LTC4075EDD - Linear Technology - Datasheet.Directory

LTC4075/LTC4075X

4075Xfa

The LTC®4075/LTC4075X are standalone linear chargers

that are capable of charging a single-cell Li-Ion battery

from both wall adapter and USB inputs. The chargers can

detect power at the inputs and automatically select the

appropriate power source for charging.

No external sense resistor or blocking diode is required

for charging due to the internal MOSFET architecture.

Internal thermal feedback regulates the battery charge

current to maintain a constant die temperature during high

power operation or high ambient temperature conditions.

The ﬂ oat voltage is ﬁ xed at 4.2V and the charge current

is programmed with an external resistor. The LTC4075

terminates the charge cycle when the charge current drops

below the programmed termination threshold after the

ﬁ nal ﬂ oat voltage is reached. With power applied to both

inputs, the LTC4075/LTC4075X can be put into shutdown

mode reducing the DCIN supply current to 20µA, the USBIN

supply current to 10µA, and the battery drain current to

less than 2µA.

Other features include automatic recharge, undervoltage

lockout, charge status outputs, and “power present”

status outputs to indicate the presence of wall adapter

or USB power.

Dual Input Battery Charger for Single-Cell Li-Ion

LTC4075

DCIN

USBIN

IUSB

IDC

BAT

ITERM

1.24k

1% 2k

WALL

ADAPTER

USB

PORT 1µF

1µF

+4.2V

SINGLE CELL

Li-Ion BATTERY

800mA (WALL)

500mA (USB)

4075 TA01

GND

Dual Input USB/AC

Adapter Standalone Li-Ion

Battery Chargers

TIME (HR)

CHARGE

CURRENT (mA)

BATTERY

VOLTAGE (V)

DCIN

VOLTAGE (V)

4.2

200

400

800

600

1000

1.5 2.5

4075 TA01b

3.6

3.4

5.0

4.0

3.8

2.5

–2.5 0.5 1.0 2.0 3.0

CONSTANT VOLTAGE

USBIN = 5V

TA = 25°C

RIDC = 1.25k

RIUSB = 2k

Complete Charge Cycle (1100mAh Battery)

, LTC and LT 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

APPLICATIO S

FEATURES DESCRIPTIO

TYPICAL APPLICATIO

■ Charges 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

■ No External MOSFET, Sense Resistor or Blocking

Diode Needed

■ Thermal Regulation Maximizes Charging Rate

Without Risk of Overheating*

■ Preset Charge Voltage with ±0.6% Accuracy

■ Programmable Charge Current Termination

■ 18µA USB Suspend Current in Shutdown

■ Independent “Power Present” Status Outputs

■ Charge Status Output

■ Automatic Recharge

■ Available Without Trickle Charge (LTC4075X)

■ Available in a Thermally Enhanced, Low Proﬁ le

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

■ Cellular Telephones

■ Handheld Computers

■ Portable MP3 Players

■ Digital Cameras

LTC4075/LTC4075X

4075Xfa

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VDCIN Supply Voltage ● 4.3 8 V

VUSBIN Supply Voltage ● 4.3 8 V

IDCIN DCIN Supply Current Charge Mode (Note 4), RIDC = 10k ● 250 800 µA

Standby Mode; Charge Terminated ● 50 100 µA

Shutdown Mode (ENABLE = 5V) 20 40 µA

IUSBIN USBIN Supply Current Charge Mode (Note 5), RIUSB = 10k, VDCIN = 0V ● 250 800 µA

Standby Mode; Charge Terminated, VDCIN = 0V ● 50 100 µA

Shutdown (VDCIN = 0V, ENABLE = 0V) 18 36 µA

DCIN > VUSBIN 10 20 µA

VFLOAT Regulated Output (Float) Voltage IBAT = 1mA 4.175 4.2 4.225 V

BAT = 1mA, 0°C < TA < 85°C 4.158 4.2 4.242 V

IBAT BAT Pin Current RIDC = 1.25k, Constant-Current Mode ● 760 800 840 mA

IUSB = 2.1k, Constant-Current Mode ● 450 476 500 mA

IDC = 10k or RIUSB = 10k ● 93 100 107 mA

Standby Mode, Charge Terminated –3 –6 µA

Shutdown Mode (Charger Disabled) –1 –2 µA

Sleep Mode (VDCIN = 0V, VUSBIN = 0V) ±1 ±2 µA

VIDC IDC Pin Regulated Voltage Constant-Current Mode 0.95 1 1.05 V

VIUSB IUSB Pin Regulated Voltage Constant-Current Mode 0.95 1 1.05 V

ITERMINATE Charge Current Termination Threshold RITERM = 1k ● 90 100 110 mA

ITERM = 2k ● 45 50 55 mA

ITERM = 10k ● 8.5 10 11.5 mA

ITERM = 20k ● 4 5 6 mA

Input Supply Voltage (DCIN, USBIN) ........... –0.3 to 10V

ENABLE,

⎯

R, USBPWR ................. –0.3 to 10V

BAT, IDC, IUSB, ITERM .................................. –0.3 to 7V

DCIN Pin Current (Note 7) ..........................................1A

USBIN Pin Current (Note 7) .................................700mA

BAT Pin Current (Note 7) ............................................1A

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

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

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

Storage Temperature Range .................. –65°C to 125°C

(Note 1)

The ● denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VDCIN = 5V, VUSBIN = 5V unless otherwise noted.

