LTC4090-5_15_技术文档

LTC4090/LTC4090-5

USB Power Manager with

2A High Voltage Bat-Track

Buck Regulator

FEATURES

DESCRIPTION

The LTC^®4090/LTC4090-5 are USB power managers plus

highvoltageLi-Ion/Polymerbatterychargers. Thedevices

control the total current used by the USB peripheral for

operation and battery charging. Battery charge current

is automatically reduced such that the sum of the load

current and the charge current does not exceed the pro-

grammed input current limit. The LTC4090/LTC4090-5

also accommodate high voltage power supplies, such as

12V AC/DC wall adapters, Firewire, or automotive power.

n

Seamless Transition Between Power Sources:

Li-Ion Battery, USB, and 6V to 36V Supply (60V Max)

n

2A Output High Voltage Buck Regulator with

Bat-Track™ Adaptive Output Control (LTC4090)

Internal 215mW Ideal Diode Plus Optional

n

External Ideal Diode Controller Provides Low Loss

PowerPath™ When External Supply/USB Not Present

n

Load Dependent Charging from USB Input

Guarantees Current Compliance

Full Featured Li-Ion Battery Charger

n

The LTC4090 provides a Bat-Track adaptive output that

tracksthebatteryvoltageforhighefficiencychargingfrom

the high voltage input. The LTC4090-5 provides a fixed 5V

output from the high voltage input to charge single-cell

Li-Ionbatteries.Thechargecurrentisprogrammableandan

end-of-charge status output (CHRG) indicates full charge.

Alsofeaturedareprogrammabletotalchargetime, anNTC

thermistorinputusedtomonitorbatterytemperaturewhile

charging and automatic recharging of the battery.

n

1.5A Maximum Charge Current with Thermal Limiting

n

NTC Thermistor Input for Temperature Qualiﬁed

Charging

n

Tiny (3mm × 6mm × 0.75mm) 22-Pin DFN Package

APPLICATIONS

n

HDD-Based Media Players

n

Personal Navigation Devices

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

and Bat-Track, PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All

other trademarks are the property of their respective owners.

n

Other USB-Based Handheld Products

Automotive Accessories

n

TYPICAL APPLICATION

LTC4090/LTC4090-5 High Voltage

Battery Charger Efficiency

0.47µF

SW

6.8µH

BOOST

HIGH (7.5V-36V)

VOLTAGE INPUT

HVIN

22µF

90

80

70

60

50

40

30

20

FIGURE 12 SCHEMATIC

WITH R = 52k

1µF

LTC4090

PROG

HVOUT

5V WALL

ADAPTER

NO OUTPUT LOAD

IN

HVPR

4.7µF

USB

LTC4090

1k

LTC4090-5

V

C

OUT

LOAD

4.7µF

TIMER

BAT

R

CLPROG

2k

GND PROG

T

59k

HVIN = 8V

HVIN = 12V

HVIN = 24V

HVIN = 36V

+

40.2k

100k

270pF

0.1µF

Li-Ion BATTERY

V

(TYP)

+ 0.3V

5V

AVAILABLE INPUT

HV INPUT (LTC4090)

HV INPUT (LTC4090-5)

USB ONLY

OUT

2.0

2.5

3.0

V

3.5

(V)

4.0

4.5

V

BAT

4090 TA01b

V

BAT

BAT ONLY

4090 TAO1

4090fd

1

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Notes 1, 2, 3, 4)

TOP VIEW

HVIN, HVEN (Note 9) ................................................60V

BOOST ......................................................................56V

BOOST above SW .....................................................30V

PG, SYNC..................................................................30V

IN, OUT, HVOUT

SYNC

PG

1

2

3

4

5

6

7

8

9

22 HVEN

21 HVIN

20 SW

R

T

V

19 BOOST

18 HVOUT

17 TIMER

16 SUSP

15 HPWR

14 CLPROG

13 OUT

C

NTC

VNTC

HVPR

CHRG

PROG

t < 1ms and Duty Cycle < 1%................... –0.3V to 7V

Steady State ............................................ –0.3V to 6V

23

BAT, HPWR, SUSP, V , CHRG, HVPR ........... –0.3V to 6V

C

NTC, TIMER, PROG, CLPROG ..........–0.3V to V + 0.3V

CC

I , I , I

IN OUT BAT

(Note 5) ..............................................2.5A

GATE 10

BAT 11

Operating Temperature Range .....................–40 to 85°C

Junction Temperature ............................................110°C

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

12 IN

DJC PACKAGE

22-LEAD (6mm × 3mm) PLASTIC DFN

T

= 110°C, θ = 47°C/W

JMAX

JA

EXPOSED PAD (PIN 23) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LTC4090EDJC#PBF

LTC4090EDJC-5#PBF

TAPE AND REEL

PART MARKING

4090

PACKAGE DESCRIPTION

22-Lead (6mm × 3mm) Plastic DFN

TEMPERATURE RANGE

–40°C to 85°C

LTC4090EDJC#TRPBF

LTC4090EDJC-5#TRPBF

40905

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/

The l denotes the specifications which apply over the full operating

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T_A= 25°C. HVIN = HVEN = 12V, BOOST = 17V, V_IN= HPWR = 5V, V_BAT= 3.7V,

R_PROG= 100k, R_CLPROG= 2k and SUSP = 0V, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

USB Input Current Limit

l

V

USB Input Supply Voltage

Input Bias Current

4.35

5.5

V

IN

l

I

= 0 (Note 6)

0.5

50

1

100

mA

µA

IN

BAT

Suspend Mode; SUSP = 5V

l

Current Limit

HPWR = 5V

HPWR = 0V

475

90

500

100

525

110

mA

LIM

Maximum Input Current Limit

(Note 7)

2.4

A

IN(MAX)

W

R

On-Resistance V to V

I = 80mA

OUT

0.215

ON

IN

OUT

l

V

CLPROG Servo Voltage in Current Limit

R

= 2k

= 1k

0.98

1.00

1.02

V

CLPROG

I

Soft-Start Inrush Current

10

mA/µs

SS

4090fd

2

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

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

temperature range, otherwise specifications are at T_A= 25°C. HVIN = HVEN = 12V, BOOST = 17V, V_IN= HPWR = 5V, V_BAT= 3.7V,

R_PROG= 100k, R_CLPROG= 2k and SUSP = 0V, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

(V - V ) Rising

MIN

TYP

MAX

UNITS

V

Input Current Limit Enable Threshold

20

–80

50

–50

80

–20

mV

CLEN

IN

OUT

Voltage (V - V

)

(V - V ) Falling

IN

OUT

IN

OUT

l

V

Input Undervoltage Lockout

V

Rising

3.6

3.8

4

V

UVLO

IN

DV

Input Undervoltage Lockout Hysteresis

V

Rising – V Falling

130

mV

UVLO

IN

High Voltage Regulator

l

V

HVIN Supply Voltage

6

60

40

V

HVIN

OVLO

HVIN

V

HVIN Overvoltage Lockout Threshold

HVIN Bias Current

36

38

I

Shutdown; HVEN = 0.2V

Not Switching, HVOUT = 3.6V

0.01

130

0.5

200

µA

l

V

Output Voltage with HVIN Present

Switching Frequency

Assumes HVOUT to OUT Connection,

3.45

4.85

V

+ 0.3

BAT

4.6

V

OUT

0 ≤ V ≤ 4.2V (LTC4090)

BAT

V

Assumes HVOUT to OUT Connection

(LTC4090-5)

5

5.15

V

f

R = 8.66k

2.1

0.9

160

2.4

1.0

200

2.7

1.15

240

MHz

kHz

SW

T

R = 29.4k

T

R = 187k

T

l

t

I

Minimum Switch Off-Time

Switch Current Limit

60

3.5

500

0.02

1.5

22

150

4.0

ns

A

OFF

Duty Cycle = 5%

3.0

SW(MAX)

V

Switch V

I = 2A

SW

mV

µA

V

SAT

CESAT

I

Boost Schottky Reverse Leakage

Minimum Boost Voltage (Note 8)

BOOST Pin Current

SW = 10V, HVOUT = 0V

2

R

l

V

2.1

35

B(MIN)

I

SW

= 1A

mA

BST

Battery Management

Battery Drain Current

l

I

V

= 4.3V, Charging Stopped

15

22

60

27

35

100

µA

BAT

Suspend Mode, SUSP = 5V

V

= 0V, BAT Powers OUT, No Load

IN

V

Regulated Output Voltage

I

= 2mA

4.165

4.158

4.200

4.235

4.242

V

FLOAT

BAT

= 2mA; 0 ≤ T ≤ 85°C

A

l

I

Constant-Current Mode Charge Current,

No Load

R

= 100k

465

900

500

535

mA

CHG

PROG

= 50k, 0 ≤ T ≤ 85°C

1000

1080

A

Maximum Charge Current

PROG Pin Servo Voltage

1.5

A

CHG(MAX)

l

V

R

PROG

R

PROG

= 100k

= 50k

0.98

1.00

1.02

V

PROG

l

k

Ratio of End-of-Charge Indication

Current to Charge Current

V

= V

(4.2V)

FLOAT

0.085

0.1

0.11

mA/mA

EOC

BAT

I

Trickle Charge Current

BAT = 2V

35

50

60

mA

V

TRKL

V

Trickle Charge Threshold Voltage

Charge Enable Threshold Voltage

BAT Rising

2.75

2.9

3.0

TRKL

CEN

(V

– V ) Falling; V = 4V

55

80

mV

OUT

BAT

– V ) Rising; V = 4V

DV

Recharge Battery Threshold Voltage

Threshold Voltage Relative to V

–65

–100

–135

mV

RECHRG

FLOAT

4090fd

3

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

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

temperature range, otherwise specifications are at T_A= 25°C. HVIN = HVEN = 12V, BOOST = 17V, V_IN= HPWR = 5V, V_BAT= 3.7V,

R_PROG= 100k, R_CLPROG= 2k and SUSP = 0V, unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

= 4.3V

MIN

TYP

MAX

UNITS

%

t

TIMER Accuracy

V

–10

10

TIMER

BAT

Recharge Time

Percent of Total Charge Time

Percent of Total Charge Time,

50

25

%

Low Battery Trickle Charge Time

%

V

<2.9V

BAT

T

Junction Temperature in Constant-

Temperature Mode

105

°C

LIM

Internal Ideal Diode

R

Incremental Resistance, V Regulation

I

= 100mA

= 600mA

125

215

mW

FWD

ON

OUT

R

On-Resistance V to V

OUT

DIO, ON

FWD

BAT

l

V

Voltage Forward Drop (V – V

)

I

= 5mA

= 100mA

= 600mA

10

30

55

160

50

mV

BAT

OUT

V

Diode Disable Battery Voltage

2.7

550

2.2

V

mA

A

OFF

I

Load Current Limit for V Regulation

FWD

ON

Diode Current Limit

D(MAX)

External Ideal Diode

External Diode Forward Voltage

Logic (CHRG, HVPR, TIMER, SUSP, HPWR, HVEN, PG, SYNC)

V

20

mV

FWD, EXT

l

V

Charger Shutdown Threshold Voltage

on TIMER

0.14

5

0.4

V

CHG, SD

I

Charger Shutdown Pull-Up Current on

TIMER

V

= 0V

14

µA

CHG, SD

TIMER

V

Output Low Voltage

Input High Voltage

Input Low Voltage

HVEN High Threshold

HVEN Low Threshold

Logic Input Pull-Down Current

HVEN Pin Bias Current

PG Threshold

(CHRG, HVPR); I

SUSP, HPWR

= 5mA

0.1

0.4

0.3

10

V

OL

SINK

1.2

2.3

IH

V

IL

V

HVEN, H

HVEN, L

PULLDN

HVEN

V

I

SUSP, HPWR

HVEN = 2.5V

HVOUT Rising

2

5

µA

V

2.8

35

0.1

900

PG

DV

PG Hysteresis

mV

µA

V

PG

PGLK

PG

I

PG Leakage

PG = 5V

1

l

PG Sink Current

PG = 0.4V

100

0.5

V

SYNC Low Threshold

SYNC High Threshold

SYNC Pin Bias Current

SYNC, L

SYNC, H

SYNC

0.8

V

I

V

SYNC

= 0V

0.1

µA

4090fd

4

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

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

temperature range, otherwise specifications are at T_A= 25°C. HVIN = HVEN = 12V, BOOST = 17V, V_IN= HPWR = 5V, V_BAT= 3.7V,

R_PROG= 100k, R_CLPROG= 2k and SUSP = 0V, unless otherwise noted.

