LTC4078XEDD-PBF_技术文档

LTC4078X

Dual Input Li-Ion Battery

Charger with Overvoltage Protection

FEATURES

DESCRIPTION

The LTC^®4078X is a standalone linear charger that is

capable of charging a single-cell Li-Ion/Polymer battery

from both wall adapter and USB inputs. The charger can

detect power at the inputs and automatically select the

appropriate power source for charging.

■

22V Maximum Voltage for Wall Adapter and

USB Inputs

■

Charge Single-Cell Li-Ion Batteries from Wall

Adapter and USB Inputs

Automatic Input Power Detection and Selection

Charge Current Programmable Up to 950mA from

Wall Adapter Input

Overvoltage Lockout for Wall Adapter and USB Inputs

Battery Detection Input Disables Charger When No

Battery is Present

No External MOSFET, Sense Resistor or Blocking

Diode Needed

■

No external sense resistor or blocking diode is required

for charging due to the internal MOSFET architecture.

The LTC4078X features a maximum 22V rating for both

wall adapter and USB inputs, although charging stops if

the selected power source exceeds the overvoltage limit.

Internal thermal feedback regulates the battery charge

currenttomaintainaconstantdietemperatureduringhigh

power operation or high ambient temperature conditions.

The ﬂoat voltage is ﬁxed at 4.2V and the charge current

is programmed with an external resistor. The LTC4078X

terminatesthechargecyclewhenthechargecurrentdrops

below the programmed termination threshold after the

ﬁnal ﬂoat voltage is reached.

■

Thermal Regulation Maximizes Charge Rate Without

Risk of Overheating*

■

Preset Charge Voltage with 0.ꢀ6 ꢁccuracy

Programmable Charge Current Termination

40µꢁ USB Suspend Current in Shutdown

Charge Status Output

ꢁutomatic Recharge

Otherfeaturesincludebatterypresentdetection,automatic

recharge,undervoltagelockout,chargestatusoutputs,and

“powerpresent”statusoutputstoindicatethepresenceof

wall adapter or USB power. The device is offered in a low

proﬁle (0.75mm) 3mm × 3mm 10-lead DFN package.

No Trickle Charge

ꢁvailable in a Thermally Enhanced, Low Proﬁle

(0.75mm) 10-Lead (3mm × 3mm) DFN Package

APPLICATIONS

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

other trademarks are the property of their respective owners.

*Protected by U.S. Patents including 6522118, 6700364.

■

Cellular Telephones

■

Handheld Computers

■

Portable MP3 Players

Digital Cameras

■

Charger Current vs Supply Voltage

TYPICAL APPLICATION

900

R

= 1.24k

= 2k

IDC

IUSB

High Voltage Dual Input Battery Charger

800

700

600

500

400

300

200

100

0

V

= 3.5V

BAT

BATDET

for Li-Ion Battery Pack

= 0V

CHARGE FROM DCIN

800mA (WALL)

500mA (USB)

LTC4078X

WALL

ADAPTER

DCIN

BAT

USB

USBIN BATDET

IUSB

4.2V

+

CHARGE

FROM USBIN

PORT

1µF

2k

3.9k

Li-Ion

BATTERY

PACK

IDC

ITERM

GND

1µF

1%

1.24k

1%

2k

1%

2

3

4

5

6

7

8

19 20

4078X TA01

SUPPLY VOLTAGE (V)

4078x TA01b

4078xf

1

LTC4078X

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

Input Supply Voltage (DCIN, USBIN) ............–0.3 to 22V

ENꢁBLE, CHRG, PWR, BꢁTDET, BꢁT...............–0.3 to ꢀV

IDC, IUSB, ITERM Pin Current .................................1mꢁ

DCIN, USBIN, BꢁT Pin Current....................................1ꢁ

BꢁT Short-Circuit Duration............................Continuous

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

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

Storage Temperature Range................... –ꢀ5°C to 125°C

TOP VIEW

USBIN

IUSB

1

2

3

4

5

10 DCIN

9

8

7

6

BAT

ITERM

PWR

11

IDC

BATDET

ENABLE

CHRG

DD PACKAGE

10-LEAD (3mm × 3mm) PLASTIC DFN

T

JMꢁX

= 125°C, θ = 40°C/W (Note 3)

Jꢁ

EXPOSED PꢁD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

TAPE AND REEL

PART MARKING

PACKAGE DESCRIPTION

10-Lead (3mm × 3mm) Plastic DFN

TEMPERATURE RANGE

–40°C to 85°C

LTC4078XEDD#PBF

LTC4078XEDD#TRPBF

LCYP

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

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

ELECTRICAL CHARACTERISTICS ^The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T = 25°C. V

= 5V, V

USBIN

= 5V unless otherwise noted.

