LTC3576-1_15_技术文档

LTC3576/LTC3576-1

Switching Power Manager

with USB On-the-Go + Triple

Step-Down DC/DCs

DESCRIPTION

FEATURES

Bidirectional Switching Regulator with Bat-Track™ The LTC^®3576/LTC3576-1 are highly integrated power

Adaptive Output Control Provides Efﬁcient Charging management and battery charger ICs for Li-Ion/Polymer

n

and a 5V Output for USB On-The-Go

Bat-Track Control of External High Voltage Step-

Down Switching Regulator

battery applications. They each include a high efﬁciency,

bidirectional switching PowerPath™ manager with auto-

maticloadprioritization,abatterycharger,anidealdiode,a

controller for an external high voltage switching regulator

andthreegeneralpurposestep-downswitchingregulators

n

Overvoltage Protection Guards Against Damage

Instant-On Operation with Discharged Battery

2

Triple Step-Down Switching Regulators with I C

with I C adjustable output voltages. The internal switch-

Adjustable Outputs (1A/400mA/400mA I

)

ing regulators automatically limit input current for USB

compatibility and can also generate 5V at 500mA for USB

on-the-go applications when powered from the battery.

BoththeUSBandexternalswitchingregulatorpowerpaths

featureBat-Trackoptimizedchargingtoprovidemaximum

180mΩ Internal Ideal Diode + External^OI^Ud^Teal Diode

Controller Powers the Load in Battery Mode

n

Li-Ion/Polymer Battery Charger (1.5A Max I

Battery Float Voltage: 4.2V (LTC3576), 4.1V (LTC3576-1)

)

CHG

Compact (4mm × 6mm × 0.75mm) 38-Pin QFN Package power to the application from supplies as high as 38V. An

overvoltage circuit protects the LTC3576/LTC3576-1 from

damageduetohighvoltageontheV

orWALLpinswith

BUS

APPLICATIONS

justtwoexternalcomponents.TheLTC3576/LTC3576-1are

available in a low proﬁle 38-pin (4mm × 6mm × 0.75mm)

QFN package.

n

HDD-Based Media Players

n

GPS, PDAs, Digital Cameras, Smart Phones

n

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

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

Corporation. All other trademarks are the property of their respective owners. Protected by U.S.

Patents, including 6522118, 6404251.

Automotive Compatible Portable Electronics

TYPICAL APPLICATION

High Efﬁciency PowerPath Manager with Overvoltage Protection

and Triple Step-Down Regulator

AUTOMOTIVE

LT3653

FIREWIRE, ETC.

PowerPath Switching Regulator Efﬁciency

to System Load (P_VOUT/P_VBUS

)

USB OR

5V AC

ADAPTER

OVERVOLTAGE

PROTECTION

EXTERNAL HIGH VOLTAGE

BUCK CONTROLLER

100

90

80

70

60

50

40

30

20

10

0

TO OTHER

LOADS

USB COMPLIANT

BIDIRECTIONAL

SWITCHING

BAT = 4.2V

BAT = 3.3V

REGULATOR

CC/CV

0V

OPTIONAL

BATTERY

CHARGER

CHARGE

LTC3576/LTC3576-1

+

Li-Ion

T

V

I

= 5V

BUS

= 0mA

BAT

10x MODE

3.3V/20mA

RTC/LOW

ALWAYS ON LDO

POWER LOGIC

10

100

1000

0.8V TO 3.6V/400mA

LOAD CURRENT (mA)

1

2

3

MEMORY

I/O

TRIPLE

HIGH EFFICIENCY

STEP-DOWN

SWITCHING

REGULATORS

6

3576 TA01b

ENABLE

CONTROLS

0.8V TO 3.6V/1A

CORE

μPROCESSOR

RST

2

I C

I C PORT

3576 TA01

3576fb

1

LTC3576/LTC3576-1

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Notes 1, 2, 3)

TOP VIEW

V

, WALL (Transient) t < 1ms,

BUS

Duty Cycle < 1% .......................................... –0.3V to 7V

V

, WALL (Static), BAT, V , V , V

,

38 37 36 35 34 33 32

BUS

IN1 IN2 IN3

CLPROG

LDO3V3

NTCBIAS

NTC

1

2

3

4

5

6

7

8

9

31 IDGATE

, ENOTG, NTC, SDA, SCL, DV ,

OUT

CC

30 CHRG

RST3, CHRG ................................................ –0.3V to 6V

, I ........ –0.3V to Max(V , V , BAT) + 0.3V

PROG

29

28

I

LIM0 ILIM1

BUS OUT

ACPR

EN1, EN2, EN3 .............................. –0.3V to V

+ 0.3V

OUT

INx

OVGATE

OVSENS

FB1

27 WALL

FBx (x = 1, 2, 3) ..............................–0.3V to V + 0.3V

V

26

25 FB2

24

C

39

I

...................................................................10mA

OVSENS

CLPROG

CHRG RST3

PROG

LDO3V3

SW1 SW2

I , I

....................................................................3mA

V

IN1

IN2

SW1

23 SW2

22 EN2

21 RST3

, I

............................................................50mA

EN1 10

........................................................................2mA

ENOTG 11

...................................................................30mA

20

FB3

DV

CC

12

, I

(Continuous).......................................600mA

13 14 15 16 17 18 19

UFE PACKAGE

, I , I

(Continuous)..............................2A

SW SW3 BAT VOUT

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

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

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

38-LEAD (4mm s 6mm) PLASTIC QFN

T

JMAX

= 125°C, θ = 34°C/W

JA

EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LTC3576EUFE#PBF

LTC3576EUFE-1#PBF

TAPE AND REEL

PART MARKING

3576

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC3576EUFE#TRPBF

LTC3576EUFE-1#TRPBF

–40°C to 85°C

38-Lead (4mm × 6mm) Plastic QFN

35761

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

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

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

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

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_BUS= 5V, BAT = 3.8V, DV_CC= 3.3V, R_CLPROG= 3.01k, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

PowerPath Switching Regulator—Step-Down Mode

V

I

Input Supply Voltage

Total Input Current

4.35

5.5

V

BUS

l

82

440

800

0.32

1.6

90

100

500

1000

0.5

mA

1× Mode

VBUS(LIM)

472

880

0.39

2.05

5× Mode

10× Mode

Low Power Suspend Mode

High Power Suspend Mode

2.5

I

(Note 4) Input Quiescent Current

7

mA

1× Mode

VBUSQ

17

5×, 10× Modes

0.045

Low/High Power Suspend Modes

3576fb

2

LTC3576/LTC3576-1

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_BUS= 5V, BAT = 3.8V, DV_CC= 3.3V, R_CLPROG= 3.01k, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

h

Ratio of Measured V

Current to

210

1160

2200

9.6

mA/mA

1× Mode

CLPROG

BUS

(Note 4)

CLPROG Program Current

5× Mode

10× Mode

Low Power Suspend Mode

High Power Suspend Mode

56

I

V

Current Available Before

OUT

121

667

1217

0.31

2

mA

1× Mode, BAT = 3.3V

VOUT(POWERPATH)

Discharging Battery

5× Mode, BAT = 3.3V

10× Mode, BAT = 3.3V

Low Power Suspend Mode

High Power Suspend Mode

0.26

1.6

0.41

2.4

V

CLPROG Servo Voltage in Current Limit

Switching Modes

Suspend Modes

1.18

100

V

CLPROG

UVLO

mV

V

Undervoltage Lockout

Rising Threshold

Falling Threshold

4.30

4.00

4.35

V

BUS

3.95

V

to BAT Differential Undervoltage

Rising Threshold

Falling Threshold

200

50

mV

DUVLO

OUT

Lockout

V

Voltage

1×, 5×, 10× Modes, 0V < BAT < 4.2V,

OUT

3.4

4.5

BAT + 0.3

4.6

4.7

V

I

= 0mA, Battery Charger Off

VOUT

USB Suspend Modes, I

= 250μA

VOUT

f

Switching Frequency

PMOS On-Resistance

1.8

2.25

0.18

2.7

MHz

ꢀ

OSC

R

PMOS_

POWERPATH

R

NMOS On-Resistance

0.30

ꢀ

NMOS_

POWERPATH

I

Peak Inductor Current Limit

1

2

3

A

1× Mode (Note 5)

5× Mode (Note 5)

10× Mode (Note 5)

PEAK_POWERPATH

R

Suspend LDO Output Resistance

Closed Loop

10

ꢀ

SUSP

PowerPath Switching Regulator—Step-Up Mode (USB On-the-Go)

V

BUS

V

OUT

Output Voltage

0mA ≤ I

≤ 500mA, V > 3.2V

OUT

4.75

2.9

5.25

5.5

V

VBUS

Input Voltage

l

I

Output Current Limit

Peak Inductor Current Limit

550

680

1.8

mA

A

VBUS

PEAK

OTGQ

(Note 5)

V

Quiescent Current

V

= 3.8V, I = 0mA (Note 6)

VBUS

1.38

1.15

mA

V

OUT

BUS

V

Output Current Limit Servo Voltage

CLPROG

V

UVLO—V

Falling

Rising

2.5

2.6

2.8

V

OUT(UVLO)

OUT

2.9

t

Short-Circuit Fault Delay

V

< 4V and PMOS Switch Off

7.2

ms

SCFAULT

Bat-Track Switching Regulator Control

V

Absolute WALL Input Threshold

Rising Threshold

Hysteresis

4.2

0

4.3

1.1

4.4

45

V

WALL

Differential WALL Input Threshold

WALL-BAT Falling

Hysteresis

30

60

mV

ΔV

WALL

V

Regulation Target Under V Control

3.55

BAT + 0.3

400

V

μA

ꢀ

V

OUT

C

I

WALL Quiescent Current

ACPR Pull-Down Strength

ACPR High Voltage

WALLQ

R

150

ACPR

V

OUT

HACPR

LACPR

ACPR Low Voltage

0

V

3576fb

3

LTC3576/LTC3576-1

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_BUS= 5V, BAT = 3.8V, DV_CC= 3.3V, R_CLPROG= 3.01k, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Overvoltage Protection

V

Overvoltage Protection Threshold

OVGATE Output Voltage

With 6.2k Series Resistor

6.1

6.35

6.7

12

V

OVCUTOFF

OVGATE

V

< V

> V

1.88•V

V

OVSENS

OVCUTOFF

OVSENS

0

t

OVGATE Time to Reach Regulation

BAT Regulated Output Voltage

OVGATE C

= 1nF

LOAD

2.2

ms

RISE

Battery Charger

V

LTC3576

4.179

4.165

4.200

4.221

4.235

V

FLOAT

l

LTC3576-1

4.079

4.065

4.100

4.121

4.135

V

I

Constant Current Mode Charger Current

Battery Drain Current

R

= 1k

= 5k

980

185

1030

206

1065

223

mA

CHG

BAT

PROG

V

VOUT

> V

, Suspend Mode,

UVLO

3.6

6

μA

BUS

I

= 0μA

= 0V, I

V

= 0μA

VOUT

28

45

μA

BUS

(Ideal Diode Mode)

V

PROG Pin Servo Voltage

1.000

0.100

100

1030

100

2.85

135

–100

4

V

PROG

PROG_TRKL

C/10

PROG Pin Servo Voltage in Trickle Charge BAT < V

C/10 Threshold Voltage at PROG

TRKL

mV

h

Ratio of I to PROG Pin Current

mA/mA

mA

PROG

BAT

I

Trickle Charge Current

BAT < V

, R

= 1k

TRKL

TRKL PROG

V

TRKL

Trickle Charge Threshold Voltage

Trickle Charge Hysteresis Voltage

Recharge Battery Threshold Voltage

Safety Timer Termination Period

Bad Battery Termination Time

End of Charge Current Ratio

CHRG Pin Output Low Voltage

CHRG Pin Leakage Current

BAT Rising

2.7

3.0

V

mV

ΔV

TRKL

Threshold Voltage Relative to V

–75

3.3

–125

5

mV

FLOAT

RECHRG

t

Timer Starts When V = V

Hour

mA/mA

mV

TERM

BADBAT

BAT

FLOAT

BAT < V

0.4

0.5

0.6

0.112

100

1

TRKL

h

(Note 7)

0.085

0.1

C/10

V

I

= 5mA

= 5V

65

CHRG

I

V

μA

CHRG

R

Battery Charger Power FET On-

0.18

110

ꢀ

ON_CHG

Resistance (Between V

and BAT)

OUT

T

LIM

Junction Temperature in Constant

Temperature Mode

°C

NTC

V

Cold Temperature Fault Threshold Voltage Rising Threshold

Hysteresis

75

76.5

1.6

78

%NTCBIAS

COLD

V

Hot Temperature Fault Threshold Voltage Falling Threshold

Hysteresis

33.4

0.7

34.9

1.5

36.4

2.7

50

%NTCBIAS

HOT

NTC Disable Threshold Voltage

Falling Threshold

Hysteresis

1.7

50

%NTCBIAS

mV

DIS

I

NTC Leakage Current

NTC = NTCBIAS = 5V

–50

nA

NTC

Ideal Diode

V

Forward Voltage

I

= 10mA

15

mV

ꢀ

FWD

VOUT

R

Internal Diode On-Resistance Dropout

Diode Current Limit

= 200mA

0.18

DROPOUT

VOUT

I

2

A

MAX_DIODE

3576fb

4

LTC3576/LTC3576-1

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_BUS= 5V, BAT = 3.8V, DV_CC= 3.3V, R_CLPROG= 3.01k, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Always On 3.3V LDO Supply

V

Regulated Output Voltage

0mA < I < 20mA

LDO3V3

3.1

3.3

2.7

23

3.5

V

ꢀ

LDO3V3

R

Closed-Loop Output Resistance

Dropout Output Resistance

CL_LDO3V3

OL_LDO3V3

Logic (I

, I

, EN1, EN2, EN3, ENOTG, and SCL, SDA when DV = 0V)

LIM0 LIM1

CC

V

Logic Low Input Voltage

Logic High Input Voltage

0.4

5.5

V

IL

IH

1.2

1.6

I

, I , EN1, EN2, EN3, ENOTG, SCL,

LIM0 LIM1

2

μA

PD1

SDA Pull-Down Current

2

I C Port

DV

Input Supply

V

μA

V

CC

I

DV Current

CC

SCL/SDA = 0kHz, DV = 3.3V

0.5

1.0

DVCC

CC

V

DV UVLO

CC

DVCC(UVLO)

2

ADDRESS

V , SDA, SCL

I C Address

0001001[0]

Input High Threshold

Input Low Threshold

Pull-Down Current

70

%DV

IH

CC

V , SDA, SCL

IL

30

I

, SDA, SCL

PD2

2

μA

V

Digital Output Low (SDA)

Clock Operating Frequency

I

= 3mA

0.4

OL

SCL

BUF

SDA

f

t

400

kHz

μs

Bus Free Time Between Stop and Start

Condition

1.3

0.6

t

Hold Time After (Repeated) Start

Condition

μs

HD_STA

t

Repeated Start Condition Setup Time

Stop Condition Setup Time

Data Hold Time Output

Data Hold Time Input

Data Setup Time

0.6

0

μs

ns

μs

ns

SU_STA

SU_STO

HD_DAT(O)

HD_DAT(I)

SU_DAT

LOW

900

0

100

1.3

0.6

20

SCL Low Period

SCL High Period

HIGH

SDA/SCL Fall Time

300

50

f

SDA/SCL Rise Time

r

Input Spike Suppression Pulse Width

SP

General Purpose Switching Regulators 1, 2 and 3

V

Input Supply Voltage

(Note 8)

Connected to V Through

OUT

2.7

2.5

5.5

2.9

V

IN1,2,3

V

UVLO—V

Falling

Rising

V

2.6

2.8

V

OUT(UVLO)

OUT

IN1,2,3

Low Impedance. Switching

Regulators are Disabled in UVLO

f

I

Switching Frequency

FBx Input Current

1.8

–50

100

2.25

2.7

50

MHz

nA

OSC

V

= 0.85V

FB1,2,3

D1,2,3

Maximum Duty Cycle

SWx Pull-Down in Shutdown

%

R

10

kꢀ

SW1,2,3_PD

3576fb

5

LTC3576/LTC3576-1

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_BUS= 5V, BAT = 3.8V, DV_CC= 3.3V, R_CLPROG= 3.01k, unless

otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

90

MAX

UNITS

μA

V

I

Pulse-Skipping Mode Input Current

Burst Mode^®Input Current

LDO Mode Input Current

Shutdown Input Current Limit

Maximum Servo Voltage

Minimum Servo Voltage

I

= 0μA (Note 9)

= 0μA, FB1,2,3 = 0V

VIN1,2,3

OUT1,2,3

20

35

25

15

1

l

V

Full Scale (1,1,1,1) (Note 10)

Zero Scale (0,0,0,0) (Note 10)

0.78

0.80

0.425

25

0.82

0.445

FBHIGH1,2,3

FBLOW1,2,3

LSB1,2,3

0.405

V

Servo Voltage Step Size

mV

ꢀ

FB1,2

R

LDO Mode Closed-Loop R

V

= V = 0.8V

OUT1,2 3

0.25

2.5

LDO_CL1,2,3

OUT

FB1,2,3

LDO Mode Open-Loop R

(Note 11)

ꢀ

LDO_OL1,2,3

OUT

General Purpose Switching Regulator 1 and 2

I

PMOS Switch Current Limit

Pulse-Skipping/Burst Mode

Operation (Note 5)

600

50

900

1300

2800

mA

LIM1,2

I

Available Output Current

LDO Mode

mA

ꢀ

OUT1,2

R

PMOS R

NMOS R

0.6

0.7

P1,2

DS(ON)

ꢀ

N1,2

DS(ON)

General Purpose Switching Regulator 3

I

PMOS Switch Current Limit

Pulse-Skipping/Burst Mode

Operation (Note 5)

1300

50

1800

mA

LIM3

I

Available Output Current

LDO Mode

mA

ꢀ

OUT3

R

PMOS R

NMOS R

0.18

0.3

P3

DS(0N)

ꢀ

N3

DS(ON)

t

Power-On Reset Time for Switching

Regulator

V

Within 92% of Final Value to

230

ms

RST3

FB3

RST3 Hi-Z

Burst Mode is a registered trademark of Linear Technology Corporation.

