BLOCK DIAGRA

–

LOGICACPR

–

C3 A1

CHARGE

GND

4050 BD

PROG

BATTERY CURRENT IBAT = (2.47V • 800Ω)/(RPROG • RSENSE)RPROG

VREF

2.47V

LBO

80Ω

VCC

800Ω54mV

RSENSE

SENSE

DRV

BAT

720Ω

32µA

TIMER OSCILLATOR

VREF

COUNTER

STOP RECHRG

SHDN SLP

C/10 C/10

2.3µA

VCC

CHRG

ACPR

–

3.88V (LTC4050-4.1)

3.98V (LTC4050-4.2)

–

28.6k

NTC

3.6V

LTC4050

4050f

at the CHRG pin and connect a weak current source to

ground, indicating that the battery is nearly fully charged

(C/10 occurs at approximately 94% charge).

An external capacitor on the TIMER pin sets the total

charge time. After a time-out occurs, the charge cycle is

terminated and the CHRG pin is forced high impedance. To

restart the charge cycle, remove the input voltage and

reapply it, or momentarily float the PROG pin.

Replacing the battery when charging will cause the timer

to be reset if the cell voltage of the new battery is below

3.88V (for 4.1V cells) or 3.98V (for 4.2V cells). If the

voltage is above 3.88V(for 4.1V cells) or 3.98V (for 4.2V

cells) the timer will continue for the remaining charge

time. In the case when a time out has occurred, a new

battery with a cell voltage of less than 3.88V or 3.98V can

be inserted and charged automatically with the full pro-

grammed charge time.

For batteries like lithium-ion that require accurate final

float voltage, the internal 2.47V reference, voltage ampli-

fier and the resistor divider provide regulation with ±1%

(max) accuracy.

The charger can be shut down by floating the PROG pin.

An internal current source will pull it high and clamp at

3.5V.

When the input voltage is not present, the charger goes

into a sleep mode, dropping I

to 5µA. This greatly

reduces the current drain on the battery and increases the

standby time.

OPERATIO

The LTC4050 is a linear battery charger controller. The

charge current is programmed by the combination of a

program resistor (R

PROG

) from the PROG pin to ground

and a sense resistor (R

SENSE

) between the V

and SENSE

pins. R

PROG

sets a program current through an internal

trimmed 800Ω resistor setting up a voltage drop from V

to the input of the current amplifier (CA). The current

amplifier servos the gate of the external P-channel MOSFET

to force the same voltage drop across R

SENSE

which sets

the charge current. When the voltage at the BAT pin

approaches the preset float voltage, the voltage amplifier

(VA) will start sinking current which reduces the voltage

drop across R

SENSE

, thus reducing the charge current.

A charge cycle begins when the voltage at V

pin rises

above the UVLO level, a program resistor is connected

from the PROG pin to ground, and the NTC thermistor

temperature is between 0°C and 50°C. At the beginning of

the charge cycle, if the battery voltage is below 2.49V, the

charger goes into trickle charge mode. The trickle charge

current is 10% of the full-scale current. If the cell voltage

stays low for one quarter of the total charge time, the

charge sequence will terminate.

The charger goes into the fast charge constant-current

mode after the voltage on the BAT pin rises above 2.49V.

In constant-current mode, the charge current is set by the

combination of R

SENSE

and R

PROG

When the battery approaches the final float voltage, the

charge current will begin to decrease. When the current

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

comparator will turn off the pull-down N-channel MOSFET

LTC4050

4050f

APPLICATIONS INFORMATION

WUUU

Figure 1. Microprocessor Interface

Charger Conditions

The charger is off when any of the following conditions exist:

the voltage at the V

pin is below 4V, the voltage at the V

pin is greater than 4V but is less than 54mV above V

BAT

the PROG pin is floating, the timer has timed out or the

thermistor temperature is outside the acceptable range. In

this condition, the DRV pin is pulled to V

and the internal

resistor divider is disconnected to reduce the current drain

on the battery.

Undervoltage Lockout (UVLO)

An internal undervoltage lockout circuit monitors the input

voltage and keeps the charger in shutdown mode until V

rises above the undervoltage lockout threshold of 4V. To

prevent oscillation around V

= 4V, the UVLO circuit has

built-in hysteresis.