SYMBOL

NTC

PARAMETER

CONDITIONS

MIN

TYP

MAX

3.5

1

UNITS

l

I

VNTC Pin Current

VNTC = 2.5V

1.4

4.4

2.5

4.85

0

mA

V

VNTC

V

VNTC Bias Voltage

I

= 500µA

VNTC

NTC

VNTC

I

NTC Input Leakage Current

NTC = 1V

µA

V

COLD

V

HOT

V

DIS

Cold Temperature Fault Threshold

Voltage

Rising NTC Voltage

Hysteresis

0.738 • VNTC

0.02 • VNTC

V

Hot Temperature Fault Threshold

Voltage

Falling NTC Voltage

Hysteresis

0.29 • VNTC

0.01 • VNTC

V

l

NTC Disable Threshold Voltage

Falling NTC Voltage

Hysteresis

75

100

35

125

mV

Note 1: Stresses beyond those listed under Absolute Maximum Ratings

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

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 4: V is the greater of V , V , and V

CC IN OUT BAT

Note 5: Guaranteed by long term current density limitations.

Note 6: Total input current is equal to this specification plus 1.002 • I

BAT

where I is the charge current.

BAT

Note 2: The LTC4090/LTC4090-5 are guaranteed to meet 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: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperatures will exceed 110°C when overtemperature protection is

active. Continuous operation above the specified maximum operating

junction temperature may result in device degradation or failure.

Note 7: Accuracy of programmed current may degrade for currents

greater than 1.5A.

Note 8: This is the minimum voltage across the boost capacitor needed to

guarantee full saturation of the switch.

Note 9: Absolute Maximum Voltage at HVIN and HVEN pins is for

nonrepetitive 1 second transients; 40V for continuous operation.

TYPICAL PERFORMANCE CHARACTERISTICS

Battery Regulation (Float)

Voltage vs Temperature

Battery Current and Voltage

vs Time (LTC4090)

V_FLOATLoad Regulation

4.220

4.215

4.210

4.205

5

4

3

2

1

0

1500

1200

900

600

300

0

4.30

4.25

V

BAT

= 5V

R

= 34k

IN

PROG

I

= 2mA

V

BAT

OUT

CHRGB

BAT

4.20

4.15

I

4.200

4.195

C/10

TERMINATION

4.10

4.05

4.00

4.190

4.185

4.180

1250mAh

CELL

HVIN = 12V

R

PROG

= 50k

–25

0

50

100

–50

75

100

0

50

150

25

200

0

200

400

I

600

(mA)

800

1000

TEMPERATURE (°C)

TIME (MIN)

BAT

4090 G02

4090 G03

4090 G01

4090fd

5

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

TYPICAL PERFORMANCE CHARACTERISTICS

Ideal Diode Current vs Forward

Voltage and Temperature

(No External Device)

Charge Current vs Temperature

Charging from USB, I_BATvs V_BAT

(Thermal Regulation)

600

500

400

300

1000

900

800

700

600

500

400

300

200

100

0

600

500

V

R

= 5V

V

= 3.7V

IN

OUT

BAT

IN

= NO LOAD

= 100k

= 0V

HPWR = 5V

PROG

= 2k

CLPROG

400

300

200

100

0

R

V

= 2.1k

–50°C

0°C

50°C

100°C

PROG

IN

HPWR = 0V

= 5V

100

0

V

= 3.5V

= 40°C/W

BAT

θ

JA

50

0

TEMPERATURE (°C)

100 125

–50 –25

25

75

0

50

100

(mV)

150

200

0

0.5

1

1.5

2

2.5

(V)

3

3.5

4

4.5

V

FWD

BAT

4090 G05

4090 G06

4090 G04

Ideal Diode Current vs Forward

Voltage and Temperature with

External Device

LTC4090 High Voltage Regulator

Efficiency vs Output Load

LTC4090-5 High Voltage Regulator

Efficiency vs Output Load

100

95

90

85

80

75

70

65

60

55

50

100

95

90

85

80

75

70

65

60

55

50

5000

4500

4000

3500

3000

2500

2000

1500

1000

500

FIGURE 12 SCHEMATIC

V

= 3.7V

BAT

IN

V

= 4.21V (I

= 0)

V

= 4.21V (I

= 0)

BAT

= 0V

Si2333 PFET

–50°C

0°C

50°C

100°C

HVIN = 8V

HVIN = 12V

HVIN = 24V

HVIN = 36V

HVIN = 8V

HVIN = 12V

HVIN = 24V

HVIN = 36V

0

0.2

0.4

0.6

(A)

0.8

1.0

0

0.2

0.4

0.6

(A)

0.8

1.0

0

20

40

V

60

80

100

I

(mV)

OUT

FWD

4090 G08

4090 G09

4090 G07

High Voltage Regulator Minimum

Switch On-Time vs Temperature

High Voltage Regulator Switch

Voltage Drop

High Voltage Regulator Maximum

Load Current

3.0

2.8

2.6

2.4

2.2

2.0

1.8

140

120

700

600

FIGURE 12 SCHEMATIC

V

= 4.21V (I

= 0)

BAT

TYPICAL

100

500

400

300

200

100

80

60

40

20

MINIMUM

0

5

15

20

25

30

35

10

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (˚C)

4090 G11

0

500

1000

1500

2000

2500

HVIN (V)

SWITCH CURRENT (mA)

4090 G10

4090 G12

4090fd

6

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

TYPICAL PERFORMANCE CHARACTERISTICS

High Voltage Regulator Switch

Frequency

High Voltage Regulator

Frequency Foldback

High Voltage Regulator Soft-Start

1000

900

800

700

600

500

400

300

200

100

0

4.0

1100

1000

900

800

700

600

500

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

1

2

3

4

75 100

2.5

HVEN PIN VOLTAGE (V)

3

3.5

–50 –25

0

25 50

125 150

0

0.5

1

1.5

2

TEMPERATURE (°C)

HVOUT (V)

4090 G14

4090 G13

4090 G15

High Voltage Regulator Switch

Current Limit

High Voltage Regulator Switch

Current Limit

High Voltage Regulator Minimum

Input Voltage

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

4.0

3.5

3.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

DUTY CYCLE = 10 %

TO START

DUTY CYCLE = 90 %

2.5

2.0

TO RUN

1.5

1.0

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

4090 G17

20

60

40

DUTY CYCLE (%)

80

100

1

10

100

1000

0

LOAD CURRENT (mA)

4090 G18

4090 G16

High Voltage Regulator Boost

Diode V_Fvs I_F

High Voltage Regulator

V_CVoltages

High Voltage Regulator Power

Good Threshold

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

2.50

2.90

2.00

1.50

2.85

2.80

CURRENT LIMIT CLAMP

SWITCHING THRESHOLD

1.00

0.50

0

2.75

2.70

2.65

0

0.5

1.0

1.5

2.0

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

4090 G20

50

–50 –25

0

25

75 100 125 150

BOOST DIODE CURRENT (A)

TEMPERATURE (°C)

4090 G19

4090 G21

4090fd

7

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

TYPICAL PERFORMANCE CHARACTERISTICS

LTC4090 Input Connect

Waveforms

LTC4090 Input Disconnect

Waveforms

LTC4090 Response to Suspend

SUSP

5V/DIV

V

IN

5V/DIV

V

OUT

5V/DIV

I

IN

I

IN

0.5A/DIV

I

BAT

0.5A/DIV

1ms/DIV

4090 G24

4090 G23

4090 G22

V

I

= 3.85V

= 50mA

V

I

= 3.85V

= 100mA

V

I

= 3.85V

= 100mA

BAT

OUT

BAT

OUT

BAT

OUT

LTC4090 High Voltage Input

Disconnect Waveforms

LTC4090 High Voltage Input

Connect Waveforms

LTC4090 Response to HPWR

V

HPWR

5V/DIV

HVIN

5V/DIV

10V/DIV

V

OUT

I

IN

5V/DIV

0.5A/DIV

I

HVIN

1A/DIV

I

BAT

0.5A/DIV

I

BAT

1A/DIV

2ms/DIV

100µs/DIV

4090 G26

4090 G25

4090 G27

V

I

= 3.85V

= 100mA

V

I

= 3.85V

= 100mA

V

I

= 3.85V

= 50mA

BAT

OUT

BAT

OUT

BAT

OUT

LTC4090 High Voltage Regulator

Load Transient

LTC4090 High Voltage Regulator

Load Transient

HVOUT

50mV/DIV

HVOUT

50mV/DIV

I

OUT

I

L

1A/DIV

25µs/DIV

4090 G28

4090 G29

I

= 500mA

I

= 500mA

LOAD

4090fd

8

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

PIN FUNCTIONS

SYNC (Pin 1): External Clock Synchronization Input. See

synchronizing section in the Applications Information

section. Ground pin when not used.

PROG (Pin 9): Charge Current Program Pin. Connecting a

resistorfromPROGtogroundprogramsthechargecurrent:

50,000V

I_CHG(A)=

PG(Pin2):OpenCollectorOutputofanInternalCompara-

tor. PG remains low until the HVOUT pin is above 2.8V. PG

output is valid when HVIN is above 3.6V and HVEN is high.

R_PROG

GATE (Pin 10): External Ideal Diode Gate Connection. This

pin controls the gate of an optional external P-channel

MOSFET transistor used to supplement the internal ideal

diode. The source of the P-channel MOSFET should be

connected to OUT and the drain should be connected to

BAT. When not in use, this pin should be left floating. It

is important to maintain high impedance on this pin and

minimize all leakage paths.