ELECTRICAL CHARACTERISTICS

ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

UUW

TOP VIEW

DD PACKAGE

10-LEAD (3mm × 3mm) PLASTIC DFN

EXPOSED PAD IS GND (PIN 11)

MUST BE SOLDERED TO PCB

811

1DCIN

BAT

IDC

USBPWR

ENABLE

USBIN

IUSB

ITERM

PWR

CHRG

ORDER PART NUMBER DD PART MARKING

LTC4075EDD

LTC4075XEDD

LBSC

LBRK

Order Options Tape and Reel: Add #TR

Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF

Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts speciﬁ ed with wider operating temperature ranges.

TJMAX = 125°C, θJA = 40°C/W (NOTE 3)

LTC4075/LTC4075X

4075Xfa

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

ITRIKL Trickle Charge Current (Note 6) VBAT < VTRIKL; RIDC = 1.25k 60 80 100 mA

BAT < VTRIKL; RIUSB = 2.1k 30 47.5 65 mA

VTRIKL Trickle Charge Threshold (Note 6) VBAT Rising 2.8 2.9 3 V

Hysteresis 100 mV

VUVDC DCIN Undervoltage Lockout Voltage From Low to High 4 4.15 4.3 V

Hysteresis 200 mV

VUVUSB USBIN Undervoltage Lockout Voltage From Low to High 3.8 3.95 4.1 V

Hysteresis 200 mV

VASD-DC V

DCIN – VBAT Lockout Threshold VDCIN from Low to High, VBAT = 4.2V 140 180 220 mV

DCIN from High to Low, VBAT = 4.2V 20 50 80 mV

VASD-USB V

USBIN – VBAT Lockout Threshold VUSBIN from Low to High, VBAT = 4.2V 140 180 220 mV

USBIN from High to Low, VBAT = 4.2V 20 50 80 mV

VENABLE ENABLE Input Threshold Voltage 0.4 0.7 1 V

RENABLE ENABLE Pulldown Resistance ● 1.2 2 5 MΩ

⎯

G Output Low Voltage I

⎯

G = 5mA 0.35 0.6 V

⎯

R Output Low Voltage I

⎯

R = 5mA 0.35 0.6 V

VUSBPWR USBPWR Output Low Voltage IUSBPWR = 300µA 0.35 0.6 V

ΔVRECHRG Recharge Battery Threshold VFLOAT – VRECHRG, 0°C < TA < 85°C 65 100 135 mV

tRECHRG Recharge Comparator Filter Time VBAT from High to Low 3 6 9 ms

tTERMINATE Termination Comparator Filter Time IBAT Drops Below Termination Threshold 0.8 1.5 2.2 ms

tSS Soft-Start Time IBAT = 10% to 90% Full-Scale 175 250 325 µs

RON-DC Power FET “ON” Resistance 400 mΩ

(Between DCIN and BAT)

RON-USB Power FET “ON” Resistance 550 mΩ

(Between USBIN and BAT)

TLIM Junction Temperature in 105 °C

Constant-Temperature Mode

The ● denotes the speciﬁ cations which apply over the full operating

temperature range, otherwise speciﬁ cations are at TA = 25°C. VDCIN = 5V, VUSBIN = 5V unless otherwise noted.

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

of a device may be impaired.

Note 2: The LTC4075E/LTC4075XE are guaranteed to meet the

performance speciﬁ cations from 0°C to 70°C. Speciﬁ cations 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

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

through the BAT pin.

Note 5: Supply current includes IUSB and ITERM pin current

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

the battery through the BAT pin.

Note 6: This parameter is not applicable to the LTC4075X.

Note 7: Guaranteed by long term current density limitations.

ELECTRICAL CHARACTERISTICS

LTC4075/LTC4075X

4075Xfa

CHARGE CURRENT (mA)

VFLOAT (V)

800500 600 700400

4075X G01

100 200 300

4.26

4.24

4.22

4.20

4.18

4.16

4.14

4.12

4.10

4075X G04

TEMPERATURE (°C)

–50 –25

VFLOAT (V)

05025 75 100

4075X G02

TEMPERATURE (°C)

–50 –25 0 5025 75 100

TEMPERATURE (°C)

–50 –25 0 5025 75 100

4.220

4.215

4.210

4.205

4.200

4.195

4.190

4.185

4.180

VIDC (V)

4075X G03

1.008

1.006

1.004

1.002

1.000

0.998

0.996

0.994

0.992

VIUSB (V)