A

DCIN

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

5.5

UNITS

●

V

Operating Supply Voltage

DCIN Supply Current

4.3

V

DCIN

USBIN

DCIN

●

4.3

5.5

●

I

Charge Mode (Note 4), R = 10k

350

70

40

70

800

120

80

µꢁ

IDC

Standby Mode; Charge Terminated

Shutdown Mode (ENꢁBLE = 5V)

Overvoltage Mode (V

= 10V)

140

DCIN

●

I

USBIN Supply Current

Charge Mode (Note 5), R

= 10k, V

= 0V

DCIN

= 0V

DCIN

350

70

40

70

23

800

120

80

140

40

µꢁ

USBIN

IUSB

●

Standby Mode; Charge Terminated, V

Shutdown (V

= 0V, ENꢁBLE = 0V)

DCIN

Overvoltage Mode (V

DCIN

= 10V)

USBIN

V

> V

USBIN

V

Regulated Output (Float) Voltage

BꢁT Pin Current

I

= 1mꢁ

4.185

4.1ꢀ5

4.2

4.215

4.235

V

FLOꢁT

BꢁT

= 1mꢁ, 0°C < T < 85°C

ꢁ

●

I

R

= 1.25k, Constant-Current Mode

770

455

93

800

47ꢀ

100

–7.5

830

495

107

–12

mꢁ

µꢁ

BꢁT

IDC

= 2.1k, Constant-Current Mode

IUSB

= 10k or R

= 10k

IDC

IUSB

Standby Mode, Charge Terminated

Shutdown Mode (Charger Disabled)

Sleep Mode (V

= 0V, V

= 0V)

DCIN

USBIN

4078xf

2

LTC4078X

ELECTRICAL CHARACTERISTICS ^The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T = 25°C. V

= 5V, V

USBIN

= 5V unless otherwise noted.

A

DCIN

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

1

MAX

UNITS

V

IDC Pin Regulated Voltage

IUSB Pin Regulated Voltage

Charge Current Termination Threshold

Constant-Current Mode

V

IDC

1

IUSB

●

I

R

ITERM

R

ITERM

R

ITERM

R

ITERM

= 1k

90

100

50

10

5

110

58

12

ꢀ.5

mꢁ

TERMINꢁTE

●

= 2k

42

●

= 10k

= 20k

8

●

3.5

V

DCIN Undervoltage Lockout Voltage

USBIN Undervoltage Lockout Voltage

DCIN Overvoltage Lockout Voltage

USBIN Overvoltage Lockout Voltage

From Low to High

Hysteresis

4

4.15

190

4.3

4.1

ꢀ.2

V

UVDC

mV

From Low to High

Hysteresis

3.8

5.8

3.95

170

V

mV

UVUSB

OVDC

From Low to High

Hysteresis

ꢀ

185

V

mV

From Low to High

Hysteresis

ꢀ

185

V

mV

OVUSB

V

– V Lockout Threshold

V

from Low to High, V = 4.2V

70

10

120

40

170

70

mV

ꢁSD-DC

DCIN

BꢁT

DCIN

BꢁT

from High to Low, V = 4.2V

BꢁT

V

– V Lockout Threshold

V

USBIN

V

USBIN

from Low to High

from High to Low

70

10

120

40

170

70

mV

ꢁSD-USB

USBIN

BꢁT

V

ENꢁBLE Input Threshold Voltage

ENꢁBLE Pulldown Resistance

BꢁTDET Input Threshold Voltage

BꢁTDET Pull-Up Current

0.ꢀ

1

0.9

2

1.2

3.5

1.85

ꢀ

V

MΩ

V

ENꢁBLE

●

R

ENꢁBLE

BDET

V

From Low to High

1.ꢀ5

2

1.75

4

I

V = 0V

BꢁTDET

µꢁ

V

BꢁTDET

V

BꢁTDET Open Circuit Voltage

V

= 5V, V

= 5V

USBIN

4

4.2

0.12

4.4

0.35

BOC

OL

DCIN

SINK

Output Low Voltage

(CHRG, PWR)

I

= 5mꢁ

V

ΔV

Recharge Battery Threshold Voltage

Recharge Comparator Filter Time

Termination Comparator Filter Time

V

– V

, 0°C < T < 85°C

90

2.25

1

125

4.1

1.ꢀ

ꢀ00

1ꢀ0

ꢀ.75

2.4

mV

ms

RECHRG

FLOꢁT

RECHRG

ꢁ

t

from High to Low

RECHRG

TERMINꢁTE

BꢁT

I

Drops Below Termination Threshold

ms

R

Power FET “ON” Resistance

(Between DCIN and BꢁT)

mΩ

ON-DC

ON-USB

LIM

R

Power FET “ON” Resistance

(Between USBIN and BꢁT)

700

120

mΩ

T

Junction Temperature in Constant-

Temperature Mode

°C

Note 1: Stresses beyond those listed under ꢁbsolute Maximum Ratings

may cause permanent damage to the device. Exposure to any ꢁbsolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: The LTC4078X is guaranteed to meet the performance

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

operating temperature range are assured by design, characterization and

correlation with statistical process controls.

Note 3: Failure to correctly solder the exposed backside of the package to

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

See Thermal Considerations.

