LTC4078XEDD#TRPBF_技术文档

LTC4078/LTC4078X

Dual Input Li-Ion Battery

Charger with Overvoltage Protection

FEATURES

DESCRIPTION

The LTC^®4078/LTC4078X are standalone linear chargers

that are capable of charging a single-cell Li-Ion/Polymer

batteryfrombothwalladapterandUSBinputs.Thechargers

can detect power at the inputs and automatically select

the appropriate power source for charging.

n

22V Maximum Voltage for Wall Adapter and

USB Inputs

n

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

n

No external sense resistor or blocking diode is required

for charging due to the internal MOSFET architecture. The

LTC4078/LTC4078Xfeatureamaximum22Vratingforboth

wall adapter and USB inputs, although charging stops if

the selected power source exceeds the overvoltage limit.

Internal thermal feedback regulates the battery charge

current to maintain a constant die temperature during

high power operation or high ambient temperature con-

ditions. The ﬂoat voltage is ﬁxed at 4.2V and the charge

current is programmed with an external resistor. The

LTC4078/LTC4078X terminate the charge cycle when the

charge current drops below the programmed termination

threshold after the ﬁnal ﬂoat voltage is reached.

n

Thermal Regulation Maximizes Charge Rate Without

Risk of Overheating*

n

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.

ꢁvailable Without Trickle Charge (LTC4078X)

ꢁvailable in a Thermally Enhanced, Low Proﬁle

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

APPLICATIONS

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

ꢁll other trademarks are the property of their respective owners.

*Protected by U.S. Patents including ꢀ522118, ꢀ7003ꢀ4.

n

Cellular Telephones

n

Handheld Computers

n

Portable MP3 Players

Digital Cameras

n

TYPICAL APPLICATION

Charger Current vs Supply Voltage

900

R

= 1.24k

= 2k

IDC

IUSB

High Voltage Dual Input Battery Charger

800

700

ꢀ00

500

400

300

200

100

0

V

= 3.5V

BꢁT

BꢁTDET

for Li-Ion Battery Pack

= 0V

800mꢁ (WꢁLL)

500mꢁ (USB)

CHꢁRGE FROM DCIN

LTC4078

WꢁLL

ꢁDꢁPTER

DCIN

BꢁT

USB

USBIN BꢁTDET

IUSB

4.2V

Li-Ion

+

CHꢁRGE

FROM USBIN

PORT

1μF

2k

3.9k

BꢁTTERY

PꢁCK

IDC

ITERM

1μF

16

1.24k

16

GND

2k

16

2

3

4

5

ꢀ

7

8

19 20

4078X Tꢁ01

SUPPLY VOLTꢁGE (V)

4078x Tꢁ01b

4078xfb

1

LTC4078/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

ꢀ

BꢁT

ITERM

PWR

11

IDC

BꢁTDET

ENꢁBLE

CHRG

DD PꢁCKꢁGE

10-LEꢁD (3mm × 3mm) PLꢁSTIC DFN

T

= 125°C, θ = 40°C/W (Note 3)

JMꢁX

Jꢁ

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

ORDER INFORMATION

LEAD FREE FINISH

LTC4078XEDD#PBF

LTC4078EDD#PBF

TAPE AND REEL

PART MARKING

LCYP

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC4078XEDD#TRPBF

LTC4078EDD#TRPBF

–40°C to 85°C

10-Lead (3mm × 3mm) Plastic DFN

LDJY

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 ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_DCIN= 5V, V_USBIN= 5V unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

4.3

TYP

MAX

5.5

UNITS

l

V

Operating Supply Voltage

DCIN Supply Current

V

DCIN

USBIN

DCIN

4.3

5.5

l

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

l

I

USBIN Supply Current

Charge Mode (Note 5), R

= 10k, V

= 2V

DCIN

= 2V

DCIN

350

70

40

70

23

800

120

80

140

40

μꢁ

USBIN

IUSB

Standby Mode; Charge Terminated, V

Shutdown (V = 2V, 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

ꢁ

l

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

4078xfb

2

LTC4078/LTC4078X

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_DCIN= 5V, V_USBIN= 5V unless otherwise noted.