1.008

1.006

1.004

1.002

1.000

0.998

0.996

0.994

0.992

VIDC (V)

0 0.2 0.6 1.0

IBAT (mA)

0.8

900

800

700

600

500

400

300

200

100

IBAT (mA)

900

800

700

600

500

400

300

200

100

4075X G05

0.4 1.2

VIUSB (V)

0 0.2 0.6 1.0

0.8

0.4 1.2

4075X G06

VPWR (V)

4075X G07

12 467

IPWR (mA)

4075X G08

RIDC = 1.25k

RIDC = RIUSB = 2k

VDCIN = VUSBIN = 5V VDCIN = VUSBIN = 5V

VDCIN = 5V

VDCIN = 8V

VDCIN = 4.3V

VUSBIN = 8V

VUSBIN = 4.3V

RIDC = 1.25k

VUSBIN = 5V

RIUSB = 1.25k

RIUSB = 2k

RIUSB = 10k

RIDC = 2k

RIDC = 10k

ICHRG (mA)

TA = –40°C

TA = 25°C

TA = 90°C

TA = –40°CTA = –40°C

TA = 25°CTA = 25°C

TA = 90°CTA = 90°C

VCHRG (V)

035

12 467

VUSBPWR (V)

IUSBPWR (mA)

035

4075X G09

12 467

VDCIN = 5V

VUSBIN = 0V

IUSB Pin Voltage vs Temperature

(Constant-Current Mode)

Charge Current vs IDC Pin

Voltage

Charge Current vs IUSB Pin

Voltage

⎯

R Pin I-V Curve

⎯

G Pin I-V Curve USBPWR Pin I-V Curve

Regulated Output (Float) Voltage

vs Charge Current

Regulated Output (Float) Voltage

vs Temperature

IDC Pin Voltage vs Temperature

(Constant-Current Mode)

TYPICAL PERFOR A CE CHARACTERISTICS

LTC4075/LTC4075X

4075Xfa

IBAT (mA)

1000

800

600

400

200

4075X G10

VDCIN (V)

IBAT (mA)

4075X G11

900

800

700

600

500

400

3004.0 5.0 6.0 6.5

4.5 5.5 7.0 7.5 8.0

TEMPERATURE (°C)

–50

RDS(ON) (mΩ)

550

500

450

400

350

300

250 25 75

4075X G13

–25 0 50 100 125

TEMPERATURE (°C)

–50 25 75

–25 0 50 100 125

TEMPERATURE (°C)

–50 25 75

–25 0 50 100 125

TEMPERATURE (°C)

–50 25 75

–25 0 50 100

TEMPERATURE (°C)

–50 25 75

–25 0 50 100

TEMPERATURE (°C)

–50 25 75

–25 0 50 100

TEMPERATURE (°C)

–50 25 75

–25 0 50 100

RDS(ON) (mΩ)

800

750

700

650

600

550

500

450

400

350

4075X G14

VENABLE (mV)

900

850

800

750

700

650

600

IDCIN (µA)

4075X G16

IUSBIN (µA)

4075X G17 4075X G18

RENABLE (MΩ)

2.8

2.6

2.4

2.2

2.0

1.8

1.6

4075X G15

VDCIN = 8V

VDCIN = 5V

VDCIN = 4.3V

VUSBIN = 8V

VUSBIN = 5V

VUSBIN = 4.3V

ENABLE = 5V ENABLE = 0V

VDCIN = VUSBIN = 5V

VBAT = 4V

θJA = 40°C/W

VBAT = 4V

IBAT = 200mA

VBAT = 4V

IBAT = 200mA

RIDC = 1.25k

VBAT = 4V

θJA = 35°C/W

RIDC = 1.25k

RIDC = RIUSB = 2k

ONSET OF

THERMAL REGULATION

ONSET OF

THERMAL REGULATION

VDCIN = VUSBIN = 5V

VBAT (V)

2.4

IBAT (mA)

1000

800

600

400

200

3.0 3.6 3.9

4075X G12

2.7 3.3 4.2 4.5

LTC4075

LTC4075X

VDCIN = VUSBIN = 5V

θJA = 40°C/W

RIDC = 1.25k

Charge Current vs Ambient

Temperature

Charge Current vs

Supply Voltage Charge Current vs Battery Voltage

DCIN Power FET “On” Resistance

vs Temperature

USBIN Power “On” Resistance

vs Temperature

ENABLE Pin Threshold (On-to-Off)

vs Temperature

DCIN Shutdown Current vs

Temperature

USBIN Shutdown Current vs

Temperature

ENABLE Pin Pulldown Resistance

vs Temperature

TYPICAL PERFOR A CE CHARACTERISTICS

LTC4075/LTC4075X

4075Xfa

TEMPERATURE (°C)

–50 –25

VUV (V)

