LTC1733EMSE#TRPBF_技术文档

LTC1733

Monolithic Linear

Lithium-Ion Battery Charger with

Thermal Regulation

U

FEATURES

DESCRIPTIO

The LTC^®1733 is a standalone constant-current/

constant-voltage linear charger for lithium-ion batteries

withanon-chippowerMOSFET.Internalthermalfeedback

regulates the charge current to limit die temperature

during high power operation or high ambient temperature

conditions. This feature allows the user to program a high

charge current without risk of damaging the LTC1733 or

the handheld product.

■

Complete Linear Charger for 1-Cell Lithium-Ion

Batteries

■

Thermal Regulation Maximizes Charging Rate

without Risk of Overheating*

No External MOSFET, Sense Resistor or Blocking

Diode Required

Up to 1.5A Charge Current

Preset Charge Voltage with 1% Accuracy

Programmable Charge Current with 7% Accuracy

Programmable Charge Termination Timer

Tiny Thermally Enhanced 10-Pin MSOP Package

Charge Current Monitor Useful for Gas Gauging*

C/10 Charge Current Detection Output

Automatic Recharge

■

No external current sense resistor is needed and no

blocking diode is required due to the internal MOSFET

architecture. The charge current and charge time can be

set externally with a single resistor and capacitor, respec-

tively. When the input supply (wall adapter) is removed,

the LTC1733 automatically enters a low current sleep

mode, dropping the battery drain current to less than 5µA.

Thermistor Input for Temperature Qualified Charging

AC Present Logic Output

4.1V/4.2V Pin Selectable Output Voltage

The LTC1733 also includes NTC temperature sensing,

C/10 detection circuitry, AC present logic, 4.1V/4.2V pin

selectability and low battery charge conditioning (trickle

charging).

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APPLICATIO S

■

Cellular Telephones

The LTC1733 is available in a 10-pin thermally enhanced

MSOP package.

■

Handheld Computers

■

Digital Still Cameras

Charging Docks and Cradles

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

■

*Patent Pending

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TYPICAL APPLICATIO

Charge Current vs Battery Voltage

Standalone Li-Ion Battery Charger

1200

T

A

= 0°C

CONSTANT

CURRENT

V

= 5V

IN

1000

800

600

400

200

0

T

= 40°C

8

2

A

T

= 25°C

A

SEL

V

I

= 1A

CC

BAT

9

7

CONSTANT

POWER

4.7µF

BAT

4.2V

LTC1733

TIMER

4

1-CELL

Li-Ion

PROG

CONSTANT

VOLTAGE

GND

NTC

6

BATTERY*

1.5k

1%

5

0.1µF

TRICKLE

CHARGE

V

= 5V

IN

1733TA01

θ

= 40°C/W

JA

2.5

3

4

4.5

2

3.5

*AN OUTPUT CAPACITOR MAY BE REQUIRED

DEPENDING ON BATTERY LEAD LENGTH

BATTERY VOLTAGE (V)

1733 TA01b

sn1733 1733fs

1

LTC1733

W W

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ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

Input Supply Voltage (V_CC) ........................................ 7V

BAT............................................................................ 7V

NTC, SEL, TIMER, PROG ................ –0.3V to V_CC+ 0.3V

CHRG, FAULT, ACPR ...................................–0.3V to 7V

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

BAT Current (Note 2) .............................................. 1.6A

PROG Current (Note 2) ........................................ 1.6mA

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

Operating Temperature Range (Note 3) ...–40°C to 85°C

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

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

ORDER PART

TOP VIEW

CHRG

1

2

3

4

5

10 ACPR

NUMBER

V

9

8

7

6

BAT

CC

FAULT

TIMER

GND

SEL

PROG

NTC

LTC1733EMSE

MSE EXPOSED PAD PACKAGE

10-LEAD PLASTIC MSOP

T_JMAX= 125°C, θ_JA= 40°C/W (Note 4)

EXPOSED PAD IS GROUND.

(MUST BE SOLDERED TO PCB

FOR MAXIMUM HEAT TRANSFER).

MSE PART MARKING

LTLX

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

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

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

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

CC

V

CC

Supply Voltage

Supply Current

●

4.5

6.5

V

CC

I

Charger On; Current Mode; R

= 30k (Note 5)

●

1

0.9

3

2

mA

CC

PROG

Shutdown Mode; V

= 3V

PROG

V

BAT

V

BAT

Regulated Output Voltage

SEL = 0V

●

4.059

4.158

4.1

4.2

4.141

4.242

V

SEL = V

CC

I

Battery Pin Current

R

= 3k; Current Mode

= 1k; Current Mode

●

465

1.395

500

1.5

±1

535

1.605

±5

mA

A

µA

BAT

PROG

Shutdown Mode; V

Sleep Mode V < V

= 3V

PROG

or V < (V – ∆V )