R (Pin3):OscillatorResistorInput. Connectingaresistor

T

to ground from this pin sets the switching frequency.

V (Pin 4): High Voltage Buck Regulator Control Pin. The

C

voltage on this pin controls the peak switch current in the

high voltage regulator. Tie an RC network from this pin to

ground to compensate the control loop.

NTC (Pin 5): Input to the NTC Thermistor Monitoring

Circuits. The NTC pin connects to a negative temperature

coefficient thermistor which is typically co-packaged with

the batterypack to determineifthebattery istoo hot ortoo

cold to charge. If the battery temperature is out of range,

charging is paused until the battery temperature re-enters

the valid range. A low drift bias resistor is required from

VNTC to NTC and a thermistor is required from NTC to

ground. If the NTC function is not desired, the NTC pin

should be grounded.

BAT (Pin 11): Single-Cell Li-Ion Battery. This pin is used

as an output when charging the battery and as an input

whensupplyingpowertoOUT.WhentheOUTpinpotential

drops below the BAT pin potential, an ideal diode function

connects BAT to OUT and prevents OUT from dropping

more than 100mV below BAT. A precision internal resistor

divider sets the final float (charging) potential on this pin.

The internal resistor divider is disconnected when IN and

HVIN are in undervoltage lockout.

IN (Pin 12): Input Supply. Connect to USB supply, V

.

BUS

VNTC (Pin 6): Output Bias Voltage for NTC. A resistor

from this pin to the NTC pin will bias the NTC thermistor.

Input current to this pin is limited to either 20% or 100%

of the current programmed by the CLPROG pin as de-

termined by the state of the HPWR pin. Charge current

(to the BAT pin) supplied through the input is set to the

current programmed by the PROG pin but will be limited

by the input current limit if charge current is set greater

than the input current limit or if the sum of charge current

plus load current is greater than the input current limit.

HVPR (Pin 7): High Voltage Present Output (Active Low).

A low on this pin indicates that the high voltage regulator

has sufficient voltage to charge the battery. This feature

is enabled if power is present on HVIN, IN, or BAT (i.e.,

above UVLO thresholds).

CHRG(Pin8):Open-DrainChargeStatusOutput.Whenthe

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

internal N-channel MOSFET. When the timer runs out or

the charge current drops below 10% of the programmed

charge current or the input supply is removed, the CHRG

pin is forced to a high impedance state.

OUT (Pin 13): Voltage Output. This pin is used to provide

controlled power to a USB device from either USB V

BUS

(IN), anexternalhighvoltagesupply(HVIN), orthebattery

(BAT) when no other supply is present. The high voltage

supply is prioritized over the USB V

input. OUT should

BUS

be bypassed with at least 4.7µF to GND.

4090fd

9

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

PIN FUNCTIONS

CLPROG (Pin 14): Current Limit Program and Input Cur-

rent Monitor. Connecting a resistor, R

programs the input to output current limit. The current

limit is programmed as follows:

Charge time is increased if charge current is reduced

due to load current, thermal regulation and current limit

selection (HPWR low).

, to ground

CLPROG

Shorting the TIMER pin to GND disables the battery

charging functions.

1000V

I_CL(A)=

R_CLPROG

HVOUT (Pin 18): Voltage Output of the High Voltage

Regulator. When sufficient voltage is present at HVOUT,

the low voltage power path from IN to OUT will be dis-

connected and the HVPR pin will be pulled low to indicate

that a high voltage wall adapter has been detected. The

LTC4090 high voltage regulator will maintain just enough

differential voltage between HVOUT and BAT to keep the

battery charger MOSFET out of dropout (typically 300mV

from OUT to BAT). The LTC4090-5 high voltage regulator

will provide a 5V output to the battery charger MOSFET.

HVOUT should be bypassed with at least 22µF to GND.

In USB applications, the resistor R

should be set

CLPROG

to no less than 2.1k. The voltage on the CLPROG pin is

alwaysproportionaltothecurrentflowingthroughtheINto

OUTpowerpath.Thiscurrentcanbecalculatedasfollows:

V_CLPROG

R_CLPROG

I_IN(A)=

•1000

HPWR(Pin15):HighPowerSelect.Thislogicinputisused

to control the input current limit. A voltage greater than

1.2V on the pin will set the input current limit to 100% of

the current programmed by the CLPROG pin. A voltage

less than 0.4V on the pin will set the input current limit to

20% of the current programmed by the CLPROG pin. A

2µA pull-down current is internally connected to this pin

to ensure it is low at power up when the pin is not being

driven externally.

BOOST (Pin 19): This pin is used to provide drive voltage,

higher than the input voltage, to the internal bipolar NPN

power switch.

SW (Pin 20): The SW pin is the output of the internal high

voltage power switch. Connect this pin to the inductor,

catch diode and boost capacitor.

HVIN(Pin21):HighVoltageRegulatorInput.TheHVINpin

suppliescurrenttotheinternalhighvoltageregulationand

to the internal high voltage power switch. The presence

SUSP (Pin 16): Suspend Mode Input. Pulling this pin

above 1.2V will disable the power path from IN to OUT.

The supply current from IN will be reduced to comply

with the USB specification for suspend mode. Both the

ability to charge the battery from HVIN and the ideal diode

function (from BAT to OUT) will remain active. Suspend

mode will reset the charge timer if OUT is less than BAT

while in suspend mode. If OUT is kept greater than BAT,

such as when the high voltage input is present, the charge

timer will not be reset when the part is put in suspend. A

2µA pull-down current is internally connected to this pin

to ensure it is low at power up when the pin is not being

driven externally.

of a high voltage input takes priority over the USB V

BUS

input (i.e., when a high voltage input supply is detected,

the USB IN to OUT path is disconnected). This pin must

be locally bypassed.

HVEN (Pin 22): High Voltage Regulator Enable Input. The

HVEN pin is used to disable the high voltage input path.

Tie to ground to disable the high voltage input or tie to at

least 2.3V to enable the high voltage path. If this feature

is not used, tie HVEN to the HVIN pin. This pin can also

be used to soft-start the high voltage regulator; see the

Applications Information section for more information.

TIMER (Pin 17): Timer Capacitor. Placing a capacitor,

C

, to GND sets the timer period. The timer period is:

TIMER

Exposed Pad (Pin 23): Ground. The exposed package pad

is ground and must be soldered to the PC board for proper

functionality and for maximum heat transfer (use several

vias directly under the LTC4090/LTC4090-5).

C_TIMER•R_PROG•3hours

t_TIMER(hours)=

0.1µF •100k

4090fd

10

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

BLOCK DIAGRAM

C2

BOOST

L1

HVIN

10

SW

Q1

INTERNAL

D1

REFERENCE

+

–

HVEN

10

I

L

+

–

R

S

Q

SOFT-START

DRIVER

R

T

OSCILLATOR

200kHz - 2.4MHz

10

R

T1

SYNC

HVOUT

10

–

V

C

C1

V

SET

GM

+

3.6V (LTC4090)

5V (LTC4090-5)

R

C

F

C

–

+

VC CLAMP

C

75mV (RISING)

25mV (FALLING)

350mV

(LTC4090)

+

–

PG

IN

10

–

+

–

+

2.8V

HVPR

4.25V (RISING)

3.15V (FALLING)

19

CURRENT LIMIT

CNTL

IN

I

LIM

ENABLE

SOFT-START

I

1V

+

–

IN

OUT

I

LIM

CURRENT

CONTROL

1000

CLPROG

21

CL

–

+

22

13

20mV

–

+

CC/CV REGULATOR

CHARGER

–

+

DIE

R

30mV

CLPROG

GATE

105°C

TEMP

ENABLE

500mA/100mA

EDA

HPWR

IDEAL

DIODE

+

–

IN OUT BAT

2µA

TA

BAT

+

–

I

CHG

CHARGE CONTROL

0.25V

2.9V

BATTERY

UVLO

SOFT-START2

+

–

1V

CHG

+

–

PROG

23

15

14

R

PROG

VOLTAGE DETECT

UVLO

4.1V

RECHARGE

+

–

V

NTC

BAT UV

–

+

10k

TOO

COLD

RECHRG

TIMER

NTCERR

NTC

21

18

OSCILLATOR

CONTROL LOGIC

C

TIMER

HOLD

CLK

CHRG

10k

T

–

+

STOP

RESET

TOO

HOT

COUNTER

EOC

C/10

+

NTC ENABLE

2µA

0.1V

–

GND

16

SUSP

11

4090 BD

4090fd

11

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

Introduction

the ideal diode instead of connecting the load directly to

the battery allows a fully charged battery to remain fully

charged until external power is removed. Once external

power is removed the output drops until the ideal diode is

forward biased. The forward biased ideal diode will then

provide the output power to the load from the battery.

TheLTC4090/LTC4090-5arecompletePowerPathcontrol-

lers for battery powered USB applications. The LTC4090/

LTC4090-5 are designed to receive power from a low volt-

age source (e.g., USB or 5V wall adapter), a high voltage

source (e.g., Firewire/IEEE1394, automotive battery, 12V

wall adapter, etc.), and a single-cell Li-Ion battery. They

can then deliver power to an application connected to the

OUT pin and a battery connected to the BAT pin (assuming

that an external supply other than the battery is present).

Power supplies that have limited current resources (such

The LTC4090/LTC4090-5 also include a high voltage

switching regulator which has the ability to receive power

fromahighvoltageinput. Thisinputtakespriorityoverthe

USB V

input (i.e., if both HVIN and IN are present, load

BUS

current and charge current will be delivered via the high

voltage path). When enabled, the high voltage regulator

regulates the HVOUT voltage using a constant frequency,

currentmoderegulator.AnexternalPFETbetweenHVOUT

(drain) and OUT (source) is turned on via the HVPR pin

allowing OUT to charge the battery and/or supply power

to the application. The LTC4090’s Bat-Track maintains

approximately 300mV between the OUT pin and the BAT

pin, while the LTC4090-5 provides a fixed 5V output.

as USB V

supplies) should be connected to the IN pin

BUS

which has a programmable current limit. Battery charge

currentwillbeadjustedtoensurethatthesumofthecharge

currentandloadcurrentdoesnotexceedtheprogrammed

input current limit (see Figure 1).

An ideal diode function provides power from the battery

whenoutput/loadcurrentexceedstheinputcurrentlimitor

when input power is removed. Powering the load through

HVIN

SW

L1

Q1

D1

HIGH VOLTAGE

BUCK REGULATOR

HVOUT

C1

+

–

4.25V (RISING)

3.15V (FALLING)

HVPR

19

+

–

LOAD

75mV (RISING)

+

25mV (FALLING)

–

ENABLE

IN

OUT

21

USB CURRENT LIMIT

–

+

30mV

–

+

30mV

+

–

GATE

BAT

CC/CV REGULATOR

CHARGER

EDA

IDEAL

DIODE

BAT

21

+

Li-Ion

4090 F01

Figure 1. Simplified PowerPath Block Diagram

4090fd

12

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

USB Input Current Limit

500mA due to LTC4090/LTC4090-5 tolerances and quies-

cent currents. A 2.1k CLPROG resistor will give a typical

current limit of 476mA in high power mode (when HPWR

is high) or 95mA in low power mode (when HPWR is low).

