LTC1730-4_15_技术文档

LTC1730-4/LTC1730-4.2

Lithium-Ion Battery

Pulse Charger with

Overcurrent Protection

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DESCRIPTIO

FEATURES

The LTC^®1730 is a complete pulse charger for 1-cell

lithium-ion batteries. When charging a depleted cell, the

internal MOSFET is fully on allowing the current limited

input power source to provide charge current to the

battery,virtuallyeliminatingheatgenerationinthecharger.

■

Complete Pulse Charger for 1-Cell Lithium-Ion

Batteries

■

Sense Resistor Limits Maximum Current for Safety

■

1% Float Voltage Accuracy

■

End-of-Charge (C/10) Detection Output

■

Programmable Charge Termination Timer

As the battery accepts charge and approaches the pro-

grammed voltage, the internal MOSFET begins switching

off and on with the duty cycle gradually decreasing as the

battery approaches a fully charged condition. A program-

mable timer ends the charge cycle. The end-of-charge

condition is indicated at the CHRG pin when the average

charge current falls to C/10. Removing the input voltage

puts the LTC1730 into a sleep mode, dropping the battery

current drain to less than 1µA (maximum).

■

Internal 0.35Ω NMOS Switch

No Blocking Diode Required

■

SEL Pin to Set Either 4.1V or 4.2V/Cell (LTC1730-4)

■

Low-Battery Drain (1µA Max) when Input Supply Is

Removed

■

Battery Temperature Sensing and Charge

Qualification

■

Automatic Trickle Charge for Low-Battery

■

Automatic Battery Refresh

An external sense resistor limits the maximum charge

current as a safety precaution against a user connecting a

wall adapter with the incorrect or no current limit. The

internal MOSFET prevents reverse battery current from

flowing if the input voltage is shorted to ground, eliminat-

ing the need for a blocking diode.

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APPLICATIO S

■

Standalone Lithium-Ion Battery Charger

Handheld Computers

Cellular Telephones

■

The LTC1730-4 is available in the 16-pin SSOP package

and the LTC1730-4.2 is available in the 8-pin SO package.

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

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TYPICAL APPLICATIO

1A, Single Cell 4.2V Li-Ion Battery Charger (8-Pin Package)

V

= 4.5V TO 12V

IN

WITH 1A CURRENT LIMIT

2

R2

10k

4.7Ω

R1

1k

V

CC

R

SENSE

0.05Ω

C1

1µF

C3

0.047µF

R3

4.1k

LTC1730ES8-4.2

D3

7

CHARGE STATUS

GATE

3

6

0.022µF

CHRG

1

8

SENSE

NTC/SHDN

BAT

1-CELL

Li-Ion

BATTERY

R4

10k

NTC*

T

TIMER

5

GND

4

C

TIMER

0.1µF

*NTC: DALE NTHS-1206N02

1730 TA01

sn1730 1730fs

1

LTC1730-4/LTC1730-4.2

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ABSOLUTE AXI U RATI GS

(Note 1)

Supply Voltage (V_CC) ............................................ 13.2V

SENSE, GATE, BAT,

TIMER, NTC/SHDN, SEL ............................ –0.3V to V_CC

CHRG, ACPR, FAULT ..............................–0.3V to 13.2V

Operating Junction

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

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

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

TOP VIEW

ORDER PART

NUMBER

1

2

3

4

5

6

7

8

GND*

BAT

16

15

14

13

12

11

10

9

GND*

NUMBER

SENSE

LTC1730EGN-4

LTC1730ES8-4.2

NC**

V

CC

TOP VIEW

GATE

ACPR

FAULT

CHRG

NC**

SEL

SENSE

1

2

3

4

8

7

6

5

BAT

NTC/SHDN

TIMER

GND*

V

GATE

CC

CHRG

GND

NTC/SHDN

TIMER

GN PART MARKING

17304

S8 PART MARKING

173042

GND*

GN PACKAGE

16-LEAD PLASTIC SSOP

S8 PACKAGE

8-LEAD PLASTIC SO

*

FOUR CORNER PINS ARE FUSED TO

INTERNAL DIE ATTACH PADDLE FOR

HEAT SINKING. CONNECT THESE FOUR

PINS TO EXPANDED PC LANDS FOR

PROPER HEAT SINKING.