±1

±5

CC

BAT

CC

UV

I

Trickle Charge Current

V

< 2V; R

Rising

= 3k

PROG

●

35

50

2.48

100

4.2

65

mA

V

TRIKL

BAT

V

Trickle Charge Trip Threshold

Trickle Charge Trip Hysteresis

TRIKL

∆V

mV

V

TRIKL

UV

V

CC

V

CC

Undervoltage Lockout Voltage

Undervoltage Lockout Hysteresis

V

CC

Rising

4.5

UV

∆V

150

2.15

100

mV

V

Manual Shutdown Threshold Voltage

Manual Shutdown Hysteresis Voltage

PROG Pin Voltage Rising

MSD

mV

MSD-HYS

ASD

Automatic Shutdown Threshold Voltage (V - V ) Voltage Falling

30

60

mV

CC

BAT

(V - V ) Voltage Rising

CC

BAT

sn1733 1733fs

2

LTC1733

ELECTRICAL CHARACTERISTICS

T_A= 25°C. V_CC= 5V unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS MIN

TYP

1.5

MAX

UNITS

V

PROG Pin Voltage

R

= 3k, I

= 1V

= 500µA; Current Mode

PROG

CHRG

PROG

CHRG

I

CHRG Pin Weak Pulldown Current

CHRG Pin Output Low Voltage

ACPR Pin Output Low Voltage

FAULT Pin Output Low Voltage

End of Charge Indication Current Level

TIMER Accuracy

V

25

µA

V

I

= 5mA

0.35

50

CHRG

ACPR

FAULT

C/10

= 5mA

V

ACPR

V

FAULT

I

t

R

PROG

= 3k

35

65

mA

%

C

= 0.1µF

±10

TIMER

V

Recharge Battery Voltage Threshold

Battery Voltage Falling, SEL = 0V

Battery Voltage Falling, SEL = 5V

3.9

4.0

V

RECHRG

V

NTC Pin Hot Threshold Voltage

NTC Pin Hot Hysteresis Voltage

NTC Pin Cold Threshold Voltage

NTC Pin Cold Hystersis Voltage

NTC Pin Disable Threshold Voltage

NTC Pin Disable Hystersis Voltage

SEL Pin Threshold Input Low

SEL Pin Threshold Input High

V

Falling

Rising

2.5

70

V

mV

V

NTC-HOT

HOT-HYS

NTC-COLD

COLD-HYS

NTC-DIS

DIS-HYS

SEL-IL

NTC

4.375

70

mV

V

100

10

0.3

1

V

SEL-IH

T

Junction Temperature in

Constant-Temperature Mode

105

375

°C

LIM

R

Power MOSFET “ON” Resistance

mΩ

ON

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

of a device may be impaired.

temperature range are assured by design, characterization and correlation

with statistical process controls.

Note 2: The Absolute Maximum BAT Current Rating of 1.6A is guaranteed

by design and current density calculations. The Absolute Maximum PROG

Current Rating is guaranteed to be 1/1000 of BAT current rating by design.

Note 4: Failure to solder the exposed backside of the package to the PC

board will result in a thermal resistance much higher than 40°C/W.

Note 5: Supply current includes PROG pin current but does not include

Note 3: The LTC1733E is guaranteed to meet performance specifications

from 0°C to 70°C. Specifications over the –40°C to 85°C operating

any current delivered to the battery through the BAT pin.

sn1733 1733fs

3

LTC1733

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TYPICAL PERFOR A CE CHARACTERISTICS

Battery Regulation Voltage vs

Battery Charge Current

Battery Regulation Voltage vs

Temperature

Battery Regulation Voltage vs V_CC

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4.08

4.06

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4.08

4.06

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4.08

4.06

V

T

= 5V

T

= 25°C

A

V

I

= 5V

CC

A

R

CC

BAT

R

= 25°C

I

= 10mA

= 1.5k

= 10mA

= 1.5k

BAT

R

PROG

V

SEL

= 5V

V

SEL

= 5V

V

SEL

= V

CC

= 1.5k

PROG

V

SEL

= 0V

V

SEL

= 0V

V

= 0V

SEL

6.0

400

I

5.5

(V)

0

100 200 300

500 600 700 800 900 1000

(mA)

25

TEMPERATURE(°C)

4.0

4.5

5.0

6.5

7.0

–50 –25

0

50

75 100 125

V

BAT

CC

1733 G01

1733 G03

1733 G02

PROG Pin Voltage vs Charge

Current

Charge Current vs Battery Voltage

Charge Current vs Input Voltage

1100

1000

900

800

700

600

500

400

300

200

100

0

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

1100

1000

900

800

700

600

500

400

300

200

100

0

V

T

= 5V

V

T

= 5V

CC

A

CC

A

= 25°C

R

V

= 1.5k

R

V

= 1.5k

PROG

= 5V

SEL

V

T

= 4.1V

BAT

A

R

= 25°C

= 1.5k

PROG

V

= 5V

SEL

4.0

4.5

5.0

5.5

(V)

6.0

6.5

7.0

400

0

0.5 1.0 1.5

2.5

(V)

3.5 4.0 4.5

3.0

0

100 200 300

500 600 700 800 900 1000

2.0

V

CHARGE CURRENT (mA)