The input current limit and charge control circuits of the

LTC4090/LTC4090-5 are designed to limit input current

as well as control battery charge current as a function of

I . OUT drives the external load and the battery charger.

OUT

When SUSP is driven to a logic high, the input power

path is disabled and the ideal diode from BAT to OUT will

supply power to the application.

If the combined load at OUT does not exceed the pro-

grammed input current limit, OUT will be connected to IN

through an internal 215mW P-channel MOSFET.

High Voltage Step Down Regulator

IfthecombinedloadatOUTexceedstheprogrammedinput

current limit, the battery charger will reduce its charge

current by the amount necessary to enable the external

load to be satisfied while maintaining the programmed

input current. Even if the battery charge current is set to

exceedtheallowableUSBcurrent,acorrectlyprogrammed

input current limit will ensure that the USB specification

is never violated. Furthermore, load current at OUT will

always be prioritized and only excess available current will

be used to charge the battery.

The power delivered from HVIN to HVOUT is controlled by

a constant-frequency, current mode step down regulator.

An external P-channel MOSFET directs this power to OUT

andpreventsreverseconductionfromOUTtoHVOUT(and

ultimately HVIN).

An oscillator, with frequency set by R , enables an RS flip-

T

flop,turningontheinternalpowerswitch.Anamplifierand

comparatormonitorthecurrentflowingbetweenHVINand

SW pins, turning the switch off when this current reaches

a level determined by the voltage at V . An error amplifier

C

The input current limit, I , can be programmed using the

CL

servos the V node to maintain approximately 300mV

C

following formula:

between OUT and BAT (LTC4090). By keeping the voltage

across the battery charger low, efficiency is optimized

because power lost to the battery charger is minimized

and power available to the external load is maximized. If

the BAT pin voltage is less than approximately 3.3V, then







1000

R_CLPROG

1000V

R_CLPROG



I =

•V

=



CL

^CLPROG





where V

is the CLPROG pin voltage (typically 1V)

CLPROG

the error amplifier will servo the V node to provide a

C

and R

is the total resistance from the CLPROG pin

CLPROG

constant HVOUT output voltage of about 3.6V (LTC4090).

to ground. For best stability over temperature and time,

1% metal film resistors are recommended.

An active clamp on the V node provides current limit. The

C

V node is also clamped to the voltage on the HVEN pin;

C

The programmed battery charge current, I , is de-

CHG

soft-start is implemented by generating a voltage ramp

fined as:

at the HVEN pin using an external resistor and capacitor.







50,000

R_PROG

50,000V

R_PROG

The switch driver operates from either the high voltage

input or from the BOOST pin. An external capacitor and

internal diode are used to generate a voltage at the BOOST

pin that is higher than the input supply. This allows the

driver to fully saturate the internal bipolar NPN power

switch for efficient operation.





I_CHG

=

•V

^PROG



=





Input current, I , is equal to the sum of the BAT pin output

IN

current and the OUT pin output current. V

the input current according to the following equation:

will track

CLPROG

V_CLPROG

R_CLPROG

To further optimize efficiency, the high voltage buck regu-

lator automatically switches to Burst Mode^®operation in

lightloadsituations.Betweenbursts,allcircuitryassociated

with controlling the output switch is shut down reducing

the input supply current.

I_IN=I_OUT+I_BAT

=

•1000

InUSBapplications,themaximumvalueforR

be 2.1k. This will prevent the input current from exceeding

should

CLPROG

4090fd

13

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

I

IN

500

400

300

200

100

500

400

300

200

100

80

60

40

20

0

I

IN

I

LOAD

I

LOAD

I

= I

BAT CHG

I

= I = I

BAT CL OUT

I

BAT

(CHARGING)

BAT

(CHARGING)

BAT

(CHARGING)

0

100

200

0

300

400

500

I

100

200

20

40

0

300

400

500

I

0

60

80

100

I

BAT

I

LOAD (mA)

I

LOAD(mA)

(IDEAL DIODE)

4090 F02c

(IDEAL DIODE)

4090 F02a

4090 F02b

(a) High Power Mode/Full Charge

R_PROG= 100k and R_CLPROG= 2k

(b) Low Power Mode/Full Charge

R_PROG= 100k and R_CLPROG= 2k

(c) High Power Mode with

I_CL= 500mA and I_CHG= 250mA

R_PROG= 100k and R_CLPROG= 2k

Figure 2. Input and Battery Currents as a Function of Load Current

The oscillator reduces the switch regulator’s operating

frequency when the voltage at the HVOUT pin is low (be-

low 2.95V). This frequency foldback helps to control the

output current during start-up and overload.

A comparison of the I-V curve of the ideal diode and a

Schottky diode can be seen in Figure 3.

If the desired input current increases beyond the pro-

grammedinputcurrentlimitadditionalcurrentwillbedrawn

from the battery via the internal ideal diode. Furthermore,

The high voltage regulator contains a power good com-

parator which trips when the HVOUT pin is at 2.8V. The

PG output is an open-collector transistor that is off when

the output is in regulation, allowing an external resistor

to pull the PG pin high. Power good is valid when the

switching regulator is enabled and HVIN is above 3.6V.

if power to IN (USB V ) or HVIN (high voltage input)

BUS

is removed, then all of the application power will be pro-

vided by the battery via the ideal diode. A 4.7µF capacitor

at OUT is sufficient to keep a transition from input power

to battery power from causing significant output voltage

droop.Theidealdiodeconsistsofaprecisionamplifierthat

enablesalargeP-channelMOSFETtransistorwheneverthe

Ideal Diode From BAT to OUT

voltage at OUT is approximately 20mV (V ) below the

FWD

The LTC4090/LTC4090-5 have an internal ideal diode as

well as a controller for an optional external ideal diode. If

a battery is the only power supply available, or if the load

current exceeds the programmed input current limit, then

the battery will automatically deliver power to the load via

an ideal diode circuit between the BAT and OUT pins. The

ideal diode circuit (along with the recommended 4.7µF

capacitor on theOUT pin)allowstheLTC4090/LTC4090-5

to handle large transient loads and wall adapter or USB

voltage at BAT. The resistance of the internal ideal diode

is approximately 215mW.

If this is sufficient for the application then no external

componentsarenecessary.Howeverifmoreconductance

is needed, an external P-channel MOSFET can be added

from BAT to OUT. The GATE pin of the LTC4090/LTC4090-

5 drives the gate of the external PFET for automatic ideal

diode control. The source of the external MOSFET should

be connected to OUT and the drain should be connected

to BAT. In order to help protect the external MOSFET in

overcurrentsituations,itshouldbeplacedinclosethermal

contact to the LTC4090/LTC4090-5.

V

BUS

connect/disconnect scenarios without the need for

large bulk capacitors. The ideal diode responds within

a few microseconds and prevents the OUT pin voltage

from dropping significantly below the BAT pin voltage.

4090fd

14

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

Suspend Mode

to bring the cell voltage up to a safe level for charging.

The charger goes into the fast charge constant-current

mode once the voltage on the BAT pin rises above 2.9V.

In constant-current mode, the charge current is set by

When SUSP is pulled above V the LTC4090/LTC4090-5

IH

entersuspendmodetocomplywiththeUSBspecification.

In this mode, the power path between IN and OUT is put

in a high impedance state to reduce the IN input current to

50µA. If no other power source is available to drive HVIN,

the system load connected to OUT is supplied through the

ideal diodes connected to BAT.

R

.Whenthebatteryapproachesthefinalfloatvoltage,

PROG

the charge current begins to decrease as the LTC4090/

LTC4090-5 switch to constant-voltage mode. When the

chargecurrentdropsbelow10%oftheprogrammedvalue

while in constant-voltage mode the CHRG pin assumes a

high impedance state.

Battery Charger

An external capacitor on the TIMER pin sets the total

minimum charge time. When this time elapses, the

charge cycle terminates and the CHRG pin assumes a

high impedance state, if it has not already done so. While

charging in constant-current mode, if the charge current

is decreased by thermal regulation or in order to maintain

the programmed input current limit, the charge time is

automatically increased. In other words, the charge time

is extended inversely proportional to the actual charge

current delivered to the battery. For Li-Ion and similar

batteries that require accurate final float potential, the

internal bandgap reference, voltage amplifier and the

resistor divider provide regulation with 0.8% accuracy.

The battery charger circuits of the LTC4090/LTC4090-5

are designed for charging single-cell lithium-ion batter-

ies. Featuring an internal P-channel power MOSFET, the

chargerusesaconstant-current/constant-voltagecharge

algorithm with programmable charge current and a pro-

grammable timer for charge termination. Charge current

can be programmed up to 1.5A. The final float voltage

accuracy is 0.8% typical. No blocking diode or sense

resistor is required when powering either the IN or the

HVIN pins. The CHRG open-drain status output provides

informationregardingthechargingstatusoftheLTC4090/

LTC4090-5 at all times. An NTC input provides the option

of charge qualification using battery temperature.

The charge cycle begins when the voltage at the OUT pin

rises above the battery voltage and the battery voltage is

below the recharge threshold. No charge current actually

flowsuntiltheOUTvoltageis100mVabovetheBAT voltage.

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

is below 2.9V, the charger goes into trickle charge mode

Trickle Charge and Defective Battery Detection

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

is below 2.9V, the charger goes into trickle charge reduc-

ing the charge current to 10% of the full-scale current.

If the low battery voltage persists for one quarter of the

programmed total charge time, the battery is assumed

to be defective, the charge cycle is terminated and the

CHRG pin output assumes a high impedance state. If

for any reason the battery voltage rises above ~2.9V the

charge cycle will be restarted. To restart the charge cycle

(i.e., when the dead battery is replaced with a discharged

battery), simply remove the input voltage and reapply it

or cycle the TIMER pin to 0V.

CONSTANT

0N

LTC4090/LTC4090-5

I

MAX

CONSTANT

0N

SLOPE: 1/R

DIO(ON)

R

I

FWD

SCHOTTKY

DIODE

CONSTANT

0N

SLOPE: 1/R

FWD

V

Programming Charge Current

The formula for the battery charge current is:

V_PROG

0

FORWARD VOLTAGE (V)

V

FWD

4090 F03

I_CHG=I_PROG•50,000=

•50,000

R_PROG

Figure 3. LTC4090/LTC4090-5 vs Schottky Diode

Forward Voltage Drop

4090fd

15

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

where V

is the PROG pin voltage and R

is the

PROG

As the LTC4090/LTC4090-5 approach constant-voltage

mode the charge current begins to drop. This change in

charge current is due to normal charging operation and

does not affect the timer duration.