T_JMAX= 125°C, θ_JA= 110°C/W

** NO INTERNAL CONNECTION

T_JMAX= 125°C, θ_JA= 90°C/W

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

DC ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

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

SYMBOL

PARAMETER

Supply Voltage

Supply Current

CONDITIONS

MIN

TYP

MAX

UNITS

V

●

4.5

12

V

CC

I

Charger On; Fast Charge Mode

●

2

5

1

mA

µA

CC

Shutdown: V

= 0V

= 4V

NTC/SHDN

Sleep Mode; V

BAT

V

Regulated Output Voltage

LTC1730ES8-4.2 (5V ≤ V ≤ 12V)

●

4.158

4.059

4.158

4.2

4.1

4.2

4.242

4.141

4.242

V

BAT

CC

LTC1730EGN-4 (5V ≤ V ≤ 12V), SEL = GND

CC

LTC1730EGN-4 (5V ≤ V ≤ 12V), SEL = V

CC

I

Maximum Charge Overcurrent

Trickle Charge Current

R

= 0.1Ω

●

0.7

15

1

1.3

60

A

mA

V

MAX

SENSE

V

= 2V

BAT

35

TRICKL

V

Trickle Charge Trip Threshold

2.45

2.55

150

TRICKL

ASD

Automatic Shutdown Threshold Voltage

(Sleep Mode)

(V – V ) Low to High

(V – V ) High to Low

mV

CC

BAT

0

CC

BAT

R

Internal Switch On-Resistance

Shutdown Threshold Voltage

V

= 4V

0.35

Ω

DS(ON)

BAT

V

NTC/SHDN Pin High to Low

50

mV

SHDN

sn1730 1730fs

2

LTC1730-4/LTC1730-4.2

DC ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating

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

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

70

UNITS

µA

I

CHRG Pin Pull-Down Current

TIMER Accuracy

V

C

= 1V, C/10 Mode

10

40

CHRG

T

= 0.1µF

10

%

TIMER

V

GATE Pin Voltage

V

= 3V

= 4V

7.5

10

V

GATE

BAT

T

Thermal Shutdown Temperature

Thermal Shutdown Hysteresis

140

5

°C

SHDN

∆T

SHDN

∆V

Recharge Battery Voltage Offset from

Full Charged Battery Voltage

V

– V (Note 3)

RECHRG

150

mV

RECHRG

NTC_HOT

NTC_COLD

BAT(Full Charged)

V

NTC/SHDN Pin Threshold Voltage (Hot)

High to Low; V = 4V

Hysteresis

●

1.95

3.4

2

50

2.05

3.6

V

mV

CC

NTC/SHDN Pin Threshold Voltage (Cold)

Low to High; V = 4V

Hysteresis

3.5

45

V

mV

CC

V

SEL Pin Threshold

LTC173ECGN-4

0.7

V

SEL

ACPR Pin Output Low Voltage

FAULT Pin Output Low Voltage

CHRG Pin Output Low Voltage

LTC1730EGN-4, I

= 5mA

0.6

1.2

0.9

ACPR

FAULT

CHRG

ACPR

= 3mA

FAULT

I

= 5mA, Charging Mode

CHRG

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

of a device may be impaired.

operating temperature range are assured by design, characterization and

correlation with statistical process controls.

Note 2: The LTC1730-4/LTC1730-4.2 are guaranteed to meet performance

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

Note 3: For the LTC1730-4 version, the full charged V

typically 4.1V.

value is

BAT

sn1730 1730fs

3

LTC1730-4/LTC1730-4.2

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TYPICAL PERFOR A CE CHARACTERISTICS

Trickle Charge Current vs Input

Supply Voltage

Trickle Charge Threshold Voltage

vs Temperature

Trickle Charge Current vs

Temperature

50

45

40

35

30

25

20

50

45

40

35

30

25

20

2.50

2.48

2.46

2.44

2.42

2.40

T

= 25°C

V

= 6V

A

V

= 6V

CC

9

11

12

–50 –25

0

25

50

75 100 125

5

6

7

8

10

50

TEMPERATURE (°C)

–50 –25

0

25

75 100 125

V

(V)

TEMPERATURE (°C)