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 5: The current limit features of this part are intended to protect the

IC from short term or intermittent fault conditions. Continuous operation

above the maximum speciﬁed pin current rating may result in device

degradation or failure.

Note 2: The LTC3576E/LTC3576E-1 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 6: The bidirectional switcher’s supply current is bootstrapped to V

BUS

and in the application will reﬂect back to V

by (V /V ) •

BUS OUT

OUT

1/efﬁciency. Total quiescent current is the sum of the current into the

pin plus the reﬂected current.

V

OUT

Note 3: The LTC3576E/LTC3576E-1 include overtemperature protection

that is intended to protect the device during momentary overload

conditions. Junction temperature will exceed 125°C when overtemperature

protection is active. Continuous operation above the speciﬁed maximum

operating junction temperature may impair device reliability.

Note 7: h

current with indicated PROG resistor.

Note 8: V not in UVLO.

Note 9: FBx above regulation such that regulator is in sleep. Speciﬁcation

does not include resistive divider current reﬂected back to V

Note 10: Applies to pulse-skipping and Burst Mode operation only.

Note 11: Inductor series resistance adds to open-loop R

is expressed as a fraction of the measured full charge

C/10

OUT

.

INx

Note 4: Total input current is the sum of quiescent current, I

, and

VBUSQ

measured current given by V /R

CLPROG

• (h

+ 1).

CLPROG

.

OUT

3576fb

6

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

Ideal Diode Resistance

V_OUTVoltage vs Load Current

Ideal Diode V-I Characteristics

vs Battery Voltage

(Battery Charger Disabled)

1.0

0.8

0.6

0.4

0.2

0

0.25

0.20

0.15

0.10

0.05

0

4.50

INTERNAL IDEAL DIODE

WITH SUPPLEMENTAL

EXTERNAL VISHAY

Si2333 PMOS

BAT = 4V

4.25

4.00

INTERNAL IDEAL

DIODE

INTERNAL IDEAL

DIODE ONLY

BAT = 3.4V

3.75

INTERNAL IDEAL DIODE

WITH SUPPLEMENTAL

EXTERNAL VISHAY

Si2333 PMOS

3.50

3.25

V

= 5V

BUS

0

0.04

0.08

0.12

0.16

0.20

2.7

3.0

3.3

3.6

3.9

4.2

0

0.1 0.2 0.3

0.6 0.7 0.8 0.9 1.0

0.4 0.5

FORWARD VOLTAGE (V)

BATTERY VOLTAGE (V)

LOAD CURRENT (A)

3576 G01

3576 G02

3576 G03

USB Limited Load Current vs Battery

Voltage (Battery Charger Disabled)

Battery and V_BUSCurrents

vs Load Current

Battery Charge Current

vs Temperature

750

500

250

900

600

500

400

300

200

100

0

R = 2k

PROG

V

= 5V

BUS

800

700

600

500

400

300

200

100

5s MODE

V

CURRENT

BUS

THERMAL REGULATION

BATTERY CURRENT

(CHARGING)

0

–250

–500

V

= 5V

BUS

BAT = 3.8V

5s MODE

R

= 3.01k

BATTERY CURRENT

(DISCHARGING)

CLPROG

= 1k

PROG

0

60 80

TEMPERATURE (°C)

–40 –20

0

20 40

100 120

0

100 200 300 400 500 600 700 800 9001000

2.7

3.9

4.2

3.0

3.3

3.6

LOAD CURRENT (mA)

BATTERY VOLTAGE (V)

3576 G06

3576 G05

3576 G04

Battery Charging Efﬁciency

vs Battery Voltage with No

PowerPath Switching Regulator

Transient Response

PowerPath Switching Regulator

Efﬁciency vs Load Current

External Load (P_BAT/P_VBUS

)

100

90

80

70

60

50

40

30

95

90

85

80

75

70

65

60

55

R

= 3.01k

CLPROG

PROG

= 1k

V

OUT

50mV/DIV

1s MODE

AC COUPLED

5s, 10s MODE

I

VOUT

500mA/DIV

0mA

5s MODE

3576 G07

V

= 5V

20μs/DIV

BUS

OUT

= 3.65V

CHARGER OFF

50

10s MODE

10

1000

100

2.7

3.9

4.2

3.0

3.3

3.6

LOAD CURRENT (mA)

BATTERY VOLTAGE (V)

3576 G08

3576 G09

3576fb

7

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

V_BUSQuiescent Current

vs V_BUSVoltage (Suspend)

V_OUTVoltage

vs Load Current in Suspend

V_BUSCurrent

vs Load Current in Suspend

60

50

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

V

= 5V

BUS

BAT = 3.3V

= 3.01k

HIGH POWER SUSPEND

R

CLPROG

40

30

HIGH POWER

SUSPEND

LOW POWER SUSPEND

20

10

0

LOW POWER SUSPEND

V

= 5V

BAT = 3.3V

BUS

R

= 3.01k

CLPROG

0

1

2

3

4

5

0

0.5

1.0

1.5

2.0

2.5

0

0.5

1.0

1.5

2.0

2.5

BUS VOLTAGE (V)

LOAD CURRENT (mA)

3576 G10

3576 G11

3576 G12

Battery Charge Current

vs V_OUTVoltage

V

_OUTVoltage vs Battery Voltage

Normalized Battery Charger Float

Voltage vs Temperature

(Charger Overprogrammed)

1.001

1.000

0.999

0.998

0.997

0.996

600

500

400

300

200

100

0

4.7

4.5

4.3

4.1

3.9

3.7

3.5

3.3

3.1

2.9

2.7

R

= 3.01k

V

I

R

= 5V

= 0V

CLPROG

PROG

5s MODE

BUS

VOUT

= 2k

= 3.01k

CLPROG

PROG

= 1k

5s MODE

1s MODE

3.65 3.70

3.40 3.45 3.50 3.55 3.60

3.75 3.80

–40

–15

10

35

60

85

2.7

3.0

3.3

3.6

3.9

4.2

V

(V)

OUT

TEMPERATURE (°C)

BATTERY VOLTAGE (V)

3576 G13

3576 G15

3576 G14

V_BUSQuiescent Current

vs Temperature

V_BUSQuiescent Current in

Suspend vs Temperature

Battery Drain Current

vs Temperature

60

50

35

30

25

20

15

10

5

25

20

15

10

5

V = 5V

BUS

V

= 5V

BUS

5s MODE

40

30

20

10

0

1s MODE

BAT = 3.8V

= 0V

V

BUS

SWITCHING

REGULATORS OFF

0

–40

–15

10

35

60

85

–40

–15

10

35

60

TEMPERATURE (°C)

85

–40

–15

10

35

60

85

TEMPERATURE (°C)

3576 G17

3576 G18

3576 G16

3576fb

8

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

OTG Boost Quiescent Current

vs V_OUTVoltage

OTG Boost Efﬁciency

vs Load Current

100

OTG Boost V_BUSVoltage

vs Load Current

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.3

2.1

1.9

1.7

1.5

1.3

1.1

0.9

0.7

0.5

90

80

70

60

V

= 4.75V

BUS

I

= 500mA

VBUS

V

= 5V

V

= 5V

OUT

= 4.4V

= 3.8V

= 3.2V

= 4.4V

= 3.8V

= 3.2V

50

40

2.90

3.55

4.20

(V)

4.85

5.50

0

100 200 300 400 500 600 700

LOAD CURRENT (mA)

1

10

LOAD CURRENT (mA)

100

1000

V

OUT

3576 G20

3576 G19

3576 G21

OTG Boost Start-Up Time into

Current Source Load

vs V_OUTVoltage

OTG Boost Efﬁciency

vs V_OUTVoltage

OTG Boost Burst Mode Current

Threshold vs V_OUTVoltage

400

300

200

100

0

2.50

2.25

2.00

1.75

95

90

85

80

75

70

500mA LOAD

100mA LOAD

22μF ON V , 22μF AND

BUS

LOAD THROUGH OVP

RISING THRESHOLD

FALLING THRESHOLD

22μF ON V

,

BUS

NO OVP

22μF ON V

,

BUS

LOAD THROUGH OVP

1.50

4.20

(V)

4.85

2.90

5.50

3.55

2.9

3.4

3.9

V

4.4

(V)

4.9

5.4

3.55

4.20

(V)

4.85

2.90

5.50

V

OUT

V

OUT

3576 G24

3576 G23

3576 G22

OTG Boost Start-Up into Current

Source Load

OTG Boost Transient Response

OTG Boost Burst Mode Operation

V

BUS

50mV/DIV

V

AC COUPLED

BUS

50mV/DIV

I

VBUS

AC COUPLED

200mA/DIV

V

SW

1V/DIV

0mA

I

VBUS

V

200mA/DIV

BUS

2V/DIV

0V

0mA

0V

3576 G26

3576 G27

3576 G25

V

I

= 3.8V

= 500mA

200μs/DIV

V

I

= 3.8V

= 10mA

50μs/DIV

V

= 3.8V

20μs/DIV

OUT

LOAD

OUT

LOAD

OUT

3576fb

9

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

Battery Charging from USB-HV

BUCK-USB

Oscillator Frequency

vs Temperature

USB OTG from BAT-HV BUCK-BAT

2.30

2.25

2.20

2.15

V

OUT

1V/DIV

AC COUPLED

V

BUS

100mV/DIV

200mV/DIV

AC COUPLED

V

SW

I

BAT

1A/DIV

5V/DIV

0V

0A

HVOK

5V/DIV

HVOK

5V/DIV

0V

V

= 5V

OUT

= 4.2V

= 3.6V

= 3V

0V

2.10

3576 G28

3576 G29

V

= 5V

500μs/DIV

V

I

= 3.8V

500μs/DIV

BUS

BAT

BUS

HV = 12V

IN

= 285mA

= 2.7V

USING LT3653

HV = 12V

IN

2.05

USING LT3653

–40

–15

10

35

60

85

TEMPERATURE (°C)

3576 G30

Rising OVP Threshold

vs Temperature

OVP Connect Waveform

OVP Disconnect Waveform

6.280

6.275

6.270

6.265

6.260

6.255

V

BUS

V

BUS

5V/DIV

OVGATE

5V/DIV

OVGATE

5V/DIV

OVP INPUT

VOLTAGE

5V TO 10V

STEP 5V/DIV

OVP INPUT

VOLTAGE

0V TO 5V

STEP 5V/DIV

3576 G32

3576 G31

500μs/DIV

–40

–15

10

35

60

85

TEMPERATURE (°C)

3576 G33

OVGATE Quiescent Current

vs Temperature

RST3, CHRG Pin Current

vs Voltage (Pull-Down State)

OVGATE vs OVSENS

12

10

37

35

33

31

29

27

100

80

60

40

20

0

V

= 5V

OVSENS CONNECTED

TO INPUT THROUGH

6.2k RESISTOR

V

= 5V

BUS

OVSENS

BAT = 3.8V

8

6

4

2

0

–15

10

35

60

85

0

1

2

3

4

5

0

2

4

6

8

–40

INPUT VOLTAGE (V)

TEMPERATURE (°C)

RST3, CHRG PIN VOLTAGE (V)

3576 G34

3576 G35

3576 G36

3576fb

10

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

3.3V LDO Output Voltage

vs Load Current, V_BUS= 0V

3.3V LDO Step Response

(5mA to 15mA)

Battery Drain Current

vs Battery Voltage

35

3.4

3.2

3.0

2.8

2.6

I

= 0mA

BAT = 3.4V

VOUT

BAT = 3.9V, 4.2V

BAT = 3.5V

BAT = 3.6V

30

I

LDO3V3

V

= 0V

BUS

5mA/DIV

25

20

15

10

5

0mA

V

LDO3V3

20mV/DIV

AC COUPLED

BAT = 3V

V

= 5V

BUS

BAT = 3.1V

BAT = 3.2V

BAT = 3.3V

3576 G38

(SUSPEND MODE)

BAT = 3.8V

20μs/DIV

0

2.7

3.0

3.3

3.6

4.2

3.9

0

5

10

15

20

25

BATTERY VOLTAGE (V)

LOAD CURRENT (mA)

3576 G39

3576 G37

Switching Regulator Soft-Start

Waveform

Switching Regulator Current Limit

vs Temperature

R_DS(ON)for Switching Regulator

Power Switches vs Temperature

2.0

1.5

1.0

0.5

0

1.0

0.8

0.6

0.4

0.2

0

REGULATOR 3

REGULATORS 1, 2

NMOS SWITCH

PMOS SWITCH

REGULATOR 3

REGULATORS 1, 2

NMOS SWITCH

PMOS SWITCH

3576 G40

50μs/DIV

V

= 3.8V

IN1,2,3

–40

–15

10

35

60

85

–40

–15

10

35

60

85

TEMPERATURE (°C)

3576 G42

3576 G41

Switching Regulators 1, 2

Pulse-Skipping Mode Efﬁciency

Switching Regulators 1, 2

Burst Mode Efﬁciency

Switching Regulator Low Power

Quiescent Currents vs Temperature

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

V

= 2.5V

V

= 3.8V

V

= 3.8V

OUT1,2

IN3

V

= 2.5V

OUT1,2

PULSE-SKIPPING MODE

V

= 1.2V

OUT1,2

V

= 1.2V

OUT1,2

= 1.8V

V

= 1.8V

OUT1,2

V

OUT1,2

Burst Mode OPERATION

LDO MODE

0.1

1

10

100

1000

0.1

1

10

100

1000

–40

–15

10

35

60

85

LOAD CURRENT (mA)

TEMPERATURE (°C)

3576 G44

3576 G45

3576 G43

3576fb

11

LTC3576/LTC3576-1

T = 25°C unless otherwise speciﬁed.

A

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Regulator Constant

Frequency Quiescent Currents

Switching Regulator 3

Pulse-Skipping Mode Efﬁciency

Switching Regulator 3

Burst Mode Efﬁciency

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

8

7

6

5

V

= 3.8V

V

= 2.5V

OUT3

V

= 3.8V

IN3

SWITCHING

REGULATOR 3

V

= 2.5V

OUT3

V

= 1.2V

OUT3

V

= 1.8V

OUT3

V

= 1.8V

OUT3

V

= 1.2V

OUT3

4

3

SWITCHING

REGULATORS 1, 2

2

1

0

–15

10

TEMPERATURE (°C)

60

0.1

1

10

100

1000

–40

85

35

0.1

1

10

100

1000

LOAD CURRENT (mA)

3576 G48

3576 G47

3576 G46

Switching Regulator Mode

Transition, Pulse-Skipping-LDO-

Pulse-Skipping

Switching Regulators 1, 2

Feedback Voltage vs Load Current

Switching Regulators 1, 2

Transient Response

0.820

V

Burst Mode

OPERATION

OUT3

V

0.815

0.810

OUT2

50mV/DIV

AC COUPLED

PULSE-SKIPPING MODE

0.805

0.800

I

OUT2

V

SW3

200mA/DIV

1V/DIV

0V

0mA

3576 G50

3576 G51

0.795

0.790

V

= 3.8V

50μs/DIV

IN2

OUT2

V

= 3.8V

50μs/DIV

IN3

= 3.4V

= 1.8V

OUT3

I

= 50mA

0.1

1

10

100

1000

LOAD CURRENT (mA)

3576 G49

Switching Regulator Mode

Transition, Pulse-Skipping–Burst

Mode Operation–Pulse-Skipping

Switching Regulator 3 Feedback

Voltage vs Load Current

Switching Regulator 3

Transient Response

0.810

0.805

0.800

V

OUT3

V

OUT3

50mV/DIV

AC COUPLED

50mV/DIV

Burst Mode

OPERATION

AC COUPLED

I

OUT3

V

500mA/DIV

SW3

1V/DIV

0V

PULSE-SKIPPING MODE

0mA

0.795

0.790

3576 G54

3576 G53

V

= 3.8V

50μs/DIV

V

= 3.8V

50μs/DIV

IN3

OUT3

= 1.8V

OUT3

I

= 100mA

0.1

1

10

100

1000

LOAD CURRENT (mA)

3576 G52

3576fb

12

LTC3576/LTC3576-1

PIN FUNCTIONS

CLPROG (Pin 1): USB Current Limit Program and Monitor

Pin. A 1% resistor from CLPROG to ground determines

the upper limit of the current drawn or sourced from the

be connected to V

and the drain should be connected

BUS

to the product’s DC input connector. In the absence of an

overvoltage condition, this pin is connected to an internal

chargepumpcapableofcreatingsufﬁcientoverdrivetofully

enhance the pass transistor. If an overvoltage condition is

detected, OVGATE is brought rapidly to GND to prevent

damage to the LTC3576/LTC3576-1. OVGATE works in

conjunction with OVSENS to provide this protection.

V

pins. A precise fraction, h

, of the V

CLPROG

cur-

BUS

rent is sent to the CLPROG pin when the PMOS switch of

the PowerPath switching regulator is on. The switching

regulator delivers power until the CLPROG pin reaches

1.18V in step-down mode and 1.15V in step-up mode.

When the switching regulator is in step-down mode,

CLPROG is used to regulate the average input current.

OVSENS (Pin 6): Overvoltage Protection Sense Input.