Note 4: Supply current includes IDC and ITERM pin current (approximately

100µꢁ each) but does not include any current delivered to the battery

through the BꢁT pin.

Note 5: Supply current includes IUSB and ITERM pin current

(approximately 100µꢁ each) but does not include any current delivered to

the battery through the BꢁT pin.

4078xf

3

LTC4078X

TYPICAL PERFORMANCE CHARACTERISTICS ^{T = 25°C, unless otherwise speciﬁed.}

A

Regulated Output (Float) Voltage

vs Charge Current

Regulated Output (Float) Voltage

vs Temperature

IDC Pin Voltage vs Temperature

(Constant-Current Mode)

4.220

4.215

4.210

4.205

4.200

4.195

4.190

4.185

4.180

1.008

1.006

1.004

1.002

1.000

0.998

0.996

0.994

0.992

4.26

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

V

= V

= 5V

USBIN

V

= V

= 5V

USBIN

V

= 5V

DCIN

R

= 1.24k

IDC

R

= R

= 2k

IUSB

IDC

–10

10

30

50

70

90

0

100 200 300 400 500 600 700 800 900

(mA)

–10

10

30

50

70

90

TEMPERATURE (°C)

I

TEMPERATURE (°C)

BAT

4078x G02

4078x G01

4078x G03

IUSB Pin Voltage vs Temperature

(Constant-Current Mode)

Charge Current

vs IDC Pin Voltage

vs IUSB Pin Voltage

1.008

1.006

1.004

1.002

1.000

0.998

0.996

0.994

0.992

900

800

700

600

500

400

300

200

100

0

900

800

700

600

500

400

300

200

100

0

V

= 5V

V

= 5V

V

= 5V

USBIN

DCIN

R

= 1.24k

R

= 1.24k

IUSB

IDC

R

= 2k

IDC

R

= 2k

IUSB

R

= 10k

R

= 10k

IUSB

IDC

–10

10

30

50

70

90

0

0.2

0.4

0.6

(V)

0.8

1.0

1.2

0

0.2

0.4

0.6

0.8

1.0

1.2

TEMPERATURE (°C)

V

(V)

IUSB

IDC

4078x G04

4078x G05

4078x G06

PWR Pin I-V Curve

CHRG Pin I-V Curve

60

50

40

30

20

10

0

60

50

40

30

20

10

0

V

= V

= 5V

V

= V

= 5V

USBIN

DCIN

USBIN

DCIN

0

1

2

3

4

5

6

0

1

2

3

4

5

6

V

(V)

V

(V)

PWR

CHRG

4078x G07

4078x G08

4078xf

4

LTC4078X

TYPICAL PERFORMANCE CHARACTERISTICS ^{T = 25°C, unless otherwise speciﬁed.}

A

Charge Current

vs Ambient Temperature

Charge Current

vs Supply Voltage

Charge Current vs Battery Voltage

1000

900

800

700

600

500

400

300

200

100

0

900

800

700

600

500

400

300

200

100

0

1000

800

600

400

200

0

R

= 1.24k

IDC

= R

= 2k

IUSB

V

θ

= V

= 4V

= 30°C/W

= 5V

USBIN

R

V

JA

= 1.24k

= 4V

DCIN

BAT

JA

V

= V

= 5V

USBIN

IDC

BAT

= 30°C/W

DCIN

IDC

R

= 1.24k

θ

= 30°C/W

JA

–10

30

50

70

90 110 130

10

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

(V)

2.4 2.7 3.0 3.3 3.6 3.9 4.2 4.5

(V)

TEMPERATURE (°C)

V

4078x G10

V

BAT

DCIN

4078x G11

4078x G12

DCIN Power FET On-Resistance

vs Temperature

USBIN Power FET On-Resistance

vs Temperature

ENABLE Pin Threshold Voltage

(On-to-Off) vs Temperature

800

750

700

650

600

550

500

1000

980

960

940

920

900

880

860

900

850

800

750

700

650

600

V

I

= 4V

= 200mA

V

= V

= 5V

USBIN

V

I

= 4V

= 200mA

BAT

DCIN

BAT

–10

10

30

50

70

90

–10

10

30

50

70

90

–10

10

30

50

70

90

TEMPERATURE (°C)

4078x G13

4078x G15

4078x G14

USBIN Shutdown Current

vs Temperature

DCIN Shutdown Current

vs Temperature

ENABLE Pin Pulldown Resistance

vs Temperature

60

55

50

45

40

35

30

25

20

60

55

50

45

40

35

30

25

20

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

V

= 0V

V

= 5V

ENABLE

V

= 5V

USBIN

V

= 5V

DCIN

V

= 4.3V

USBIN

V

= 4.3V

DCIN

–50

–25

0

25

50

75

100

–50

–25

0

25

50

75

100

–50

–25

0

25

50

75

100

TEMPERATURE (°C)

4078x G16

4078x G17

4078x G18

4078xf

5

LTC4078X

TYPICAL PERFORMANCE CHARACTERISTICS

T = 25°C, unless otherwise speciﬁed.