CC

1730 G01

1730 G03

1730 G02

Internal Switch On-Resistance vs

Temperature

Timer Accuracy vs Temperature

Overcurrent vs Temperature

115

110

105

100

95

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.50

0.45

0.40

0.35

0.30

0.25

0.20

V

= 6V

SEN

V

BAT

= 4V

V

C

= 6V

CC

TIMER

R

= 0.1Ω

= 0.1µF

90

85

80

50

–50 –25

0

25

75 100 125

–50 –25

0

25

75 100 125

–50 –25

0

25

75 100 125

TEMPERATURE (°C)

1730 G06

1730 G07

1730 G05

Battery Recharge Threshold Offset

from V_BATvs Temperature

CHRG Pin Output Low Voltage vs

Temperature

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

300

250

200

150

100

50

V

= 6V

CC

0

50

TEMPERATURE (°C)

–50 –25

0

25

75 100 125

50

TEMPERATURE (°C)

–50 –25

0

25

75 100 125 150

1730 G08

1730 G09

sn1730 1730fs

4

LTC1730-4/LTC1730-4.2

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PI FU CTIO S

LTC1730ES8-4.2

above 0.875 • V_CC, or 3.5V at cold (with V_CC= 4V), the

charge cycle is suspended and the internal timer is frozen.

The CHRG pin output status is not affected in this hold

state.

SENSE (Pin 1): Maximum Overcurrent Sense Input. A

sense resistor (R_SENSE) should be connected from V_CCto

the SENSE pin. When the voltage drop across R_SENSE

exceeds 100mV, the pass transistor immediately turns off

and turns back on after a 400ms time-out period (C_TIMER

= 0.1µF). The on-off cycle will continue, as long as the

overcurrent condition persists or until the timer runs out.

If overcurrent protection is not needed, short SENSE to

V_CC.

When this pin is pulled below 50mV, the IC goes into the

shutdown mode. The charging stops (the GATE pin is

pulled to ground) the timer is reset and the CHRG pin goes

into a high impedance state.

GATE (Pin 7): Gate Drive Output Pin for Internal and

ExternalPassTransistors. AnexternalN-MOSFETtransis-

tor can be connected in parallel with the internal transistor

to reduce the on-resistance for higher charge current. In

this case, an external blocking diode is required to prevent

damage to the battery if V_CCis shorted to ground. A 10µA

current source pulls this pin up to the charge pump

potential when turned on and a 40µA current source pulls

it down to ground to turn it off. If an overcurrent condition

is detected, the GATE pin is immediately pulled to ground.

V

_CC(Pin 2): Positive Input Supply Voltage (4.5V ≤ V_CC≤

13.2V). Bypass this pin with a 1µF capacitor in series with

a 4.7Ω resistor. An RC network from the V_CCpin to the

GATE pin is also required. The capacitor controls the slew

rate at the V_CCpin, while the resistor limits the inrush

current when the input voltage is first applied. When the

pass transistor turns on, V_CCramps down in a controlled

manner, with a slope equal to 10µA/C. When the pass

transistor turns off, V_CCramps up with a slope of 40µA/C.

A series RC network from the GATE to the V_CCpin is

required to control the slew rate at the V_CCpin when the

switch is turned on or off. The slew rate control prevents

excessive current from the capacitor located in the wall

adapter from flowing into the battery when the pass

transistor is turned on. The voltage at this pin is internally

clamped to 12V above the BAT pin.

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

depleted battery is being charged, the CHRG pin is pulled

to ground by an N-MOSFET capable of driving an LED.

Once the duty cycle at the GATE pin drops below 10%, the

N-MOSFET turns off and a weak 40µA current source to

ground turns on to indicate a near end-of-charge (C/10)

condition. When a time-out occurs or the input supply is

removed, the CHRG pin goes high impedance.

BAT (Pin 8): Battery Sense Input Pin. This pin is clamped

to 4.7V if the battery is disconnected while charging. An

internal resistor divider presets the final float voltage to

4.2V.

GND (Pin 4): Electrical Ground Connection and provides

a thermal path from the IC to the PC board copper. Use

large copper pads and traces for maximum heat transfer.

If the voltage at the BAT pin drops 150mV below final float

voltage after the charge cycle has ended, the timer resets

and a new charge cycle begins.

TIMER (Pin 5): Timer Set Pin. The timer period is set by a

capacitor (C_TIMER) to ground. The timer period is:

t_TIMER= (C_TIMER• 3Hr)/(0.1µF). The minimum ON time,

OFF time and the overcurrent time-out period are all set by

the same timer period.