05025 75 100

4075X G19

4.30

4.25

4.20

4.15

4.10

4.05

4.00

3.95

3.90

TEMPERATURE (°C)

–50 –25 0 5025 75 100

VRECHRG (V)

4.16

4.14

4.12

4.10

4.08

4.06

4.04

4075X G20

4075X G22

DCIN UVLO

USBIN UVLO

VDCIN = VUSBIN = 4.3V

VDCIN = 5V

RIDC = 1.25k

VDCIN = VUSBIN = 8V

100µs/DIV

IBAT

500mA/DIV

ENABLE

5V/DIV

TEMPERATURE (°C)

–50

IBAT (µA)

–1 –25 02550

4075X G21

75 100

VBAT = 4.2V

VDCIN, VUSBIN (NOT CONNECTED)

Undervoltage Lockout Threshold

vs Temperature

Recharge Threshold

vs Temperature

Charge Current During Turn-On

and Turn-Off

Battery Drain Current

vs Temperature

TYPICAL PERFOR A CE CHARACTERISTICS

LTC4075/LTC4075X

4075Xfa

USBIN (Pin 1): USB Input Supply Pin. Provides power to

the battery charger. The maximum supply current is 650mA.

This pin should be bypassed with a 1µF capacitor.

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

The charge current is set by connecting a resistor, RIUSB,

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:

BAT IUSB

IUSB

=•1000

ITERM (Pin 3): Termination Current Threshold Program.

The termination current threshold, ITERMINATE, is set by

connecting a resistor, RITERM, to ground. ITERMINATE is set

by the following formula:

TERMINATE ITERM

=100

When the battery current, IBAT, falls below the termination

threshold, charging stops and the

⎯

G output becomes

high impedance.

This pin is internally clamped to approximately 1.5V. Driving

this pin to voltages beyond the clamp voltage can draw

large currents and should be avoided.

⎯

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

When the DCIN or USBIN pin voltage is sufﬁ cient to begin

charging (i.e. when the supply is greater than the under-

voltage lockout threshold and at least 180mV above the

battery terminal), the

⎯

R pin is pulled low by an internal

N-channel MOSFET. Otherwise

⎯

R is high impedance.

This output is capable of sinking up to 10mA, making it

suitable for driving an LED.

⎯

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

the LTC4075 is charging, the

⎯

G pin is pulled low by

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

completed,

⎯

G becomes high impedance. This output

is capable of sinking up to 10mA, making it suitable for

driving an LED.

ENABLE (Pin 6): Enable Input. When the LTC4075 is

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

enables the charger. When the LTC4075 is charging from

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

charger. If this input is left ﬂ oating, an internal 2MΩ

pulldown resistor defaults the LTC4075 to charge when

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

source is applied.

USBPWR (Pin 7): Open-Drain USB Power Status Output.

When the voltage on the USBIN pin is sufﬁ cient to begin

charging and there is insufﬁ cient power at DCIN, the USB-

PWR pin is high impedance. In all other cases, this pin is

pulled low by an internal N-channel MOSFET, provided that

there is power present at the DCIN, USBIN, or BAT inputs.

This output is capable of sinking up to 1mA, making it

suitable for driving high impedance logic inputs.

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

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

tor, RIDC, 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

DC input using the following formula:

BAT IDC

IDC

=•1000

BAT (Pin 9): Charger Output and Regulator Input. This pin

provides charge current to the battery and regulates the

ﬁ nal ﬂ oat voltage to 4.2V.

DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides

power to the battery charger. The maximum supply

current is 950mA. This should be bypassed with a 1μF

capacitor.

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

package is ground and must be soldered to PC board ground

for electrical connection and maximum heat transfer.

PI FU CTIO S

UUU

LTC4075/LTC4075X

4075Xfa

–

RECHRG

TRICKLE

TERM

LOGIC

4.1V

BAT

4.15V

BAT

3.95V

BAT

2.9V

100mV

IBAT/1000 IBAT/1000 IBAT/1000

3 8 211

DC_ENABLE USB_ENABLE

CHARGER CONTROL

CC/CV

REGULATOR

CC/CV

REGULATOR

910 1

RITERM RIUSB

RIDC

ITERM IUSBIDCGND

105°C

TDIE

USB

SOFT-START

USBIN UVLODCIN UVLO

DCIN BAT USBIN

USBPWR

ENABLE

RENABLE

PWR

CHRG

TERMINATION

*TRICKLE

CHARGE

RECHARGE

THERMAL

REGULATION

*TRICKLE CHARGE DISABLED ON THE LTC4075X

1mA MAX

10mA MAX

4075 BD

BLOCK DIAGRA

LTC4075/LTC4075X

4075Xfa

The LTC4075 is designed to efﬁ ciently manage charging of

a single-cell lithium-ion battery from two separate power

sources: a wall adapter and USB power bus. Using the

constant-current/constant-voltage algorithm, the charger

can deliver up to 950mA of charge current from the wall

adapter supply or up to 650mA of charge current from the

USB supply with a ﬁ nal ﬂ oat voltage accuracy of ±0.6%.