PROG

total resistance from the PROG pin to ground. Keep in

mind that when the LTC4090/LTC4090-5 are powered

from the IN pin, the programmed input current limit takes

precedence over the charge current. In such a scenario,

the charge current cannot exceed the programmed input

current limit.

Consider, for example, a USB charge condition where

R

= 2k, R

= 100k and C

= 0.1µF. This

CLPROG

PROG

TIMER

corresponds to a three hour charge cycle. However, if the

HPWR input is set to a logic low, then the input current

limit will be reduced from 500mA to 100mA. With no

additional system load, this means the charge current will

be reduced to 100mA. Therefore, the termination timer

will automatically slow down by a factor of five until the

For example, if typical 500mA charge current is required,

calculate:

1V

500mA

R_PROG

=

•50,000=100k

charger reaches constant-voltage mode (i.e., V

ap-

BAT

Forbeststabilityovertemperatureandtime,1%metalfilm

resistors are recommended. Under trickle charge condi-

tions,thiscurrentisreducedto10%ofthefull-scalevalue.

proaches 4.2V) or HPWR is returned to a logic high. The

charge cycle is automatically lengthened to account for

the reduced charge current. The exact time of the charge

cycle will depend on how long the charger remains in

constant-current mode and/or how long the HPWR pin

remains logic low.

The Charge Timer

The programmable charge timer is used to terminate the

charge cycle. The timer duration is programmed by an

external capacitor at the TIMER pin. The charge time is

typically:

Once a timeout occurs and the voltage on the battery is

greater than the recharge threshold, the charge current

stops, and the CHRG output assumes a high impedance

state if it has not already done so.

C_TIMER•R_PROG•3hours

t_TIMER(hours)=

0.1µF •100k

Connecting the TIMER pin to ground disables the battery

charger.

The timer starts when an input voltage greater than the

undervoltage lockout threshold level is applied or when

leavingshutdownandthevoltageonthebatteryislessthan

the recharge threshold. At power-up or exiting shutdown

with the battery voltage less than the recharge threshold,

the charge time is a full cycle. If the battery is greater than

therechargethresholdthetimerwillnotstartandcharging

is prevented. If after power-up the battery voltage drops

below the recharge threshold, or if after a charge cycle

the battery voltage is still below the recharge threshold,

the charge time is set to one-half of a full cycle.

CHRG Status Output Pin

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

groundbyaninternalN-channelMOSFETcapableofdriving

an LED. When the charge current drops below 10% of the

programmed full charge current while in constant-voltage

mode,thepinassumesahighimpedancestate,butcharge

current continues to flow until the charge time elapses. If

this state is not reached before the end of the program-

mable charge time, the pin will assume a high impedance

state when a timeout occurs. The CHRG current detection

threshold can be calculated by the fol-lowing equation:

TheLTC4090/LTC4090-5haveafeaturethatextendscharge

time automatically. Charge time is extended if the charge

current in constant-current mode is reduced due to load

current or thermal regulation. This change in charge time

is inversely proportional to the change in charge current.

0.1V

R_PROG

5000V

R_PROG

I_DETECT

=

•50,000=

4090fd

16

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

OPERATION

For example, if the full charge current is programmed

to 500mA with a 100k PROG resistor the CHRG pin will

change state at a battery charge current of 50mA.

ofthe LTC4090/LTC4090-5 thermalregulation loop is that

charge current can be set according to actual conditions

rather than worst-case conditions with the assurance that

the battery charger will automatically reduce the current

in worst-case conditions.

Note: The end-of-charge (EOC) comparator that monitors

the charge current latches its decision. Therefore, the

first time the charge current drops below 10% of the

programmed full charge current while in constant-volt-

age mode, it will toggle CHRG to a high impedance state.

If, for some reason the charge current rises back above

the threshold, the CHRG pin will not resume the strong

pull-down state. The EOC latch can be reset by a recharge

Undervoltage Lockout

Aninternalundervoltagelockoutcircuitmonitorstheinput

voltage (IN) and the output voltage (OUT) and disables

either the input current limit or the battery charger circuits

or both. The input current limit circuitry is disabled until

V

IN

rises above the undervoltage lockout threshold and

cycle (i.e., V

drops below the recharge threshold) or

IN

BAT

V exceeds V

by 50mV. The battery charger circuits

toggling the input power to the part.

OUT

are disabled until V

exceeds V by 50mV. Both un-

BAT

OUT

Automatic Recharge

dervoltage lockout comparators have built-in hysteresis.

After the battery charger terminates, it will remain off

drawing only microamperes of current from the battery. If

the product remains in this state long enough, the battery

will eventually self discharge. To ensure that the battery is

always topped off, a charge cycle will automatically begin

NTC Thermistor

The battery temperature is measured by placing a neg-

ative temperature coefficient (NTC) thermistor close to

the battery pack. To use this feature connect the NTC

thermistor, R , between the NTC pin and ground and a

when the battery voltage falls below V

(typically

from

NTC

RECHRG

bias resistor, R

, from VNTC to NTC. R

should be

4.1V). To prevent brief excursions below V

NOM

RECHRG

a 1% resistor with a value equal to the value of the chosen

resetting the safety timer, the battery voltage must be

below V for more than a few milliseconds. The

NTC thermistor at 25°C (denoted R ).

25C

RECHRG

charge cycle and safety timer will also restart if the IN

UVLO cycles low and then high (e.g., IN is removed and

then replaced).

The LTC4090/LTC4090-5 will pause charging when the

resistance of the NTC thermistor drops to 0.41 times the

value of R or approximately 4.1k (for a Vishay curve 2

25C

thermistor, this corresponds to approximately 50°C). The

safety timer also pauses until the thermistor indicates a

return to a valid temperature. As the temperature drops,

the resistance of the NTC thermistor rises. The LTC4090/

LTC4090-5arealsodesignedtopausecharging(andtimer)

when the value of the NTC thermistor increases to 2.82

Thermal Regulation

To prevent thermal damage to the IC or surrounding

components, an internal thermal feedback loop will

automatically decrease the programmed charge current

if the die temperature rises to approximately 105°C.

Thermal regulation protects the LTC4090/LTC4090-5

from excessive temperature due to high power operation

or high ambient thermal conditions and allows the user

to push the limits of the power handling capability with a

given circuit board design without risk of damaging the

LTC4090/LTC4090-5orexternalcomponents. Thebenefit

times the value of R . For a Vishay curve 2 thermistor

25C

this resistance, 28.2k, corresponds to approximately 0°C.

The hot and cold comparators each have approximately

3°Cofhysteresistopreventoscillationaboutthetrippoint.

Grounding the NTC pin disables all NTC functionality.

4090fd

17

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

USB and 5V Wall Adapter Power

5V WALL

ADAPTER

I

CHG

BAT

850mA I

CHG

Although the LTC4090/LTC4090-5 are designed to draw

power from a USB port, a higher power 5V wall adapter

can also be used to power the application and charge the

battery (higher voltage wall adapters can be connected

directlytoHVIN).Figure4showsanexampleofcombining

a 5V wall adapter and a USB power input. With its gate

grounded by 1k, P-channel MOSFET MP1 provides USB

power to the LTC4090/LTC4090-5 when 5V wall power is

not available. When 5V wall power is available, diode D1

supplies power to the LTC4090/LTC4090-5, pulls the gate

of MN1 high to increase the charge current (by increasing

the input current limit), and pulls the gate of MP1 high to

disable it and prevent conduction back to the USB port.

D1

LTC4090

USB POWER

IN

PROG

500mA I

+

CHG

Li-Ion

BATTERY

MP1

1k

CLPROG

2.87k

MN1

2k

59k

4090 F04

Figure 4. USB or 5V Wall Adapter Power

Operating Frequency Trade-Offs

Selection of the operating frequency for the high voltage

buck regulator is a trade-off between efficiency, compo-

nent size, minimum dropout voltage, and maximum input

voltage. The advantage of high frequency operation is that

smaller inductor and capacitor values may be used. The

disadvantages are lower efficiency, lower maximum input

voltage,andhigherdropoutvoltage.Thehighestacceptable

Setting the Switching Frequency

The high voltage switching regulator uses a constant-fre-

quency PWM architecture that can be programmed to

switch from 200kHz to 2.4MHz by using a resistor tied

switchingfrequency(f

)foragivenapplicationcan

from the R pin to ground. A table showing the necessary

SW(MAX)

T

be calculated as follows:

V_D+V_HVOUT

t_ON(MIN)• V +V_HVIN– V

R value for a desired switching frequency is in Table 1.

T

Table 1. Switching Frequency vs R_TValue

f_SW(MAX)

=

SWITCHING FREQUENCY (MHz)

R VALUE (kW)

T

(

)

D

SW

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

187

121

where V

is the typical high voltage input voltage,

HVIN

V

is the output voltage of the switching regulator,

88.7

68.1

56.2

46.4

40.2

34.0

29.4

23.7

19.1

16.2

13.3

11.5

9.76

8.66

HVOUT

V is the catch diode drop (~0.5V), and V is the internal

D

SW

switch drop (~0.5V at max load). This equation shows

that slower switching frequency is necessary to safely

accommodate high V

/V

ratio. Also, as shown in

HVIN HVOUT

the next section, lower frequency allows a lower dropout

voltage. The reason input voltage range depends on the

switching frequency is because the high voltage switch

has finite minimum on and off times. The switch can turn

on for a minimum of ~150ns and turn off for a minimum

of ~150ns. This means that the minimum and maximum

duty cycles are:

DC

= f • t

SW ON(MIN)

MIN

= 1 – f • t

MAX

SW OFF(MIN)

where f

is the switching frequency, t

is the

SW

ON(MIN)

OFF(MIN)

minimum switch-on time (~150ns), and t

4090fd

18

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

minimumswitch-offtime(~150ns).Theseequationsshow

that duty cycle range increases when switching frequency

is decreased.

enter pulse-skipping operation where some switching

pulses are skipped to maintain output regulation. In this

mode the output voltage ripple and inductor current rip-

ple will be higher than in normal operation. Above 38V,

switching will stop.

A good choice of switching frequency should allow ade-

quate input voltage range (see next section) and keep the

inductor and capacitor values small.

The minimum input voltage is determined by either the

highvoltageregulator’sminimumoperatingvoltageof~6V

or by its maximum duty cycle (see equation in previous

section). The minimum input voltage due to duty cycle is:

HVIN Input Voltage Range

The maximum input voltage range for the LTC4090/

LTC4090-5 applications depends on the switching fre-

V_HVOUT+V_D

1− f_SWt_OFF(MIN)

V_HVIN(MIN)

=

− V_D+V_SW

quency, the Absolute Maximum Ratings of the V

BOOST pins, and the operating mode.

and

HVIN

where V

OFF(MIN)

is the minimum input voltage, and

The high voltage switching regulator can operate from

input voltages up to 36V, and safely withstand input

HVIN(MIN)

t

is the minimum switch-off time (150ns). Note

thathigherswitchingfrequencywillincreasetheminimum

input voltage. If a lowerdropoutvoltage is desired, a lower

switching frequency should be used.

voltages up to 60V. Note that while V

> 38V (typical),

HVIN

the LTC4090/LTC4090-5 will stop switching, allowing the

output to fall out of regulation.