A

Undervoltage Lockout Threshold

vs Temperature

Overvoltage Lockout Threshold

vs Temperature

4.25

4.20

4.15

4.10

4.05

4.00

3.95

3.90

3.85

6.10

6.05

6.00

5.95

5.90

5.85

5.80

DCIN UVLO

USBIN OVLO

DCIN OVLO

USBIN UVLO

–10

10

30

50

70

90

–10

10

30

50

70

90

TEMPERATURE (°C)

4078x G19

4078x G20

Recharge Threshold Voltage

vs Temperature

Battery Drain Current

vs Temperature

4.11

4.09

4.07

4.05

4.03

9.0

8.5

8.0

7.5

7.0

6.5

6.0

V

= V

= 5V

USBIN

V

= V

= NOT CONNECTED

USBIN

DCIN

BAT

= 4.2V

–10

10

30

50

70

90

–50

–25

0

25

50

75

100

TEMPERATURE (°C)

4078x G21

4078x G22

BATDET Pin Threshold Voltage

(On-to-Off) vs Temperature

BATDET Voltage/Current

vs Temperature

2.0

1.9

1.8

1.7

1.6

1.5

1.4

4.4

4.3

4.2

4.1

4.0

6.00

V

= V

= 5V

USBIN

V

= V

= 5V

USBIN

DCIN

V

BOC

5.25

4.50

3.75

3.00

I

BATDET

–10

10

30

50

70

90

–10

10

30

50

70

90

TEMPERATURE (°C)

4078x G23

4078x G24

4078xf

6

LTC4078X

PIN FUNCTIONS

USBIN (Pin 1): USB Input Supply Pin. This input provides

an internal N-channel MOSFET. When the charge cycle is

completed, CHRG becomes high impedance. This output

is capable of driving an LED.

power to the battery charger assuming a voltage greater

than V

and less than V

is present (typically

UVUSB

OVUSB

3.95V to ꢀV respectively). However, the DCIN input will

take priority if a voltage greater than V is present at

DCIN (typically 4.15V). The USBIN input allows charge

currents up to 850mꢁ. This pin should be bypassed with

a 1µF capacitor.

ENABLE (Pin 6): Enable Input. When the LTC4078X is

charging from the DCIN source, a logic low on this pin

enables the charger. When the LTC4078X is charging

from the USBIN source, a logic high on this pin enables

the charger. If this input is left ﬂoating, an internal 2MΩ

pulldown resistor defaults the LTC4078X to charge when

a wall adapter is applied and to shut down if only the USB

source is applied.

UVDC

IUSB (Pin 2): Charge Current Program for USB Power.

The charge current is set by connecting a resistor, R

,

IUSB

to ground. When charging in constant-current mode, this

pin servos to 1V. The voltage on this pin can be used to

measure the battery current delivered from the USB input

using the following formula:

BATDET (Pin 7): Battery Detection Input. When the volt-

age on this pin falls below V

(typically 1.75V), the

BDET

charger is on and ready for charging a battery. If this

input is left ﬂoating, an internal pull-up resistor will dis-

able charging.

V

R_IUSB

IUSB

I_BAT

=

•1000

IDC (Pin 8): Charge Current Program for Wall ꢁdapter

ITERM (Pin 3): Termination Current Threshold Program.

Power. The charge current is set by connecting a resis-

The termination current threshold, I

, is set by

is set

tor, R , to ground. When charging in constant-current

TERMINꢁTE

IDC

connecting a resistor, R

, to ground. I

mode, this pin servos to 1V. The voltage on this pin can

be used to measure the battery current delivered from the

DC input using the following formula:

ITERM

TERMINꢁTE

by the following formula:

100V

R_ITERM

I_TERMINATE

=

V

R_IDC

IDC

I_BAT

=

•1000

When the battery current, I , falls below the termination

BꢁT

threshold, charging stops and the CHRG output becomes

high impedance. This pin is internally clamped to approxi-

mately 1.5V. Driving this pin to voltages beyond the clamp

voltage should be avoided.

BAT (Pin 9): Battery Charger Output. This pin provides

charge current to the battery and regulates the ﬁnal ﬂoat

voltage to 4.2V.

DCIN (Pin 10): Wall ꢁdapter Input Supply Pin. This input

PWR (Pin 4): Open-Drain Power Supply Status Output.

WhentheDCINorUSBINpinvoltageisvalidtobegincharg-

ing (i.e. when the supply is greater than the undervoltage

lockoutthreshold,lessthantheovervoltagelockoutthresh-

old and at least 120mV above the battery terminal), the

PWR pin is pulled low by an internal N-channel MOSFET.

Otherwise PWR is high impedance. This output is capable

of driving an LED.

provides power to the battery charger assuming a voltage

greater than V

and less than V

is present (typi-

UVDC

OVDC

cally4.15VtoꢀVrespectively). ꢁvalidvoltageontheDCIN

input will always take priority over the USBIN input. The

DCIN input allows charge currents up to 950mꢁ. This pin

should be bypassed with a 1µF capacitor.