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

l

I

R

ITERM

R

ITERM

R

ITERM

R

ITERM

= 1k

90

42

8

100

50

10

5

110

58

12

ꢀ.5

mꢁ

TERMINꢁTE

= 2k

= 10k

= 20k

3.5

I

Trickle Charge Current (Note ꢀ)

V

< V ; R = 1.25k

TRIKL IDC

ꢀ0

30

80

47.5

100

ꢀ5

mꢁ

TRIKL

BꢁT

< V

; R = 2.1k

TRIKL IUSB

V

Trickle Charge Threshold (Note ꢀ)

DCIN Undervoltage Lockout Voltage

USBIN Undervoltage Lockout Voltage

DCIN Overvoltage Lockout Voltage

USBIN Overvoltage Lockout Voltage

V

Rising

2.8

2.9

3

V

TRIKL

BꢁT

Hysteresis

100

mV

V

From Low to High

Hysteresis

4

4.15

190

4.3

4.1

ꢀ.2

V

mV

UVDC

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

2

V

MΩ

V

ENꢁBLE

l

R

ENꢁBLE

BDET

V

From Low to High

= 0V

1.25

2

1.75

4

I

V

ꢀ

μꢁ

V

BꢁTDET

V

BꢁTDET Open Circuit Voltage

4

4.2

0.12

4.4

0.35

BOC

OL

Output Low Voltage

(CHRG, PWR)

I

= 5mꢁ

V

SINK

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

°C

T

Junction Temperature in Constant-

Temperature Mode

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 LTC4078/LTC4078X are 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.

Note 6: This parameter is not applicable to the LTC4078X.

4078xfb

3

LTC4078/LTC4078X

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

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

1.00ꢀ

1.004

1.002

1.000

0.998

0.99ꢀ

0.994

0.992

4.2ꢀ

4.24

4.22

4.20

4.18

4.1ꢀ

4.14

4.12

4.10

V

DCIN

= V

= 5V

V

DCIN

= 5V

V

= V

USBIN

= 5V

USBIN

DCIN

R

= 1.24k

IDC

R

IDC

= R

= 2k

IUSB

–10

10

30

50

70

90

–10

10

30

50

70

90

0

100 200 300 400 500 ꢀ00 700 800 900

(mꢁ)

TEMPERꢁTURE (°C)

I

BꢁT

4078x G02

4078x G03

4078x G01

IUSB Pin Voltage vs Temperature

(Constant-Current Mode)

Charge Current

vs IDC Pin Voltage

vs IUSB Pin Voltage

1.008

1.00ꢀ

1.004

1.002

1.000

0.998

0.99ꢀ

0.994

0.992

900

800

700

ꢀ00

500

400

300

200

100

0

900

800

700

ꢀ00

500

400

300

200

100

0

V

= 5V

V

DCIN

= 5V

V

= 5V

USBIN

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.ꢀ

(V)

0.8

1.0

1.2

0

0.2

0.4

0.ꢀ

0.8

1.0

1.2

TEMPERꢁTURE (°C)

V

IUSB

(V)

IDC

4078x G04

4078x G05

4078x G0ꢀ

PWR Pin I-V Curve

CHRG Pin I-V Curve

ꢀ0

50

40

30

20

10

0

ꢀ0

50

40

30

20

10

0

V

DCIN

= V

= 5V

USBIN

V

= V

= 5V

USBIN

DCIN

0

1

2

3

4

5

ꢀ

0

1

2

3

4

5

ꢀ

V

CHRG

(V)

V

PWR

(V)

4078x G08

4078x G07

4078xfb

4

LTC4078/LTC4078X

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

Charge Current

vs Ambient Temperature

vs Supply Voltage

Charge Current vs Battery Voltage

1000

900

800

700

ꢀ00

500

400

300

200

100

0

1000

900

800

700

ꢀ00

500

400

300

200

100

0

R

= 1.24k

IDC

800

ꢀ00

400

200

R

= R

IUSB

= 2k

R

V

Jꢁ

= 1.24k

= 4V

V

θ

= V

= 5V

50

V

= V

= 5V

USBIN

IDC

BꢁT

= 30°C/W

DCIN

BꢁT

Jꢁ

USBIN

DCIN

IDC

= 4V

R

= 1.24k

θ

= 30°C/W

θ

= 30°C/W

Jꢁ

0

70

90 110 130

4.0 4.5 5.0 5.5 ꢀ.0 ꢀ.5 7.0 7.5 8.0

(V)