LTC1730EGN-4

GND (Pins 1, 8, 9, 16): Refer to LTC1730ES8-4.2

SENSE (Pin 2): Refer to LTC1730ES8-4.2

V_CC(Pin 3): Refer to LTC1730ES8-4.2

NTC/SHDN (Pin 6): Input to the NTC (Negative Tempera-

ture Coefficient) Thermistor Monitoring and Shutdown

Circuitry.Withanexternal10kΩNTCthermistortoground

and a 1% resistor to V_CC, this pin can sense the tempera-

ture of the battery pack and stop charging when the

temperature is out of range. When the voltage at this pin

drops below 0.5 • V_CC, or 2V at hot temperature or rises

ACPR (Pin 4): Wall Adapter Present Open-Drain Output.

When the input voltage (wall adapter) is applied to the

LTC1730, this pin is pulled to ground by an internal

sn1730 1730fs

5

LTC1730-4/LTC1730-4.2

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PI FU CTIO S

N-channel MOSFET. This output can sink up to 5mA

suitable for driving an LED.

condition is detected, the FAULT pin is pulled low and

latched.

FAULT (Pin 5): Fault Condition Detection Open-Drain

Output. Thisoutputcansinkupto3mAsuitablefordriving

anexternalLED.TheinternalN-channelMOSFETpullsthis

pin to ground when either one of the following conditions

is detected:

CHRG (Pin 6): Refer to LTC1730ES8-4.2

NC(Pins7,14):NoInternalConnection.Connectingthese

pins to ground will help transfer heat from the package.

TIMER (Pin 10): Refer to LTC1730ES8-4.2

NTC/SHDN (Pin 11): Refer to LTC1730ES8-4.2

1. ThevoltageattheNTCpinisoutofthenormaloperation

range. Thisusuallymeansthebatterypacktemperature

is too high or too low. Once the temperature is back to

normal, the FAULT pin becomes high impedance.

SEL (Pin 12): 4.1V/4.2V Battery Selection Input. Ground-

ing this pin will set the output float voltage to 4.1V, while

connecting to V_CCwill set the voltage to 4.2V.

2. The BAT pin potential stays below 2.45V for more

than 1/4 of the programmed charge time. When this

GATE (Pin 13): Refer to LTC1730ES8-4.2

BAT (Pin 15): Refer to LTC1730ES8-4.2

W

BLOCK DIAGRA

V

CC

CHRG

100mV

+

–

C5

+

35mA

N1

SENSE

GATE

–

40µA

Q-PUMP

(3X)

+

40mV

0.125R

–

C/10

STOP

I

MAX

N

SW

C6

C7

C8

C4

–

+

COLD

ACPR

BAT

–

0.375R

R1

R2

R3

C3

C2

C1

NTC/SHDN

–

+

–

LOGIC

HOT

V

MAX

+

0.5R

+

–

+

SHDN

V

BAT

121mV

OSCILLATOR

CLK

–

+

FAULT

ACPR

V

MIN

R5

FAULT

C9

SEL

ON

RECHRG

R4

+

–

4.1V/4.2V

1.21V

+

150mV

–

1703 BD

TIMER

GND

sn1730 1730fs

6

LTC1730-4/LTC1730-4.2

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OPERATIO

The LTC1730 is a complete lithium-ion battery pulse

charger with an internal 0.35Ω N-MOSFET switch driven

by an internal charge pump. The charge current is set by

the current limit of the input supply (wall adapter). An

external R_SENSEsets the maximum allowable charge over

current (I_MAX= 0.1V/R_SENSE) and prevents a wall adapter

with the wrong current limit from damaging the battery. If

the current limit of the input supply is above I_MAX, the

chargingwillbeimmediatelyterminatedandwillretryafter

400ms (C_TIMER= 0.1µF). If the battery is disconnected

while in fast charge mode, the N-channel MOSFET turns

off when the voltage at the BAT pin rises above 4.7V, and

turns back on when the voltage drops below the float

voltage.