Trickle Charge and Defective Battery Detection

At the beginning of the charging sequence, if the battery

voltage is low (below 2.49V), the charger goes into trickle

mode. In this mode, the charge current is reduced to 10%

of the full-scale current. If the low cell voltage persists for

one quarter of the total charge time, the battery is consid-

ered defective, the charge cycle is terminated and the

CHRG pin output becomes high impedance.

Shutdown

The LTC4050 can be forced into shutdown by floating the

PROG pin and allowing the internal 2.3µA current source

to pull the pin above the 3.6V shutdown threshold voltage.

In shutdown, the DRV pin is pulled up to V

, turning off

the external P-channel MOSFET and resetting the internal

timer.

Programming Charge Current

The formula for the battery charge current (see Block

Diagram) is:

BAT

= (I

PROG

)(800Ω/R

SENSE

)

= (2.47V/R

PROG

)(800Ω/R

SENSE

) or

PROG

= (2.47V/I

BAT

)(800Ω/R

SENSE

)

where R

PROG

is the total resistance from the PROG pin to

ground.

For example, if 0.5A charge current is needed, select a

value for R

SENSE

that will drop 100mV at the maximum

charge current. R

SENSE

= 0.1V/0.5A = 0.2Ω, then calculate:

PROG

= (2.47V/500mA)(800Ω/0.2Ω) = 19.76k

For best stability over temperature and time, 1% resistors

are recommended. The closest 1% resistor value is 19.6k.

Programming the Timer

The programmable timer terminates the charge cycle.

Typically when charging at a 1C rate, a discharged Li-Ion

battery will become fully charged in 3 hours. For lower

charge current rates, extend the time accordingly. The

length of the timer is programmed by an external capaci-

tor at the TIMER pin. The total charge time is:

Time (Hours) = (3 Hours) • (CTIMER/0.1µF) or

CTIMER = 0.1µF • Time (Hours)/3 Hours

The timer starts when an input voltage greater than 4V is

applied and the program resistor is connected to ground.

After a time-out occurs, the CHRG output will go high

impedance to indicate that charging has stopped. To dis-

able the timer function, short the TIMER pin to GND.

400k

CHRG

4050 F01

VCC

LTC4050

V+

OUT

µPROCESSOR

VDD

LTC4050

4050f

APPLICATIONS INFORMATION

WUUU

CHRG Status Output Pin (C/10)

When the charge cycle starts, the CHRG pin is pulled to

ground by an internal N-channel MOSFET that can drive an

LED. When the charge current drops to 10% of the full-

scale current (C/10), the N-channel MOSFET turns off and

a weak 32µA current source to ground is connected to the

CHRG pin. After a time-out occurs, the pin goes high

impedance. By using two different value pull-up resistors,

a microprocessor can detect three states from this pin

(charging, C/10 and stop charging). See Figure 1.

When the LTC4050 is in charge mode, the CHRG pin is

pulled low by an internal N-channel MOSFET. To detect

this mode, force the digital output pin, OUT, high and

measure the voltage at the CHRG pin. The N-channel

MOSFET will pull the pin low even with a 2k pull-up

resistor. Once the charge current drops to 10% of the full-

scale current (C/10), the N-channel MOSFET turns off and

a 32µA current source is connected to the CHRG pin. The

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

the OUT pin into a high impedance state, the current

source will pull the pin low through the 400k resistor.

When the internal timer has expired, the CHRG pin will

change to high impedance state and the 400k resistor will

then pull the pin high to indicate charging has stopped.

The CHRG pin open-drain device will turn on if the BAT pin

falls below the trickle charge threshold and the LTC4050

has neither timed out nor been put into shutdown. For

example, if the battery and NTC thermistor are both

disconnected from the typical application circuit, the BAT

voltage will collapse due to the thermal fault and CHRG will

pull low. Entering shutdown by floating the PROG pin will

prevent the CHRG pulldown from turning␣ on.

ACPR Output Pin

The LTC4050 has an ACPR output pin to indicate that the

input supply (wall adapter) is higher than 4V and 54mV or

more above the voltage at the BAT pin. When both condi-

tions are met, the ACPR pin is pulled to ground by an

N-channel MOSFET that is capable of driving an LED.