OVSENS should be connected through a 6.2k resistor to

the input power connector and the drain of an external

N-channel MOS pass transistor. When the voltage on this

Several V

current limit settings are available via user

BUS

input which will typically correspond to the 500mA and

100mA USB speciﬁcations. When the switching regulator

is in step-up mode (USB on-the-go), CLPROG is used to

limit the average output current to 680mA. A multilayer

ceramic averaging capacitor or R-C network is required

at CLPROG for ﬁltering.

pin exceeds

V

, the OVGATE pin will be pulled

OVCUTOFF

to GND to disable the pass transistor and protect the

LTC3576/LTC3576-1. The OVSENS pin shunts current

during an overvoltage transient in order to keep the pin

voltage at 6V.

LDO3V3 (Pin 2): 3.3V LDO Output Pin. This pin provides

FB1 (Pin 7): Feedback Input for Switching Regulator 1.

Whenregulator1’scontrolloopiscomplete,thispinservos

to 1 of 16 possible set points based on the commanded

a regulated always-on 3.3V supply voltage. LDO3V3

gets its power from V . It may be used for light loads

OUT

such as a watchdog microprocessor or real time clock.

A 1μF capacitor is required from LDO3V3 to ground. If

the LDO3V3 output is not used it should be disabled by

2

value from the I C serial port. See Table 4.

V

(Pin 8): Power Input for Switching Regulator 1.

IN1

This pin will generally be connected to V . A 1μF MLCC

connecting it to V

.

OUT

capacitor is recommended on this pin.

NTCBIAS (Pin 3): NTC Thermistor Bias Output. If NTC

operation is desired, connect a bias resistor between

NTCBIAS and NTC, and an NTC thermistor between NTC

and GND. To disable NTC operation, connect NTC to GND

and leave NTCBIAS open.

SW1 (Pin 9): Power Transmission Pin for Switching

Regulator 1.

EN1 (Pin 10): Logic Input. This logic input pin indepen-

dently enables switching regulator 1. Active high. This

pin is logically ORed with its corresponding bit in the

NTC (Pin 4): Input to the Thermistor Monitoring Circuits.

TheNTCpinconnectstoanegativetemperaturecoefﬁcient

thermistor,whichistypicallyco-packagedwiththebattery,

to determine if the battery is too hot or too cold to charge.

If the battery’s temperature is out of range, charging is

paused until it re-enters the valid range. A low drift bias

resistorisrequiredfromNTCBIAStoNTCandathermistor

is required from NTC to ground. To disable NTC operation,

connect NTC to GND and leave NTCBIAS open.

2

I C serial port. See Table 3. Has a 2μA internal pull-down

current source.

ENOTG (Pin 11): Logic Input. This logic input pin inde-

pendently enables the bidirectional switching regulator to

step up the voltage on V

and provide a 5V output on

OUT

V

for USB on-the-go applications. Active high. This

BUS

pin is logically ORed with its corresponding bit in the

2

I C serial port. See Table 3. Has a 2μA internal pull-down

current source.

OVGATE (Pin 5): Overvoltage Protection Gate Output.

Connect OVGATE to the gate pin of an external N-channel

MOS pass transistor. The source of the transistor should

3576fb

13

LTC3576/LTC3576-1

PIN FUNCTIONS

2

DV (Pin 12): Logic Supply for the I C Serial Port. If the

RST3 (Pin 21): Logic Output. This in an open-drain output

which indicates that switching regulator 3 has settled to

its ﬁnal value. It can be used as a power-on reset for the

primary microprocessor or to enable the other switching

regulators for supply sequencing.

CC

serial port is not needed, it can be disabled by grounding

2

DV . When DV is grounded, the I C bits are set to their

CC

default values. See Table 3.

2

SCL (Pin 13): Clock Input Pin for the I C Serial Port. The

2

I C logic levels are scaled with respect to DV . If DV

EN2 (Pin 22): Logic Input. This logic input pin indepen-

dently enables switching regulator 2. Active high. This

pin is logically ORed with its corresponding bit in the

CC

is grounded, the SCL pin is equivalent to the C2, C4 and

2

C6 bits in the I C serial port. SCL in conjunction with SDA

2

determine the operating modes of switching regulators 1,

I C serial port. See Table 3. Has a 2μA internal pull-down

2 and 3 when DV is grounded. See Tables 3 and 5. Has

current source.

CC

a 2μA internal pull-down current source.

SW2 (Pin 23): Power Transmission Pin for Switching

Regulator 2.

2

SDA (Pin 14): Data Input Pin for the I C Serial Port. The

2

I C logic levels are scaled with respect to DV . If DV

CC

V

(Pin 24): Power Input for Switching Regulator 2.

IN2

is grounded, the SDA pin is equivalent to the C3, C5 and

This pin will generally be connected to V . A 1μF MLCC

OUT

2

C7 bits in the I C serial port. SDA in conjunction with SCL

capacitor is recommended on this pin.

determine the operating modes of switching regulators 1,

FB2 (Pin 25): Feedback Input for Switching Regulator 2.

Whenregulator2’scontrolloopiscomplete,thispinservos

to 1 of 16 possible set points based on the commanded

2 and 3 when DV is grounded. See Tables 3 and 5. Has

CC

a 2μA internal pull-down current source.

NC (Pin 15): Unconnected Pin. This pin is not connected

2

value from the I C serial port. See Table 4.

internally to the part. It is permissible to tie this pin to V

IN3

V (Pin 26): Bat-Track External Switching Regulator

in order to make the V PCB trace wider.

C

IN3

Control Output. This pin drives the V pin of an external

C

V

IN3

(Pin 16): Power Input for Switching Regulator 3.

Linear Technology step-down switching regulator. An

This pin will generally be connected to V . A 1μF MLCC

OUT

external P-channel MOSFET is sometimes required to

capacitor is recommended on this pin.

provide power to V

with its gate tied to the ACPR pin

OUT

SW3 (Pin 17): Power Transmission Pin for Switching

(seetheApplicationsInformationsection). Inconcertwith

Regulator 3.

WALL and ACPR, it will regulate V

charger efﬁciency

to maximize battery

OUT

NC (Pin 18): Unconnected Pin. This pin is not connected

internally to the part. It is permissible to tie this pin to SW3

in order to make the SW3 PCB trace wider.

WALL(Pin27):ExternalPowerSourceSenseInput.WALL

should be connected to the output of the external high

voltage switching regulator and to the drain of an external

P-channel MOSFET if used. It is used to determine when

power is applied to the external regulator. When power

is detected, ACPR is driven low and the USB input is au-

tomatically disabled. Pulling this pin above 4.3V enables

EN3 (Pin 19): Logic Input. This logic input pin indepen-

dently enables switching regulator 3. Active high. This

pin is logically ORed with its corresponding bit in the

2

I C serial port. See Table 3. Has a 2μA internal pull-down

current source.

the V pin.

C

FB3 (Pin 20): Feedback Input for Switching Regulator 3.

Whenregulator3’scontrolloopiscomplete,thispinservos

to 1 of 16 possible set points based on the commanded

2

value from the I C serial port. See Table 4.

3576fb

14

LTC3576/LTC3576-1

PIN FUNCTIONS

BAT (Pin 32): Single Cell Li-Ion Battery Pin. Depending on

ACPR (Pin 28): External Power Source Present Output

(ActiveLow).ACPRindicatesthattheoutputoftheexternal

high voltage step-down switching regulator is suitable for

use by the LTC3576/LTC3576-1. It should be connected to

the gate of an external P-channel MOSFET whose source

available V

power, a Li-Ion battery on BAT will either

BUS

deliverpowertoV throughtheidealdiodeorbecharged

OUT

from V

via the battery charger.

OUT

V_OUT(Pin 33): Output Voltage of the Bidirectional

PowerPath Switching Regulator in step-down mode and

Input Voltage of the Battery Charger. The majority of the

portable product should be powered from V_OUT. The

LTC3576/LTC3576-1 will partition the available power

between the external load on V_OUTand the internal bat-

tery charger. Priority is given to the external load and any

extra power is used to charge the battery. An ideal diode

from BAT to V_OUTensures that V_OUTis powered even if

the load exceeds the allotted power from V_BUSor if the

V_BUSpower source is removed. In on-the-go mode, this

pin delivers power to V_BUSvia the SW pin. V_OUTshould

be bypassed with a low impedance ceramic capacitor.

is connected to V

and whose drain is connected to

OUT

WALL. ACPR has a high level of V

and a low level of

OUT

GND. The USB bidirectional switcher is disabled when

ACPR is low.

PROG (Pin 29): Charge Current Program and Charge Cur-

rent Monitor Pin. Connecting a 1% resistor from PROG

to ground programs the charge current. If sufﬁcient input

powerisavailableinconstant-currentmode,thispinservos

to 1V. The voltage on this pin always represents the actual

charge current by using the following formula:

V_PROG

R_PROG

I_BAT

=

•1030

V

(Pins 34, 35): Power Pins. These pins deliver power

OUT

BUS

to V

via the SW pin by drawing controlled current from

CHRG (Pin 30): Open-Drain Charge Status Output. The

CHRG pin indicates the status of the battery charger.

Four possible charger states are represented by CHRG:

charging, not charging, unresponsive battery and battery

temperature out of range. In addition, CHRG is used to

a DC source such as a USB port or DC output wall adapter.

In on-the-go mode these pins provide power to external

loads.TiethetwoV

pinstogetheratthepartandbypass

BUS

with a low impedance multilayer ceramic capacitor.

indicate whether there is a short-circuit condition on V

BUS

SW (Pin 36): The SW pin transfers power between V

BUS

when the bidirectional switching regulator is in step-up

mode (on-the-go). CHRG is modulated at 35kHz and

switches between a low and a high duty cycle for easy

recognition by either humans or microprocessors. See

Table 1. CHRG requires a pull-up resistor and/or LED to

provide indication.

and V

via the bidirectional switching regulator. See

OUT

the Applications Information section for a discussion of

inductance value and current rating.

I

,I

(Pins37,38):I

andI

controlthecurrent

LIM0 LIM1

LIM0

LIM1

limit of the PowerPath switching regulator. See Table 1.

Both the I

and I

pins are logically ORed with their

LIM0

LIM1

2

IDGATE (Pin 31): Ideal Diode Ampliﬁer Output. This pin

correspondingbitsintheI Cserialport.SeeTables3and6.

Each has a 2μA internal pull-down current source.

controlsthegateofanoptionalexternalP-channelMOSFET

used as an ideal diode between V

and BAT. The external

OUT

Exposed Pad (Pin 39): Ground. The Exposed Pad should

be connected to a continuous ground plane on the second

layer of the printed circuit board by several vias directly

under the LTC3576/LTC3576-1.

idealdiodeoperatesinparallelwiththeinternalidealdiode.

ThesourceoftheP-channelMOSFETshouldbeconnected

to V

and the drain should be connected to BAT. If the

OUT

external ideal diode MOSFET is not used, IDGATE should

be left ﬂoating.

3576fb

15

LTC3576/LTC3576-1

BLOCK DIAGRAM

V

C

26

OVSENS

OVGATE

6

OVP

5

27 WALL

V

WALL

DETECT

C

V

35

34

BUS

CONTROL

ACPR

28

2.25MHz

BIDIRECTIONAL

PowerPath

SWITCHING

REGULATOR

SW

36

2

LDO3V3

3.3V LDO

SUSPEND LDO

V

33

31

OUT

500μA/2.5mA

+

–

+

–

IDGATE

IDEAL

CC/CV

CLPROG

1

–

CHARGER

+

–

+

5.1V

NTCBIAS

NTC

3

4

BATTERY

TEMPERATURE

MONITOR

15mV

0.3V

–

+

–

+

BAT

32

29

3.6V

1.18V

OR 1.15V

PROG

CHRG 30

CHARGE

STATUS

V

8

9

IN1

ENABLE

SW1

FB1

400mA 2.25MHz

BUCK

D/A

REGULATOR

7

4

V

24

IN2

ENABLE

23 SW2

400mA 2.25MHz

BUCK

REGULATOR

FB2

25

16

4

I

LIM

DECODE

LOGIC

V

IN3

ENABLE

17 SW3

1A 2.25MHz

BUCK

REGULATOR

I

37

38

LIM0

FB3

20

21

I

LIM1

4

RST3

ENOTG 11

EN1 10

EN2 22

EN3 19

DV 12

CC

2

SDA 14

SCL 13

I C PORT

39

3576 BD

GND

3576fb

16

LTC3576/LTC3576-1

TIMING DIAGRAM

SDA

t

SU,DAT

SU,STA

BUF

t

SU,STO

t

LOW

HD,STA

HD,DAT

3208 F05

SCL

t

SP

t

HIGH

HD,STA

START

CONDITION

REPEATED START

CONDITION

STOP

CONDITION

START

CONDITION

t

r

t

f

I²C WRITE PROTOCOL

WRITE ADDRESS

R/W

SUB-ADDRESS

INPUT DATA BYTE

0

1

0

1

0

A7

1

A6

2

A5

3

A4

A3

A2

6

A1

7

A0

8

B7

1

B6

2

B5

B4

B3

B2

B1

7

B0

START

STOP

SDA

SCL

0

1

0

8

ACK

9

ACK

9

ACK

9

1

2

3

4

5

6

7

4

5

3

4

5

6

8

3576 I2C

3576fb

17

LTC3576/LTC3576-1

OPERATION

Introduction

For automotive, ﬁrewire, and other high voltage applica-

tions,theLTC3576/LTC3576-1provideBat-Trackcontrolof

anexternalLTCstep-downswitchingregulatortomaximize

battery charger efﬁciency and minimize heat production.

WhenpowerisavailablefromboththeUSBandanauxiliary

input, the auxiliary input is given priority.

TheLTC3576/LTC3576-1arehighlyintegratedpowerman-

agement ICs designed to make optimal use of the power

availablefromavarietyofsources,whileminimizingpower

dissipation and easing thermal budgeting constraints.

They include a high efﬁciency bidirectional PowerPath

switching regulator, a controller for an external high volt-

age step-down switching regulator, a battery charger, an

ideal diode, an always-on LDO, an overvoltage protection

circuit and three general purpose step-down switching

regulators. The entire chip is controlled by either direct

The LTC3576/LTC3576-1 contain both an internal 180mΩ

ideal diode as well as an ideal diode controller for use

with an optional external P-channel MOSFET. The ideal

diode(s) from BAT to V

guarantee that ample power

even if there is insufﬁcient or

OUT

is always available to V

absent power at V

OUT

2

digital control or by an I C serial port or both.

or WALL.

BUS

The innovative PowerPath architecture ensures that the

applicationispoweredimmediatelyafterexternalvoltageis

applied,evenwithacompletelydeadbattery,byprioritizing

power to the application.

An always-on LDO provides a regulated 3.3V from avail-

able power at V . Drawing very little quiescent current,

OUT

this LDO will be on at all times and can be used to supply

20mA.

When acting as a step-down converter, the LTC3576/

LTC3576-1’s bidirectional switching regulator takes

power from USB, wall adapters, or other 5V sources and

provides power to the application and efﬁciently charges

the battery using Bat-Track. Because power is conserved

TheLTC3576/LTC3576-1featureanovervoltageprotection

circuit which is designed to work with an external N-chan-

nel MOSFET to prevent damage to their inputs caused by

accidental application of high voltage.

To prevent battery drain when a device is connected to a

the LTC3576/LTC3576-1 allow the load current on V

to

OUT

suspended USB port, an LDO from V

to V

provides

BUS

OUT

exceed the current drawn by the USB port making maxi-

mumuseoftheallowableUSBpowerforbatterycharging.

For USB compatibility the switching regulator includes

a precision average input current limit. The PowerPath

switching regulator and battery charger communicate to

ensure that the average input current never exceeds the

USB speciﬁcations.

either low power or high power USB suspend current to

the application.

The three general purpose switching regulators can be

independently enabled either by direct digital control or

2

by operating the I C serial port. Under I C control, all

three switching regulators have adjustable set points so

that voltages can be reduced when high processor perfor-

manceisnotneeded. AlongwithconstantfrequencyPWM

mode, all three switching regulators have automatic Burst

Mode operation and LDO modes for signiﬁcantly reduced

quiescent current under light load conditions.

Additionally, the bidirectional switching regulator can also

operate as a 5V synchronous step-up converter taking

power from V

and delivering up to 500mA to V

OUT

BUS

without the need for any additional external components.

This enables systems with USB dual-role transceivers to

function as USB on-the-go dual-role devices. True output

disconnect and average output current limit features are

included for short-circuit protection.

3576fb

18

LTC3576/LTC3576-1

OPERATION

Bidirectional PowerPath Switching Regulator—

Step-Down Mode

If the combined external load plus battery charge current

is large enough to cause the switching regulator to reach

the programmed input current limit, the battery charger

will reduce its charge current by precisely the amount

necessary to enable the external load to be satisﬁed. Even

if the battery charge current is programmed to exceed the

allowable USB current, the USB speciﬁcation for average

input current will not be violated; the battery charger will

reduce its current as needed. Furthermore, if the load cur-

The power delivered from V

to V

is controlled by

BUS

OUT

a 2.25MHz constant frequency bidirectional switching

regulator operating in step-down mode. V drives the

OUT

combination of the external load (step-down switching

regulators 1, 2 and 3) and the battery charger. To meet the

maximum USB load speciﬁcation, the switching regulator

contains a measurement and control system that ensures

that the average input current remains below the level

programmed at CLPROG.

rent at V

exceeds the programmed power from V

,

OUT

BUS

load current will be drawn from the battery via the ideal

diode(s) even when the battery charger is enabled.

If the combined load does not cause the switching regu-

lator to reach the programmed input current limit, V

will track approximately 0.3V above the battery voltage.

By keeping the voltage across the battery charger at this

low level, power lost to the battery charger is minimized.

Figure 1 shows the power ﬂow in step-down mode.