Exposed Pad (Pin 11): GND. The exposed backside of the

packageisgroundandmustbesolderedtoPCboardground

for electrical connection and maximum heat transfer.

CHRG (Pin 5): Open-Drain Charge Status Output. When

the LTC4078X is charging, the CHRG pin is pulled low by

4078xf

7

LTC4078X

BLOCK DIAGRAM

DCIN

10

BAT

9

USBIN

1

CC/CV

REGULATOR

CC/CV

REGULATOR

V

BOC

DC_ENABLE

CHARGER CONTROL

DISABLE

USB_ENABLE

7

+

–

BATDET

1.75V

4

PWR

+

–

+

–

3.95V

BAT

6V

4.15V

BAT

6V

DCIN UVLO

DCIN OVLO

RECHARGE

USBIN UVLO

+

–

+

–

+

–

+

–

USBIN OVLO

T

6

ENABLE

+

–

+

–

DIE

2M

120°C

0.9V

THERMAL

REGULATION

4.075V

BAT

+

–

0.1V

CHRG

5

–

+

I

/1000

I

/1000

I

/1000

BAT

TERMINATION

GND

11

ITERM

IDC

IUSB

3

8

2

4078X BD

R

ITERM

R

IUSB

IDC

4078xf

8

LTC4078X

OPERATION

Charge current out of the BꢁT pin can be determined at

any time by monitoring the IDC or IUSB pin voltage and

applying the following equations:

The LTC4078X is designed to efﬁciently manage charg-

ing of a single-cell lithium-ion battery from two separate

power sources: a wall adapter and USB power bus. Us-

ing the constant-current/constant-voltage algorithm, the

charger can deliver up to 950mꢁ of charge current from

the wall adapter supply or up to 850mꢁ of charge current

from the USB supply with a ﬁnal ﬂoat voltage accuracy of

0.ꢀ6. The LTC4078X has two internal P-channel power

MOSFETs and thermal regulation circuitry. No blocking

diodes or external sense resistors are required.

V

R_IDC

IDC

I_BAT

=

•1000,(charging from wall adapter)

V

IUSB

•1000,(charging from USBsupply)

R_IUSB

Battery Detection

Power Source Selection

By default, the BꢁTDET pin is pulled high with an internal

resistor, disabling the charger. To enable the charger, the

The LTC4078X can charge a battery from either the wall

adapter input or the USB port input. The LTC4078X auto-

matically senses the presence of voltage at each input. If

both power sources are present, the LTC4078X defaults to

the wall adapter source provided a valid voltage is present

at the DCIN input. “Valid voltage” is deﬁned as:

BꢁTDET pin must be pulled below the V

threshold

BDET

(typically 1.75V). ꢁn external resistor to ground less than

100k (typically 3.9k) located in the battery pack is used to

detect battery presence.

Programming Charge Termination

• Supply voltage is greater than the UVLO threshold

and less than the OVLO threshold.

The charge cycle terminates when the charge current

falls below the programmed termination threshold level

during constant-voltage mode. This threshold is set by

• Supply voltage is greater than the battery voltage by

40mV.

connecting an external resistor, R , from the ITERM

ITERM

pin to ground. The charge termination current threshold

(I ) is set by the following equation:

The open-drain power status output (PWR) indicates

which power source has been selected. Table 1 describes

the behavior of this status output.

TERMINꢁTE

100V

R_ITERM

=

,I_TERMINATE=

I_TERMINATE

R_ITERM

Programming and Monitoring Charge Current

The charge current delivered to the battery from the wall

adapter or USB supply is programmed using a single re-

sistor from the IDC or IUSB pin to ground. Both program

The termination condition is detected by using an internal

ﬁltered comparator to monitor the ITERM pin. When the

ITERM pin voltage drops below 100mV* for longer than

resistors and charge currents (I

the following equations:

) are calculated using

t

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

CHRG

TERMINꢁTE

charge current is latched off and the LTC4078X enters

standby mode.

1000V

I_CHRG−DC

1000V

R_IDC

=

,I_CHRG−DC=

When charging, transient loads on the BꢁT pin can cause

the ITERM pin to fall below 100mV for short periods of

time before the DC charge current has dropped below the

1000V

R_IUSB

=

, I_CHRG−USB=

I_CHRG−USB

*ꢁny external sources that hold the ITERM pin above 100mV will prevent the LTC4078X from

terminating a charge cycle.

4078xf

9

LTC4078X

OPERATION

programmed termination current. The 1.ꢀms ﬁlter time

logiclowenablesthechargerandlogichighdisablesit(the

pulldown defaults the charger to the charging state). The

opposite is true when the USB input is supplying power;

logic low disables the charger and logic high enables it

(the default is the shutdown state).

(t ) on the termination comparator ensures that

TERMINꢁTE

transient loads of this nature do not result in premature

chargecycletermination.Oncetheaveragechargecurrent

drops below the programmed termination threshold, the

LTC4078Xterminatesthechargecycleandstopsproviding

current out of the BꢁT pin. In this state, any load on the

BꢁT pin must be supplied by the battery.