2.4 2.7 3.0 3.3 3.ꢀ 3.9 4.2 4.5

(V)

–10

30

10

TEMPERꢁTURE (°C)

V

BꢁT

V

4078x G10

DCIN

4078x G12

4078x G11

DCIN Power FET On-Resistance

vs Temperature

USBIN Power FET On-Resistance

vs Temperature

ENABLE Pin Threshold Voltage

(On-to-Off) vs Temperature

900

850

800

750

700

ꢀ50

ꢀ00

800

750

700

ꢀ50

ꢀ00

550

500

1000

980

9ꢀ0

940

920

900

880

8ꢀ0

V

I

= 4V

= 200mꢁ

V

DCIN

= V

= 5V

USBIN

V

I

= 4V

= 200mꢁ

BꢁT

–10

10

30

50

70

90

–10

10

30

50

70

90

–10

10

30

50

70

90

TEMPERꢁTURE (°C)

4078x G14

4078x G15

4078x G13

USBIN Shutdown Current

vs Temperature

DCIN Shutdown Current

vs Temperature

ENABLE Pin Pulldown Resistance

vs Temperature

ꢀ0

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.ꢀ

ꢀ0

55

50

45

40

35

30

25

20

V

= 0V

V

= 5V

ENꢁBLE

V

= 5V

USBIN

V

DCIN

= 5V

V

= 4.3V

USBIN

V

DCIN

= 4.3V

–50

–25

0

25

50

75

100

–50

–25

0

25

50

75

100

–50

–25

0

25

50

75

100

TEMPERꢁTURE (°C)

4078x G1ꢀ

4078x G17

4078x G18

4078xfb

5

LTC4078/LTC4078X

TYPICAL PERFORMANCE CHARACTERISTICS

T_A= 25°C, unless otherwise speciﬁed.

Undervoltage Lockout Threshold

vs Temperature

Overvoltage Lockout Threshold

vs Temperature

ꢀ.10

4.25

4.20

4.15

4.10

4.05

4.00

3.95

3.90

3.85

ꢀ.05

ꢀ.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

TEMPERꢁTURE (°C)

4078x G20

4078x G19

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

ꢀ.5

ꢀ.0

V

DCIN

= V

= 5V

USBIN

V

= V

= NOT CONNECTED

USBIN

DCIN

BꢁT

= 4.2V

–10

10

30

50

70

90

–50

–25

0

25

50

75

100

TEMPERꢁTURE (°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.ꢀ

1.5

1.4

4.4

4.3

4.2

4.1

4.0

ꢀ.00

V

DCIN

= V

= 5V

USBIN

V

DCIN

= V

= 5V

USBIN

V

BOC

5.25

4.50

3.75

3.00

I

BꢁTDET

–10

10

30

50

70

90

–10

10

30

50

70

90

TEMPERꢁTURE (°C)

4078x G23

4078x G24

4078xfb

6

LTC4078/LTC4078X

PIN FUNCTIONS

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

low by 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(Pin6):EnableInput.WhentheLTC4078/LTC4078X

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

pin enables the charger. When the LTC4078/LTC4078X are

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 LTC4078/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

TERMINꢁTE

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

IDC

connecting a resistor, R

, to ground. I

is set

ITERM

TERMINꢁTE

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:

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(Pin5):Open-DrainChargeStatusOutput.Whenthe