ThecurrentoutofCLPROGisaprecisefractionoftheV

BUS

OUT

current. When a programming resistor and an averaging

capacitor are connected from CLPROG to GND, the volt-

age on CLPROG represents the average input current of

the switching regulator. As the input current approaches

the programmed limit, CLPROG reaches 1.18V and power

delivered by the switching regulator is held constant.

TO AUTOMOTIVE,

FIREWIRE, ETC.

HIGH VOLTAGE

V

SW

FB

IN

STEP-DOWN

SWITCHING

REGULATOR

C

26

27

V

C

WALL

OVERVOLTAGE PROTECTION

OVSENS

OVGATE

–

+

–

+

V

6

5

OUT

3.6V

BAT + 0.3V 4.3V

ACPR

–

+

28

6V

s2

+

–

Bat-Track HV CONTROL

3.5V TO

(BAT + 0.3V)

TO SYSTEM LOAD

TO USB

OR WALL

ADAPTER

V

SW

BUS

35

34

36

33

V

BUS

V

OUT

PWM AND

GATE DRIVE

V

BUS

IDEAL

VOLTAGE

DIODE

CONTROLLER

+

–

IDGATE

OPTIONAL EXTERNAL

IDEAL DIODE PMOS

I

/N

CONSTANT CURRENT

CONSTANT VOLTAGE

BATTERY CHARGER

SWITCH

OmV

31

32

–

+

5V

+

15mV

–

+

–

+

0.3V

CLPROG

1.18V

1

BAT

+

–

3.6V

AVERAGE V

CURRENT LIMIT

CONTROLLER

INPUT

V

VOLTAGE

BUS

OUT

CONTROLLER

+

SINGLE CELL

Li-Ion

3576 F01

USB INPUT

BATTERY POWER

HV INPUT

Figure 1. PowerPath Block Diagram—Power Available from USB/Wall Adapter

3576fb

19

LTC3576/LTC3576-1

OPERATION

4.5

4.2

3.9

3.6

3.3

3.0

2.7

2.4

The input current limit is programmed by the I

and

LIM0

2

I

pins or by the I C serial port. The input current limit

LIM1

has ﬁve possible settings ranging from the USB suspend

limit of 500μA up to 1A for wall adapter applications. Two

of these settings are speciﬁcally intended for use in the

100mA and 500mA USB applications. Refer to Table 1 for

current limit settings using the I

Table 6 for current limit settings using the I C port.

NO LOAD

300mV

and I

pins and

LIM0

LIM1

2

Table 1. USB Current Limit Settings Using I_LIM0and I_LIM1

I

USB SETTING

LIM1

LIM0

3.6

4.2

2.4

2.7

3.0

3.3

3.9

0

BAT (V)

1× Mode (USB 100mA Limit)

10× Mode (Wall 1A Limit)

Low Power Suspend (USB 500μA Limit)

5× Mode (USB 500mA Limit)

3576 F02

0

1

0

1

Figure 2. V_OUTvs BAT

For very low-battery voltages, the battery charger acts like

a load and, due to limited input power, its current will tend

When the switching regulator is activated, the average

input current will be limited by the CLPROG programming

resistor according to the following expression:

to pull V

OUT

below the 3.6V instant-on voltage. To prevent

from falling below this level, an undervoltage circuit

OUT

V

automatically detects that V

is falling and reduces the

OUT

V_CLPROG

R_CLPROG

I_VBUS=I_VBUSQ

where I

LTC3576-1, V

current limit, R

+

• h

(

+1

battery charge current as needed. This reduction ensures

that load current and voltage are always prioritized while

allowing as much battery charge current as possible. See

Battery Charger Over Programming in the Applications

Information section.

)

CLPROG

is the quiescent current of the LTC3576/

CLPROG

VBUSQ

is the CLPROG servo voltage in

is the value of the programming

is the ratio of the measured cur-

CLPROG

The voltage regulation loop is compensated by the ca-

resistor and h

rent at V

CLPROG

pacitance on V . A 10μF MLCC capacitor is required

to the sample current delivered to CLPROG.

OUT

BUS

for loop stability. Additional capacitance beyond this value

Refer to the Electrical Characteristics table for values of

, V and I . Given worst-case circuit

will improve transient response.

h

CLPROG CLPROG

VBUSQ

tolerances, the USB speciﬁcation for the average input

current in 100mA or 500mA mode will not be violated,

AninternalundervoltagelockoutcircuitmonitorsV and

BUS

rises above

keeps the switching regulator off until V

BUS

provided that R

is 3.01k or greater.

CLPROG

4.30V and is about 200mV above the battery voltage.

Hysteresis on the UVLO turns off the regulator if V

While not in current limit, the switching regulator’s

Bat-Track feature will set V to approximately 300mV

BUS

falls below 4V or to within 50mV of the battery voltage.

OUT

When this happens, system power at V

from the battery via the ideal diode(s).

will be drawn

above the voltage at BAT. However, if the voltage at BAT

OUT

is below 3.3V, and the load requirement does not cause

the switching regulator to exceed its current limit, V

OUT

Bidirectional PowerPath Switching Regulator—

Step-Up Mode

will regulate at a ﬁxed 3.6V as shown in Figure 2. This

instant-on operation will allow a portable product to run

immediatelywhenpowerisappliedwithoutwaitingforthe

battery to charge. If the load does exceed the current limit

For USB on-the-go applications, the bidirectional

PowerPathswitchingregulatoractsasastep-upconverter

at V , V

will range between the no-load voltage and

todeliverpowerfromV

toV .ThepowerfromV

BUS OUT

OUT

BUS OUT

slightly below the battery voltage, indicated by the shaded

region of Figure 2.

can come from the battery or the output of the external

3576fb

20

LTC3576/LTC3576-1

OPERATION

TO AUTOMOTIVE,

FIREWIRE, ETC.

HIGH VOLTAGE

STEP-DOWN

SWITCHING

REGULATOR

V

SW

FB

IN

C

26

27

V

WALL

C

OVERVOLTAGE PROTECTION

OVSENS

–

+

–

+

V

6

5

OUT

3.6V

BAT + 0.3V 4.3V

ACPR

–

+

28

6V

OVGATE

s2

+

–

Bat-Track HV CONTROL

3.5V TO

(BAT + 0.3V)

TO SYSTEM LOAD

V

SW

OUT

BUS

TO USB

CABLE

35

34

36

33

V

BUS

V

PWM AND

GATE DRIVE

V

BUS

IDEAL

VOLTAGE

DIODE

CONTROLLER

+

–

IDGATE

OPTIONAL EXTERNAL

IDEAL DIODE PMOS

I

/N

CONSTANT CURRENT

CONSTANT VOLTAGE

BATTERY CHARGER

SWITCH

OmV

31

32

–

+

–

5V

+

15mV

–

+

–

+

0.3V

CLPROG

1.15V

1

BAT

+

–

3.6V

AVERAGE V

CURRENT LIMIT

CONTROLLER

OUTPUT

V

VOLTAGE

BUS

OUT

CONTROLLER

+

SINGLE CELL

Li-Ion

3576 F03

BATTERY POWER

HV INPUT

Figure 3. PowerPath Block Diagram—USB On-the-Go

transient response. The V

3% load regulation up to an output current of 500mA. At

light loads, the switching regulator goes into Burst Mode

operation. The regulator will deliver power to V

reaches 5.1V after which the NMOS and PMOS switches

shut off. The regulator delivers power again to V

it falls below 5.1V.

voltage has approximately

high voltage switching regulator. As a step-up converter,

the bidirectional switching regulator produces 5V on

BUS

V

and is capable of delivering at least 500mA. USB

until it

on-the-go can be enabled by either the external control

BUS

2

pin, ENOTG, or via I C. Figure 3 shows the power ﬂow

once

in step-up mode.

BUS

An undervoltage lockout circuit monitors V

and pre-

OUT

The switching regulator features both peak inductor and

average output current limit. The peak current mode

architecture limits peak inductor current on a cycle-by-

vents step-up conversion until V

rises above 2.8V. To

OUT

preventbackdrivingofV

wheninputpowerisavailable,

BUS

the V

undervoltage lockout circuit prevents step-up

BUS

cycle basis. The peak current limit is equal to V /2ꢀ to

conversion if V

is greater than 4.3V at the time step-up

BUS

a maximum of 1.8A so that in the event of a sudden short

circuit, the current limit will fold back to a lower value.

In step-up mode, the voltage on CLPROG represents the

average output current of the switching regulator when

a programming resistor and an averaging capacitor are

connected from CLPROG to GND. With a 3.01k resistor

on CLPROG, the bidirectional switching regulator has an

output current limit of 680mA. As the output current ap-

mode is enabled. The switching regulator is also designed

to allow true output disconnect by eliminating body diode

conduction of the internal PMOS switch. This allows V

BUS

to go to zero volts during a short-circuit condition or while

shut down, drawing zero current from V

.

OUT

The voltage regulation loop is compensated by the capaci-

tance on V . A 4.7μF MLCC is required for loop stability.

BUS

Additional capacitance beyond this value will improve

3576fb

21

LTC3576/LTC3576-1

OPERATION

proachesthislimitCLPROGservosto1.15VandV

falls

WALL will rise toward this programmed output voltage.

WhenWALLexceedsapproximately4.3V,ACPRisbrought

low and the Bat-Track control of the LTC3576/LTC3576-1

BUS

there may not

rapidly to V . When V

is close to V

OUT

BUS

OUT

be sufﬁcient negative slope on the inductor current when

the PMOS switch is on to balance the rise in the inductor

current when the NMOS switch is on. This will cause the

inductor current to run away and the voltage on CLPROG

to rise. When CLPROG reaches 1.2V the switching of the

overdrives the local V control of the external high volt-

C

age step-down switching regulator. Therefore, once the

Bat-Track control is enabled, the output voltage is set in-

dependent of the switching regulator feedback network.

synchronous PMOS is terminated and V

is applied

OUT

Bat-Trackcontrolprovidesasigniﬁcantefﬁciencyadvantage

over the simple use of a 5V switching regulator output to

statically to its gate. This ensures that the inductor current

will have sufﬁcient negative slope during the time current

is ﬂowing to the output. The PMOS will resume switching

when CLPROG drops down to 1.15V.

drive the battery charger. With a 5V output driving V

battery charger efﬁciency is approximately:

,

OUT

V

5V

BAT

η_TOTAL= η_BUCK

•

TheLTC3576/LTC3576-1maintainvoltageregulationeven

if V

is above V . This is achieved by disabling the

OUT

BUS

PMOS switch. The PMOS switch is enabled when V

BUS

where

η

BUCK

istheefﬁciencyofthehighvoltageswitching

rises above V

below V

+ 180mV and is disabled when it falls

OUT

regulator and 5V is the output voltage of the switching

regulator. With a typical switching regulator efﬁciency of

87% and a typical battery voltage of 3.8V, the total bat-

tery charger efﬁciency is approximately 66%. Assuming

a 1A charge current, 1.7W of power is dissipated just to

charge the battery!

+ 70mV to prevent the inductor current from

OUT

running away when not in current limit. Since the PMOS

no longer acts as a low impedance switch in this mode,

there will be more power dissipation within the IC. This

will cause a sharp drop in efﬁciency.

If V

is less than 4V and the PMOS switch is disabled

BUS

With Bat-Track, battery charger efﬁciency is approxi-

mately:

for more than 7.2ms a short-circuit fault will be declared

and the part will shut off. The CHRG pin will blink at 35kHz

with a duty cycle that varies between 12% and 88% at a

4Hz rate. See Table 2. To re-enable step-up mode, the

ENOTG pin or, with ENOTG grounded, the B0 bit in the

V

BAT

η_TOTAL= η_BUCK

•

V

_BAT+ 0.3V

2

With the same assumptions as above, the total battery

charger efﬁciency is approximately 81%. This example

works out to less than 1W of power dissipation, or almost

60% less heat.

I C port must be cycled low and then high.

Bat-Track Auxiliary High Voltage Switching Regulator

Control

See the Typical Applications section for complete circuits

using the LT3480 and the LT3653 with Bat-Track control.

The WALL, ACPR and

V pins can be used in conjunction

C

with an external high voltage step-down switching regula-

tor such as the LT^®3480 or the LT3653 to minimize heat

production when operating from higher voltage sources,

as shown in Figures 1 and 3. Bat-Track control circuitry

regulatestheexternalswitchingregulator’soutputvoltage

to the larger of (BAT + 300mV) or 3.6V. This maximizes

battery charger efﬁciency while still allowing instant-on

operation when the battery is deeply discharged.

Ideal Diode(s) from BAT to V

OUT

TheLTC3576/LTC3576-1eachhaveaninternalidealdiodeas

wellasacontrollerforanoptionalexternalidealdiode.Both

the internal and the external ideal diodes are always on and

will respond quickly whenever V

drops below BAT.

OUT

If the load current increases beyond the power allowed

from the switching regulator, additional power will be

pulled from the battery via the ideal diode(s). Further-

Thefeedbacknetworkofthehighvoltageregulatorshould

be set to generate an output voltage between 4.5V and

5.5V.Whenhighvoltageisappliedtotheexternalregulator,

more, if power to V

(USB or wall adapter) is removed,

BUS

3576fb

22

LTC3576/LTC3576-1

OPERATION

2200

2000

1800

1600

1400

1200

copy of the V

current to the CLPROG pin, which will

BUS

VISHAY Si2333

OPTIONAL EXTERNAL

IDEAL DIODE

servo to approximately 100mV in this mode. To remain

compliant with the USB speciﬁcation, the input to the LDO

is current limited so that it will not exceed the low power

LTC3576/

LTC3576-1

IDEAL DIODE

or high power suspend speciﬁcation. If the load on V

OUT

1000

800

600

400

200

0

exceeds the suspend current limit, the additional current

will come from the battery via the ideal diode(s).

ON

SEMICONDUCTOR

MBRM120LT3

3.3V Always-On LDO Supply

The LTC3576/LTC3576-1 include a low quiescent current

low dropout regulator that is always powered. This LDO

can be used to provide power to a system pushbutton

controller, standby microcontroller or real time clock. De-

signed to deliver up to 20mA, the always-on LDO requires

at least a 1ꢁF low impedance ceramic bypass capacitor

0

120 180 240 300 360 420 480

60

FORWARD VOLTAGE (mV) (BAT – V

)

OUT

3576 F04

Figure 4. Ideal Diode V-I Characteristics

then all of the application power will be provided by the

battery via the ideal diodes. The ideal diode(s) will be fast

for compensation. The LDO is powered from V , and

therefore will enter dropout at loads less than 20mA as

OUT

enough to keep V

from drooping with only the stor-

OUT

age capacitance required for the switching regulator. The

internal ideal diode consists of a precision ampliﬁer that

activates a large on-chip P-channel MOSFET whenever

V

falls near 3.3V. If the LDO3V3 output is not used, it

OUT

should be disabled by connecting it to V

.

OUT

the voltage at V

is approximately 15mV (V

) below

Battery Charger

OUT

FWD

the voltage at BAT. Within the ampliﬁer’s linear range, the

small-signal resistance of the ideal diode will be quite low,

keeping the forward drop near 15mV. At higher current

levels, the MOSFET will be in full conduction.

The LTC3576/LTC3576-1 include a constant-current/con-

stant-voltage battery charger with automatic recharge,

automatic termination by safety timer, low voltage trickle

charging, bad cell detection and thermistor sensor input

for out-of-temperature charge pausing.

To supplement the internal ideal diode, an external

P-channel MOSFET may be added from BAT to V . The

OUT

Battery Preconditioning

IDGATE pin of the LTC3576/LTC3576-1 drives the gate of

the external P-channel MOSFET for automatic ideal diode

control. The source of the external P-channel MOSFET

When a battery charge cycle begins, the battery charger

ﬁrst determines if the battery is deeply discharged. If the

should be connected to V

and the drain should be con-

OUT

batteryvoltageisbelowV ,typically2.85V,anautomatic

TRKL

nected to BAT. Capable of driving a 1nF load, the IDGATE

pin can control an external P-channel MOSFET transistor

having an on-resistance of 30mΩ or lower.

trickle charge feature sets the battery charge current to

10% of the programmed value. If the low voltage persists

for more than 1/2 hour, the battery charger automatically

terminates and indicates via the CHRG pin that the battery

was unresponsive.

Suspend LDO

IftheLTC3576/LTC3576-1areconﬁguredforUSBsuspend

mode,thebidirectionalswitchingregulatorisdisabledand

Oncethebatteryvoltageisabove2.85V,thechargerbegins

charging in full power constant-current mode. The cur-

thesuspendLDOprovidespowertotheV

pin(presum-

OUT

rent delivered to the battery will try to reach 1030/R

.

PROG

ingthereispoweravailabletoV ). ThisLDOwillprevent

BUS

Depending on available input power and external load

conditions, the battery charger may or may not be able

to charge at the full programmed rate. The external load

will always be prioritized over the battery charge current.

the battery from running down when the portable product

has access to a suspended USB port. Regulating at 4.6V,

thisLDOonlybecomesactivewhentheswitchingconverter

isdisabled (suspended). Thesuspend LDOsendsa scaled

3576fb

23

LTC3576/LTC3576-1

OPERATION

Likewise, the USB current limit programming will always

be observed and only additional power will be available to

charge the battery. When system loads are light, battery

charge current will be maximized.

Ineithertheconstant-currentorconstant-voltagecharging

modes, the voltage at the PROG pin will be proportional to

the actual charge current delivered to the battery. There-

fore, the actual charge current can be determined at any

time by monitoring the PROG pin voltage and using the

following equation:

Charge Termination

The battery charger has a built-in safety timer. When the

voltage on the battery reaches the pre-programmed ﬂoat

voltage, the battery charger will regulate the battery volt-

age and the charge current will decrease naturally. Once

the battery charger detects that the battery has reached

the ﬂoat voltage, the four hour safety timer is started.