When the battery voltage reaches the final float voltage,

the pass transistor turns off for 100ms (minimum off-

time). It remains off as long as the battery voltage stays

above the float voltage after the 100ms off-time. After the

minimum off-time, if the battery voltage drops below the

float voltage, the pass transistor turns back on for at least

380ms(minimumon-time).Asthebatteryapproachesfull

charge, the off-time will get longer and the on-time will

stay at 380ms. The voltage at the BAT pin will be slightly

higher than the final float voltage due to the ESR associ-

ated with the battery pack. This voltage level should not

turn on the overvoltage protection circuitry often located

in the battery pack. When the duty cycle at the GATE pin

drops below 10%, a comparator turns off the N-FET at the

CHRG pin and connects a weak current source (40µA) to

ground to indicate a near end-of-charge (C/10) condition.

The pulse charging will continue until the timer stops.

AchargecyclebeginswhenthevoltageattheV_CCpinrises

above the BAT pin by 40mV and the voltage at the NTC/

SHDN pin is in between 0.5 • V_CCand 0.875 • V_CC. The

charger will go into trickle charge mode if the battery

voltageisbelow2.45V. Thetricklechargecurrentispreset

to 35mA and is provided by an internal current source. In

trickle mode, the charge pump and pass transistor are off.

AnexternalcapacitorattheTIMERpinsetsthetotalcharge

time, the minimum on- and off-time and the overcurrent

retry period. After a time-out has occurred, the charge

cycle is terminated and the CHRG pin is forced high

impedance. To restart the charge cycle, momentarily pull

theNTC/SHDNpinbelow50mVorremoveandreapplythe

input voltage. After the charging stops, if the battery

voltage drops 150mV below the final float voltage, due to

external loading or internal leakage, a new charge cycle

will automatically begins.

When the battery voltage exceeds 2.45V, the charger goes

into the fast charge mode. In this mode, the charge pump

turns on and ramps up the gate voltage of the pass

transistor turning it on. The voltage at the V_CCpin then

ramps down to V_BATplus the voltage drop across the pass

transistor and R_SENSE, thus reducing the power dissipa-

tion in the pass transistor. The charge current is deter-

mined by the current limit of the input supply.

The charger can be shut down by pulling the NTC/SHDN

pin to ground. When the input voltage is not present, the

charger goes into a sleep mode, dropping battery drain

current to less than 1µA.

sn1730 1730fs

7

LTC1730-4/LTC1730-4.2

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APPLICATIO S I FOR ATIO

an external capacitor from the TIMER pin to ground. The

total charge time is:

Stop Charging

The charger is off when any of the following conditions

exist. The voltage at the V_CCpin is less than 40mV above

V_BAT(sleep mode), or the potential at the NTC/SHDN pin

is less than 50mV (shutdown mode). The trickle charge

current source and the internal pass transistor are turned

off. The internal resistor divider is disconnected to reduce

the current drain on the battery when in sleep mode.

Time (Hours)= (3 Hour)(C_TIMER/0.1µF)

The timer starts when the input voltage (at least 40mV

greater than V_BAT) is applied and the potential at the NTC/

SHDN pin is between 0.5 • V_CCand 0.875 • V_CC. After a

time-out has occurred, the charging stops and the CHRG

pin becomes high impedance.

Input Voltage (Wall Adapter)

CHRG Status Output Pin

The input voltage to the LTC1730 must have some

method of current limit capability. The current limit level

of the input power source must be lower than the

This open-drain output requires a pull-up resistor and can

be used to indicate three charging conditions. When fast

charging begins, an N-FET (capable of driving an LED)

turns on, pulling this pin to ground. Once the duty cycle at

the GATE pin drops below 10%, the N-FET turns off and a

40µA current source to ground turns on. When a time-out

occurs or the input supply is removed, the CHRG pin goes

highimpedanceindicatingthatthechargecyclehasended.

By using two different value resistors, a microprocessor

can detect three states from this pin: charging, C/10 and

stop charging (see Figure 1).

overcurrent limit (I_MAX) set by the sense resistor (I_MAX

=

100mV/R_SENSE). If a wall adapter without current limit is

used, or the current limit level is above I_MAX, the charger

will turn on briefly and then immediately turn off after the

overcurrent condition is detected. This cycle will be re-

sumedevery400ms(C_TIMER=0.1µF)untilthetotalcharge

time has run out. If overcurrent protection is not needed,

short the SENSE pin to V_CC.

+

V

DD

Trickle Charge and Defective Battery Detection

2

At the begining of the charge cycle, if the cell voltage is low

(less than 2.45V) the charger goes into a 35mA trickle

charge mode. If the low cell voltage persists for one

quarter of the total charge time, the battery is considered

defective and the charge cycle is terminated. The CHRG

pin output is then forced to a high impedance state.