LTC4078/LTC4078X are charging, the CHRG pin is pulled

4078xfb

7

LTC4078/LTC4078X

BLOCK DIAGRAM

DCIN

10

BꢁT

9

USBIN

1

CC/CV

REGULꢁTOR

CC/CV

REGULꢁTOR

V

BOC

TRICKLE

DC_ENꢁBLE

CHꢁRGER CONTROL

TRICKLE DISꢁBLE

USB_ENꢁBLE

CHꢁRGE*

7

+

–

BꢁTDET

+

2.9V

1.75V

BꢁT

–

4

PWR

+

–

+

–

3.95V

BꢁT

ꢀV

4.15V

BꢁT

ꢀV

DCIN UVLO

DCIN OVLO

RECHꢁRGE

USBIN UVLO

+

–

+

–

+

–

+

–

USBIN OVLO

T

ꢀ

ENꢁBLE

+

–

+

–

DIE

2M

120°C

0.9V

THERMꢁL

REGULꢁTION

4.075V

BꢁT

+

–

0.1V

CHRG

5

–

+

I

/1000

I

/1000

I

/1000

BꢁT

TERMINꢁTION

GND

11

ITERM

IDC

IUSB

3

8

2

4078X BD

R

IUSB

ITERM

IDC

*TRICKLE CHꢁRGE DISꢁBLED ON THE LTC4078X

4078xfb

8

LTC4078/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 LTC4078/LTC4078X are designed to efﬁciently man-

age charging of a single-cell lithium-ion battery from two

separatepowersources:awalladapterandUSBpowerbus.

Usingtheconstant-current/constant-voltagealgorithm,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.TheLTC4078/LTC4078XhavetwointernalP-chan-

nel power MOSFETs and thermal regulation circuitry. No

blocking diodes or external sense resistors are required.

V

IDC

I_BAT

=

•1000,(charging from wall adapter)

R_IDC

V

IUSB

•1000,(charging fromUSBsupply)

R_IUSB

Battery Detection

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

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

Power Source Selection

The LTC4078/LTC4078X can charge a battery from ei-

ther the wall adapter input or the USB port input. The

LTC4078/LTC4078X automatically sense the presence of

voltage at each input. If both power sources are present,

the LTC4078/LTC4078X default to the wall adapter source

providedavalidvoltageispresentattheDCINinput. “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

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 UVLO threshold

and less than the OVLO threshold.

connecting an external resistor, R , from the ITERM

ITERM

• Supply voltage is greater than the battery voltage by

40mV.

pin to ground. The charge termination current threshold

(I ) is set by the following equation:

TERMINꢁTE

Theopen-drainpowerstatusoutput(PWR)indicateswhich

power source has been selected. Table 1 describes the

behavior of this status output.

100V

I_TERMINATE

100V

R_ITERM

=

,I_TERMINATE=

Programming and Monitoring Charge Current

The termination condition is detected using an internal

ﬁltered comparator to monitor the ITERM pin. When the

ITERM pin voltage drops below 100mV* for longer than

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

t

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

TERMINꢁTE

charge current is latched off and the LTC4078/LTC4078X

enter standby mode.

resistors and charge currents (I

the following equations:

) are calculated using

CHRG

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

I_CHRGꢀDC

1000V

R_IDC

=

,I_CHRGꢀDC=

1000V

R_IUSB

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

terminating a charge cycle.

R_IUSB

=

, I_CHRGꢀUSB=

I_CHRGꢀUSB

4078xfb

9

LTC4078/LTC4078X

OPERATION

programmed termination current. The 1.ꢀms ﬁlter time

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.

(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

LTC4078/LTC4078X terminate the charge cycle and stops

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

on the BꢁT pin must be supplied by the battery.

Manual Shutdown

TheENꢁBLEpinhasa2MΩpulldownresistortoGND. The

deﬁnitionofthispindependsonwhichsourceissupplying

power. When the wall adapter input is supplying power,

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).

Low-Battery Charge Conditioning (Trickle Charge)

Thisfeatureensuresthatnear-deadbatteriesaregradually

charged before applying full charge current. If the BꢁT pin

voltageisbelow2.9V,theLTC4078supply1/10thofthefull

charge current to the battery until the BꢁT pin rises above

2.9V. For example, if the charger is programmed to charge

at 800mꢁ from the wall adapter input and 500mꢁ from

the USB input, the charge current during trickle charge

mode would be 80mꢁ and 50mꢁ, respectively.

TheDCINinputdraws40μꢁwhenthechargerisinshutdown

mode. The USBIN input draws 40μꢁ during shutdown if

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

V

DCIN

provides valid voltage (see Table 1).

The LTC4078X does not include the trickle charge feature;

it outputs full charge current to the battery when the

BꢁT pin voltage is below 2.9V. The LTC4078X are useful

in applications where the trickle charge current may be

insufﬁcient to supply a load during low-battery voltage

conditions.