After the safety timer expires, charging of the battery will

discontinue and no more current will be delivered.

V_PROG

R_PROG

I_BAT

=

•1030

In many cases, the actual battery charge current, I , will

BAT

belowerthanI

duetolimitedinputpoweravailableand

CHG

prioritization with the system load drawn from V

.

OUT

The Battery Charger Flow Chart illustrates the battery

charger’s algorithm.

Automatic Recharge

Charge Status Indication

After the battery charger terminates, it will remain off

drawing only microamperes of current from the battery.

If the portable product remains in this state long enough,

thebatterywilleventuallyselfdischarge.Toensurethatthe

batteryisalwaystoppedoff,achargecyclewillautomatically

begin when the battery voltage falls below the recharge

threshold which is typically 100mV less than the charger’s

ﬂoat voltage. In the event that the safety timer is running

whenthebatteryvoltagefallsbelowtherechargethreshold,

it will reset back to zero. To prevent brief excursions below

the recharge threshold from resetting the safety timer, the

battery voltage must be below the recharge threshold for

more than 1ms. The charge cycle and safety timer will

The CHRG pin indicates the status of the battery charger.

Four possible states are represented by CHRG which

include charging, not charging, unresponsive battery and

battery temperature out of range.

The signal at the CHRG pin can be easily recognized as

one of the above four states by either a human or a mi-

croprocessor. An open-drain output, the CHRG pin can

drive an indicator LED through a current limiting resistor

for human interfacing or simply a pull-up resistor for

microprocessor interfacing.

To make the CHRG pin easily recognized by both humans

and microprocessors, the pin is either low for charging,

high for not charging, or it is switched at high frequency

(35kHz) to indicate the two possible faults, unresponsive

battery and battery temperature out of range.

also restart if the V

UVLO cycles low and then high

BUS

(e.g., V

is removed and then replaced), or if the battery

BUS

2

charger is cycled on and off by the I C port.

Charge Current

When charging begins, CHRG is pulled low and remains

low for the duration of a normal charge cycle. When

charging is complete, i.e., the BAT pin reaches the ﬂoat

voltage and the charge current has dropped to one-tenth

oftheprogrammedvalue, theCHRGpinisreleased(Hi-Z).

If a fault occurs, the pin is switched at 35kHz. While

switching, its duty cycle is modulated between a high

and low value at a very low frequency. The low and high

duty cycles are disparate enough to make an LED appear

to be on or off thus giving the appearance of “blinking”.

The charge current is programmed using a single resis-

tor from PROG to ground. 1/1030th of the battery charge

current is sent to PROG which will attempt to servo to

1.000V. Thus, the battery charge current will try to reach

1030 times the current in the PROG pin. The program

resistor and the charge current are calculated using the

following equation:

V_PROG

R_PROG

I_CHG

=

•1030

3576fb

24

LTC3576/LTC3576-1

OPERATION

Battery Charger Flow Chart

POWER ON/

ENABLE CHARGER

CLEAR EVENT TIMER

ASSERT CHRG LOW

YES

NTC OUT OF RANGE

NO

INHIBIT CHARGING

PAUSE EVENT TIMER

BAT < 2.85V

BAT > V

– E

FLOAT

BATTERY STATE

2.85V < BAT < V

– E

FLOAT

YES

CHRG CURRENTLY

HIGH-Z

CHARGE WITH

FIXED VOLTAGE

(V

CHARGE AT

100V/R (C/10 RATE)

CHARGE AT

1030V/R

PROG

RATE

PROG

)

FLOAT

NO

INDICATE

NTC FAULT

AT CHRG

RUN EVENT TIMER

PAUSE EVENT TIMER

RUN EVENT TIMER

TIMER > 4 HOURS

NO

TIMER > 30 MINUTES

YES

NO

INHIBIT CHARGING

STOP CHARGING

I

< C/10

YES

BAT

YES

BAT RISING

THROUGH

RECHRG

INDICATE BATTERY

FAULT AT CHRG

CHRG HIGH-Z

V

NO

BAT FALLING

THROUGH

RECHRG

NO

YES

BAT > 2.85V

YES

BAT < V

RECHRG

V

YES

NO

3576 FLOW

3576fb

25

LTC3576/LTC3576-1

OPERATION

Each of the two faults has its own unique “blink” rate for

human recognition as well as two unique duty cycles for

machine recognition.

In addition to charge status, the CHRG pin is also used

to indicate whether there is a short-circuit condition on

V

when the bidirectional switching regulator is in on-

BUS

the-go mode. When a short-circuit condition is detected,

CHRG will blink with the same modulation frequency and

duty cycle as a bad battery fault. If the charger is on at the

same time that on-the-go is enabled, a 4Hz modulation of

12% and 88% duty cycles on CHRG could indicate a bad

The CHRG pin does not respond to the C/10 threshold

if the LTC3576/LTC3576-1 is in V

current limit. This

BUS

preventsfalseendofchargeindicationsduetoinsufﬁcient

power available to the battery charger.

Table 2 illustrates the four possible states of the CHRG

pin when the battery charger is active.

battery or a short-circuit fault on V . System software

BUS

should turn off the charger or on-the-go to determine

which fault has occurred.

Table 2. CHRG Signal

MODULATION

Although very improbable, it is possible that a duty cycle

reading could be taken at the bright-dim transition (low

duty cycle to high duty cycle). When this happens the

duty cycle reading will be precisely 50%. If the duty cycle

reading is 50%, system software should disqualify it and

take a new duty cycle reading.

STATUS

Charging

FREQUENCY (BLINK) FREQUENCY

DUTY CYCLES

100%

0Hz

0Hz (Low-Z)

0Hz (Hi-Z)

Not Charging

NTC Fault

0%

35kHz

1Hz at 50%

4Hz at 50%

6%, 94%

12%, 88%

Bad Battery

or On-The-Go

Short-Circuit

Fault

NTC Thermistor

The battery temperature is measured by placing a nega-

tive temperature coefﬁcient (NTC) thermistor close to the

battery pack.

An NTC fault is represented by a 35kHz pulse train whose

duty cycle alternates between 6% and 94% at a 1Hz rate. A

human will easily recognize the 1Hz rate as a “slow” blink-

ing which indicates the out-of-range battery temperature

while a microprocessor will be able to decode either the

6% or 94% duty cycles as an NTC fault.

To use this feature connect the NTC thermistor, R , be-

NTC

tween the NTC pin and ground and a bias resistor, R

,

NOM

from NTCBIAS to NTC. R

should be a 1% 200ppm

NOM

resistor with a value equal to the value of the chosen NTC

thermistor at 25°C (R25).

If a battery is found to be unresponsive to charging (i.e.,

its voltage remains below 2.85V for 1/2 hour), the CHRG

pin gives the bad battery fault indication. For this fault, a

human would easily recognize the 4Hz “fast” blink of the

LEDwhileamicroprocessorwouldbeabletodecodeeither

the 12% or 88% duty cycles as a bad battery fault.

The LTC3576/LTC3576-1 pauses charging when the re-

sistance of the NTC thermistor drops to 0.54 times the

value of R25 or approximately 54k for a 100k thermistor.

For a Vishay Curve 1 thermistor, this corresponds to ap-

proximately 40°C. If the battery charger is in constant

voltage (ﬂoat) mode, 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 LTC3576/LTC3576-1 are also designed to pause

charging when the value of the NTC thermistor increases

to 3.25 times the value of R25. For a Vishay Curve 1

100k thermistor, this resistance, 325k, corresponds to

approximately 0°C. The hot and cold comparators each

have approximately 3°C of hysteresis to prevent oscilla-

tion about the trip point. Grounding the NTC pin disables

all NTC functionality.

Note that the LTC3576/LTC3576-1 are 3-terminal

PowerPath products where system load is always priori-

tized over battery charging. Due to excessive system load,

there may not be sufﬁcient power to charge the battery

beyond the trickle charge threshold voltage within the bad

battery timeout period. In this case, the battery charger

will falsely indicate a bad battery. System software may

then reduce the load and reset the battery charger to try

again.

3576fb

26

LTC3576/LTC3576-1

OPERATION

Thermal Regulation

voltage is removed, the drain of the external MOSFET

will return to 5V.

To prevent thermal damage to the LTC3576/LTC3576-1 or

surrounding components, an internal thermal feedback

loop will automatically decrease the programmed charge

current if the die temperature rises to 105°C. This thermal

regulation technique protects the LTC3576/LTC3576-1

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. The beneﬁt of the LTC3576/

LTC3576-1 thermal regulation loop is that charge current

can be set according to actual conditions rather than

worst-case conditions for a given application with the

assurance that the charger will automatically reduce the

current in worst-case conditions.

The charge pump output on OVGATE has limited output

drive capability. Care must be taken to avoid leakage on

this pin as it may adversely affect operation.

SeetheApplicationsInformationsectionforresistorpower

dissipation rating calculations, a table of recommended

components, and examples of dual-input and reverse

input protection.

2

I C Interface

The LTC3576/LTC3576-1 may receive commands from a

2

host (master) using the standard 2-wire I C interface. The

Timing Diagram shows the timing relationship of the sig-

nals on the bus. The two bus lines, SDA and SCL, must be

HIGH when the bus is not in use. External pull-up resistors

Overvoltage Protection

2

or current sources, such as the LTC1694 I C accelerator,

TheLTC3576/LTC3576-1canprotectitselffromtheinadver-

are required on these lines. The LTC3576/LTC3576-1are

2

tent application of excessive voltage to V

or WALL with

BUS

receive-only slave devices. The I C control signals, SDA

just two external components: an N-channel MOSFET and

a 6.2k resistor. The maximum safe overvoltage magnitude

will be determined by the choice of the external MOSFET

and its associated drain breakdown voltage.

and SCL are scaled internally to the DV supply. DV

CC

should be connected to the same power supply as the

2

microcontroller generating the I C signals.

2

The I C port has an undervoltage lockout on the DV

CC

2

The overvoltage protection module consists of two pins.

The ﬁrst, OVSENS, is used to measure the externally ap-

plied voltage through an external resistor. The second,

OVGATE, is an output used to drive the gate pin of the

external MOSFET. When OVSENS is below 6V, an internal

charge pump will drive OVGATE to approximately 1.88 ×

OVSENS. This will enhance the N-channel MOSFET and

provide a low impedance connection to V_BUSor WALL

which will, in turn, power the LTC3576/LTC3576-1. If

OVSENS should rise above 6V due to a fault or use of

an incorrect wall adapter, OVGATE will be pulled to GND

disabling the external MOSFET and therefore protecting

downstream circuitry. When the voltage drops below 6V

again, the external MOSFET will be re-enabled.

pin. When DV is below approximately 1V, the I C serial

CC

port is cleared and switching regulators 1, 2 and 3 are

set to full scale.

Bus Speed

2

The I C port is designed to be operated at speeds of up

to 400kHz. It has built-in timing delays to ensure correct

2

operation when addressed from an I C compliant master

device. It also contains input ﬁlters designed to suppress

glitches should the bus become corrupted.

Start and Stop Conditions

A bus master signals the beginning of a communication

to a slave device by transmitting a START condition. A

START condition is generated by transitioning SDA from

high to LOW while SCL is HIGH. When the master has

ﬁnished communicating with the slave, it issues a STOP

condition by transitioning SDA from LOW to HIGH while

SCL is high. The bus is then free for communication with

When USB on-the-go is enabled, the bidirectional switch-

ingregulatorpowersuptheovervoltageprotectioncircuit

through the body diode of the external MOSFET, thus pro-

viding protection to the part even when V_BUSis sourcing

power. When high voltage is applied to the drain of the

external MOSFET, V_BUSwill remain at 5V. Once the high

2

another I C device.

3576fb

27

LTC3576/LTC3576-1

OPERATION

Byte Format

Bus Write Operation

EachbytesenttotheLTC3576/LTC3576-1mustbeeightbits

long followed by an extra clock cycle for the acknowledge

bit. The data should be sent to the LTC3576/LTC3576-1

with the most signiﬁcant bit (MSB) ﬁrst.

The master initiates communication with the LTC3576/

LTC3576-1 with a START condition and a 7-bit address

followed by the R/W bit = 0. If the address matches that

oftheLTC3576/LTC3576-1,theLTC3576/LTC3576-1return

an acknowledge. The master should then deliver the sub-

address. Again the LTC3576/LTC3576-1 acknowledge and

the cycle is repeated for the data byte. The data byte is

transferredtoaninternalholdinglatchuponthereturnofits

acknowledge by the LTC3576/LTC3576-1. This procedure

must be repeated for each sub-address that requires new

data. After one or more data bytes have been transferred

to the LTC3576/LTC3576-1, the master may terminate the

communication with a STOP condition. Alternatively, a

repeated START condition can be initiated by the master

Acknowledge

The acknowledge signal is used for handshaking between

the master and the slave. An acknowledge (active low)

generatedbytheslave(LTC3576/LTC3576-1)letsthemas-

ter know that the latest byte of information was received.

The acknowledge related clock pulse is generated by the

master. The master releases the SDA line (HIGH) during

the acknowledge clock cycle. The slave-receiver must pull

down the SDA line during the acknowledge clock pulse

so that it remains a stable LOW during the HIGH period

of this clock pulse.

2

and another chip on the I C bus can be addressed. This

cyclecancontinueindeﬁnitelyandtheLTC3576/LTC3576-1

remembers the last input of valid data that it received.

Once all chips on the bus have been addressed and sent

valid data, a global STOP condition can be sent and the

LTC3576/LTC3576-1 will update their command latches

with the data that they have received.

Slave Address

The address byte consists of the 7-bit address and the

read/write (R/W) bit. The LTC3576/LTC3576-1 respond to

onlyone7-bitaddresswhichhasbeenfactoryprogrammed

to 0001001. The R/W bit is the least signiﬁcant bit of the

address byte. It must be 0 for the LTC3576/LTC3576-1 to

recognize the address since they are write only devices.

Thus the address byte is 0x12. If the correct seven bit ad-

dressisgivenbuttheR/Wbitis1,theLTC3576/LTC3576-1

will not respond.

2

In certain circumstances the data on the I C bus may be-

come corrupted. In these cases, the LTC3576/LTC3576-1

respond appropriately by preserving only the last set

of complete data that they have received. For example,

assume the LTC3576/LTC3576-1 have been successfully

addressed and are receiving data when a STOP condition

mistakenlyoccurs.TheLTC3576/LTC3576-1willignorethis

STOP condition and will not respond until a new START

condition, correct address and sub-address, new set of

data and STOP condition are transmitted.

Sub-Addressed Writing

The LTC3576/LTC3576-1 have four command registers

2

for control input. They are accessed by the I C port via a

sub-addressed writing system.

Likewise, with only one exception, if the LTC3576/

LTC3576-1 were previously addressed and sent valid data

but not updated with a STOP, they will respond to any

STOP that appears on the bus, independent of the num-

ber of repeated STARTs that have occurred. If a repeated

START is given and the LTC3576/LTC3576-1 successfully

acknowledge their address and sub-address, they will not

respond to a STOP until a full byte of the new data has

been received and acknowledged.

Each write to the LTC3576/LTC3576-1 consists of three

bytes. The ﬁrst byte is always the LTC3576/LTC3576-1’s

write address. The second byte represents the LTC3576/

LTC3576-1’s sub-address. The sub-address acts as

pointer to direct the subsequent data byte within the

LTC3576/LTC3576-1.Thethirdbyteconsistsofthedatato

be written to the location pointed to by the sub-address.

The LTC3576/LTC3576-1 contain four sub-addresses at

locations 0x00, 0x01, 0x02 and 0x03.

3576fb

28

LTC3576/LTC3576-1

OPERATION

Input Data

sub-address 1 controls the servo voltage of switching

regulator 3 and the enable signals for all three switching

regulators, as well as the enable signal for the PowerPath

Table 3 illustrates the four data bytes that may be written

to the LTC3576/LTC3576-1.

switching regulator to power up V

for USB on-the-go.

BUS

The ﬁrst byte at sub-address 0 controls the servo volt-

age for switching regulators 1 and 2. The second byte at

The servo voltages are decoded in Table 4. The default

servo voltage is 0.8V.

Table 3. I²C Serial Port Mapping*

A7

A6

A5

A4

A3

A2

A1

A0

B7

B6

B5

B4

B3

B2

B1

B0

Switching Regulator 1 Voltage

(See Table 4)

Switching Regulator 2 Voltage

(See Table 4)

Switching Regulator 3 Voltage

(See Table 4)

Reset Value

1

0

C7

C6

C5

C4

C3

C2

C1

C0

D7

D6

D5

D4

D3

D2

D1

D0

Switching

Input Current

Limit

(See Table 6)

Unused

Regulator 1

Modes

Regulator 2

Modes

Regulator 3

Modes

(See Table 5)

Reset Value

0

*The A7-A0 and B7-B4 bits default to 1 and all other bits default to 0 when the chip is powered and DV = 0.

CC

Table 4. Switching Regulator Servo Voltage

A7

A3

B7

0

A6

A2

B6

0

A5

A1

B5

0

A4

A0

B4

0

Switching Regulator 1 Servo Voltage

Switching Regulator 2 Servo Voltage

Switching Regulator 3 Servo Voltage

0.425

0.450

0.475

0.500

0.525

0.550

0.575

0.600

0.625

0.650

0.675

0.700

0.725

0.750

0.775

0.800

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

3576fb

29

LTC3576/LTC3576-1

OPERATION

2

Disabling the I C Port

Thethirddatabyteatsub-address2controlstheoperating

modes of each switching regulator as well as the input

current limit settings. Each switching regulator can be

independently set to one of three operating modes listed

in Table 5.