V

CC

620k

2k

LTC1730

CHRG

MICROPROCESSOR

OUT

3

IN

1730 F01

Figure 1. Interfacing with Microprocessor

Battery Charge Current

When the LTC1730 is in charge mode, the CHRG pin is

pulled to ground by an internal N-MOSFET. To detect this

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

the voltage at the CHRG pin. The N-MOSFET will pull the

pin low even with a 2k pull-up resistor. Once the charge

current drops below 10% of the full scale current (C/10),

the N-MOSFET is turned off and a 40µA current source is

connected to the CHRG pin. By forcing the OUT pin to a

high impedance state, the current source will pull the pin

lowthroughthe620kresistor. Whentheinternaltimerhas

expired, the CHRG pin becomes high impedance and the

620kresistorwillpullthepinhightoindicatethatcharging

The battery charge current is determined by the current

limit of the input supply (wall adapter). However, this

currentmustnotexceedthemaximumchargeovercurrent,

I_MAX. If an overcurrent condition is detected, the charging

is immediately terminated, the GATE pin is pulled to

ground and the charge pump turns off. The charging will

resume after a 400ms time off (C_TIMER= 0.1µF).

Programming the Timer

The programmable timer is used to terminate the charge

and sets the minimum ON/OFF time and the overcurrent

time-off period. The length of the timer is programmed by

has stopped.

sn1730 1730fs

8

LTC1730-4/LTC1730-4.2

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APPLICATIO S I FOR ATIO

10µA/C

40µA/C

End-of-Charge (C/10)

V

CC

The LTC1730 includes a comparator to monitor the duty

cycle at the GATE pin to detect a near end-of-charge

condition. When the duty cycle falls below 10%, the

comparatortripsandturnsofftheN-MOSFETattheCHRG

pin and switches in a weak (40µA) current source to

ground. The end-of-charge comparator is disabled in

trickle charge mode.

40µA/C

GATE

VOLTAGE

10µA/C

40µA/C

1730 TA02

10µA/C

Figure 2. Slew Rate at GATE and V_CCPins

with the RC Network from GATE to V_CC

above V_BAT, the external N-MOSFET gate to source break-

down voltage should be rated at 20V or more.

Internal Pass Transistor

AnN-channelMOSFET(0.35Ω)isincludedintheLTC1730

as the pass transistor. The gate of the MOSFET is con-

trolled by an internal charge pump. The body is connected

to ground instead of source terminal. There is no body

diode from the BAT pin back to the V_CCpin; therefore, no

blocking diode is required in series with the battery or the

inputsupply. Thiswillnotonlyreducethecostbutalsothe

heat generated when in fast charge mode. An internal

thermal shutdown circuit turns off the pass transistor if

the die temperature exceeds approximately 140°C with

5°C of thermal hysteresis.

Battery Temperature Detection

A negative temperature coefficient (NTC) thermistor lo-

cated close to the battery pack can be used to monitor

battery temperature and will not allow charging unless the

batterytemperatureiswithinanacceptablerange. Connect

a 10kΩ thermistor between ground and the NTC/SHDN pin

and a 4.1k resistor from the NTC/SHDN pin to V_CC. If the

temperature rises to 50°C, the resistance of the thermister

will be approximately 4.1kΩ (Dale NTHS-1206N02) and

the LTC1730 will go into a hold mode. For cold tempera-

tures, the threshold of the hold mode is at 0°C (R_NTC

≈

Gate Drive

28kΩ). The pass transistor turns off and the timer is frozen

at hold mode while the output status at the CHRG pin

remains the same. The charge cycle begins or resumes

once the temperature is within the acceptable range.

Thepasstransistorgatedriveconsistsofaregulated10µA

current source charge pump. A series RC network is

required from the GATE pin to the V_CCpin. When the pass

transistor is turned on, the voltage at the V_CCpin starts

slewing down to a voltage equal to V_BATplus the voltage

drop across the pass transistor and R_SENSE. The slew rate

is equal to 10µA/C. By ramping the V_CCpin down slowly,

the inrush current is reduced. The resistor in series with

thecapacitorisrequiredtolimitthetransientcurrentwhen

the input supply is first applied.