The LTC4075 has two internal P-channel power MOSFETs

and thermal regulation circuitry. No blocking diodes or

external sense resistors are required.

Power Source Selection

The LTC4075 can charge a battery from either the wall

adapter input or the USB port input. The LTC4075 automati-

cally senses the presence of voltage at each input. If both

power sources are present, the LTC4075 defaults to the

wall adapter source provided sufﬁ cient power is present

at the DCIN input. “Sufﬁ cient power” is deﬁ ned as:

• Supply voltage is greater than the UVLO threshold.

• Supply voltage is greater than the battery voltage by

50mV (180mV rising, 50mV falling).

The open drain power status outputs (

⎯

R and USBPWR)

indicate which power source has been selected. Table 1

describes the behavior of these status outputs.

Table 1. Power Source Selection

VUSBIN > 3.95V and VUSBIN < 3.95V or

USBIN > BAT + 50mV VUSBIN < BAT + 50mV

VDCIN > 4.15V and Device powered from Device powered from

VDCIN > BAT + 50mV wall adapter source; wall adapter source

USBIN current < 25µA

⎯

R: LOW

⎯

R: LOW

USBPWR: LOW USBPWR: LOW

VDCIN < 4.15V or Device powered from No charging

VDCIN < BAT + 50mV USB source;

⎯

R: LOW

⎯

R: Hi-Z

USBPWR: Hi-Z USBPWR: LOW

Programming and Monitoring Charge Current

The charge current delivered to the battery from the wall

adapter supply is programmed using a single resistor

from the IDC pin to ground. Likewise, the charge current

from the USB supply is programmed using a single resis-

tor from the IUSB pin to ground. The program resistor

and the charge current (ICHRG) are calculated using the

following equations:

IIV

IDC CHRG DC CHRG DC IDC

IUSB CHRG USB CHRG USB IUSB

−

1000 1000

Charge current out of the BAT pin can be determined at

any time by monitoring the IDC or IUSB pin voltage and

using the following equations:

Rch ing fromwall adapter

Rch ing fromUSB ply

BAT IDC

IDC

BAT IUSB

IUSB

• , ( arg )

• , ( arg sup )

1000

Programming Charge Termination

The charge cycle terminates when the charge current falls

below the programmed termination threshold during con-

stant-voltage mode. This threshold is set by connecting an

external resistor, RITERM, from the ITERM pin to ground.

The charge termination current threshold (ITERMINATE) is

set by the following equation:

IIV

ITERM TERMINATE TERMINATE ITERM

100 100

OPERATIO

LTC4075/LTC4075X

4075Xfa

*Any external sources that hold the ITERM pin above 100mV will prevent the LTC4075 from

terminating a charge cycle.

The termination condition is detected by using an internal

ﬁ ltered comparator to monitor the ITERM pin. When the

ITERM pin voltage drops below 100mV

for longer than

tTERMINATE (typically 1.5ms), charging is terminated. The

charge current is latched off and the LTC4075 enters

standby mode.

When charging, transient loads on the BAT pin can cause

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

time before the DC charge current has dropped below the

programmed termination current. The 1.5ms ﬁ lter time

(tTERMINATE) on the termination comparator ensures that

transient loads of this nature do not result in premature

charge cycle termination. Once the average charge current

drops below the programmed termination threshold, the

LTC4075 terminates the charge cycle and ceases to provide

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

the BAT pin must be supplied by the battery.

Low Battery Charge Conditioning (Trickle Charge)

This feature ensures that near-dead batteries are gradually

charged before reapplying full charge current . If the BAT

pin voltage is below 2.9V, the LTC4075 supplies 1/10th

of the full charge current to the battery until the BAT pin

rises back above 2.9V. For example, if the charger is

programmed to charge at 800mA from the wall adapter

input and 500mA from the USB input, the charge current

during trickle charge mode would be 80mA and 50mA,

respectively.

The LTC4075X does not include the trickle charge feature;

it outputs full charge current to the battery when the

BAT pin voltage is below 2.9V. The LTC4075X is useful

in applications where the trickle charge current may be

insufﬁ cient to supply the load during low battery voltage

conditions.

Automatic Recharge

In standby mode, the charger sits idle and monitors the

battery voltage using a comparator with a 6ms ﬁ lter time

(tRECHRG). A charge cycle automatically restarts when the

battery voltage falls below 4.1V (which corresponds to

approximately 80%-90% battery capacity). This ensures

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

tion and eliminates the need for periodic charge cycle

initiations.

If the battery is removed from the charger, a sawtooth

waveform of approximately 100mV appears at the battery

output. This is caused by the repeated cycling between

termination and recharge events. This cycling results in

pulsing at the

⎯

G output; an LED connected to this pin

will exhibit a blinking pattern, indicating to the user that

a battery is not present. The frequency of the sawtooth is

dependent on the amount of output capacitance.