CC

BAT

1733 G06

1733 G04

1733 G05

Charge Current vs Temperature

with Thermal Regulation

Charge Current vs Temperature

Charge Current vs V_CC

1100

1000

900

800

700

600

500

400

535

530

525

520

515

510

505

500

495

490

485

480

475

470

465

1000

900

800

700

600

500

400

300

200

100

0

V

= 5V

CC

R

= 1.5k

PROG

= 4V

BAT

PROG

R

= 3k

V

= 5V

SEL

V

T

= 3.5V

BAT

A

SEL

THERMAL CONTROL

LOOP IN OPERATION

= 25°C

V

= V

CC

V

= 5V

CC

R

= 3k

PROG

= 3.5V

BAT

PROG

R

= 1.5k

V

= 5V

SEL

50

TEMPERATURE (°C)

100

4.0

4.5

5.0

5.5

6.0

6.5

7.0

–50

–25

0

25

75

–50

–25

0

25

50

75

100

V

(V)

TEMPERATURE (°C)

CC

1733 G07

1733 G09

1733 G08

sn1733 1733fs

4

LTC1733

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TYPICAL PERFOR A CE CHARACTERISTICS

PROG Pin Voltage vs V_CC

Constant Current Mode

PROG Pin Voltage vs Temperature

Constant Current Mode

Trickle Charge Current vs

Temperature

1.515

1.510

1.505

1.500

1.495

1.490

1.485

130

120

110

100

90

1.515

1.510

1.505

1.500

1.495

1.490

1.485

T

= 25°C

V

= 5V

= 2V

V

= 5V

= 4V

A

CC

BAT

PROG

CC

BAT

V

= 3.5V

BAT

PROG

SEL

R

V

= 3k

R

V

= 1.5k

R

V

= 3k

PROG

= 5V

SEL

80

70

6.0

7.0

4.0

4.5

5.0

5.5

(V)

6.5

50

TEMPERATURE (°C)

100

50

TEMPERATURE (°C)

100

–50

–25

0

25

75

–50

–25

0

25

75

V

CC

1733 G10

1733 G12

1733 G11

Trickle Charge Current vs V_CC

Timer Accuracy vs V_CC

Timer Accuracy vs Temperature

13

12

11

10

9

105

104

103

102

101

100

99

105

104

103

102

101

100

99

T

= 25°C

BAT

V

I

= 5V

CC

BAT

V

SEL

T

I

V

C

= 25°C

A

V

= 2V

= 0mA

= 5V

= 0mA

= 5V

= 0.1µF

BAT

SEL

R

V

= 1.5k

PROG

SEL

= 5V

C

= 0.1µF

TIMER

98

97

8

96

7

4.0

95

6.0

7.0

4.5

5.0

5.5

(V)

6.5

25

TEMPERATURE(°C)

–50 –25

0

50

75 100 125

6.0

7.0

4.0

4.5

5.0

5.5

(V)

6.5

V

CC

1733 G13

1733 G14

1733 G15

sn1733 1733fs

5

LTC1733

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PI FU CTIO S

CHRG: Open-Drain Charge Status Output. When the

battery is being charged, the CHRG pin is pulled low by an

internal N-channel MOSFET. When the charge current

drops to 10% of the full-scale current, the N-channel

MOSFET latches off and a 25µA current source is con-

nected from the CHRG pin to ground. The C/10 latch can

be cleared by momentarily pulling the PROG pin above the

2.15V shutdown threshold, or by toggling V_CC. When the

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

source is disconnected and the CHRG pin is forced to a

high impedance state.

GND: Ground. Connect exposed back package to ground.

NTC: Input to the NTC (Negative Temperature Coefficient)

Thermistor Temperature Monitoring Circuit. With an ex-

ternal 10kΩ NTC thermistor to ground and a 1% resistor

to V_CC, this pin can sense the temperature of the battery

pack and stop charging when it is out of range. When the

voltage at this pin drops below (0.5)•(V_CC) at hot tempera-

tures or rises above (0.875)•(V_CC) at cold, charging is

suspended and the internal timer is frozen. The CHRG pin

output status is not affected in this hold state. The FAULT

pinispulledtoground,butnotlatched.Whenthetempera-

ture returns to an acceptable range, charging will resume

and the FAULT pin is released. The NTC feature can be

disabled by grounding the NTC pin.

V_CC: Positive Input Supply Voltage. When V_CCis within

30mV of V_BATor less than the undervoltage lockout

threshold, the LTC1733 enters sleep mode, dropping I_BAT

to less than 5µA. V_CCcan range from 4.5V to 6.5V. Bypass

this pin with at least a 4.7µF ceramic capacitor to ground.

PROG: Charge Current Program, Shutdown Input and

Charge Current Monitor Pin. The charge current is pro-

grammed by connecting a resistor, R_PROGto ground.