The DCIN input draws 40µꢁ when the charger is in shut-

downmode.TheUSBINinputdraws40µꢁduringshutdown

if no voltage is applied to DCIN, but draws only 23µꢁ when

V

provides valid voltage (see Table 1).

DCIN

Automatic Recharge

Status Indicators

In standby mode, the charger sits idle and monitors the

batteryvoltageusingacomparatorwitha4.1msﬁltertime

The charge status open-drain output (CHRG) has two

states: pulldown and high impedance. The pulldown state

indicates that the LTC4078X is in a charge cycle. Once the

charge cycle has terminated or the LTC4078X is disabled,

the pin state becomes high impedance.

(t

). ꢁ charge cycle automatically restarts when the

RECHRG

battery voltage falls below 4.075V (which corresponds to

approximately806to906batterycapacity).Thisensures

that the battery is kept at, or near, a fully charged condi-

tion and eliminates the need for periodic charge cycle

initiations.

The power supply status open-drain output (PWR) has

two states: pulldown and high impedance. The pulldown

state indicates that power is present at either DCIN or

USBIN. This output is strong enough to drive an LED. If

no valid voltage is applied at either pin, the PWR pin is

high impedance, indicating that the LTC4078X lacks valid

input voltage (see Table 1) to charge the battery.

Manual Shutdown

TheENꢁBLEpinhasa2MΩpulldownresistortoGND. The

deﬁnitionofthispindependsonwhichsourceissupplying

power. When the wall adapter input is supplying power,

Table 1. Power Source Selection (V

< 1.75V)

BATDET

V

USBIN

< 3.95V or

6V > V

> 3.95V and

22V > V

> 6V

USBIN

V

< BAT + 50mV

V

> BAT + 50mV

USBIN

ENABLE

HIGH

LOW or No Connect

HIGH

LOW or No Connect

HIGH

LOW or No Connect

V

< 4.15V or

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

Charging from

USBIN source.

PWR: LOW

No Charging.

PWR: LOW

CHRG: Hi-Z

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

DCIN

< BꢁT + 50mV PWR: Hi-Z

CHRG: Hi-Z

CHRG: LOW

ꢀV > V

> 4.15V

No Charging.

PWR: LOW

CHRG: Hi-Z

Charging from DCIN No Charging.

Charging from DCIN

source.

DCIN

and V

> BꢁT +

source.

PWR: LOW

CHRG: Hi-Z

source.

PWR: LOW

CHRG: Hi-Z

DCIN

50mV

PWR: LOW

CHRG: LOW

PWR: LOW

CHRG: LOW

PWR: LOW

CHRG: LOW

22V > V

> ꢀV

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

No Charging.

PWR: LOW

CHRG: Hi-Z

No Charging.

PWR: LOW

CHRG: Hi-Z

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

No Charging.

PWR: Hi-Z

CHRG: Hi-Z

DCIN

4078xf

10

LTC4078X

OPERATION

Thermal Limiting

ing the device. The charge current can be set according

to typical (not worst-case) ambient temperature with the

assurance that the charger will automatically reduce the

current in worst case conditions. DFN package power

considerations are discussed further in the ꢁpplications

Information section.

ꢁninternalthermalfeedbackloopreducestheprogrammed

charge current if the die temperature attempts to rise

above a preset value of approximately 120°C. This feature

protects the LTC4078X from excessive temperature and

allows the user to push the limits of the power handling

capability of a given circuit board without risk of damag-

DCIN POWER REMOVED

ENABLE = LOW

USB POWER REMOVED

NO POWER

POWER APPLIED

ENABLE = HIGH

YES

NO

DCIN > 4.15V

AND DCIN > BAT

NO

6V > DCIN > 4.15V

AND DCIN > BAT

6V > USBIN > 3.95V

AND USBIN > BAT

YES

BATDET < 1.75V

YES

BATDET < 1.75V

YES

NO

CHARGE MODE

(DCIN)

CHARGE MODE

(USBIN)

FULL CURRENT

CHRG STATE: PULLDOWN

I

< I

I

< I

BAT TERMINATE

IN VOLTAGE MODE

STANDBY MODE

(DCIN)

(USBIN)

BAT < 4.075V

NO CHARGE CURRENT

CHRG STATE: Hi-Z

NO CHARGE CURRENT

CHRG STATE: Hi-Z

SHUTDOWN MODE

(DCIN)

SHUTDOWN MODE

(USBIN)

CHRG STATE: Hi-Z

4078X F01

Figure 1. LTC4078X State Diagram of a Charge Cycle

4078xf

11

LTC4078X

APPLICATIONS INFORMATION

Using a Single Charge Current Program Resistor

Stability Considerations

TheLTC4078Xcanprogramthewalladapterchargecurrent

andUSBchargecurrentindependentlyusingtwoprogram

Theconstant-voltagemodefeedbackloopisstablewithout

any compensation provided a battery is connected to the

charger output. However, a 1µF capacitor with a 1Ω series

resistor is recommended at the BꢁT pin to keep the ripple

voltage low when the battery is disconnected.

resistors, R and R

. Figure 2 shows a charger circuit

IDC

IUSB

that sets the wall adapter charge current to 800mꢁ and

the USB charge current to 500mꢁ.