Manual Shutdown

The ENABLE pin has a 2MΩ pulldown resistor to GND. The

deﬁ nition of this pin depends on which source is supplying

power. When the wall adapter input is supplying power,

logic low enables the charger and logic high disables it (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).

The DCIN input draws 20µA when the charger is in shut-

down. The USBIN input draws 18µA during shutdown if

no power is applied to DCIN, but draws only 10µA when

VDCIN > VUSBIN.

Charge Current Soft-Start and Soft-Stop

The LTC4075 includes a soft-start circuit to minimize

the inrush current at the start of a charge cycle. When a

charge cycle is initiated, the charge current ramps from

zero to full-scale current over a period of 250µs. Likewise,

internal circuitry slowly ramps the charge current from

full-scale to zero in a period of approximately 30µs when

the charger shuts down or self terminates. This minimizes

the transient current load on the power supply during

start-up and shut-off.

Status Indicators

The charge status output (

⎯

G) has two states: pull-down

and high impedance. The pull-down state indicates that

the LTC4075 is in a charge cycle. Once the charge cycle

has terminated or the LTC4075 is disabled, the pin state

becomes high impedance. The pull-down state is capable

of sinking up to 10mA.

OPERATIO

LTC4075/LTC4075X

4075Xfa

The power supply status output (

⎯

R) has two states: pull-

down and high impedance. The pull-down state indicates

that power is present at either DCIN or USBIN. This output

is strong enough to drive an LED. If no power is applied at

either pin, the

⎯

R pin is high impedance, indicating that

the LTC4075 lacks sufﬁ cient power to charge the battery.

The pull-down state is capable of sinking up to 10mA.

The USB power status output (USBPWR) has two states:

pull-down and high impedance. The high impedance

state indicates that the LTC4075 is being powered from

the USBIN input. The pull-down state indicates that the

charger is either powered from DCIN or is in a UVLO

condition (see Table 1). The pull-down state is capable of

sinking up to 1mA.

Thermal Limiting

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise above

a preset value of approximately 105°C. This feature protects

the LTC4075 from excessive temperature and allows the

user to push the limits of the power handling capability of

a given circuit board without risk of damaging 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 power considerations are discussed

further in the Applications Information section.

TRICKLE CHARGE

MODE*

1/10th FULL CURRENT

CHRG STATE: PULLDOWN

SHUTDOWN

MODE

IUSBIN DROPS TO 18µA

CHRG STATE: Hi-Z

CHARGE

MODE

FULL CURRENT

CHRG STATE: PULLDOWN

CHARGE

MODE

FULL CURRENT

CHRG STATE: PULLDOWN

STANDBY

MODE

NO CHARGE CURRENT

CHRG STATE: Hi-Z

SHUTDOWN

MODE

IDCIN DROPS TO 20µA

CHRG STATE: Hi-Z

BAT > 2.9V

BAT < 2.9V BAT < 2.9V

2.9V < BAT

BAT > 2.9V

BAT < 4.1VBAT < 4.1V

IBAT < ITERMINATE

IN VOLTAGE MODE

IBAT < ITERMINATE

IN VOLTAGE MODE

POWER SELECTION

STANDBY

MODE

NO CHARGE CURRENT

CHRG STATE: Hi-Z

TRICKLE CHARGE

MODE*

1/10th FULL CURRENT

CHRG STATE: PULLDOWN

ENABLE

DRIVEN LOW

ENABLE

DRIVEN LOW

ENABLE

DRIVEN HIGH

DCIN POWER

REMOVED

DCIN POWER

REMOVED

USBIN POWER

REMOVED OR

DCIN POWER

APPLIED

USBIN POWER

REMOVED OR

DCIN POWER

APPLIED

DCIN POWER APPLIED ONLY USB POWER APPLIED

STARTUP

4075 F01

ENABLE

DRIVEN HIGH

*LTC4075 ONLY

Figure 1. LTC4075 State Diagram of a Charge Cycle

OPERATIO

LTC4075/LTC4075X

4075Xfa

RISET

RITERM

WALL

ADAPTER

USB

PORT 1µF

1µF+

500mA

4075 F03

LTC4075

DCIN

USBIN

IUSB

IDC

BAT

ITERM

GND

Figure 2. Full Featured Dual Input Charger Circuit

RIDC

1.24k

RIUSB

RITERM

WALL

ADAPTER

USB

PORT 1µF

1µF+

800mA (WALL)

500mA (USB)

4075 F02

LTC4075

DCIN

USBIN

IUSB

IDC

BAT

ITERM

GND

Figure 3. Dual Input Charger Circuit. The Wall

Adapter Charge Current and USB Charge Current

are Both Programmed to be 500mA

Using a Single Charge Current Program Resistor

The LTC4075 can program the wall adapter charge current

and USB charge current independently using two program

resistors, RIDC and RIUSB. Figure 2 shows a charger circuit

that sets the wall adapter charge current to 800mA and

the USB charge current to 500mA.