When in constant-current mode, the LTC1733 servos the

PROG pin voltage to 1.5V. In all modes the voltage on the

PROG pin can be used to measure the charge current as

follows:

FAULT:Open-DrainFaultStatusOutput. TheFAULTopen-

drain logic signal indicates that the charger has timed out

undertricklechargeconditions(1/4oftotaltimeperiod)or

the NTC comparator is indicating an out-of-range battery

temperature condition. When V_BATis less that 2.48V,

trickle charging activates whereby the charge current

drops to one tenth of its programmed value and the timer

period is reduced by a factor of four. When one fourth of

the timing period has elapsed, if V_BATis still less than

2.48V, trickle charging stops and the FAULT pin latches to

ground. The fault can be cleared by toggling V_CC, momen-

tarily pulling the PROG pin above the 2.15V shutdown

threshold, or pulling the BAT pin above 2.48V. If the NTC

comparatorisindicatinganout-of-rangebatterytempera-

ture condition, then the FAULT pin will pull to ground until

the temperature returns to the acceptable range.

I_CHG= (V_PROG/R_PROG) • 1000.

The IC can be forced into shutdown by pulling the PROG

pin above the 2.15V shutdown threshold voltage (note: it

will not be pulled up when allowed to float).

SEL: 4.1V/4.2V Battery Selection Input. Grounding this

pin sets the battery float voltage to 4.1V, while connecting

to V_CCsets the voltage to 4.2V.

BAT: ChargeCurrentOutput. Abypasscapacitorofatleast

1µFwitha1Ωseriesresistorisrequiredtominimizeripple

voltage when the battery is not present. A precision

internal resistor divider sets the final float potential on this

pin. The internal resistor divider is disconnected in sleep

and shutdown modes.

TIMER:TimerCapacitor. Thetimerperiodissetbyplacing

a capacitor, C_TIMER, to ground. The timer period is:

Time (Hours) = (C_TIMER• 3 hr)/(0.1µF)

ACPR: Open-Drain Power Supply Status Output. When

V_CCis greater than the undervoltage lockout threshold

and at least 30mV above V_BAT, the ACPR pin will pull to

ground. Otherwise, the pin is forced to a high impedance

state.

ShorttheTIMERpintogroundtodisabletheinternaltimer

function.

sn1733 1733fs

6

LTC1733

W

SI PLIFIED BLOCK DIAGRA

V

CC

2

105°C

–

D1

TA

D2

D3

T

+

DIE

M2

×1

M1

×1000

+

–

MA

BAT

9

30µA

R1

R2

NTC

6

NTC

MP

+

–

VA

CA

+

–

2.485V

R4

REF

HOT COLD DISABLE

–

+

1

CHRG

C1

SHDN

STOP

2.15V

1.5V

R3

8

SEL

C/10

R5

R6

R7

2.5µA

25µA

LOGIC

10

3

ACPR

0.15V

+

–

C2

FAULT

CHARGE

COUNTER

OSCILLATOR

4

C3

+

–

2.485V

TO BAT

7

5

1733 F01

PROG

GND

TIMER

R

PROG

C

TIMER

Figure 1.

sn1733 1733fs

7

LTC1733

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OPERATIO

TheLTC1733isalinearbatterychargerdesignedprimarily

for charging single cell lithium-ion batteries. Featuring an

internal P-channel power MOSFET, the charger uses a

constant-current/constant-voltage charge algorithm with

programmable current and a programmable timer for

charge termination. Charge current can be programmed

up to 1.5A with a final float voltage accuracy of ±1%. No

blocking diode or sense resistor is required thus dropping

the external component count to three for the basic

charger circuit. The CHRG, ACPR, and FAULT open-drain

status outputs provide information regarding the status of

the LTC1733 at all times. An NTC thermistor input

provides the option of charge qualification using battery

temperature.

into the fast charge constant-current mode once the

voltage on the BAT pin rises above 2.48V. In constant-

current mode, the charge current is set by R_PROG

.

When the battery approaches the final float voltage, the

chargecurrentbeginstodecreaseastheLTC1733switches

toconstant-voltagemode.Whenthecurrentdropsto10%

of the full-scale charge current, an internal comparator

latches off the MOSFET at the CHRG pin and connects a

weak current source to ground to indicate a near end-of-

charge (C/10) condition. The C/10 latch can be cleared by

momentarily pulling the PROG pin above the 2.15V

shutdown threshold, or momentarily removing and reap-

plying V_CC.

An external capacitor on the TIMER pin sets the total

charge time. When this time elapses the charge cycle

terminates and the CHRG pin assumes a high impedance

state. To restart the charge cycle, simply remove the input

voltage and reapply it, or force the PROG pin above the

2.15Vshutdownthreshold(note:simplyfloatingthePROG

pin will not restart the charging cycle.

An internal thermal limit reduces the programmed charge

current if the die temperature attempts to rise above a

presetvalueofapproximately105°C. Thisfeatureprotects

the LTC1733 from excessive temperature, and allows the

user to push the limits of the power handling capability of

agivencircuitboardwithoutriskofdamagingtheLTC1733

ortheexternalcomponents.AnotherbenefitoftheLTC1733

thermal limit is that charge current can be set according to

typical, not worst-case, ambient temperatures for a given

application with the assurance that the charger will auto-

matically reduce the current in worst-case conditions.