2

The I C serial port can be disabled by grounding the DV

CC

pin. In this mode, the LTC3576/LTC3576-1 are controlled

through the individual logic input pins EN1, EN2, EN3,

ENOTG, I

, I

, SDA and SCL. Some functionality is

LIM0 LIM1

not available in this mode such as the programmability of

switchingregulators1,2and3’soutputvoltage,thebattery

chargerdisablefeatureandthehighpowersuspendmode.

Inthismode,theprogrammableswitchingregulatorshave

a ﬁxed servo voltage of 0.8V. Because the SDA and SCL

Table 5. General Purpose Switching Regulator Modes

C7 (SDA)*

C6 (SCL)* Switching Regulator 1 Mode

C4 (SCL)* Switching Regulator 2 Mode

C2 (SCL)* Switching Regulator 3 Mode

C5 (SDA)*

C3 (SDA)*

0

1

X

0

1

Pulse-Skipping Mode

LDO Mode

pins have no other context when DV is grounded, these

CC

pins are re-mapped to control the switching regulator

mode bits C2 to C7. SCL maps to C2, C4 and C6 while

SDA maps to C3, C5 and C7.

Burst Mode Operation

*SDA and SCL take on this context only when DV = 0V.

CC

The input current limit settings are decoded according

to Table 6. This table indicates the maximum current

RST3 Pin

that will be drawn from the V

pin in the event that the

BUS

The RST3 pin is an open-drain output used to indicate that

switching regulator 3 has been enabled and has reached

itsﬁnalvoltage.RST3remainslowimpedanceuntilregula-

tor 3 reaches 92% of its regulation value.

load at V

(battery charger plus system load) exceeds

OUT

the power available. Any additional power will be drawn

from the battery. The start-up state for the input current

limit setting is 00 representing the low power 100mA

USB setting.

A230msdelayisincludedtoallowasystemmicrocontroller

ample time to reset itself. RST3 may be used as a power-

on reset to the microprocessor powered by regulator 3

or may be used to enable regulators 1 and/or 2 for supply

sequencing. RST3 is an open-drain output and requires

a pull-up resistor to the output voltage of regulator 3 or

another appropriate power source.

Table 6. USB Current Limit Settings

C1

LIM1

0

C0

LIM0

0

D6

X

(I

)* (I

)* USB SETTING

1× Mode (USB 100mA Limit)

X

0

1

0

1

10× Mode (Wall 1A Limit)

0

Low Power Suspend (USB 500μA Limit)

High Power Suspend (USB 2.5mA Limit)

5× Mode (USB 500mA Limit)

1

Shutdown Mode

X

The bidirectional USB switching regulator in step-down

*I

and I

can only be used to enable the low power suspend mode

LIM1

LIM0

mode is enabled whenever V

is above V

and the

and are logically ORed with C1 and C0, respectively.

BUS

UVLO

LTC3576/LTC3576-1arenotinoneofthetwoUSBsuspend

modes (500μA or 2.5mA). When power is available from

boththeUSBandauxiliaryinputs,theauxiliaryinputisgiven

priority and the USB switching regulator is disabled.

The fourth and ﬁnal byte of input data at sub-address 3

providesbitsfordisablingthebatterychargerandenabling

the high power suspend mode current limit of 2.5mA.

The ideal diode(s) are enabled at all times and cannot be

disabled.

3576fb

30

LTC3576/LTC3576-1

OPERATION

Step-Down Switching Regulators

Step-Down Switching Regulator Operating Modes

The LTC3576/LTC3576-1 contain three general purpose

2.25MHz step-down constant-frequency current mode

switchingregulators. Tworegulatorsprovideupto400mA

and a third switching regulator can provide up to 1A.

All three switching regulators can be programmed for

a minimum start-up output voltage of 0.8V and can be

used to power a microcontroller core, microcontroller

I/O, memory, disk drive or other logic circuitry. All three

The LTC3576/LTC3576-1’s general purpose switching

regulatorsincludethreepossibleoperatingmodestomeet

the noise/power needs of a variety of applications.

In pulse-skipping mode, an internal latch is set at the start

ofeverycyclewhichturnsonthemainP-channelMOSFET

switch.Duringeachcycle,acurrentcomparatorcompares

thepeakinductorcurrenttotheoutputofanerrorampliﬁer.

The output of the current comparator resets the internal

latch which causes the main P-channel MOSFET switch to

turn off and the N-channel MOSFET synchronous rectiﬁer

to turn on. The N-channel MOSFET synchronous rectiﬁer

turns off at the end of the 2.25MHz cycle or if the current

through the N-channel MOSFET synchronous rectiﬁer

drops to zero. Using this method of operation, the error

ampliﬁer adjusts the peak inductor current to deliver the

required output power. All necessary compensation is

internal to the switching regulator requiring only a single

ceramicoutputcapacitorforstability.AtlightloadsinPWM

mode, the inductor current may reach zero on each pulse

which will turn off the N-channel MOSFET synchronous

rectiﬁer. In this case, the switch node (SW) goes high

impedance and the switch node voltage will “ring”. This

is discontinuous mode operation, and is normal behavior

for a switching regulator. At very light loads in pulse-skip-

pingmode,theswitchingregulatorswillautomaticallyskip

pulses as needed to maintain output regulation.

2

switchingregulatorshaveI Cprogrammablesetpointsfor

on-the-ﬂy power savings. They also support 100% duty

cycle operation (low dropout mode) when their input volt-

agedropsveryclosetotheiroutputvoltage.Tosuitavariety

of applications, selectable mode functions can be used to

trade off noise for efﬁciency. Three modes are available to

control the operation of the LTC3576/LTC3576-1’s general

purposeswitchingregulators.Atmoderatetoheavyloads,

the pulse skip mode provides the lowest noise switching

solution. At lighter loads, Burst Mode operation or LDO

mode may be selected. The switching regulators include

soft-start to limit inrush current when powering on, short-

circuit current protection and switch node slew limiting

circuitry to reduce radiated EMI. No external compensa-

tion components are required. The operating mode of the

2

regulators may be set by either I C control or by manual

2

control of the SDA and SCL pins if the I C port is not used.

Each converter may be individually enabled by either their

2

external control pins EN1, EN2, EN3 or by the I C port. All

At high duty cycles (V

> V /2) it is possible for the

INx

three switching regulators have individual programmable

OUTx

2

inductorcurrenttoreverse,causingtheregulatortooperate

continuouslyatlightloads.Thisisnormalandregulationis

maintained, but the supply current will increase to several

mA due to continuous switching.

feedback servo voltages via I C control. The switching

regulator input supplies V , V and V will generally

IN1 IN2

IN3

be connected to the system load pin V

.

OUT

3576fb

31

LTC3576/LTC3576-1

OPERATION

InBurstModeoperation,theswitchingregulatorautomati-

callyswitchesbetweenﬁxedfrequencyPWMoperationand

hystereticcontrolasafunctionoftheloadcurrent. Atlight

loads, the regulator operates in hysteretic mode and uses

a constant current algorithm to control the inductor cur-

rent. While in Burst Mode operation, the output capacitor

is charged to a voltage slightly higher than the regulation

point. The step-down switching regulator then goes into

sleep mode, during which the output capacitor provides

the load current. In sleep mode, most of the regulator’s

circuitry is powered down, conserving battery power.

When the output voltage drops below a pre-determined

value, the switching regulator circuitry is powered on and

another burst cycle begins. The duration for which the

regulator operates in sleep mode depends on the load

current. The sleep time decreases as the load current

increases. Burst Mode operation provides a signiﬁcant

improvement in efﬁciency at light loads at the expense

of higher output ripple when compared to pulse-skipping

mode. At heavy loads Burst Mode operation functions in

the same manner as pulse-skipping mode.

dropoutcondition,therespectiveoutputvoltageequalsthe

regulator’s input voltage minus the voltage drops across

the internal P-channel MOSFET and the inductor.

Step-Down Switching Regulator Low Supply Operation

The LTC3576/LTC3576-1 incorporate an undervoltage

lockout circuit on V

which shuts down the general

OUT

purpose switching regulators when V

drops below

OUT

V . This UVLO prevents unstable operation.

OUT(UVLO)

Step-Down Switching Regulator Soft-Start Operation

Soft-start is accomplished by gradually increasing the

peak inductor current for each switching regulator over a

500ꢁs period. This allows each output to rise slowly, help-

ing minimize the battery surge current. A soft-start cycle

occurs whenever a given switching regulator is enabled,

or after a fault condition has occurred (thermal shutdown

or UVLO). A soft-start cycle is not triggered by changing

operating modes. This allows seamless output operation

when transitioning between Burst Mode operation, pulse-

skipping mode or LDO mode.

Finally, the switching regulators have an LDO mode that

gives a DC option for regulating their output voltages. In

LDOmode,theswitchingregulatorsareconvertedtolinear

regulators and deliver continuous power from their SWx

pins through their respective inductors. This mode gives

the lowest possible output noise as well as low quiescent

current at light loads.

Step-Down Switching Regulator Switching

Slew Rate Control

The step-down switching regulators contain new patent

pending circuitry to limit the slew rate of the switch node

(SWx). This new circuitry is designed to transition the

switch node over a period of a couple of nanoseconds,

signiﬁcantly reducing radiated EMI and conducted supply

noise.

Thestep-downswitchingregulatorsallowon-the-ﬂymode

transitions,providingseamlesstransitionbetweenmodes

even under load. This allows the user to switch back and

forth between modes to reduce output ripple or increase

low current efﬁciency as needed.

Step-Down Switching Regulator in Shutdown

Thestep-downswitchingregulatorsareinshutdownwhen

not enabled for operation. In shutdown, all circuitry in

the step-down switching regulator is disconnected from

the switching regulator input supply leaving only a few

nanoamperesofleakagecurrent.Thestep-downswitching

regulatoroutputsareindividuallypulledtogroundthrough

a 10k resistor on their SWx pins when in shutdown.

Step-Down Switching Regulator Dropout Operation

It is possible for a switching regulator’s input voltage,

V

, to approach its programmed output voltage (e.g., a

INx

battery voltage of 3.4V with a programmed output voltage

of 3.3V). When this happens, the PMOS switch duty cycle

increasesuntilitisturnedoncontinuouslyat100%.Inthis

3576fb

32

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

Bidirectional PowerPath Switching Regulator

CLPROG Resistor and Capacitor Selection

Bidirectional PowerPath Switching Regulator V

BUS

and V

Bypass Capacitor Selection

OUT

The type and value of capacitors used with the LTC3576/

LTC3576-1 determine several important parameters such

asregulatorcontrol-loopstabilityandinputvoltageripple.

Because the LTC3576/LTC3576-1 use a bidirectional

As described in the Bidirectional Switching Regula-

tor—Step-Down Mode section, the resistor on the

CLPROG pin determines the average V

input current

BUS

limit when the switching regulator is set to either the 1×

switching regulator between V

and V , the V

mode (USB 100mA), the 5× mode (USB 500mA) or the

BUS

OUT BUS

current waveform contains high frequency components.

It is strongly recommended that a low equivalent series

resistance (ESR) multilayer ceramic capacitor (MLCC) be

10× mode. The V

input current will be comprised of

BUS

two components, the current that is used to drive V

OUT

and the quiescent current of the switching regulator. To

ensure that the USB speciﬁcation is strictly met, both

components of the input current should be considered.

The Electrical Characteristics table gives the typical values

forquiescentcurrentsinallsettingsaswellascurrentlimit

programming accuracy. To get as close to the 500mA or

100mA speciﬁcations as possible, a precision resistor

should be used. Recall that:

used to bypass V . Tantalum and aluminum capacitors

BUS

arenotrecommendedbecauseoftheirhighESR.Thevalue

of the capacitor on V

directly controls the amount of

BUS

input ripple for a given load current. Increasing the size

of this capacitor will reduce the input ripple.

The inrush current limit speciﬁcation for USB devices is

calculatedintermsofthetotalnumberofCoulombsneeded

to charge the V

bypass capacitor to 5V. The maximum

I

= I

+ V

/R

• (h

+1).

BUS

VBUS

VBUSQ

CLPROG CLPPROG

CLPROG

inrush charge for USB on-the-go devices is 33μC. This

places a limit of 6.5μF of capacitance on V assuming

An averaging capacitor is required in parallel with the

resistor so that the switching regulator can determine the

average input current. This capacitor also provides the

dominant pole for the feedback loop when current limit

is reached. To ensure stability, the capacitor on CLPROG

should be 0.1μF or larger.

BUS

a linear capacitor. However, most ceramic capacitors have

a capacitance that varies with bias voltage. The average

capacitanceneedstobelessthan6.5μFovera0Vto5Vbias

voltagerangetomeettheinrushcurrentlimitspeciﬁcation.

A 10μF capacitor in a 0805 package, such as the Murata

GRM21BR71A106KE51LwouldbeasuitableV

bypass

BUS

Bidirectional PowerPath Switching Regulator

Inductor Selection

capacitor. If more capacitance is required for better noise

performanceandstabilityitshouldbeconnecteddirectlyto

Because the input voltage range and output voltage range

of the PowerPath switching regulator are both fairly nar-

row, the LTC3576/LTC3576-1 were designed for a speciﬁc

inductance value of 3.3μH. Some inductors which may be

suitable for this application are listed in Table 7.

theV

pinwhenusingtheovervoltageprotectioncircuit.

BUS

This extra capacitance will be soft-connected over several

milliseconds to limit inrush current and avoid excessive

transient voltage drops on V

.

BUS

To prevent large V

voltage steps during transient load

OUT

Table 7. Recommended PowerPath Inductors for the LTC3576

MAX MAX

conditions, it is also recommended that an MLCC be used

to bypass V . The output capacitor is used in the com-

OUT

INDUCTOR

TYPE

L

I

DCR SIZE IN mm

(Ω) (L × W × H) MANUFACTURER

DC

pensation of the switching regulator. At least 10μF with

(μH) (A)

low ESR are required on V . Additional capacitance will

OUT

LPS4018

3.3 2.2 0.08

Coilcraft

www.coilcraft.com

3.9 × 3.9 × 1.7

improve load transient performance and stability.

D53LC

3.3 2.26 0.034

3.3 1.55 0.070

Toko

5 × 5 × 3

MLCCs typically have exceptional ESR performance.

MLCCscombinedwithatightboardlayoutandanunbroken

ground plane will yield very good performance and low

EMI emissions.

DB318C

www.toko.com

3.8 × 3.8 × 1.8

WE-TPC

Type M1

3.3 1.95 0.065

Wurth Electronik

www.we-online.com

4.8 × 4.8 × 1.8

CDRH6D12

CDRH6D38

3.3

2.2 0.063

3.5 0.020

Sumida

www.sumida.com

6.7 × 6.7 × 1.5

7 × 7 × 4

3576fb

33

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

ThereareMLCCsavailablewithseveraltypesofdielectrics

each having considerably different characteristics. For

example, X7R MLCCs have the best voltage and tempera-

ture stability. X5R MLCCs have apparently higher packing

density but poorer performance over their rated voltage

and temperature ranges. Y5V MLCCs have the highest

packing density, but must be used with caution, because

of their extreme nonlinear characteristic of capacitance

versus voltage. The actual in-circuit capacitance of a

ceramic capacitor should be measured with a small AC

signal and DC bias as is expected in-circuit. Many vendors

to improve transient response for output voltages much

greater than 0.8V. A variety of capacitor sizes can be used

for C but a value of 10pF is recommended for most ap-

FB

plications. Experimentation with capacitor sizes between

2pF and 22pF may yield improved transient response.

Step-Down Switching Regulator Inductor Selection

Many different sizes and shapes of inductors are avail-

able from numerous manufacturers. Choosing the right

inductor from such a large selection of devices can be

overwhelming, but following a few basic guidelines will

make the selection process much simpler.

specify the capacitance versus voltage with a 1V

AC

RMS

test signal and, as a result, over state the capacitance that

the capacitor will present in the application. Using similar

operating conditions as the application, the user must

measureorrequestfromthevendortheactualcapacitance

to determine if the selected capacitor meets the minimum

capacitance that the application requires.

Thegeneralpurposestep-downconvertersaredesignedto

work with inductors in the range of 2ꢁH to 10ꢁH. For most

applications a 4.7ꢁH inductor is suggested for the lower

current switching regulators 1 and 2 and 2ꢁH is recom-

mendedforthehighercurrentswitchingregulator 3.Larger

valueinductorsreduceripplecurrentwhichimprovesout-

put ripple voltage. Lower value inductors result in higher

ripple current and improved transient response time. To

maximize efﬁciency, choose an inductor with a low DC

resistance. For a 1.2V output, efﬁciency is reduced about

2% for 100mꢀ series resistance at 400mA load current,

and about 2% for 300mꢀ series resistance at 100mA load

current. Choose an inductor with a DC current rating at

least 1.5 times larger than the maximum load current to

ensure that the inductor does not saturate during normal

operation. If output short circuit is a possible condition,

the inductor should be rated to handle the maximum peak

current speciﬁed for the step-down converters. Different

core materials and shapes will change the size/current

and price/current relationship of an inductor. Toroid or

shielded pot cores in ferrite or Permalloy materials are

small and don’t radiate much energy, but generally cost

more than powdered iron core inductors with similar

electrical characteristics. Inductors that are very thin or

have a very small volume typically have much higher

core and DCR losses, and will not give the best efﬁciency.

The choice of which style inductor to use often depends

more on the price vs size, performance and any radiated

EMI requirements than on what the LTC3576/LTC3576-1

require to operate.

Step-Down Switching Regulator Output Voltage

Programming

2

All three switching regulators have I C programmable

set points and can be programmed for start-up output

voltages of at least 0.8V. The full-scale output voltage for

each switching regulator is programmed using a resistor

divider from the switching regulator output connected to

the FBx pins such that:

⎛

⎞

R1

R2

V_OUTx= V

+1

⎜

⎝

⎟

FBx

⎠

where V ranges from 0.425V to 0.8V. See Figure 5.