While the high voltage regulator output is in start-up,

short-circuit, or other overload conditions, the switching

frequency should be chosen according to the following

discussion.

Inductor Selection and Maximum Output Current

A good choice for the inductor value is L = 6.8µH (assum-

ing a 800kHz operating frequency). With this value the

maximum load current will be ~2.4A. The RMS current

rating of the inductor must be greater than the maximum

load current and its saturation current should be about

30% higher. Note that the maximum load current will be

programmed charge current plus the largest expected

application load current. For robust operation in fault

conditions, the saturation current should be ~3.5A. To

keep efficiency high, the series resistance (DCR) should

be less than 0.1W. Table 2 lists several vendors and types

that are suitable.

For safe operation at inputs up to 60V the switching fre-

quency must be low enough to satisfy V

≥ 40V

HVIN(MAX)

according to the following equation. If lower V

is desired, this equation can be used directly.

V_HVOUT+V_D

f_SW•t_ON(MIN)

V_HVIN(MAX)

whereV

=

– V_D+V_SW

isthemaximumoperatinginputvoltage,

HVIN(MAX)

V

is the high voltage regulator output voltage, V is

HVOUT

D

the catch diode drop (~0.5V), V is the internal switch

SW

Table 2. Inductor Vendors

drop (~0.5V at max load), f is the switching frequency

SW

VENDOR URL

PART SERIES

TYPE

(set by R ), and t

is the minimum switch-on time

T

ON(MIN)

Murata

TDK

www.murata.com

LQH55D

Open

(~150ns). Note that a higher switching frequency will de-

press the maximum operating input voltage. Conversely,

a lower switching frequency will be necessary to achieve

safe operation at high input voltages.

www.componenttdk.com SLF7045

Shielded

SLF10145

Toko

www.toko.com

D62CB

D63CB

D75C

Shielded

Open

D75F

Iftheoutputisinregulationandnoshort-circuit,start-up,or

overloadeventsareexpected,theninputvoltagetransients

of up to 60V are acceptable regardless of the switching

frequency. In this mode, the LTC4090/LTC4090-5 may

Sumida www.sumida.com

CR54

Open

CDRH74

CDRH6D38

CR75

Shielded

Open

4090fd

19

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

Catch Diode

lent series resistance (ESR) and provide the best ripple

performance. A good starting value is:

The catch diode conducts current only during switch-off

time. Average forward current in normal operation can

be calculated from:

100

C_OUT

=

V_{OUT SW}

f

V

_HVIN– V_HVOUT

(

)

where f

is in MHz, and C

is the recommended

OUT

I

_D(AVG)=I_HVOUT

•

SW

V_HVIN

output capacitance in µF. Use X5R or X7R types. This

choice will provide low output ripple and good transient

response. Transient performance can be improved with a

higher value capacitor if the compensation network is also

adjusted to maintain the loop bandwidth. A lower value of

output capacitor can be used to save space and cost but

transient performance will suffer. See the High Voltage

Regulator Frequency Compensation section to choose an

appropriate compensation network.

whereI

istheoutputloadcurrent. Theonlyreasonto

HVOUT

consideradiodewithalargercurrentratingthannecessary

for nominal operation is for the worst-case condition of

shorted output. The diode current will then increase to the

typical peak switch current. Peak reverse voltage is equal

to the regulator input voltage. Use a Schottky diode with a

reverse voltage rating greater than the input voltage. The

overvoltageprotectionfeatureinthehighvoltageregulator

When choosing a capacitor, look carefully through the

data sheet to find out what the actual capacitance is under

operating conditions (applied voltage and temperature).

A physically larger capacitor, or one with a higher voltage

rating, may be required. High performance tantalum or

electrolyticcapacitorscanbeusedfortheoutputcapacitor.

Low ESR is important, so choose one that is intended for

use in switching regulators. The ESR should be specified

by the supplier, and should be 0.05W or less. Such a

capacitor will be larger than a ceramic capacitor and will

have a larger capacitance, because the capacitor must be

large to achieve low ESR.

will keep the switch off when V

the use of 40V rated Schottky even when V

up to 60V. Table 3 lists several Schottky diodes and their

manufacturers.

> 40V which allows

HVIN

ranges

HVIN

Table 3. Diode Vendors

V

I

V AT 1A

V AT 2A

R

AVE

F

PART NUMBER

(V)

(A)

(MV)

On Semiconductor

MBRM120E

MBRM140

20

40

1

530

550

595

Diodes Inc.

B120

20

30

20

30

40

1

2

500

B130

B220

500

B230

Ceramic Capacitors

DFLS240L

Ceramic capacitors are small, robust and have very low

ESR. However, ceramic capacitors can cause problems

whenusedwiththehighvoltageswitchingregulatordueto

their piezoelectric nature. When in Burst Mode operation,

the LTC4090/LTC4090-5’s switching frequency depends

on the load current, and at very light loads the LTC4090/

LTC4090-5 can excite the ceramic capacitor at audio fre-

quencies, generating audible noise. Since the LTC4090/

LTC4090-5 operate at a lower current limit during Burst

Mode operation, the noise is typically very quiet to a ca-

sual ear. If this is unacceptable, use a high performance

tantalum or electrolytic capacitor at the output.

International Rectifier

10BQ030

30

1

2

420

470

20BQ030

High Voltage Regulator Output Capacitor Selection

The high voltage regulator output capacitor has two

essential functions. Along with the inductor, it filters the

square wave generated at the switch pin to produce the

DC output. In this role it determines the output ripple, and

low impedance at the switching frequency is important.

The second function is to store energy in order to satisfy

transient loads and stabilize the LTC4090/LTC4090-5’s

control loop. Ceramic capacitors have very low equiva-

4090fd

20

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

High Voltage Regulator Frequency Compensation

Low Ripple Burst Mode Operation and

Pulse-Skipping Mode

The LTC4090/LTC4090-5 high voltage regulator uses

current mode control to regulate the output. This sim-

plifies loop compensation. In particular, the high voltage

regulator does not require the ESR of the output capacitor

for stability, so you are free to use ceramic capacitors to

achieve low output ripple and small circuit size. Frequen-

cy compensation is provided by the components tied to

The LTC4090/LTC4090-5 are capable of operating in

either low ripple Burst Mode operation or pulse-skipping

mode which are selected using the SYNC pin. Tie the

SYNC pin below V

(typically 0.5V) for low ripple

SYNC,L

Burst Mode operation or above V

(typically 0.8V)

SYNC,H

for pulse-skipping mode.

the V pin, as shown in Figure 1. Generally a capacitor

C

To enhance efficiency at light loads, the LTC4090/

LTC4090-5 can be operated in low ripple Burst Mode

operation which keeps the output capacitor charged to

the proper voltage while minimizing the input quiescent

current. During Burst Mode operation, the LTC4090/

LTC4090-5 deliver single cycle bursts of current to the

output capacitor followed by sleep periods where the out-

put power is delivered to the load by the output capacitor.

Because the LTC4090/LTC4090-5 deliver power to output

with single, low current pulses, the output ripple is kept

below 15mV for a typical application. As the load current

decreases towards a no load condition, the percentage

of time that the high voltage regulator operates in sleep

mode increases and the average input current is greatly

reducedresulting in high efficiency evenatvery low loads.

See Figure 6.

(C ) and a resistor (R ) in series to ground are used. In

C

addition, there may be a lower value capacitor in parallel.

This capacitor (C ) is not part of the loop compensation

F

but is used to filter noise at the switching frequency, and

is required only if a phase-lead capacitor is used or if the

output capacitor has high ESR.

Loop compensation determines the stability and transient

performance.Designingthecompensationnetworkisabit

complicatedandthebestvaluesdependontheapplication

and in particular the type of output capacitor. A practical

approach is to start with the front page schematic and

tune the compensation network to optimize performance.

Stability should then be checked across all operating con-

ditions, includingloadcurrent, inputvoltageandtempera-

ture. The LTC1375 data sheet contains a more thorough

discussion of loop compensation and describes how to

test the stability using a transient load. Figure 5 shows

the transient response when the load current is stepped

from 500mA to 1500mA and back to 500mA.

At higher output loads (above 70mA for the front page

application) the LTC4090/LTC4090-5 will be running at

the frequency programmed by the R resistor, and will be

T

operating in standard PWM mode. The transition between

PWM and low ripple Burst Mode operation is seamless,

and will not disturb the output voltage.

V

LOAD

= 12V; FIGURE 12 SCHEMATIC

IN

FIGURE 12 SCHEMATIC

I

= 10mA

I

HVOUT

50mV/DIV

L

0.5A/DIV

V

I

SW

L

5V/DIV

1A/DIV

V

OUT

10mV/DIV

4090 F05

25µs/DIV

Figure 5. Transient Load Response of the LTC4090 High

Voltage Regulator Front Page Application as the Load

Current is Stepped from 500mA to 1500mA.

4090 F06

5µs/DIV

Figure 6. High Voltage Regulator Burst Mode Operation

4090fd

21

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

If low quiescent current is not required, the LTC4090/

LTC4090-5canoperateinpulse-skippingmode.Thebenefit

of this mode is that the LTC4090/LTC4090-5 will enter full

frequency standard PWM operation at a lower output load

currentthanwheninBurstModeoperation.Thefrontpage

application circuit will switch at full frequency at output

loads higher than about 60mA.

SynchronizingtheLTC4090/LTC4090-5internaloscillator

to an external frequency can be done by connecting a

square wave (with 20% to 80% duty cycle) to the SYNC

pin. The square wave amplitude should be such that the

valleys are below 0.3V and the peaks are above 0.8V (up

to 6V). The high voltage regulator may be synchronized

over a 300kHz to 2MHz range. The R resistor should be

T

chosen such that the LTC4090/LTC4090-5 oscillate 25%

lowerthantheexternalsynchronizationfrequencytoensure

adequate slope compensation. While synchronized, the

high voltage regulator will turn on the power switch on

positive going edges of the clock. When the power good

(PG) output is low, such as during start-up, short-circuit,

and overload conditions, the LTC4090/LTC4090-5 will

disable the synchronization feature. The SYNC pin should

be grounded when synchronization is not required.

Boost Pin Considerations

Capacitor C2 (see Block Diagram) and an internal diode

are used to generate a boost voltage that is higher than

the input voltage. In most cases, a 0.47µF capacitor will

work well. The BOOST pin must be at least 2.3V above

the SW pin for proper operation.

High Voltage Regulator Soft-Start

The HVEN pin can be used to soft-start the high voltage

regulatoroftheLTC4090/LTC4090-5, reducingmaximum

input current during start-up. The HVEN pin is driven

through an external RC filter to create a voltage ramp at

this pin. Figure 7 shows the start-up and shutdown wave-

forms with the soft-start circuit. By choosing a large RC

time constant, the peak start-up current can be reduced

to the current that is required to regulate the output, with

no overshoot. Choose the value of the resistor so that it

can supply 20µA when the HVEN pin reaches 2.3V.