Otherwise, this pin is in a high impedance state.

Gate Drive

Typically the LTC4050 controls an external P-channel

MOSFET to supply current to the battery. An external PNP

transistor can also be used as the pass transistor instead

of the P-channel MOSFET. Due to the low current gain of

the current amplifier (CA), a high gain Darlington PNP

transistor is recommended to avoid excessive charge

current error. The gain of the current amplifier is around

0.6µA/mV. For every 1µA of base current, a 1.6mV of gain

error shows up at the inputs of CA. With R

PROG

= 19.6k

(100mV across R

SENSE

), it represents 1.67% of error in

charge current.

Battery Detection

The LTC4050 can detect the insertion of a new battery.

When a battery with a voltage of less than 3.88V (for 4.1V

cells) or 3.98V (for 4.2V cells) is inserted, the LTC4050

resets the timer and starts a new charge cycle. If the cell

voltage of the new battery is above 3.88V (for 4.1V cells)

or 3.98V (for 4.2V cells), a new charge cycle will not begin.

If a new battery (with cell voltage above 3.88V) is inserted

while in the charging process, the timer will not be reset,

but will continue until the timer runs out.

After a time out has occurred and the battery remains

connected, a new charge cycle will begin if the battery

voltage drops below the recharge threshold of 3.88V (for

4.1V cells) or 3.98V (for 4.2V cells) due to self-discharge

or external loading.

Stability

The charger is stable without any compensation when a

P-channel MOSFET is used as the pass transistor.

However, a 10µF capacitor is recommended at the BAT

pin to keep the ripple voltage low when the battery is

disconnected.

LTC4050

4050f

If a PNP transistor is chosen as the pass transistor, a

1000pF capacitor is required from the DRV pin to V

. This

capacitor is needed to help stabilize the voltage loop. A

10µF capacitor at the BAT pin is also recommended when

a battery is not present.

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 hot power source. These transients can be minimized

by using X5R dielectric capacitors and/or by adding a 1.5Ω

resistor in series with the ceramic input capacitor. For

more information, refer to Application Note 88.

Thermistor Interface

A thermistor connected to the NTC (negative temperature

coefficient) pin can be used to sense the battery tempera-

ture to determine if the battery is within an acceptable

temperature range for charging (between 0°C and 50°C).

A Dale (curve 2) 10k thermistor is recommended although

many other types of thermistors can also be used. For

example, a BetaCHIP (curve 7) 10k thermistor or other 10k

thermistors with a room temperature beta of approxi-

mately 3400 will work well. The thermistor is connected

from NTC (pin 2) to ground and is biased up by an internal

28.6k trimmed thin film resistor that connects to V

through a P-channel MOSFET. This MOSFET also biases

an internal resistor string to ground, from which voltage

thresholds of approximately V

/2 and V

/8 are derived.

The NTC pin is compared to these thresholds by two

comparators that have wired-OR outputs. The thresholds

are selected such that an overtemperature condition will

occur when the thermistor resistance is less than approxi-

mately 4.1k and undertemperature condition will occur

when the thermistor resistance is greater than approxi-

mately 28.5k. These correspond to thermistor tempera-

tures of 50°C and 0°C for the specific type of thermistor

listed above (many others will be close enough for most

purposes). The MOSFET is turned off during undervoltage

conditions, preventing the dividers that are biased from it

from drawing current from the battery when input power

is removed. The drop across the MOSFET is common to

both resistor dividers and does not cause any loss of

accuracy in the circuit. The comparators have approxi-

mately 10mV of hysteresis to prevent oscillations around

the trip points.

When an undertemperature or overtemperature condition

is sensed, the current amplifier pulldown is disabled and

DRV is pulled high, the timer is placed in a hold condition

with the count frozen until the battery temperature is

within an acceptable range. The end-of-charge compara-

tor is also disabled to prevent a premature end of charge

signal due to the lack of battery charging current.

APPLICATIONS INFORMATION

WUUU

–

28.6k

4050 AI

10k DALE

CURVE 2

NTC

THERMISTOR

TBAD

(TO CA,

EOC, TIMER)

NTC

NTC Interface Circuitry

LTC4050

4050f

PACKAGE DESCRIPTIO

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.