For lithium-ion and similar batteries that require accurate

final float potential, the internal reference, voltage ampli-

fier and the resistor divider provide regulation with ±1%

(max) accuracy.

When the input voltage is not present, the charger goes

into a sleep mode, dropping battery drain current, I_BAT, to

lessthan5µA.Thisgreatlyreducesthecurrentdrainonthe

batteryandincreasesthestandbytime.Thechargercanbe

shut down (I_CC= 0.9mA) by forcing the PROG pin above

2.15V.

The charge cycle begins when the voltage at the V_CCpin

rises above the UVLO level and a program resistor is

connected from the PROG pin to ground. At the beginning

of the charge cycle, if the battery voltage is below 2.48V,

the charger goes into trickle charge mode to bring the cell

voltage up to a safe level for charging. The charger goes

sn1733 1733fs

8

LTC1733

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APPLICATIO S I FOR ATIO

Undervoltage Lockout (UVLO)

recharge comparator is disabled and a new charge cycle

willnotbeginunlesstheinputvoltageistoggled,thePROG

pin is pulled above the 2.15V shutdown threshold, or the

BATpinispulledabovethe2.48Vtricklechargethreshold.

Aninternalundervoltagelockoutcircuitmonitorstheinput

voltageandkeepsthechargerinshutdownmodeuntilV_CC

risesabovetheundervoltagelockoutthreshold. TheUVLO

circuit has a built-in hysteresis of 150mV. 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 until V_CCrises 60mV above the battery voltage.

Programming Charge Current

The formula for the battery charge current (see Figure 1)

is:

I_CHG= (I_PROG) • 1000

= (1.5V / R_PROG) • 1000 or

R_PROG= 1500/I_CHG

Trickle Charge and Defective Battery Detection

At the beginning of a charge cycle, if the battery voltage is

low (below 2.48V) the charger goes into trickle charge

reducing the charge current to 10% of the full-scale

current. If the low battery voltage persists for one quarter

of the total charge time, the battery is assumed to be

defective, the charge cycle is terminated, the CHRG pin

output assumes a high impedance state, and the FAULT

pin latches low. The fault can be cleared by toggling V_CC,

temporarily forcing the PROG pin above 2.15V, or tempo-

rarily forcing the BAT pin voltage above 2.48V.

where R_PROGis the total resistance from the PROG pin to

ground. Under trickle charge conditions, this current is

reduced to 10% of the full-scale value.

For example, if 500mA charge current is required,

calculate:

R_PROG= 1500/0.5A = 3kΩ

For best stability over temperature and time, 1% metal-

film resistors are recommended.

If the charger is in constant-temperature or constant-

voltage mode, the battery current can be monitored by

measuring the PROG pin voltage as follows:

Shutdown

The LTC1733 can be shutdown (I_CC= 0.9mA) by pulling

the PROG pin above the 2.15V shutdown threshold volt-

age. In shutdown the internal linear regulator is turned off,

and the internal timer is reset.

I_CHG= (V_PROG/ R_PROG) • 1000

Programming the Timer

The programmable timer is used to terminate the charge

cycle. The timer duration is programmed by an external

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

Recharge

The LTC1733 has the ability to recharge a battery

assuming that the battery voltage has been charged above

4.05V (SEL = 5V) or 3.95V (SEL = 0V). Once above these

thresholds, a new charge cycle will begin if the battery

voltage drops below 4V (SEL = 5V) or 3.9V (SEL = 0V) due

to either a load on the battery or self-discharge. The

recharge circuit integrates the BAT pin voltage for a few

milliseconds to prevent a transient from restarting the

charge cycle.

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

C_TIMER= 0.1µF • Time (Hours)/3 (Hours)

The timer starts when an input voltage greater than the

undervoltage lockout threshold level is applied and the

program resistor is connected to ground. After a time-out

occurs, the charge current stops, and the CHRG output

assumes a high impedance state to indicate that the

charginghasstopped.ConnectingtheTIMERpintoground

disables the timer function.

If the battery voltage remains below 2.48V during trickle

chargefor1/4oftheprogrammedtime, thebatterymaybe

defective and the charge cycle will end. In addition, the

sn1733 1733fs

9

LTC1733

W U U

U

APPLICATIO S I FOR ATIO

+

Open-Drain Status Outputs

V

DD

V

8

The LTC1733 has three open-drain status outputs: ACPR,

CHRG and FAULT. The ACPR pin pulls low when an input

voltage greater than the undervoltage lockout threshold is

applied and goes high impedance when power (V_IN< V_UV)

is removed. CHRG and FAULT work together to indicate

the status of the charge cycle. Table 1 describes the status

of the charge cycle based on the CHRG and FAULT

outputs.

V

CC

400k

µPROCESSOR

LTC1733

2k

3

OUT

IN

CHRG

1733 F02

Figure 2. Microprocessor Interface

Table 1.

FAULT

CHRG

Description

When the LTC1733 is in charge mode, the CHRG pin is

pulled low by the 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 the 2k pull-up

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

scale current (C/10), the N-channel MOSFET is turned off

and a 25µA 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 to 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

assume a high impedance state and the 400k resistor will

then pull the pin high to indicate that charging has termi-

nated.