Alternate NTC Thermistors and Biasing

The LTC4090/LTC4090-5 provide temperature qualified

charging if a grounded thermistor and a bias resistor are

connected to NTC (see Figure 8). By using a bias resistor

whose value is equal to the room temperature resistance

ofthethermistor(R )theupperandlowertemperatures

25C

are preprogrammed to approximately 50°C and 0°C, re-

spectively (assuming a Vishay curve 2 thermistor).

The upper and lower temperature thresholds can be ad-

justed by either a modification of the bias resistor value

or by adding a second adjustment resistor to the circuit.

If only the bias resistor is adjusted, then either the upper

or the lower threshold can be modified but not both. The

other trip point will be determined by the characteristics

of the thermistor. Using the bias resistor in addition to an

adjustmentresistor,boththeupperandthelowertempera-

ture trip points can be independently programmed with

the constraint that the difference between the upper and

lower temperature thresholds cannot decrease. Examples

of each technique are given below.

Synchronization and Mode

The SYNC pin allows the high voltage regulator to be

synchronized to an external clock.

I

RUN

15k

L

1A/DIV

HVEN

GND

HVEN

2V/DIV

NTC thermistors have temperature characteristics which

areindicatedonresistance-temperatureconversiontables.

The Vishay-Dale thermistor NTHS0603N02N1002J, used

in the following examples, has a nominal value of 10k and

follows the Vishay curve 2 resistance-temperature charac-

teristic.TheLTC4090/LTC4090-5’strippointsaredesigned

0.22µF

V

OUT

2V/DIV

4090 F07

2ms/DIV

Figure 7. To Soft-Start the High Voltage Regulator,

Add a Resistor and Capacitor to the HVEN Pin

4090fd

22

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

to work with thermistors whose resistance-temperature

characteristicsfollowVishayDale’sR-Tcurve2.TheVishay

NTHS0603N02N1002Jisanexampleofsuchathermistor.

However, Vishay Dale has many thermistor products that

follow the R-T curve 2 characteristic in a variety of sizes.

Therefore, the hot trip point is set when:

R_NTC|HOT

•VNTC=0.29•VNTC

R

_NOM+R_NTC|HOT

and the cold trip point is set when:

R_NTC|COLD

Furthermore, any thermistor whose ratio of r

to r

COLD

HOT

is about 7.0 will also work (Vishay Dale R-T curve 2 shows

•VNTC=0.74•VNTC

a ratio of 2.815/0.409 = 6.89).

R_NOM+R_NTC|COLD

In the explanation below, the following notation is used.

SolvingtheseequationsforR

in the following:

andR

results

NTC|COLD

NTC|HOT

R

= Value of the Thermistor at 25°C

25C

= Value of Thermistor at the Cold Trip Point

NTC|COLD

R

= 0.409 • R

NOM

NTC|HOT

= Value of the Thermistor at the Hot Trip Point

NTC|HOT

and

r

= Ratio of R

to R

COLD

NTC|COLD

NTC|HOT

25C

R

= 2.815 • R

NOM

NTC|COLD

= Ratio of R

to R

HOT

By setting R

equal to R , the above equations result

25C

NOM

=0.409andr

inr

=2.815.Referencingtheseratios

HOT

COLD

R

= Primary Thermistor Bias Resistor (see Figure 8)

NOM

to the Vishay Resistance-Temperature curve 2 chart gives

a hot trip point of about 50°C and a cold trip point of about

0°C. The difference between the hot and cold trip points

is approximately 50°C.

R1 = Optional Temperature Range Adjustment resistor

(see Figure 9)

ThetrippointsfortheLTC4090/LTC4090-5’stemperature

qualification are internally programmed at 0.29 • VNTC for

the hot threshold and 0.74 • VNTC for the cold threshold.

By using a bias resistor, R

25C

direction.Thetemperaturespanwillchangesomewhatdue

to the nonlinear behavior of the thermistor. The following

, different in value from

NOM

R

, the hot and cold trip points can be moved in either

VNTC

6

NTC BLOCK

VNTC

NTC BLOCK

6

0.738 • VNTC

R

NOM

R

NOM

13.2k

–

+

–

+

10k

TOO_COLD

TOO_HOT

TOO_COLD

TOO_HOT

NTC

5

R

10k

NTC

R1

1.97k

–

+

–

+

0.29 • VNTC

R

NTC

10k

+

–

+

–

NTC_ENABLE

0.1V

4090 F08

4090 F09

Figure 8. Typical NTC Thermistor Circuit

Figure 9. NTC Thermistor Circuit with Additional Bias Resistor

4090fd

23

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

equations can be used to easily calculate a new value for

the bias resistor:

not a concern unless the ambient temperature is above

85°C. The total power dissipated inside the LTC4090/

LTC4090-5 depend on many factors, including input

voltage(INorHVIN), batteryvoltage, programmedcharge

current,programmedinputcurrentlimit,andloadcurrent.

r_HOT

0.409

r_COLD

R_NOM

=

•R_25C

In general, if the LTC4090/LTC4090-5 is being powered

fromINthepowerdissipationcanbecalculatedasfollows:

2.815

where r

and r

are the resistance ratios at the de-

HOT

COLD

P = (V – V ) • I + (V – V ) • I

OUT

D

IN

BAT

IN

OUT

sired hot and cold trip points. Note that these equations

are linked. Therefore, only one of the two trip points can

be chosen, the other is determined by the default ratios

designed in the IC. Consider an example where a 40°C

hot trip point is desired.

whereP isthepowerdissipated,I isthebatterycharge

D

BAT

current, and I

typicalapplication,anexampleofthiscalculationwouldbe:

is the application load current. For a

OUT

P

= (5V – 3.7V) • 0.4A + (5V – 4.75V) • 0.1A

D

= 545mW

FromtheVishaycurve2R-Tcharacteristics,r is0.5758

at 40°C. Using the above equation, R

14.0k. With this value of R

–7°C. Notice that the span is now 47°C rather than the

previous 50°C. This is due to the increase in temperature

gain of the thermistor as absolute temperature decreases.

HOT

should be set to

This examples assumes V = 5V, V

= 4.75V, V

=

BAT

NOM

IN

OUT

, the cold trip point is about

NOM

3.7V, I = 400mA, and I

= 100mA resulting in slightly

BAT

OUT

more than 0.5W total dissipation.

If the LTC4090 is being powered from HVIN, the power

dissipation can be estimated by calculating the regulator

powerlossfromanefficiencymeasurement,andsubtract-

ing the catch diode loss.

The upper and lower temperature trip points can be inde-

pendentlyprogrammedbyusinganadditionalbiasresistor

as shown in Figure 9. The following formulas can be used

P =(1−h)• V_HVOUT•(I_BAT+I_OUT

)

[

]

D

to compute the values of R

and R1:

NOM







V_{HVOUT }

r_COLD–r_HOT



−V_D•_1−



• I_BAT+I )+0.3V •I_BAT

(

)

R_NOM

=

•R_25C

OUT



V_HVIN

2.815





R1=0.409•R_NOM–r_HOT•R_25C

where h is the efficiency of the high voltage regulator and

V is the forward voltage of the catch diode at I = I

D

BAT

For example, to set the trip points to –5°C and 55°C with

a Vishay curve 2 thermistor choose

+ I . The first term corresponds to the power lost in

OUT

converting V

to V

, the second term subtracts

HVOUT

HVIN

3.532–0.3467

2.815–0.409

the catch diode loss, and the third term is the power dis-

sipated in the battery charger. For a typical application,

an example of this calculation would be:

R_NOM

=

•10k =13.2k

the nearest 1% value is 13.3k.

P =(1−0.87)• 4V •(1A+0.6A)

[

4V

12V

]

D

R1 = 0.409 • 13.3k – 0.3467 • 10k = 1.97k











the nearest 1% value is 1.96k. The final solution is shown

in Figure 9 and results in an upper trip point of 55°C and

a lower trip point of –5°C.

−0.4V • 1−

• 1A+0.6A +0.3V •1A =0.7W

(

)





This example assumes 87% efficiency, V

= 12V, V

=

HVIN

BAT

3.7V(V

isabout4V),I =1A,I =600mAresulting

HVOUT

BAT OUT

Power Dissipation and High Temperature Considerations

in about 0.7W total dissipation. If the LTC4090-5 is being

poweredfromHVIN,thepowerdissipationcanbeestimated

The die temperature of the LTC4090/LTC4090-5 must be

lower than the maximum rating of 110°C. This is generally

4090fd

24

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

by calculating the regulator power loss from an efficiency

measurement, and subtracting the catch diode loss.

reduce thermal resistance further. With these steps, the

thermal resistance from die (i.e., junction) to ambient can

be reduced to θ = 40°C/W.

JA









5V

V_HVIN



P = 1–h • 5V • I_BAT+I

– V • 1–

•

(

)

(

)

(

)

D

D 



OUT



Board Layout Considerations



As discussed in the previous section, it is critical that

the exposed metal pad on the backside of the LTC4090/

LTC4090-5 package be soldered to the PC board ground.

Furthermore,properoperationandminimumEMIrequires

acarefulprintedcircuitboard(PCB)layout.Notethatlarge,

switched currents flow in the power switch (between the

HVIN and SW pins), the catch diode and the HVIN input

capacitor. Thesecomponents, alongwiththeinductorand

output capacitor, should be placed on the same side of

the circuit board, and their connections should be made

on that layer. Place a local, unbroken ground plane below

thesecomponents.Theloopformedbythesecomponents

should be as small as possible.

I

_BAT+I

+ 5V – V

•I

(

)

(

)

BAT

OUT

The difference between this equation and that for the

LTC4090 is the last term, which represents the power

dissipationinthebatterycharger.Foratypicalapplication,

an example of this calculation would be:









5V

12V



P = 1–0.87 • 5V • 1A+0.6A –0.4V • 1–

•

(

)

(

)

(

D





1A+0.6A + 5V –3.7V •1A =1.97W

) (

(

)

Like the LTC4090 example, this examples assumes 87%

efficiency, V

= 12V, V = 3.7V, I

= 1A and I

BAT OUT

HVIN

BAT

= 600mA resulting in about 2W total power dissipation.

Additionally, the SW and BOOST nodes should be kept

as small as possible. Figure 10 shows the recommended

component placement with trace and via locations.

It is important to solder the exposed backside of the pack-

age to a ground plane. This ground should be tied to other

copper layers below with thermal vias; these layers will

spread the heat dissipated by the LTC4090/LTC4090-5.

Additional vias should be placed near the catch diode.

Adding more copper to the top and bottom layers and

tying this copper to the internal planes with vias can

High frequency currents, such as the high voltage input

current of the LTC4090/LTC4090-5, tend to find their way

along the ground plane on a mirror path directly beneath

the incident path on the top of the board. If there are slits

or cuts in the ground plane due to other traces on that

layer, the current will be forced to go around the slits.