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.

In this circuit, the programmed charge current from both the

wall adapter supply is the same value as the programmed

charge current from the USB supply:

II V

CHRG DC CHRG USB ISET

−−

1000

Stability Considerations

The constant-voltage mode feedback loop is stable without

any compensation provided a battery is connected to the

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

resistor is recommended at the BAT pin to keep the ripple

voltage low when the battery is disconnected.

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

affected by the impedance at the charge current program

pin. With no additional capacitance on this pin, the char-

ger is stable with program resistor values as high as 20k

(ICHRG = 50mA); however, additional capacitance on these

nodes reduces the maximum allowed program resistor.

Power Dissipation

When designing the battery charger circuit, it is not neces-

sary to design for worst-case power dissipation scenarios

because the LTC4075 automatically reduces the charge

current during high power conditions. The conditions

that cause the LTC4075 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:

D = (VIN – VBAT) • IBAT

APPLICATIO S I FOR ATIO

WUUU

LTC4075/LTC4075X

4075Xfa

PD is the power dissipated, VIN is the input supply volt-

age (either DCIN or USBIN), VBAT is the battery voltage

and IBAT is the charge current. The approximate ambient

temperature at which the thermal feedback begins to

protect the IC is:

A = 105°C – PD • θJA

A = 105°C – (VIN – VBAT) • IBAT • θJA

Example: An LTC4075 operating from a 5V wall adapter (on

the DCIN input) is programmed to supply 800mA full-scale

current to a discharged Li-Ion battery with a voltage of 3.3V.

Assuming θJA is 40°C/W (see Thermal Considerations),

the ambient temperature at which the LTC4075 will begin

to reduce the charge current is approximately:

A = 105°C – (5V – 3.3V) • (800mA) • 40°C/W

A = 105°C – 1.36W • 40°C/W = 105°C – 54.4°C

TA = 50.6°C

The LTC4075 can be used above 50.6°C ambient, but

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

proximate current at a given ambient temperature can be

approximated by:

ICT

BAT A

IN BAT JA

=°105 –

(– •

)θ

Using the previous example with an ambient temperature

of 60°C, the charge current will be reduced to approxi-

mately:

ICC

VVCW

ImA

BAT

=°°

°=°

105 60

53340

662

–

(–.)• / /

It is important to remember that LTC4075 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

105°C.

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 LTC4075 package is properly soldered

to the PC board ground. When correctly soldered to a

2500mm2 double sided 1oz copper board, the LTC4075

has a thermal resistance of approximately 40°C/W. Failure

to make thermal contact between the exposed pad on the

backside of the package and the copper board will result in

thermal resistances far greater than 40°C/W. As an example,

a correctly soldered LTC4075 can deliver over 800mA to

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

a good backside thermal connection, this number would

drop to much less than 500mA.

Protecting the USB Pin and Wall Adapter Input from

Overvoltage Transients

Caution must be exercised when using ceramic capacitors

to bypass the USBIN pin or the wall adapter inputs. High

voltage transients can be generated when the USB or wall

adapter is hot plugged. When power is supplied via the

USB bus or wall adapter, the cable inductance along with

the self resonant and high Q characteristics of ceramic

capacitors can cause substantial ringing which could

exceed the maximum voltage pin ratings and damage the

LTC4075. Refer to Linear Technology Application Note 88,

entitled “Ceramic Input Capacitors Can Cause Overvoltage

Transients” for a detailed discussion of this problem. The

long cable lengths of most wall adapters and USB cables

APPLICATIO S I FOR ATIO

WUUU

LTC4075/LTC4075X

4075Xfa

Figure 5. Low Loss Input Reverse Polarity Protection

WALL

ADAPTER DCIN

LTC4075

DRAIN-BULK

DIODE OF FET

4075 F05

makes them especially susceptible to this problem. To

bypass the USB pin and the wall adapter input, add a 1Ω

resistor in series with a ceramic capacitor to lower the

effective Q of the network and greatly reduce the ringing.

A tantalum, OS-CON, or electrolytic capacitor can be used

in place of the ceramic and resistor, as their higher ESR

reduces the Q, thus reducing the voltage ringing.

The oscilloscope photograph in Figure 4 shows how

serious the overvoltage transient can be for the USB

and wall adapter inputs. For both traces, a 5V supply is

hot-plugged using a three foot long cable. For the top

trace, only a 4.7µF capacitor (without the recommended

1Ω series resistor) is used to locally bypass the input.

This trace shows excessive ringing when the 5V cable

is inserted, with the overvoltage spike reaching 10V. For

the bottom trace, a 1Ω resistor is added in series with the

4.7µF capacitor to locally bypass the 5V input. This trace

shows the clean response resulting from the addition of

the 1Ω resistor.