Status Indicators

Thechargestatusopen-drainoutput(CHRG)hastwostates:

pulldownandhighimpedance.Thepulldownstateindicates

thattheLTC4078/LTC4078Xareinachargecycle.Oncethe

chargecyclehasterminatedortheLTC4078/LTC4078Xare

disabled, the pin state becomes high impedance.

Automatic Recharge

Thepowersupplystatusopen-drainoutput(PWR)hastwo

states: pulldown and high impedance. The pulldown state

indicates that power is present at either DCIN or USBIN.

In standby mode, the charger sits idle and monitors the

batteryvoltageusingacomparatorwitha4.1msﬁltertime

(t

). ꢁ charge cycle automatically restarts when the

RECHRG

Table 1. Power Source Selection (V_BATDET< 1.75V)

V

USBIN

< 3.95V or

6V > V

> 3.95V and

USBIN

V

< BAT + 50mV

V

> BAT + 50mV

22V > V

> 6V

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

4078xfb

10

LTC4078/LTC4078X

OPERATION

This output is strong enough to drive an LED. If no valid

voltage is applied at either pin, the PWR pin is high im-

pedance, indicating that the LTC4078/LTC4078X lack valid

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

the LTC4078/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-

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.

Thermal Limiting

ꢁninternalthermalfeedbackloopreducestheprogrammed

chargecurrentifthedietemperatureattemptstoriseabove

apresetvalueofapproximately120°C.Thisfeatureprotects

DCIN POWER REMOVED

ENꢁBLE = LOW

USB POWER REMOVED

NO POWER

POWER ꢁPPLIED

ENꢁBLE = HIGH

YES

NO

DCIN > 4.15V

ꢁND DCIN > BꢁT

NO

ꢀV > DCIN > 4.15V

ꢁND DCIN > BꢁT

ꢀV > USBIN > 3.95V

ꢁND USBIN > BꢁT

YES

NO

BꢁTDET < 1.75V

YES

FULL CURRENT (BꢁT > 2.9V)

1/10TH FULL CURRENT

(BꢁT < 2.9V)*

1/10TH FULL CURRENT

(BꢁT < 2.9V)*

CHRG STꢁTE: PULLDOWN

I

< I

I

< I

BꢁT TERMINꢁTE

IN VOLTꢁGE MODE

STꢁNDBY MODE

(DCIN)

(USBIN)

BꢁT < 4.075V

NO CHꢁRGE CURRENT

CHRG STꢁTE: Hi-Z

NO CHꢁRGE CURRENT

CHRG STꢁTE: Hi-Z

SHUTDOWN MODE

(DCIN)

SHUTDOWN MODE

(USBIN)

CHRG STꢁTE: Hi-Z

4078X F01

*LTC4078 ONLY

Figure 1. LTC4078 State Diagram of a Charge Cycle

4078xfb

11

LTC4078/LTC4078X

APPLICATIONS INFORMATION

Using a Single Charge Current Program Resistor

Stability Considerations

The LTC4078/LTC4078X can program the wall adapter

chargecurrentandUSBchargecurrentindependentlyusing

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.

two program resistors, R and R

. Figure 2 shows a

IDC

IUSB

charger circuit 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

800mꢁ (WꢁLL)

LTC4078

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

reduces the maximum allowed program resistor.

500mꢁ (USB)

WꢁLL

ꢁDꢁPTER

DCIN

BꢁT

USB

USBIN BꢁTDET

IUSB

4.2V

+

3.9k

R4

PORT

C2, 1μF

Li-Ion

Power Dissipation

BꢁTTERY

PꢁCK

R1

2k

16

IDC

ITERM

GND

C1

1μF

R3

2k

16

When designing the battery charger circuit, it is not

necessary to design for worst-case power dissipation

scenarios because the LTC4078/LTC4078X automatically

reduce the charge current during high power conditions.