MS Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1661)

MSOP (MS) 0802

0.53 ± 0.01

(.021 ± .006)

SEATING

PLANE

0.18

(.007)

1.10

(.043)

MAX

0.17 – 0.27

(.007 – .011)

TYP

0.13 ± 0.076

(.005 ± .003)

0.86

(.034)

REF

0.50

(.0197)

BSC

12345

4.90 ± 0.15

(1.93 ± .006)

0.497 ± 0.076

(.0196 ± .003)

REF

8910 76

3.00 ± 0.102

(.118 ± .004)

(NOTE 3)

3.00 ± 0.102

(.118 ± .004)

NOTE 4

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

0.254

(.010) 0° – 6° TYP

DETAIL “A”

GAUGE PLANE

5.23

(.206)

MIN

3.2 – 3.45

(.126 – .136)

0.889 ± 0.127

(.035 ± .005)

RECOMMENDED SOLDER PAD LAYOUT

0.305 ± 0.038

(.0120 ± .0015)

TYP

0.50

(.0197)

BSC

LTC4050

4050f

 LINEAR TECHNOLOGY CORPORATION 2002

LT/TP 0203 2K • PRINTED IN THE USA

PART NUMBER DESCRIPTION COMMENTS

LT®1510-5 500kHz Constant-Voltage/Constant-Current Battery Charger Most Compact, Up to 1.5A, Charges NiCd, NiMH, Li-Ion Cells

LT1512 SEPIC Battery Charger V

Can Be Higher or Lower Than Battery Voltage, 1.5A Switch

LT1620 Rail-to-Rail Current Sense Amplifier Precise Output Current Programming, Up to 32V V

OUT

, Up to 10A I

OUT

LTC1729 Termination Controller for Li-Ion Time or Charge Current Termination, Automatic Charger/Battery

Detection, Status Output, Preconditioning, 8-Lead MSOP;

Timer; AC Adapter Present Detection; No Firmware Required

LTC1731 Li-Ion Linear Battery Charger Controller CC/CV Charges Li-Ion Cells, 8-Lead MSOP, Programmable Timer; No

Firmware Required

LTC1732 Li-Ion Linear Battery Charger Controller Adapter Present Detection; Programmable Timer; No Firmware Required

LTC1733 Li-Ion Linear Charger with Thermal Regulation Complete Standalone Charger, Thermal Regulator Prevents Overheating

LTC1734 ThinSOT Li-Ion Linear Battery Charger Controller Only Two External Components; No Diode; No Sense Resistor; V

PROG

LTC1734L Allows Monitoring I

CHARGE

LTC4052 Li-Ion Linear Battery Pulse Charger Detects Maximum I

CHARGE

for Safety; No MOSFET; No Diode; No

Firmware Required

LTC4053 USB Compatible Li-Ion Battery Charger USB and Wall Adapter Input, 100mA/500mA or Up to 1.25A Charge

Current Standalone Charger

ThinSOT is a trademark of Linear Technology Corporation.

RELATED PARTS

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900

●

FAX: (408) 434-0507

●

www.linear.com

Single Cell 4.1V, 1.5A High Efficiency Li-Ion Battery Charger

TYPICAL APPLICATIO S

Linear Charger Using a PNP Transistor

SENSE

DRV

1k 0.2Ω

10k

19.6k 4.2V

Li-Ion

CELL

LTC4050-4.2

BAT

CHRG 9

MBRM120T3

10µF

1nF 1µF

BAT

= 500mA

0.1µF

2N5087

4TIMER

PROG

GND

NTC

ACPR

ZTX749

4050 TA02

10k NTC

DALE NTHS-1206N02

SENSE

DRV

0.082Ω

1/4W

MBRS130LT3

19.6k

LTC4050-4.1

BAT

CHRG

LTC1693-5 4

4050 TA04

22µF

0.1µF

Si2305DS

4TIMER

PROG

GND

NTC

ACPR

0.47µF

4.7Ω

220µF

15µH

CDRH6D28-150NC

10k NTC

DALE

NTHS-1206N02

4.1V

Li-Ion

CELL