High

Low

Charge cycle has started, C/10 has not been

reached and charging is proceeding normally.

Low

Charge cycle has started, C/10 has not been

reached, but the charge current and timer

have been paused due to an NTC out-of-

temperature condition.

High

Low

25µA

C/10 has been reached and charging is

pulldown proceeding normally.

25µA

C/10 has been reached but the charge current

pulldown and timer have paused due to an

NTC out-of-temperature condition.

High

Low

High

Normal timeout (charging has terminated).

If FAULT goes low and CHRG goes high

impedance simultaneously, then the LTC1733

has timed out due to a bad cell (V

after one-quarter the programmed charge time).

If CHRG goes high impedance first, then

the LTC1733 has timed out normally (charging

has terminated), but NTC is indicating an out-

of-temperature condition.

<2.48V

BAT

NTC Thermistor

Thebatterytemperatureismeasuredbyplacinganegative

temperature coefficient (NTC) thermistor close to the

batterypack.TheNTCcircuitryisshowninFigure3.Touse

this feature, connect a 10k NTC thermistor between the

NTCpinandgroundandaresistor(R_HOT)fromtheNTCpin

to V_CC. R_HOTshould be a 1% resistor with a value equal to

the value of the chosen NTC thermistor at 50°C (this value

is 4.1k for a Vishay NTHS0603N02N1002J thermistor).

The LTC1733 goes into hold mode when the resistance of

the NTC thermistor drops below 4.1k which should be

at 50°C. The hold mode freezes the timer and stops

the charge cycle until the thermistor indicates a return

to a valid temperature. As the temperature drops, the

CHRG Status Output Pin

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

ground by an internal N-channel MOSFET capable of

driving an LED. When the charge current drops to 10% of

the full-scale current (C/10), the N-channel MOSFET is

latched off and a weak 25µA current source to ground is

connected to the CHRG pin. After a time-out occurs, the

pin assumes a high impedance state. By using two differ-

ent value pull-up resistors a microprocessor can detect

three states from this pin (charging, C/10, and time-out).

See Figure 2.

sn1733 1733fs

10

LTC1733

W U U

APPLICATIO S I FOR ATIO

U

resistance of the NTC thermistor rises. The LTC1733 is

designed to go into hold mode when the value of the NTC

thermistor increases to seven times the value of R_HOT. For

a Vishay NTHS0603N02N1002J thermistor, this value is

28.2k which corresponds to approximately 0°C. The hot

and cold comparators each have approximately 2°C of

hysteresis to prevent oscillation about the trip point. The

NTC function can be disabled by grounding the NTC pin.

package temperature rather than the battery temperature.

This problem can be eliminated by thermally coupling the

NTC thermistor to the battery and not to the LTC1733.

Furthermore, it is essential that the V_CCconnection to

R_HOTis made according to standard Kelvin sense tech-

niques. Since V_CCis a high current path into the LTC1733,

it is essential to minimize voltage drops between the V_CC

input pin and the top of R_HOT

.

V

CC

NTC Trip Point Errors

7/8 V

–

+

CC

When a 1% resistor is used for R_HOT, the major error in

the 50°C trip point is determined by the tolerance of the

NTC thermistor. A typical 10k NTC thermistor has a ±10%

tolerance. By looking up the temperature coefficient of the

thermistor at 50°C, the tolerance error can be calculated

in degrees centigrade. Consider the Vishay

NTHS0603N02N1002J thermistor which has a tempera-

ture coefficient of –3.3%/°C at 50°C. Dividing the toler-

ance by the temperature coefficient, ±10%/(–3.3%/°C) =

±3°C, gives the temperature error of the hot trip point.

R

HOT

1%

TOO COLD

TOO HOT

NTC

1/2 V

R

+

–

NTC

10k

3/160 V

+

–

DISABLE NTC

The cold trip point is a little more complicated because its

error depends on the tolerance of the NTC thermistor and

thedegreetowhichtheratioofitsvalueat0°Canditsvalue

at 50°C varies from 7 to 1. Therefore, the cold trip point

error can be calculated using the tolerance, TOL, the

temperature coefficient of the thermistor at 0°C, TC

(in %/°C), the value of the thermistor at 0°C, R_COLD, and

the value of the thermistor at 50°C, R_HOT. The formula is:

LTC1733

1733 F03

Figure 3.

Thermistors

The LTC1733 NTC trip points were designed to work with

thermistors whose resistance-temperature characteris-

tics follow Vishay Dale’s “R-T Curve 2”. The Vishay

NTHS0603N02N1002J is an example of such a ther-

mistor. However, Vishay Dale has many thermistor prod-

uctsthatfollowthe“R-TCurve2”characteristicinavariety

of sizes. Futhermore, any thermistor whose ratio of R_COLD

to R_HOTis about 7.0 will also work (Vishay Dale R-T Curve

2 shows a ratio of R_COLDto R_HOTof 2.816/0.4086 = 6.9).