FBx

Typical values for R1 are in the range of 40k to 1M. The

capacitorC cancelsthepolecreatedbyfeedbackresistors

FB

and the input capacitance of the FBx pin and also helps

V

INx

L

V

SWx

OUTx

LTC3576/

C

R1

C

OUT

FB

LTC3576-1

FBx

R2

GND

3576 F05

Figure 5. Buck Converter Application Circuit

3576fb

34

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

The inductor value also has an effect on Burst Mode op-

eration. Lower inductor values will cause the Burst Mode

operation switching frequency to increase.

tor is sufﬁcient for most applications. For good transient

response and stability the output capacitor should retain

atleast4ꢁFofcapacitanceoveroperatingtemperatureand

biasvoltage.Eachswitchingregulatorinputsupplyshould

be bypassed with a 1ꢁF capacitor. Consult with capacitor

manufacturers for detailed information on their selection

and speciﬁcations of ceramic capacitors. Many manufac-

turers now offer very thin (<1mm tall) ceramic capacitors

ideal for use in height-restricted designs. Table 9 shows a

list of several ceramic capacitor manufacturers.

Table 8 shows several inductors that work well with the

LTC3576/LTC3576-1’s general purpose regulators. These

inductors offer a good compromise in current rating, DCR

and physical size. Consult each manufacturer for detailed

information on their entire selection of inductors.

Table 8. Recommended Inductors

MAX MAX

INDUCTOR

TYPE

L

I

DCR

(Ω)

SIZE IN mm

(L × W × H) MANUFACTURER

DC

Table 9. Recommended Ceramic Capacitor Manufacturers

(μH) (A)

AVX

www.avxcorp.com

www.murata.com

www.t-yuden.com

www.vishay.com

www.tdk.com

DE2818C

4.7 1.25 0.072

3.3 1.45 0.053

4.7 0.79 0.24

3.3 0.90 0.20

2.2 1.14 0.14

Toko

www.toko.comm

3.0 × 2.8 × 1.8

3.6 × 3.6 × 1.2

3.0 × 2.8 × 1.2

Murata

D312C

Taiyo Yuden

Vishay Siliconix

TDK

DE2812C

4.7

3.3

2.0

1.2 1.13*

1.4 0.10*

1.8 0.067*

Overvoltage Protection

CDRH3D16

CDRH2D11

4.7

3.3

2.2

4.7

3.3

0.9

0.11

Sumida

4.0 × 4.0 × 1.8

3.2 × 3.2 × 1.2

4.9 × 4.9 × 1.0

3.1 × 3.1 × 1.8

3.1 × 3.1 × 1.2

5.2 × 5.2 × 1.2

5.2 × 5.2 × 1.0

1.1 0.085

1.2 0.072

www.sumida.com

V

BUS

can be protected from overvoltage damage with two

additional components, a resistor R1 and an N-channel

MOSFET MN1, as shown in Figure 6. Suitable choices for

MN1 are listed in Table 10.

0.5

0.6 0.123

2.2 0.78 0.098

4.7 0.75 0.19

0.17

CLS4D09

SD3118

4.7

1.3 0.162

Cooper

www.cooperet.com

Table 10. Recommended N-channel MOSFETs for the

Overvoltage Protection Circuit

3.3 1.59 0.113

2.2

4.7

2.0 0.074

0.8 0.246

PART NUMBER

Si1472DH

BVDSS

30V

R

PACKAGE

SC70-6

SOT-23

WDFN6

ON

SD3112

SD12

3.3 0.97 0.165

2.2 1.12 0.14

4.7 1.29 0.117*

3.3 1.42 0.104*

2.2 1.80 0.075*

4.7 1.08 0.153*

3.3 1.31 0.108*

2.2 1.65 0.091*

82mΩ

60mΩ

65mΩ

80mΩ

35mΩ

50mꢀ

35mΩ

Si2302ADS

Si2306BDS

Si2316BDS

IRLML2502

FDN372S

20V

30V

SD10

20V

30V

LPS3015

4.7

3.3

2.2

1.1

1.3

1.5

0.2

0.13

0.11

Coilcraft

www.coilcraft.com

3.0 × 3.0 × 1.5

NTLJS4114N

30V

R1 is a 6.2k resistor and must be rated for the power dis-

sipated during maximum overvoltage. In an overvoltage

condition the OVSENS pin will be clamped at 6V. R1 must

be sized appropriately to dissipate the resultant power.

For example, a 1/10W 6.2k resistor can have at most

*Typical DCR

Step-Down Switching Regulator Input/Output Bypass

Capacitor Selection

Low ESR (equivalent series resistance) MLCCs should

be used at each switching regulator output as well as at

√P

• 6.2kꢀ = 25V applied across its terminals. With

MAX

the 6V at OVSENS, the maximum overvoltage magnitude

thatthisresistorcanwithstandis31V.A1/4W6.2kresistor

raises this value to 45V. OVSENS’s absolute maximum

current rating of 10mA imposes an upper limit of 68V

each switching regulator input supply (V ). Only X5R

INx

or X7R ceramic capacitors should be used because they

retaintheircapacitanceoverwidervoltageandtemperature

ranges than other ceramic types. A 10ꢁF output capaci-

protection.

3576fb

35

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

MP1

MN1

USB/WALL

ADAPTER

V

BUS

D1

C1

MN1

USB/WALL

ADAPTER

V

LTC3576/

BUS

LTC3576-1

C1

LTC3576/

R1

R2

LTC3576-1

OVGATE

OVSENS

R1

OVGATE

OVSENS

3576 F08

V

BUS

V

BUS

POSITIVE PROTECTION UP TO BVDSS OF MN1

NEGATIVE PROTECTION UP TO BVDSS OF MP1

3576 F06

Figure 6. Overvoltage Protection

Figure 8. Dual Polarity Voltage Protection

transforms the voltage at V

to a voltage just above

BUS

M1

V1

V2

WALL

the level at BAT, while limiting power to less than the

amount programmed at CLPROG. The charger should be

programmed (with the PROG pin) to deliver the maximum

safe charging current without regard to the USB speciﬁ-

cations. If there is insufﬁcient current available to charge

the battery at the programmed rate, it will reduce charge

OVGATE

LTC3576/

LTC3576-1

BUS

V

M2

D2

D1

C1

GND

R1

OVSENS

current until the system load on V

is satisﬁed and the

OUT

3576 F07

V

current limit is satisﬁed. Programming the charger

BUS

for more current than is available will not cause the aver-

age input current limit to be violated. It will merely allow

the battery charger to make use of all available power to

chargethebatteryasquicklyaspossible,andwithminimal

dissipation within the charger.

Figure 7. Dual-Input Overvoltage Protection

I

t is possible to protect both V_BUSand WALL from

overvoltage damage with several additional components,

as shown in Figure 7. Schottky diodes D1 and D2 pass the

larger of V1 and V2 to R1 and OVSENS. If either V1 or V2

exceeds 6V plus V_F(Schottky), OVGATE will be pulled to

GNDandboththeWALLandUSBinputswillbeprotected.

Eachinputisprotecteduptothedrain-sourcebreakdown,

BVDSS, of MN1 and MN2. R1 must also be rated for the

power dissipated during maximum overvoltage.

Battery Charger Stability Considerations

TheLTC3576/LTC3576-1’sbatterychargercontainsbotha

constant-voltage and a constant-current control loop. The

constant-voltage loop is stable without any compensation

when a battery is connected with low impedance leads.

Excessive lead length, however, may add enough series

inductance to require a bypass capacitor of at least 1μF

from BAT to GND.

Reverse Voltage Protection

The LTC3576/LTC3576-1 can also be easily protected

against the application of reverse voltages, as shown in

Figure 8. D1 and R1 are necessary to limit the maximum

High value, low ESR MLCCs reduce the constant-voltage

loop phase margin, possibly resulting in instability. Up

to 22μF may be used in parallel with a battery, but larger

capacitors should be decoupled with 0.2Ω to 1Ω of series

resistance.

V

seenbyMP1duringpositiveovervoltageevents.D1’s

GS

breakdownvoltagemustbesafelybelowMP1’sBVGS.The

circuit shown in Figure 8 offers forward voltage protection

up to MN1’s BVDSS and reverse voltage protection up to

MP1’s BVDSS.

Furthermore, a 100μF MLCC in series with a 0.3Ω resistor

from BAT to GND is required to prevent oscillation when

the battery is disconnected.

Battery Charger Over Programming

The USB high power speciﬁcation allows for up to 2.5W

to be drawn from the USB port. The LTC3576/LTC3576-1’s

bidirectional switching regulator in step-down mode

In constant-current mode, the PROG pin is in the feed-

back loop rather than the battery voltage. Because of the

additional pole created by any PROG pin capacitance,

3576fb

36

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

capacitance on this pin must be kept to a minimum. With

no additional capacitance on the PROG pin, the charger

is stable with program resistor values as high as 25k.

However, additional capacitance on this node reduces the

maximumallowedprogramresistor.Thepolefrequencyat

the PROG pin should be kept above 100kHz. Therefore, if

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.

the PROG pin has a parasitic capacitance, C

, the fol-

PROG

NTC thermistors have temperature characteristics which

areindicatedonresistance-temperatureconversiontables.

TheVishay-DalethermistorNTHS0603N011-N1003F,used

in the following examples, has a nominal value of 100k

and follows the Vishay Curve 1 resistance-temperature

characteristic.

lowing equation should be used to calculate the maximum

resistance value for R

:

PROG

1

R_PROG

≤

2π • 100kHz • C_PROG

In the explanation below, the following notation is used.

R25 = Value of the Thermistor at 25°C

Alternate NTC Thermistors and Biasing

The LTC3576/LTC3576-1 provide temperature qualiﬁed

charging if a grounded thermistor and a bias resistor

are connected to NTC. By using a bias resistor whose

value is equal to the room temperature resistance of the

thermistor (R25) the upper and lower temperatures are

pre-programmed to approximately 40°C and 0°C respec-

tively assuming a Vishay Curve 1 thermistor.

R

= Value of thermistor at the cold trip point

= Value of the thermistor at the hot trip

NTC|COLD

NTC|HOT

point

r

= Ratio of R

to R25

COLD

NTC|COLD

= Ratio of R

to R25

HOT

NTC|HOT

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

R

– Primary thermistor bias resistor

NOM

(see Figure 9)

R1 = Optional temperature range adjustment resistor

(see Figure 10)

LTC3576/LTC3576-1

NTC BLOCK

NTCBIAS

LTC3576/LTC3576-1

NTC BLOCK

NTCBIAS

3

4

3

0.765 • NTCBIAS

R

0.765 • NTCBIAS

NOM

–

+

R

NOM

100k

105k

–

+

TOO_COLD

TOO_HOT

TOO_COLD

TOO_HOT

NTC

4

R1

12.7k

R

NTC

100k

T

–

+

–

+

R

NTC

100k

T

0.349 • NTCBIAS

+

–

+

–

NTC_ENABLE

0.1V

3576 F10

3576 F09

Figure 9. Standard NTC Conﬁguration

Figure 10. Modiﬁed NTC Conﬁguration

3576fb

37

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

The trip points for the LTC3576/LTC3576-1’s temperature

qualiﬁcationareinternallyprogrammedat0.349•NTCBIAS

for the hot threshold and 0.765•NTCBIAS for the cold

threshold.

From the Vishay Curve 1 R-T characteristics, r

is

HOT

0.2488 at 60°C. Using the above equation, R

should

NOM

be set to 46.4k. With this value of R

, r

is 1.436

NOM COLD

and the cold trip point is about 16°C. Notice that the span

is now 44°C rather than the previous 40°C. This is due to

the decrease in “temperature gain” of the thermistor as

absolute temperature increases.

Therefore, the hot trip point is set when:

R_{NTC HOT}

•NTCBIAS= 0.349 •NTCBIAS

R_NOM+R_{NTC HOT}

The upper and lower temperature trip points can be inde-

pendentlyprogrammedbyusinganadditionalbiasresistor

asshowninFigure10. Thefollowingformulascanbeused

And the cold trip point is set when:

to compute the values of R

and R1:

NOM

R_{NTC COLD}

•NTCBIAS= 0.765•NTCBIAS

R_NOM+R_{NTC COLD}

r_COLD–r_HOT

R_NOM

=

•R25

2.714

R1= 0.536 •R_NOM–r_HOT•R25

Solving these equations for R

results in the following:

and R

NTC|HOT

NTC|COLD

For example, to set the trip points to 0°C and 45°C with

a Vishay Curve 1 thermistor choose:

R

= 0.536 • R

NTC|HOT

NOM

and

3.266 – 0.4368

R_NOM

=

•100k =104.2k

R

= 3.25 • R

2.714

NTC|COLD

NOM

By setting R

equal to R25, the above equations result

NOM

= 0.536 and r

the nearest 1% value is 105k:

in r

= 3.25. Referencing these ratios

HOT

COLD

R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k

to the Vishay Resistance-Temperature Curve 1 chart gives

a hot trip point of about 40°C and a cold trip point of about

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

is approximately 40°C.

the nearest 1% value is 12.7k. The ﬁnal solution is shown

in Figure 10 and results in an upper trip point of 45°C and

a lower trip point of 0°C.

By using a bias resistor, R

, different in value from

NOM

Hot Plugging and USB Inrush Current Limiting

R25, the hot and cold trip points can be moved in either

direction. The temperature span will change somewhat

due to the nonlinear behavior of the thermistor. The fol-

lowing equations can be used to calculate a new value for

the bias resistor:

The overvoltage protection circuit provides inrush current

limiting due to the long time it takes for OVGATE to fully

enhancetheN-channelMOSFET. Thispreventsthecurrent

from building up in the cable too quickly thus dampen-

ing out any resonant overshoot on V . It is possible to

BUS

r_HOT

R_NOM

=

•R25

observe voltage overshoot on V

when connecting the

BUS

0.536

r

LTC3576/LTC3576-1toalabpowersupplyiftheovervoltage

protection circuit is not used. This overshoot is caused by

the inductance of the long leads from the power supply to

R_NOM

^COLD•R25

3.25

V

. Twisting the wires together from the supply to V

BUS

where r

and r

are the resistance ratios at the de-

HOT

COLD

can greatly reduce the parasitic inductance of these long

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 60°C

hot trip point is desired.

leadskeepingthevoltageatV tosafelevels.USBcables

BUS

are generally manufactured with the power leads in close

proximity, and thus have fairly low parasitic inductance.

3576fb

38

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

Hot Plugging and USB On-the-Go

For V

pulsing, the limit on the V

capacitance on

BUS

the A device allows a B device to differentiate between

a powered down on-the-go device and a powered down

standardhost. TheBdevicewillsendoutapulseofcurrent

If there is more than 4.3V on V

when on-the-go is

BUS

enabled, the bidirectional switching regulator will not try

to drive V . If USB on-the-go is enabled and an external

BUS

that will raise V

to a voltage between 2.1V and 5.25V if

BUS

supply is then connected to V , one of three things will

BUS

connected to an on-the-go A device which must have no

more than 6.5μF. An on-the-go A device must drive V

happen depending on the properties of the external sup-

ply. If the external supply has a regulation voltage higher

than 5.1V, the bidirectional switching regulator will stop

BUS

as soon as the current pulse raises V

above 2.1V if the

BUS

device is capable of responding to V

pulsing.