The conditions that cause the LTC4078/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

16

4078X F02

Figure 2. Dual Input Charger with Independent Charge Currents

LTC4078

WꢁLL

500mꢁ

ꢁDꢁPTER

DCIN

BꢁT

USB

USBIN BꢁTDET

IUSB

4.2V

+

R4

3.9k

PORT

C2, 1μF

Li-Ion

BꢁTTERY

PꢁCK

C1

1μF

IDC

ITERM

GND

P = (V – V ) • I

BꢁT

R3

2k

16

D

IN

BꢁT

R1

2k

16

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

D

IN

BꢁT

age (either DCIN or USBIN), V

is the battery voltage

4078X F03

and I is the charge current. The approximate ambient

BꢁT

Figure 3. Dual Input Charger Circuit. The Wall Adapter

Charge Current and USB Charge Current Are Both

Programmed to Be 500mA

temperature at which the thermal feedback begins to

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 LTC4078/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_CHRGꢀDC= I_CHRGꢀUSB=

R_ISET

4078xfb

12

LTC4078/LTC4078X

APPLICATIONS INFORMATION

LTC4078/LTC4078X can deliver over 800mꢁ to a battery

from a 5V supply at room temperature. Without a good

backside thermal connection, this number would drop to

much less than 500mꢁ.

ꢁssumingθ is40°C/W(seeThermalConsiderations),the

Jꢁ

ambienttemperatureatwhichtheLTC4078/LTC4078Xwill

begin 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.WhiletheLTC4078/

LTC4078X are 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 possible 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 LTC4078/LTC4078X during a hot insertion, it is best to

have a low voltage coefﬁcient capacitor at the input pins

to the LTC4078/LTC4078X. This is achievable by select-

ing 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 LTC4078/LTC4078X can be used above 70.ꢀ°C ambi-

ent, but the charge current will be reduced from 800mꢁ.

The approximate current at a given ambient temperature

can be approximated by:

120°C – T_A

I_BAT

=

(V – V_BAT)•ꢀ_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

_BAT= 662mA

45°C

I_BAT

=

I

It is important to remember that LTC4078/LTC4078X

applications do not need to be designed for worst-case

thermal conditions, since the IC will automatically reduce

power dissipation when the junction temperature reaches

approximately 120°C.

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.

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 LTC4078/LTC4078X DFN package is

properly soldered to the PC board ground. When cor-

ꢁlternatively, the following soft connect circuit can be

employed (as shown in Figure 4).

DCIN/USBIN

R1

2

rectly soldered to a 2500mm double sided 1oz copper

+15V

INPUT

40k

C1

1μF

board, the LTC4078/LTC4078X 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

INPUT CꢁBLE

LTC4078

C2

100nF

MN1

GND

4078X F04

Figure 4. Input Soft Connect Circuit

4078xfb

13

LTC4078/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.

DRꢁIN-BULK

DIODE OF FET

LTC4078

WꢁLL

ꢁDꢁPTER

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

4078xfb

14

LTC4078/LTC4078X

PACKAGE DESCRIPTION

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1ꢀ99)

0.675 ±0.05

3.50 ±0.05

2.15 ±0.05 (2 SIDES)

1.65 ±0.05

PACKAGE

OUTLINE

0.25 ± 0.05

0.50

BSC

2.38 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

R = 0.115

0.38 ± 0.10

TYP

6

10

3.00 ±0.10

(4 SIDES)

1.65 ± 0.10

(2 SIDES)

PIN 1

TOP MARK

(SEE NOTE 6)

(DD) DFN 1103

5

1

0.25 ± 0.05

0.50 BSC

0.75 ±0.05

0.200 REF

2.38 ±0.10

(2 SIDES)

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

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

4078xfb

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

LTC4078/LTC4078X

TYPICAL APPLICATION

Full Featured Li-Ion Charger

800mꢁ (WꢁLL)

475mꢁ (USB)

LTC4078

WꢁLL

ꢁDꢁPTER

BꢁT

DCIN

USB

POWER

1k

USBIN

1μF

PWR

CHRG

BꢁTDET

4.2V Li-Ion

BꢁTTERY

PꢁCK

IUSB

IDC

+

3.9k

ITERM

GND

2.1k

16

1.24k

16

1k

16

4078X Tꢁ02

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4078xfb

LT 0308 REV B • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

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


型号：	LTC4078XEDD#TRPBF
厂家：	Linear
描述：	LTC4078/LTC4078X - Dual Input Li-Ion Battery Charger with Overvoltage Protection; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C 电池光电二极管
文件：	总16页 (文件大小：197K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC4078XEDD#TRPBF [Linear]

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