Even with the additional 1Ω resistor, bad design techniques

and poor board layout can often make the overvoltage

problem even worse. System designers often add extra

inductance in series with input lines in an attempt to mini-

mize the noise fed back to those inputs by the application.

In reality, adding these extra inductances only makes the

overvoltage transients worse. Since cable inductance is

one of the fundamental causes of the excessive ringing,

adding a series ferrite bead or inductor increases the ef-

fective cable inductance, making the problem even worse.

For this reason, do not add additional inductance (ferrite

beads or inductors) in series with the USB or wall adapter

inputs. For the most robust solution, 6V transorbs or zener

diodes may also be added to further protect the USB and

wall adapter inputs. Two possible protection devices are

the SM2T from STMicroelectronics and the EDZ series

devices from ROHM.

Always use an oscilloscope to check the voltage wave-

forms at the USBIN and DCIN pins during USB and wall

adapter hot-plug events to ensure that overvoltage

transients have been adequately removed.

Reverse Polarity Input Voltage Protection

In some applications, protection from reverse polarity

voltage on the input supply pins is desired. If the sup-

ply voltage is high enough, 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).

APPLICATIO S I FOR ATIO

WUUU

Figure 4. Waveforms Resulting from Hot-Plugging a

5V Input Supply

4.7µF ONLY

2V/DIV

4.7µF + 1Ω

2V/DIV

20µs/DIV 3455 F04

LTC4075/LTC4075X

4075Xfa

DD Package

10-Lead Plastic DFN (3mm × 3mm)

(Reference LTC DWG # 05-08-1699)

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 representation that

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

PACKAGE DESCRIPTIO

3.00 ±0.10

(4 SIDES)

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

0.38 ± 0.10

BOTTOM VIEW—EXPOSED PAD

1.65 ± 0.10

(2 SIDES)

0.75 ±0.05

R = 0.115

TYP

2.38 ±0.10

(2 SIDES)

106

PIN 1

TOP MARK

(SEE NOTE 6)

0.200 REF

0.00 – 0.05

(DD10) DFN 1103

0.25 ± 0.05

2.38 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

1.65 ±0.05

(2 SIDES)2.15 ±0.05

0.50

BSC

0.675 ±0.05

3.50 ±0.05

PACKAGE

OUTLINE

0.25 ± 0.05

0.50 BSC

LTC4075/LTC4075X

4075Xfa

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

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

LT 1105 REV A • PRINTED IN USA

PART NUMBER DESCRIPTION COMMENTS

LTC3455 Dual DC/DC Converter with USB Power Efﬁ ciency >96%, Accurate USB Current Limiting (500mA/100mA),

Management and Li-Ion Battery Charger 4mm × 4mm QFN-24 Package

LTC4053 USB Compatible Monolithic Li-Ion Battery Charger Standalone Charger with Programmable Timer, Up to 1.25A Charge Current

LTC4054/LTC4054X Standalone Linear Li-Ion Battery Charger Thermal Regulation Prevents Overheating, C/10 Termination,

with Integrated Pass Transistor in ThinSOT C/10 Indicator, Up to 800mA Charge Current

LTC4055 USB Power Controller and Battery Charger Charges Single-Cell Li-Ion Batteries Directly from USB Port,

Thermal Regulation, 4mm × 4mm QFN-16 Package

LTC4058/LTC4058X Standalone 950mA Lithium-Ion Charger in DFN C/10 Charge Termination, Battery Kelvin Sensing, ±7% Charge Accuracy

LTC4061 Standalone Li-Ion Charger with Thermistor Interface 4.2V, ±0.35% Float Voltage, Up to 1A Charge Current

LTC4066 USB Power Controller and Li-Ion Linear Battery Seamless Transition Between Input Power Sources: Li-Ion Battery, USB and

Charger with Low-Loss Ideal Diode Wall Adapter, Low-Loss (50Ω) Ideal Diode, 4mm × 4mm QFN-24 Package

LTC4068/LTC4068X Standalone Linear Li-Ion Battery Charger with Charge Current up to 950mA, Thermal Regulation,

Programmable Termination 3mm × 3mm DFN-8 Package

LTC4410 USB Power Manager and Battery Charger Manages Total Power Between a USB Peripheral and Battery Charger,

Ultralow Battery Drain: 1µA, ThinSOTTM Package

LTC4411/LTC4412 Low Loss PowerPathTM Controller in ThinSOT Automatic Switching Between DC Sources, Load Sharing,

Replaces ORing Diodes

Full Featured Li-Ion Charger

1.24k

WALL

ADAPTER

USB

POWER 1µF

1µF

800mA (WALL)

475mA (USB)

4075 TA03

2.1k

1k 1k

1-CELL

Li-Ion

BATTERY

LTC4075

DCIN

USBIN

IUSB

IDC

BAT

PWR

CHRG

ITERM

GND

ThinSOT and PowerPath are trademarks of Linear Technology Corporation

TYPICAL APPLICATIO

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