If high frequency currents are not allowed to flow back

throughtheirnaturalleast-areapath,excessivevoltagewill

build up and radiated emissions will occur. See Figure 11.

C1 AND D1

GND PADS

SIDE-BY-SIDE

AND SEPERATED

WITH C3 GND PAD

MINIMIZE D1, L1,

C3, U1, SW PIN LOOP

U1 THERMAL PAD

SOLDERED TO PCB.

VIAS CONNECTED TO ALL

4090 F11

GND PLANES WITHOUT

MINIMIZE TRACE LENGTH

THERMAL RELIEF

Figure 11. Ground Currents Follow Their Incident

Path at High Speed. Slices in the Ground Plane

Cause High Voltage and Increased Emissions.

4090 F10

Figure 10. Suggested Board Layout

4090fd

25

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

APPLICATIONS INFORMATION

IN and HVIN Bypass Capacitor

Battery Charger Stability Considerations

Many types of capacitors can be used for input bypassing;

however,cautionmustbeexercisedwhenusingmultilayer

ceramic capacitors. Because of the self-resonant and high

Q characteristics of some types of ceramic capacitors,

high voltage transients can be generated under some

start-up conditions, such as from connecting the charger

input to a hot power source. For more information, refer

to Application Note 88.

Theconstant-voltagemodefeedbackloopisstablewithout

any compensation when a battery is connected with low

impedanceleads.Excessiveleadlength,however,mayadd

enough series inductance to require a bypass capacitor

of at least 1µF from BAT to GND. Furthermore, a 4.7µF

capacitor with a 0.2W to 1W series resistor to GND is

recommended at the BAT pin to keep ripple voltage low

when the battery is disconnected.

TYPICAL APPLICATIONS

L1

0.47µF

HIGH

6.8µH

16V

(7.5V TO 36V)

HVIN

BOOST SW

VOLTAGE

C1

C3

INPUT

1µF

D1

22µF

6.3V

1206

HVEN

IN

50V

1206

USB

680Ω

4.7µF

6.3V

HVOUT

LTC4090

HPWR

59k

1%

V

C

270pF

SUSP

HVPR

OUT

Q1

0.1µF

1k

TIMER

CLPROG

PROG

2.1k

1%

LOAD

4.7µF

6.3V

71.5k

1%

GATE

BAT

Q2

40.2k

1%

R

T

+

VNTC

NTC

Li-Ion

BATTERY

PG

10k

1%

SYNC

T

10k

680Ω

D: DIODES INC. B360A

L: SUMIDA CDR6D28MN-GR5

Q1, Q2: SILICONIX Si2333DS

CHRG

4090 F12

Figure 12. 800kHz Switching Frequency

4090fd

26

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

TYPICAL APPLICATIONS

L

0.47µF

SW

10µH

BOOST

HIGH (7.5V TO 36V)

TRANSIENT TO 60V*

HVIN

IN

4.7µF

1µF

HVOUT

Q1

USB

HVPR

LTC4090

4.7µF

1k

V

C

OUT

BAT

LOAD

4.7µF

R

T

TIMER

CLPROG

2.1k

GND PROG

35k

88.7k

+

71.5k

Li-Ion BATTERY

330pF

0.1µF

L: SUMIDA CDRH8D28/HP-100

* USE SCHOTTKY DIODE RATED AT V > 45V

R

4090 TAO3

Figure 13. 400kHz Switching Frequency

L

0.47µF

SW

2.2µH

BOOST

HIGH (7.5V TO 16V)

VOLTAGE INPUT

HVIN

IN

22µF

1µF

HVOUT

Q1

USB

HVPR

LTC4090

4.7µF

1k

V

C

OUT

BAT

GND PROG

LOAD

4.7µF

R

T

TIMER

CLPROG

2.1k

30k

11.5k

+

71.5k

330pF

0.1µF

Li-Ion BATTERY

L: SUMIDA CDRH4D22/HP-2R2

4090 TAO4

Figure 14. 2MHz Switching Frequency

4090fd

27

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

PACKAGE DESCRIPTION

DJC Package

22-Lead Plastic DFN (6mm × 3mm)

(Reference LTC DWG # 05-08-1714)

0.889

0.70 0.05

R = 0.10

0.889

3.60 0.05

1.65 0.05

2.20 0.05

(2 SIDES)

PACKAGE

OUTLINE

0.25 0.05

0.50 BSC

5.35 0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

NOTE:

1. DIMENSIONS ARE IN MILLIMETERS

2. APPLY SOLDER MASK TO AREAS THAT

ARE NOT SOLDERED

3. DRAWING IS NOT TO SCALE

R = 0.115

TYP

0.40 0.05

6.00 0.10

(2 SIDES)

0.889

12

22

R = 0.10

TYP

0.889

3.00 0.10

(2 SIDES)

1.65 0.10

(2 SIDES)

PIN 1

TOP MARK

(NOTE 6)

PIN #1 NOTCH

R0.30 TYP OR

0.25mm × 45°

CHAMFER

11

1

0.25 0.05

0.50 BSC

0.75 0.05

0.200 REF

5.35 0.10

(2 SIDES)

(DJC) DFN 0605

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WXXX)

IN JEDEC PACKAGE OUTLINE M0-229

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 TOP AND BOTTOM OF PACKAGE

4090fd

28

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

REVISION HISTORY

REV

DATE

DESCRIPTION

PAGE NUMBER

D

03/15 Corrected comparator hookup on block diagram

11

4090fd

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

However,noresponsibilityisassumedforitsuse.LinearTechnologyCorporationmakesnorepresentation

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

29

For more information www.linear.com/LTC4090

LTC4090/LTC4090-5

RELATED PARTS

PART NUMBER

Battery Chargers

LTC1733

DESCRIPTION

COMMENTS

Monolithic Lithium-Ion Linear Battery

Charger

Standalone Charger with Programmable Timer, Up to 1.5A Charge Current

Simple ThinSOT Charger, No Blocking Diode, No Sense Resistor Needed

LTC1734

LTC4002

LTC4053

LTC4054

Lithium-Ion Linear Battery Charger in

ThinSOT™

Switch Mode Lithium-Ion Battery

Charger

Standalone, 4.7V ≤ V ≤ 24V, 500kHz Frequency, Three-Hour Charge Termination

IN

USB Compatible Monolithic Li-Ion

Battery Charger

Standalone Charger with Programmable Timer, Up to 1.25A Charge Current

Standalone Linear Li-Ion Battery

Charger with Integrated Pass Transistor Charge Current

in ThinSOT

Thermal Regulation Prevents Overheating, C/10 Termination, C/10 Indicator, Up to 800mA

LTC4057

LTC4058

Lithium-Ion Linear Battery Charger

Up to 800mA Charge Current, Thermal Regulation, ThinSOT Package

Standalone 950mA Lithium-Ion Charger C/10 Charge Termination, Battery Kelvin Sensing, 7% Charge Accuracy

in DFN

LTC4059

900mA Linear Lithium-Ion Battery

Charger

2mm 2mm DFN Package, Thermal Regulation, Charge Current Monitor Output

LTC4065/

LTC4065A

Standalone Li-Ion Battery Chargers

in 2mm 2mm DFN

4.2V, 0.6% Float Voltage, Up to 750mA Charge Current, 2mm 2mm DFN,

“A” Version Has ACPR Function.

LTC4095

Standalone USB Lithium-Ion/Polymer

Battery Charger in 2mm 2mm DFN

950mA Charge Current, Timer Termination + C/10 Detection Output, 4.2V, 0.6% Accurate

Float Voltage, Four CHRG Pin Indicator States

Power Management

LTC3406/

LTC3406A

600mA (I ), 1.5MHz, Synchronous

95% Efficiency, V : 2.5V to 5.5V, V

= 0.6V, I = 20µA, I < 1µA, ThinSOT Package

Q SD

OUT

IN

OUT

Step-Down DC/DC Converter

LTC3411

LTC3440

LTC3455

LT3493

1.25A (I ), 4MHz, Synchronous

95% Efficiency, V : 2.5V to 5.5V, V

= 0.8V, I = 60µA, I < 1µA, MS10 Package

Q SD

OUT

IN

Step-Down DC/DC Converter

600mA (I ), 2MHz, Synchronous

95% Efficiency, V : 2.5V to 5.5V, V

= 2.5V, I = 25µA, I < 1µA, MS Package

Q SD

OUT

IN

Buck-Boost DC/DC Converter

Dual DC/DC Converter with USB Power Seamless Transition Between Power Sources: USB, Wall Adapter and Battery;

Manager and Li-Ion Battery Charger

95% Efficient DC/DC Conversion

1.2A, 750kHz Step-Down Switching

Regulator

88% Efficiency, V : 3.6V to 36V (40V Maximum), V

= 0.8V, I < 2µA, 2mm 3mm

OUT SD

IN

DFN Package

LTC4055

LTC4066

LTC4067

LTC4085

USB Power Controller and Battery

Charger

Charges Single-Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation,

200m Ideal Diode, 4mm 4mm QFN16 Package

USB Power Controller and Li-Ion Battery Charges Single-Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation, 50m

Charger with Low Loss Ideal Diode

Ideal Diode, 4mm 4mm QFN24 Package

USB Power Controller with OVP, Ideal

Diode and Li-Ion Battery Charger

13V Overvoltage Transient Protection, Thermal Regulation, 200mW Ideal Diode with

<50mW Option, 4mm × 3mm DFN-14 Package

USB Power Manager with Ideal Diode

Controller and Li-Ion Charger

Charges Single-Cell Li-Ion Batteries Directly from a USB Port, Thermal Regulation,

200mW Ideal Diode with <50mW Option, 4mm 3mm DFN14 Package

LTC4089/

LTC4089-5

USB Power Manager with Ideal Diode

Controller and High Efficiency Li-Ion

Battery Charger

High Efficiency 1.2A Charger from 6V to 36V (40V Max) Input Charges Single-Cell Li-Ion

Batteries Directly from a USB Port, Thermal Regulation, 200mW Ideal Diode with <50mW

Option, Bat-Track Adaptive Output Control (LTC4089), Fixed 5V Output (LTC4089-5),

6mm × 3mm DFN-22 Package

LTC4411/LTC4412 Low Loss PowerPath Controller in

ThinSOT

Automatic Switching Between DC Sources, Load Sharing, Replaces ORing Diode

LTC4412HV

High Voltage Power Path Controllers in V : 3V to 36V, More Efficient than Diode ORing, Automatic Switching Between DC

IN

ThinSOT

Sources, Simplified Load Sharing, ThinSOT Package.

4090fd

LT 0315 REV D • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

30

For more information www.linear.com/LTC4090

●

 LINEAR TECHNOLOGY CORPORATION 2007

(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC4090-5


型号：	LTC4090-5_15
厂家：	Linear
描述：	USB Power Manager with 2A High Voltage Bat-Track Buck Regulator
文件：	总30页 (文件大小：852K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC4090-5_15 [Linear]

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