Thermal Considerations

The power handling capability is limited by the maximum

rated junction temperature (125°C) and the amount of PC

board copper used as a heat sink. The power dissipated by

the device consists of two components:

1. Input supply current multiplied by the input voltage

When the charge pump is turned off, a 40µA current

source to ground starts pulling the GATE voltage down.

Once the pass transistor is off, the voltage at the V_CCpin

begins slewing up with the rate equal to 40µA/C. With this

external capacitor, the voltage at the V_CCpin is ramping at

a controlled manner (Figure 2).

2. The voltage drop across the switch (SENSE pin to BAT

pin) multiplied by the charge current

The LTC1730 has internal thermal shutdown designed to

protect the IC from overtemperature conditions. For con-

tinuous charging in the fast charge mode, the maximum

junction temperature must not be exceeded. It is important

to give careful consideration to all sources of thermal

resistancefromjunctiontoambient.Additionalheatsources

mounted nearby must also be considered.

ForhighercurrentapplicationsanexternalpowerN-MOSFET

can be connected in parallel with the internal pass transis-

tor. Because the charge pump output is clamped to 12V

sn1730 1730fs

9

LTC1730-4/LTC1730-4.2

U

W

U U

APPLICATIO S I FOR ATIO

Table 1. SO-8 Package Thermal Resistance

COPPER AREA TOTAL THERMAL RESISTANCE

TOPSIDE BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)

Surfacemountpackagesrelyprimarilyonthecopperleads

(pins) to conduct the heat from the package to the sur-

rounding PC board copper which is acting as a heat sink.

The ground pin is especially important for conducting heat

as well as providing an electrical connection. Use gener-

ous amounts of copper around the ground pin and also

consider feedthrough vias (plated through holes) to back-

sideorinnercopperlayerstomaximizepowerdissipation.

2

2500mm

1000mm

2500mm

80°C/W

85°C/W

2

250mm

*Device is mounted on topside.

Output Voltage Selection (LTC1730EGN-4)

Table 1 lists the thermal resistance for the SO-8 package.

Measured values of thermal resistance for several differ-

ent board sizes and copper areas are listed. All measure-

ments were taken in still air on 0.062" FR-4 board with one

ounce copper.

The float voltage at the BAT pin can be selected by the SEL

pin. Shorting the SEL pin to ground will set the float

voltage to 4.1V, while connecting it to V_CCsets it to 4.2V.

This feature allows the charger to be used with different

types of Li-Ion cells.

Calculating Junction Temperature

ACPR Output Pin (LTC1730EGN-4)

Example: Find the maximum junction temperature for a

battery voltage of 4V (V_CCwill collapse to approximately

V_BATin the fast charge mode), charge current of 1A and a

maximum ambient temperature of 75°C.

When the input voltage is 40mV higher than the voltage at

the BAT pin, the ACPR pin is pulled low to ground to

indicate that the input supply (wall adapter) is applied.

After the input supply is removed, this pin becomes high

impedance. An internal 80ms delay prevents the LTC1730

from turning off if the voltage at the V_CCpin rings and gets

too close to V_BATbecause of the parasitic inductance.

The power dissipated by the IC is:

P = (I_BAT• I_BAT• R_DS(ON)) + (V_CC• I_CC)

= (1A • 1A • 0.35Ω) + (4V • 1mA)

= 0.35 + 0.004

FAULT Output Pin (LTC1730EGN-4)

The FAULT pin is pulled to ground when either one of the

following conditions is detected:

= 0.354W

The SO-8 package for the LTC1730 features a special lead

frame with a lower thermal resistance and higher allow-

able power dissipation. The junction-to-ambient thermal

resistance of this package when soldered to a PC board is

approximately 80°C/W depending on the copper area. So

the junction temperature rise above ambient will be

approximately:

1. The voltage at the NTC/SHDN pin is out of the operation

range. With a 10k negative temperature coefficient

thermistor placed near the battery pack, this pin indi-

cates that the temperature of the pack is either too cold

or too hot and the charger is suspended. Once the

temperatureisbacktotheoperationalrange,theFAULT

pin becomes high impedance and the charging re-

sumes.