In applications where the programmed wall adapter

charge current and USB charge current are the same, a

single program resistor can be used to set both charge

currents. Figure 3 shows a charger circuit that uses one

charge current program resistor.

When the charger is in constant-current mode, the charge

current program pin (IDC or IUSB) is in the feedback loop,

not the battery. The constant-current mode stability is af-

fectedbytheimpedanceatthechargecurrentprogrampin.

With no additional capacitance on this pin, the charger is

stable with program resistor values as high as 20k (I

CHRG

800mA (WALL)

LTC4078X

= 50mꢁ); however, additional capacitance on these nodes

reduces the maximum allowed program resistor.

500mA (USB)

WALL

ADAPTER

DCIN

BAT

USB

USBIN BATDET

IUSB

4.2V

+

3.9k

R4

PORT

C2, 1µF

Li-Ion

Power Dissipation

BATTERY

PACK

R1

2k

1%

IDC

ITERM

GND

C1

1µF

R3

2k

1%

Whendesigningthebatterychargercircuit, itisnotneces-

sary to design for worst-case power dissipation scenarios

because the LTC4078X automatically reduces the charge

current during high power conditions. The conditions that

cause the LTC4078X to reduce charge current through

thermal feedback can be approximated by considering the

power dissipated in the IC. Most of the power dissipation

is generated from the internal charger MOSFET. Thus, the

power dissipation is calculated to be:

R2

1.24k

1%

4078X F02

Figure 2. Dual Input Charger with Independent Charge Currents

LTC4078X

WALL

500mA

ADAPTER

DCIN

BAT

USB

USBIN BATDET

IUSB

4.2V

+

R4

3.9k

PORT

C2, 1µF

Li-Ion

BATTERY

PACK

P = (V – V ) • I

BꢁT

D

IN

BꢁT

C1

1µF

IDC

ITERM

GND

R3

2k

1%

R1

2k

1%

P is the dissipated power, V is the input supply volt-

D

IN

BꢁT

age (either DCIN or USBIN), V

is the battery voltage

and I is the charge current. The approximate ambient

BꢁT

4078X F03

temperature at which the thermal feedback begins to

Figure 3. Dual Input Charger Circuit. The Wall Adapter

Charge Current and USB Charge Current Are Both

Programmed to Be 500mA

protect the IC is:

T = 120°C – P • θ

Jꢁ

ꢁ

D

Inthiscircuit,theprogrammedchargecurrentfromboththe

wall adapter supply is the same value as the programmed

charge current from the USB supply:

T = 120°C – (V – V ) • I • θ

Jꢁ

ꢁ

IN

BꢁT

Example: ꢁn LTC4078X operating from a 5V wall adapter

(on the DCIN input) is programmed to supply 800mꢁ

full-scale current to a discharged Li-Ion battery with a

voltage of 3.3V.

1000V

I_CHRG−DC= I_CHRG−USB

=

R_ISET

4078xf

12

LTC4078X

APPLICATIONS INFORMATION

ꢁssuming θ is 40°C/W (see Thermal Considerations),

800mꢁtoabatteryfroma5Vsupplyatroomtemperature.

Withoutagoodbacksidethermalconnection, thisnumber

would drop to much less than 500mꢁ.

Jꢁ

theambienttemperatureatwhichtheLTC4078Xwillbegin

to reduce the charge current is approximately:

T = 120°C – (5V – 3.3V) • (800mꢁ) • 40°C/W

ꢁ

Input Capacitor Selection

T = 120°C – 1.3ꢀW • 40°C/W = 120°C – 54.4°C

When an input supply is connected to a portable product,

the inductance of the cable and the high-Q ceramic input

capacitorformanL-Cresonantcircuit.WhiletheLTC4078X

is capable of withstanding input voltages as high as 22V,

if the input cable does not have adequate mutual coupling

or if there is not much impedance in the cable, it is pos-

sible for the voltage at the input of the product to reach

as high as 2x the input voltage before it settles out. To

prevent excessive voltage from damaging the LTC4078X

during a hot insertion, it is best to have a low voltage coef-

ﬁcient capacitor at the input pins to the LTC4078X. This is

achievable by selecting an X5R or X7R ceramic capacitor

that has a higher voltage rating than that required for the

application. For example, if the maximum expected input

voltage is 15V, a 25V X5R 1µF capacitor would be a better

choice than the smaller 1ꢀV X5R capacitor. Note that no

charging will occur with 15V in.