1+ TOL R_COLD

•

– 1 •100

7

R_HOT

TC

TemperatureError(°C)=

Forexample,theVishayNTHS0603N02N1002Jthermistor

with a tolerance of ±10%, TC of –4.5%/°C, and R_COLD

R_HOTof 6.89, has a cold trip point error of:

/

NTC Layout Considerations

1± 0.10

It is important that the NTC thermistor not be in close

thermal contact with the LTC1733. Because the LTC1733

package can reach temperatures in excess of the 50°C trip

point, the NTC function can cause a hysteretic oscillation

which turns the charge current on and off according to the

•6.89 – 1 •100

7

Temperature Error (°C) =

–4.5

= –1.8°C, +2.5°C

sn1733 1733fs

11

LTC1733

W U U

U

APPLICATIO S I FOR ATIO

Ifathermistorwithatolerancelessthan±10%isused, the

trip point errors begin to depend on errors other than

thermistor tolerance including the input offset voltage of

theinternalcomparatorsoftheLTC1733andtheeffectsof

internal voltage drops due to high charging currents.

105°C. As the battery voltage rises, the LTC1733 either

returns to constant-current mode or it enters constant-

voltage mode straight from constant-temperature mode.

Regardless of mode, the voltage at the PROG pin is

proportional to the current being delivered to the battery.

Constant-Current/Constant-Voltage/

Constant-Temperature

Power Dissipation

The conditions that cause the LTC1733 to reduce charge

current due to the thermal protection feedback can be

approximated by considering the power dissipated in the

IC. For high charge currents, the LTC1733 power dissipa-

tion is approximately:

The LTC1733 uses a unique architecture to charge a

battery in a constant-current, constant-voltage, constant-

temperature fashion. Figure 1 shows a simplified block

diagram of the LTC1733. Three of the amplifier feedback

loops shown control the constant-current, CA, constant-

voltage, VA, and constant-temperature, TA modes. A

fourth amplifier feedback loop, MA, is used to increase the

output impedance of the current source pair, M1 and M2

(note that M1 is the internal P-channel power MOSFET). It

ensures that the drain current of M1 is exactly 1000 times

greater than the drain current of M2.

P_D= (V_CC– V_BAT) • I_BAT

where P_Dis the power dissipated, V_CCis the input supply

voltage, V_BATis the battery voltage, and I_BATis the battery

charge current. It is not necessary to perform any worst-

case power dissipation scenarios because the LTC1733

will automatically reduce the charge current to maintain

the die temperature at approximately 105°C. However, the

approximate ambient temperature at which the thermal

feedback begins to protect the IC is:

Amplifiers CA, TA, and VA are used in three separate

feedback loops to force the charger into constant-current,

temperature, or voltage mode, respectively. Diodes, D1,

D2, and D3 provide priority to whichever loop is trying to

reduce the charging current the most. The outputs of the

other two amplifiers saturate low which effectively re-

moves their loops from the system. When in constant-

current mode, CA servos the voltage at the PROG pin to be

precisely 1.50V (or 0.15V when in trickle-charge mode).

TA limits the die temperature to approximately 105°C

when in constant-temperature mode and the PROG pin

voltage gives an indication of the charge current as dis-

cussed in “Programming Charge Current” . VA servos its

inverting input to precisely 2.485V when in constant-

voltage mode and the internal resistor divider made up of

R1 and R2 ensures that the battery voltage is maintained

at either 4.1V or 4.2V. Again, the PROG pin voltage gives

an indication of the charge current.

T_A= 105°C – P_Dθ_JA

T_A= 105°C – (V_CC– V_BAT) • I_BAT• θ_JA

Example: Consider an LTC1733 operating from a 5V wall

adapter providing 1.2A to a 3.75V Li-Ion battery. The

ambient temperature above which the LTC1733 will begin

to reduce the 1.2A charge current is approximately:

T_A= 105°C – (5V – 3.75V) • 1.2A • 40°C/W

T_A= 105°C – 1.5W • 40°C/W = 105°C – 60°C = 45°C

The LTC1733 can be used above 45°C, but the charge

current will be reduced below 1.2A. The approximate

charge current at a given ambient temperature can be

approximated by:

105°C – T_A

(V_CC– V_BAT)•θ_JA

In typical operation, the charge cycle begins in constant-

current mode with the current delivered to the battery

equal to 1500V/R_PROG. If the power dissipation of the

LTC1733 results in the junction temperature approaching

105°C, the amplifier (TA) will begin decreasing the charge

current to limit the die temperature to approximately

I_BAT

=

Consider the above example with an ambient temperature

of 55°C. The charge current will be reduced to approxi-

mately:

sn1733 1733fs

12

LTC1733

W U U

APPLICATIO S I FOR ATIO

U

Stability

105°C – 55°C

(5V – 3.75V)•40°C / W 50°C /A

50°C

I_BAT

=

= 1A

The constant-voltage mode feedback loop is stable

without any compensation when a battery is connected.

However, a 1µF capacitor with a 1Ω series resistor to GND

is recommended at the BAT pin to keep ripple voltage low

when the battery is disconnected.