(0.354W)(80°C/W) = 28.3°C

2. The voltage at the BAT pin stays below 2.45V for 1/4 of

the programmed charge time. If V_BATremains low even

with 35mA of trickle charge current for 1/4 of the total

The maximum junction temperature is equal to the maxi-

mum junction temperature rise above ambient plus the

maximum ambient temperature or:

T_JMAX= 75°C + 28.3°C = 103.3°C

sn1730 1730fs

10

LTC1730-4/LTC1730-4.2

U

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APPLICATIO S I FOR ATIO

shutting down the charger. After reset, the charger is

back in the charge mode and the FAULT pin becomes

high impedance again.

charge time, the battery is considered defective. The

charger turns off and the FAULT pin is pulled low. This

pin will stay low until the LTC1730 is reset by either

removing the input power supply or momentarily

U

PACKAGE DESCRIPTIO

GN Package

16-Lead Plastic SSOP (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1641)

0.189 – 0.196*

(4.801 – 4.978)

0.009

(0.229)

REF

0.015 ± 0.004

(0.38 ± 0.10)

16 15 14 13 12 11 10 9

× 45°

0.053 – 0.068

(1.351 – 1.727)

0.004 – 0.0098

(0.102 – 0.249)

0.007 – 0.0098

(0.178 – 0.249)

0° – 8° TYP

0.229 – 0.244

(5.817 – 6.198)

0.150 – 0.157**

(3.810 – 3.988)

0.016 – 0.050

(0.406 – 1.270)

0.0250

(0.635)

BSC

0.008 – 0.012

(0.203 – 0.305)

* DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

GN16 (SSOP) 1098

1

2

3

4

5

6

7

8

S8 Package

8-Lead Plastic Small Outline (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1610)

0.189 – 0.197*

(4.801 – 5.004)

0.010 – 0.020

(0.254 – 0.508)

7

5

8

6

× 45°

0.053 – 0.069

(1.346 – 1.752)

0.004 – 0.010

(0.101 – 0.254)

0.008 – 0.010

(0.203 – 0.254)

0°– 8° TYP

0.150 – 0.157**

(3.810 – 3.988)

0.228 – 0.244

(5.791 – 6.197)

0.016 – 0.050

(0.406 – 1.270)

0.050

(1.270)

BSC

0.014 – 0.019

(0.355 – 0.483)

TYP

*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

SO8 1298

**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

1

2

3

4

sn1730 1730fs

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.

11

LTC1730-4/LTC1730-4.2

U

TYPICAL APPLICATIO S

Single Cell 4.2V Li-Ion Battery Charger (16-Pin Package)

V

IN

= 5V TO 12V WITH 600mA CURRENT LIMIT

3

4.1k

1k

4.7Ω

V

CC

LTC1730EGN-4

CHRG

10k

1µF

6

4

0.047µF

0.1Ω

2

ACPR

SENSE

GATE

BAT

5

13

15

FAULT

11

0.022µF

NTC/SHDN

V

CC

12

SEL

10k

NTC*

1, 8, 9,16

Li-Ion

BATTERY

GND

NC

TIMER

10

7, 14

0.1µF

*NTC: DALE NTHS-1206N02

1730 TA04

Using External N-MOSFET for Higher Charge Current

V

= 5V TO 12V WITH 2A CURRENT LIMIT

IN

D1

MBRS120T3

2

R2

10k

4.7Ω

V

CC

R4

4.1k

R1

1k

R

SENSE

C3

0.047µF

C1

1µF

25mΩ

LTC1730ES8-4.2

D3

1

SENSE

GATE

BAT

CHARGE

STATUS

3

6

7

Q1

Si2302DS

CHRG

8

NTC/SHDN

0.022µF

Li-Ion

BATTERY

R3

10k

NTC*

TIMER

5

GND

4

C

TIMER

0.1µF

1730 TA03

*NTC: DALE NTHS-1206N02

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sn1730 1730fs

LT/TP 0902 1K • PRINTED IN USA

12 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

LINEAR TECHNOLOGY CORPORATION 2001

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


型号：	LTC1730-4_15
厂家：	Linear
描述：	Lithium-Ion Battery Pulse Charger with Overcurrent Protection 电池
文件：	总12页 (文件大小：169K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC1730-4_15 [Linear]

相关型号：

LTC1730EGN-4

LTC1730EGN-4#PBF

LTC1730EGN-4#TR

LTC1730EGN-4#TRPBF

LTC1730ES8-4.2

LTC1730ES8-4.2#PBF

LTC1730ES8-4.2#TR

LTC1730ES8-4.2#TRPBF

LTC1731

LTC1731-4.1

LTC1731-4.1_15

LTC1731-4.2