ꢁ

T = ꢀ5.ꢀ°C

ꢁ

The LTC4078X can be used above ꢀ5.ꢀ°C ambient, but

the charge current will be reduced from 800mꢁ. The ap-

proximate current at a given ambient temperature can be

approximated by:

120°C – T_A

I_BAT

=

(V – V_BAT)• θ_JA

IN

Using the previous example with an ambient temperature

of 75°C, the charge current will be reduced to approxi-

mately:

120°C – 75°C

(5V – 3.3V) • 40°C / W 68°C / A

45°C

I_BAT

=

Using a tantalum capacitor or an aluminum electrolytic

capacitorforinputbypassing,orparallelingwithaceramic

capacitor will also reduce voltage overshoot during a hot

insertion. Ceramic capacitors with Y5V or Z5U dielectrics

are not recommeded.

I_BAT= 662mA

ItisimportanttorememberthatLTC4078Xapplicationsdo

notneedtobedesignedforworst-casethermalconditions,

since the IC will automatically reduce power dissipation

when the junction temperature reaches approximately

120°C.

ꢁlternatively, the following soft connect circuit can be

employed (as shown in Figure 4).

Thermal Considerations

In order to deliver maximum charge current under all

conditions, it is critical that the exposed metal pad on the

backside of the LTC4078X DFN package is properly sol-

dered to the PC board ground. When correctly soldered to

DCIN/USBIN

R1

+15V

INPUT

40k

C1

1µF

INPUT CABLE

LTC4078X

C2

100nF

MN1

2

a2500mm doublesided1ozcopperboard,theLTC4078X

GND

4078X F04

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. ꢁs an

example, a correctly soldered LTC4078X can deliver over

Figure 4. Input Soft Connect Circuit

4078xf

13

LTC4078X

APPLICATIONS INFORMATION

supply voltage, a series blocking diode can be used. In

other cases where the voltage drop must be kept low, a

P-channel MOSFET can be used (as shown in Figure 5).

In this circuit, capacitor C2 holds MN1 off when the cable

isﬁrstconnected. EventuallyC2beginstochargeuptothe

USB input voltage applying increasing gate drive to MN1.

The long time constant of R1 and C1 prevent the current

from rapidly building up in the cable, thus dampening out

any resonant overshoot.

DRAIN-BULK

DIODE OF FET

LTC4078X

WALL

ADAPTER

DCIN

Reverse Polarity Input Voltage Protection

4078X F05

In some applications, protection from reverse polarity

voltage on the input supply pins is desired. With sufﬁcient

Figure 5. Low Loss Reverse Polarity Protection

4078xf

14

LTC4078X

PACKAGE DESCRIPTION

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1ꢀ99)

R = 0.115

0.38 0.10

TYP

6

10

0.675 0.05

3.50 0.05

2.15 0.05 (2 SIDES)

1.65 0.05

3.00 0.10

(4 SIDES)

1.65 0.10

(2 SIDES)

PIN 1

PACKAGE

OUTLINE

TOP MARK

(SEE NOTE 6)

(DD10) DFN 1103

5

1

0.25 0.05

0.50 BSC

0.75 0.05

0.200 REF

0.25 0.05

0.50

BSC

2.38 0.10

(2 SIDES)

2.38 0.05

(2 SIDES)

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

NOTE:

1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).

CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

4078xf

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 representa-

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

15

LTC4078X

TYPICAL APPLICATION

Full Featured Li-Ion Charger

800mA (WALL)

475mA (USB)

LTC4078X

WALL

ADAPTER

BAT

DCIN

USB

POWER

1k

USBIN

1µF

PWR

CHRG

BATDET

4.2V Li-Ion

BATTERY

PACK

IUSB

IDC

+

3.9k

ITERM

GND

2.1k

1%

1.24k

1%

1k

1%

4078X TA02

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PART NUMBER

DESCRIPTION

COMMENTS

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LTC4075HVX

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LTC4077

950mꢁ Charger Current, Thermal Regulation, C/X Charge Termination,

Fixed C or C/5 USB Charge Current for Low Power USB Operation, 3mm × 3mm

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Fixed C/10 Wall ꢁdapter and C/10 or C/2 Charge Current Termination,

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LTC4085

USB Power Manager with Ideal Diode Controller Charges Single-Cell Li-Ion Batteries Directly from USB Port, Thermal Regulation,

and Li-Ion Charger 200mΩ Ideal Diode with <50mΩ Option, 4mm × 3mm DFN-14 Package

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and High Efﬁciency Li-Ion Battery Charger

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ꢁutomatic Switching Between DC Sources, Load Sharing, Replaces ORing Diodes

ThinSOT and PowerPath are trademarks of Linear Technology Corporation.

4078xf

LT 0907 • PRINTED IN USA

LinearTechnology Corporation

1ꢀ30 McCarthy Blvd., Milpitas, Cꢁ 95035-7417

16

●

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


型号：	LTC4078XEDD-PBF
厂家：	Linear
描述：	Dual Input Li-Ion Battery Charger with Overvoltage Protection 双输入锂离子电池充电器，具有过压保护电池
文件：	总16页 (文件大小：182K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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