Furthermore, the voltage at the PROG pin will change

proportionally with the charge current as discussed in the

Programming Charge Current section.

It is important to remember that LTC1733 applications do

notneedtobedesignedforworst-casethermalconditions

since the IC will automatically reduce power dissipation

when the junction temperature reaches approximately

105°C. See Design Note 283 for additional information.

In the constant-current mode it is the PROG pin that is in

the feedback loop and 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, stability is acceptable with program resistor values as

high as 50k. However, additional capacitance on this node

reduces the maximum allowed program resistor. The pole

frequency at the PROG pin should be kept above 500kHz.

Therefore, if the PROG pin is loaded with a capacitance, C,

the following equation should be used to calculate the

Board Layout Considerations

In order to be able to deliver maximum charge current

under all conditions, it is critical that the exposed pad on

the backside of the LTC1733 package is soldered to the

board. Correctly soldered to a 2500mm²double-sided

1oz. copper board the LTC1733 has a thermal resistance

of approximately 40°C/W. Failure to make thermal contact

between the exposed pad on the backside of the package

and the copper board will result in thermal resistances far

greater than 40°C/W. As an example, a correctly soldered

LTC1733 can deliver over 1250mA to a battery from a 5V

supply at room temperature. Without a backside thermal

connection, this number could drop to less than 500mA.

maximum resistance value for R_PROG

:

R_PROG< 1/(6.283 • 500E3 • C)

Average, rather than instantaneous, battery current may

beofinteresttotheuser.Forexample,ifaswitchingpower

supply operating in low-current mode is connected in

parallel with the battery the average current being pulled

out of the BAT pin is typically of more interest than the

instantaneous current pulses. In such a case, a simple RC

filter can be used on the PROG pin to measure the average

battery current as shown in Figure 4. A 10k resistor is

added between the PROG pin and the filter capacitor and

monitoring circuit to ensure stability.

V_CCBypass 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. For more information refer to

Application Note 88.

LTC1733

CHARGE

10k

7

CURRENT

MONITOR

CIRCUITRY

PROG

GND

R

PROG

C

FILTER

5

1733 F04

Figure 4. Isolating Capacitive Load on PROG Pin and Filtering.

sn1733 1733fs

13

LTC1733

U

TYPICAL APPLICATIO

Basic Li-Ion Battery Charger with Reverse Polarity Input Protection

I

= 1A

BAT

LTC1733

9

7

2

8

5V WALL

ADAPTER

V

BAT

CC

SEL

+

4.2V Li-Ion

BATTERY

4.7µF

4

TIMER

PROG

GND

5

NTC

6

1.5k

1%

0.1µF

1733 F06

sn1733 1733fs

14

LTC1733

U

PACKAGE DESCRIPTIO

MSE Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1663)

BOTTOM VIEW OF

EXPOSED PAD OPTION

2.06 ± 0.102

(.081 ± .004)

2.794 ± 0.102

(.110 ± .004)

0.889 ± 0.127

(.035 ± .005)

1

1.83 ± 0.102

(.072 ± .004)

5.23

(.206)

MIN

2.083 ± 0.102 3.2 – 3.45

(.082 ± .004) (.126 – .136)

10

0.50

(.0197)

BSC

0.305 ± 0.038

(.0120 ± .0015)

TYP

3.00 ± 0.102

(.118 ± .004)

(NOTE 3)

0.497 ± 0.076

(.0196 ± .003)

REF

10 9

8

7 6

RECOMMENDED SOLDER PAD LAYOUT

3.00 ± 0.102

(.118 ± .004)

NOTE 4

4.88 ± 0.10

(.192 ± .004)

DETAIL “A”

0.254

(.010)

0° – 6° TYP

1

2

3

4 5

GAUGE PLANE

0.53 ± 0.01

(.021 ± .006)

0.86

(.034)

REF

1.10

(.043)

MAX

DETAIL “A”

0.18

(.007)

SEATING

PLANE

0.17 – 0.27

(.007 – .011)

0.13 ± 0.05

(.005 ± .002)

MSOP (MSE) 1001

0.50

(.0197)

TYP

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

sn1733 1733fs

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

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

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

15

LTC1733

U

TYPICAL APPLICATIO

Full Featured Single Cell Li-Ion Charger

V

= 5V

IN

1k

8

2

1k

SEL

V

CC

10

3

4k

ACPR

FAULT

BAT

1%

1

6

4

CHRG

I

= 500mA

4.7µF

LTC1733

NTC

BAT

9

1µF

7

TIMER

PROG

+

R

4.2V Li-Ion

BATTERY

NTC

10k

GND

3k

1%

1Ω

5

0.1µF

1733 F05

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Thermistor Interface

sn1733 1733fs

LT/TP 0602 2K • PRINTED IN USA

16 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

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


型号：	LTC1733EMSE#TRPBF
厂家：	Linear
描述：	LTC1733 - Monolithic Linear Lithium-Ion Battery Charger with Thermal Regulation; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C 电池
文件：	总16页 (文件大小：170K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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