BUS

switching and V

will be held at the regulation voltage

BUS

of the external supply. If the external supply has a lower

This same current pulse must not raise V

any higher

BUS

regulation voltage and is capable of only sourcing current

than 2V when connected to a standard host which must

haveatleast96μF. The96μFforastandardhostrepresents

then V

will be regulated to 5.1V. The external supply

BUS

will not source current to V

.

the minimum capacitance with V

between 4.75V and

BUS

5.25V. Since the SRP pulse must not drive V

greater

BUS

For a supply that can also sink current and has a regula-

tion voltage less than 5.1V, the bidirectional switching

regulator will source current into the external supply in an

than2V, thecapacitanceseenatthesevoltagelevelscanbe

greaterthan96μF,especiallyifMLCCsareused.Therefore,

the 96μF represents a lower bound on the standard host

bypass capacitance for determining the amplitude and

duration of the current pulse. More capacitance will only

attempt to bring V

up to 5.1V. As long as the external

BUS

supply holds V

to more than 4V or V

+ 70mV, the

BUS

OUT

bidirectional switching regulator will source up to 680mA

into the supply. If V is held to a voltage that is less than

decrease the maximum level that V

given current pulse.

will rise to for a

BUS

4V and V

+ 70mV then the short circuit timer will shut

OUT

off the switching regulator after 7.2ms. The CHRG pin will

Figure 11 shows an on-the-go device using the LTC3576/

LTC3576-1 acting as the A device. Additional capacitance

then blink indicating a short circuit current fault.

can be placed on the V

pin of the LTC3576/LTC3576-1

BUS

V

Bypass Capacitance and USB On-The-Go

when using the overvoltage protection circuit. A B device

may not be able to distinguish between a powered down

LTC3576/LTC3576-1 with overvoltage protection and a

powered down standard host because of this extra ca-

BUS

Session Request Protocol

Whentwoon-the-godevicesareconnected,onewillbethe

A device and the other will be the B device depending on

whether the device is connected to a micro A or micro B

plug. The A device provides power to the B device and

starts as the host. To prolong battery life, the A device can

pacitance. In addition, if the SRP pulse raises V

above

BUS

its UVLO threshold of 4.3V the LTC3576/LTC3576-1 will

assume input power is available and will not attempt to

drive V . Therefore, it is recommended that an on-

BUS

power down V

when the bus is not being used. If the A

BUS

the-go device using the LTC3576/LTC3576-1 respond to

device has powered down V , the B device can request

BUS

data-line pulsing.

the A device to power up V

and start a new session us-

BUS

ing the session request protocol (SRP). The SRP consists

of data-line pulsing and V pulsing. The B device must

When an on-the-go device using the LTC3576/LTC3576-1

becomes the B device, as in Figure 12, it must send out

BUS

+

–

ﬁrst pulse the D or D data line. The B device must then

a data line pulse followed by a V

pulse to request a

BUS

pulse V only if the A device does not respond to the

session from the A device. The on-the-go device designer

can choose how much capacitance will be placed on the

BUS

data-linepulse. TheAdeviceisrequiredtorespondtoonly

one of the pulsing methods. A devices that never power

V

pin of the LTC3576/LTC3576-1 and then generate

pulse that can distinguish between a powered

BUS

down V

are not required to respond to the SRP.

a V

BUS

3576fb

39

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

OVP

(OPTIONAL)

OVSENS

ON-THE-GO

POWER

MANAGER

OVGATE

LTC3576/

LTC3576-1

V

BUS

ENOTG

C

A

C

B

<6.5μF

WITHOUT OVP

–

+

D

ON-THE-GO

TRANSCEIVER

ON-THE-GO

TRANSCEIVER

3576 F11

A DEVICE

B DEVICE

Figure 11. LTC3576/LTC3576-1 as the A Device

OVP

(OPTIONAL)

OVSENS

STANDARD

USB HOST OR

ON-THE-GO

POWER

OVGATE

LTC3576/

LTC3576-1

V

BUS

MANAGER

ENOTG

C

A

B

<6.5μF FOR OTG DEVICES

<6.5μF

>96μF FOR STANDARD HOST

WITHOUT OVP

–

STANDARD OR

ON-THE-GO

TRANSCEIVER

D

ON-THE-GO

TRANSCEIVER

+

D

3576 F12

B DEVICE

A DEVICE

Figure 12. LTC3576/LTC3576-1 as the B Device

down on-the-go A device and a powered down standard

host. A suitable pulse can be generated because of the

disparity in the bypass capacitances of an on-the-go A

device and a standard host even if there is somewhat

high frequency components. High frequency currents,

such as the V , V , V and V currents tend to ﬁnd

BUS IN1 IN2

IN3

their way on the ground plane along 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 through their natural least-area path, excessive

voltage will build up and radiated emissions will occur

(see Figure 13). There should be a group of vias directly

under the grounded backside leading directly down to an

internal ground plane. To minimize parasitic inductance,

the ground plane should be as close as possible to the

top plane of the PC board (layer 2).

more than 6.5μF capacitance connected to the V

of the LTC3576/LTC3576-1.

BUS

Board Layout Considerations

The Exposed Pad on the backside of the LTC3576/

LTC3576-1 package must be securely soldered to the PC

board ground. This is the primary ground pin in the pack-

age, and it serves as the return path for both the control

circuitry and the N-channel MOSFET switches.

Furthermore, duetoitshighfrequencyswitchingcircuitry,

it is imperative that the input capacitor, inductor, and

output capacitor be as close to the LTC3576/LTC3576-1

as possible and that there be an unbroken ground plane

under the LTC3576/LTC3576-1 and all of their external

The IDGATE pin for the external ideal diode controller has

extremely limited drive current. Care must be taken to

minimize leakage to adjacent PC board traces. 100nA of

leakage from this pin will introduce an additional offset to

3576fb

40

LTC3576/LTC3576-1

APPLICATIONS INFORMATION

3576 F13

Figure 13. Higher Frequency Ground Current Follow Their

Incident Path. Slices in the Ground Plane Create Large Loop

Areas. The Large Loop Areas Increase the Inductance of the

Path Leading to Higher System Noise

theidealdiodeofapproximately10mV.Tominimizeleakage,

the trace can be guarded on the PC board by surrounding

as possible. Use area ﬁlls whenever possible. This

also applies to the PowerPath switching regulator

it with V

connected metal, which should generally be

inductor and the output capacitor on V . The GND

OUT

less than one volt higher than IDGATE.

side of the output capacitors should connect directly

to the thermal ground plane of the part.

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of

the LTC3576/LTC3576-1:

4. The switching power traces connecting SW, SW1,

SW2, SW3 and the switch node of the external step-

down switching regulator to their respective induc-

tors should be minimized to reduce radiated EMI and

parasitic coupling. Due to the large voltage swing

of the switching nodes, sensitive nodes such as the

feedback nodes (FB1, FB2 and FB3) should be kept

far away or shielded from the switching nodes or

poor performance could result.

1. The Exposed Pad of the package (Pin 39) should

connect directly to a large ground plane to minimize

thermal and electrical impedance.

2. The traces connecting V , V , V , V and

BUS IN1 IN2 IN3

V of the external step-down switching regulator

IN

to their respective decoupling capacitors should be

as short as possible. The GND side of these capaci-

tors should connect directly to the ground plane of

the part. These capacitors provide the AC current to

the internal power MOSFETs and their drivers. It is

critical to minimize inductance from these capacitors

to the LTC3576/LTC3576-1 and external step-down

switching regulator.

5. Keep the feedback pin traces (FB1, FB2, FB3 and FB

of the external step-down switching regulator) as

short as possible. Minimize any parasitic capacitance

between the feedback traces and any switching node

(i.e., SW, SW1, SW2, SW3 and logic signals). If nec-

essary shield the feedback nodes with a GND trace

6. Connect V , V and V to V through a short

OUT

IN1 IN2

low impedance trace.

IN3

3. Connections between the step-down switching regu-

lator (both internal and external) inductors and their

respective output capacitors should be kept as short

3576fb

41

LTC3576/LTC3576-1

TYPICAL APPLICATIONS

Minimum Parts Count USB Power Manager with Low-Battery Start-Up and USB On-the-Go

USB

26

27

28

L1

ON-THE-GO

3.3μH

V

WALL ACPR

C

35

34

36

33

31

32

TO OTHER

LOADS

USB,

WALL ADAPTER

V

SW

OUT

BUS

C1

10μF

0805

V

C3

22μF

0805

5

6

3

OVGATE

IDGATE

BAT

OVSENS

NTCBIAS

+

Li-Ion

4

29

1

NTC

8

9

7

PROG

CLPROG

V

IN1

L2

4.7μH

1.76V TO 3.3V

400mA

C2

0.1μF

0402

MEMORY

SW1

FB1

1k

3.01k

1.02M

324k

10pF

1μF

10μF

LTC3576/LTC3576-1

LDO3V3

2

24

23

25

V

IN2

12

L3

1.61V TO 3.03V

400mA

1μF

DV

CC

4.7μH

I/O

SW2

FB2

1μF

1.02M

365k

30

PUSHBUTTON

MICROCONTROLLER

CHRG

MICROPROCESSOR

13, 14

16

17

20

2

I C

V

IN3

L4

2μH

0.8V TO 1.51V

1A

10

22

CORE

POR

SW3

FB3

EN1

751k

806k

1μF

EN2

C1: MURATA GRM21BR7A106KE51L

C3: TAIYO YUDEN JMK212BJ226MG

L1: COILCRAFT LPS4018-332LM

L2, L3: TOKO 1098AS-4R7M

19

11

37

38

EN3

10k

ENOTG

L4: TOKO 1098AS-2R0M

I

LIM0

LIM1

21

3576 TA02

RST3

3576fb

42

LTC3576/LTC3576-1

TYPICAL APPLICATIONS

High Efﬁciency USB/Automotive Power Manager with Overvoltage Protection,

Reverse-Voltage Protection, Low-Battery Start-Up and USB On-the-Go

AUTOMOTIVE

FIREWIRE, ETC.

2

M1

4

L1

V

BOOST

SW

IN

6.8μH

0.47μF

D1

3

150k

4.7μF

68nF

5

LT3480

RUN/SS

22μF

499k

100k

40.2k

8

10

R

FB

T

PG

V

GND BD SYNC

C

7

11

1

6

9

M4

USB

26

27

28

L2

ON-THE-GO

3.3μH

V

WALL ACPR

USB,

WALL

ADAPTER

C

M3

35

34

36

33

31

32

TO OTHER

LOADS

V

SW

OUT

BUS

M2

C1

22μF

0805

V

C3

22μF

0805

2.2k

IDGATE

BAT

M5

5

6

R1

6.2k

OVGATE

OVSENS

+

Li-Ion

30

8

3

CHRG

NTCBIAS

100k

R2

V

IN1

4

29

1

L3

4.7μH

1.76V TO 3.3V

400mA

NTC

9

7

PROG

CLPROG

MEMORY

SW1

FB1

T

1.02M

324k

10pF

1μF

C2

0.1μF

0402

100k

1k

3.01k

10μF

LTC3576/LTC3576-1

LDO3V3

2

24

23

25

V

IN2

12

L4

4.7μH

1.61V TO 3.03V

400mA

1μF

DV

CC

I/O

SW2

FB2

1μF

1.02M

365k

10pF

PUSHBUTTON

MICROCONTROLLER

10μF

MICROPROCESSOR

13, 14

16

17

20

2

I C

V

IN3

L5

2μH

0.8V TO 1.51V

1A

10

22

CORE

POR

SW3

FB3

EN1

751k

806k

10pF

1μF

EN2

19

11

37

38

10μF

EN3

10k

ENOTG

I

LIM0

LIM1

21

3576 TA03

RST3

C1, C3: TAYIO YUDEN JMK212BJ226MG L5: TOKO 1098AS-2R0M

D1: DIODES INC. DFLS240L

M1,M2,M4, M5: SILICONIX Si2333DS

L1: TAIYO YUDEN NP06DZB6R8M

L2: COILCRAFT LPS4018-332LM

L3, L4: TOKO 1098AS-4R7M

M3: ON SEMICONDUCTOR NTLJS4114N

R1: 1/10W RESISTOR

R2: CURVE 1

3576fb

43

LTC3576/LTC3576-1

TYPICAL APPLICATIONS

High Efﬁciency USB/Automotive Power Manager with Overvoltage Protection, USB On-the-Go, Pushbutton Start,

Automatic Supply Sequencing and 10 Second Push-and-Hold Hard Shutdown

AUTOMOTIVE

FIREWIRE, ETC.

2

3

4

L1

V

BOOST

SW

IN

6.8μH

0.47μF

D1

4.7μF

150k

68nF

5

LT3480

499k

RUN/SS

22μF

100k

40.2k

8

10

R

FB

T

PG

V

GND BD SYNC

C

7

11

1

6

9

M2

USB

26

27

28

L2

ON-THE-GO

3.3μH

V

WALL ACPR

USB,

WALL

ADAPTER

C

M1

35

34

36

33

31

32

TO OTHER

LOADS

V

SW

OUT

BUS

C1

22μF

0805

V

C3

22μF

0805

2.2k

IDGATE

BAT

M3

5

6

R1

6.2k

OVGATE

OVSENS

+

Li-Ion

30

8

3

CHRG

NTCBIAS

100k

V

IN1

4

29

1

1.76V TO 3.3V

400mA

NTC

9

7

PROG

CLPROG

MEMORY

SW1

FB1

L3

4.7μH

R2

100k

T

1.02M

324k

10pF

1μF

C2

0.1μF

0402

1k

3.01k

10μF

LTC3576/LTC3576-1

14

13

12

16

22

17

SDA

SCL

V

IN3

0.8V TO 1.51V

1A

EN2

CORE

POR

DV

SW3

CC

L5

2μH

1μF

751k

806k

10pF

1μF

10k

20

FB3

10μF

2

LDO3V3

1k

1μF

21

24

10

23

RST3

V

IN2

1.61V TO 3.03V

400mA

EN1

1M

I/O

SW2

4.7k

EN3

M4

L4

4.7μH

1.02M

365k

10pF

1μF

5.1k 5.1k

25

11

37

38

FB2

10μF

ENOTG

SDA

SCL

10k

10μF

I

LIM0

LIM1

2

SEND I C CODE: “0s1201F8”

3576 TA04

C1, C3: TAYIO YUDEN JMK212BJ226MG M1: ON SEMICONDUCTOR NTLJS4114N

D1: DIODES INC. DFLS240L

L1: TAIYO YUDEN NP06DZB6R8M

L2: COILCRAFT LPS4018-332LM

L3, L4: TOKO 1098AS-4R7M

L5: TOKO 1098AS-2R0M

M2, M3: SILICONIX Si2333DS

M4: 2N7002

R1: 1/10W RESISTOR

R2: CURVE 1

3576fb

44

LTC3576/LTC3576-1

TYPICAL APPLICATIONS

High Efﬁciency USB/Automotive Power Manager with Current Limiting and

Overvoltage Protection on Both Inputs, Low-Battery Start-Up and USB On-the-Go

AUTOMOTIVE

FIREWIRE, ETC.

7.5V TO 36V

TRANSIENTS TO 60V

7

8

1

3

L1

4.7μH

V

BOOST

SW

IN

0.47μF

D1

4.7μF

34.2k

LT3653

22μF

6

5

I

SENSE

LIM

V

OUT

V

GND HVOK

C

9

2

4

USB

26

28

27

L2

ON-THE-GO

3.3μH

ACPR WALL

USB,

C

M1

35

34

36

33

31

32

TO OTHER

LOADS

WALL

V

SW

OUT

BUS

C1

22μF

0805

ADAPTER

V

BUS

C3

22μF

0805

IDGATE

BAT

5

6

R1

6.2k

OVGATE

OVSENS

+

Li-Ion

3

NTCBIAS

8

9

7

100k

R2

V

IN1

4

29

1

L3

1.76V TO 3.3V

400mA

NTC

4.7μH

PROG

CLPROG

MEMORY

SW1

FB1

T

1.02M

10pF

1μF

C2

0.1μF

0402

100k

1k

3.01k

10μF

324k

LTC3576/LTC3576-1

LDO3V3

2

24

23

25

V

IN2

12

L4

4.7μH

1.61V TO 3.03V

400mA

1μF

DV

CC

I/O

SW2

FB2

1μF

1.02M

365k

10pF

30

PUSHBUTTON

MICROCONTROLLER

CHRG

MICROPROCESSOR

13, 14

16

17

20

2

I C

V

IN3

L5

2μH

0.8V TO 1.51V

1A

10

22

CORE

POR

SW3

FB3

EN1

751k

806k

10pF

1μF

EN2

19

11

37

38

EN3

10k

ENOTG

I

LIM0

LIM1

21

3576 TA05

RST3

C1, C3: TAYIO YUDEN JMK212BJ226MG M1: FAIRCHILD FDN327S

D1: DIODES INC. DFLS140

R1: 1/10W RESISTOR

R2: CURVE 1

L1: COILCRAFT MSS6132-472MLC

L2: COILCRAFT LPS4018-332LM

L3, L4: TOKO 1098AS-4R7M

L5: TOKO 1098AS-2R0M

3576fb

45

LTC3576/LTC3576-1

TYPICAL APPLICATIONS

High Efﬁciency USB/Wall Power Manager with Dual Overvoltage Protection,

Reverse-Voltage Protection, Low-Battery Start-Up and USB On-The-Go

5V WALL

ADAPTER

M3

M4

M1

M2

C1

22μF

0805

M5

USB

5

27

28

L1

ON-THE-GO

3.3μH

OVGATE WALL ACPR

35

34

26

36

33

31

32

TO OTHER

LOADS

USB

V

SW

BUS

C2

V

BUS

C

OUT

22μF

C4

22μF

0805

2.2k

IDGATE

BAT

M6

R1

6.2k

+

6

3

OVSENS

NTCBIAS

Li-Ion

30

8

CHRG

100k

R2

V

IN1

4

29

1

L2

4.7μH

1.76V TO 3.3V

400mA

NTC

9

7

PROG

CLPROG

MEMORY

SW1

FB1

T

1.02M

324k

10pF

1μF

C3

100k

1k

0.1μF

0402

3.01k

10μF

LTC3576/LTC3576-1

LDO3V3

2

24

23

25

V

IN2

12

L3

4.7μH

1.61V TO 3.03V

400mA

1μF

DV

CC

I/O

SW2

FB2

1μF

1.02M

365k

10pF

PUSHBUTTON

MICROCONTROLLER

10μF

MICROPROCESSOR

13, 14

16

17

20

2

I C

V

IN3

L4

2μH

0.8V TO 1.51V

1A

10

22

CORE

POR

SW3

FB3

EN1

751k

806k

10pF

1μF

EN2

19

11

37

38

10μF

EN3

10k

ENOTG

I

LIM0

LIM1

21

3576 TA07

RST3

C1, C2, C4: TAYIO YUDEN JMK212BJ226MG M1, M2, M5, M6: SILICONIX Si2333DS

L1: COILCRAFT LPS4018-332LM

L2, L3: TOKO 1098AS-4R7M

L4: TOKO 1098AS-2R0M

M3, M4: FAIRCHILD FDN327S

R1: 1/10W RESISTOR

R2: CURVE 1

3576fb

46

LTC3576/LTC3576-1

PACKAGE DESCRIPTION

UFE Package

38-Lead Plastic QFN (4mm × 6mm)

(Reference LTC DWG # 05-08-1750 Rev B)

0.70 p0.05

4.50 p 0.05

3.10 p 0.05

2.40 REF

2.65 p 0.05

4.65 p 0.05

PACKAGE OUTLINE

0.20 p0.05

0.40 BSC

4.40 REF

5.10 p 0.05

6.50 p 0.05

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

PIN 1 NOTCH

R = 0.30 OR

0.35 s 45o

CHAMFER

2.40 REF

R = 0.10

0.75 p 0.05

TYP

4.00 p 0.10

37 38

0.40 p 0.10

PIN 1

TOP MARK

(NOTE 6)

1

2

4.65 p 0.10

4.40 REF

6.00 p 0.10

2.65 p 0.10

(UFE38) QFN 0708 REV B

0.200 REF

R = 0.115

TYP

0.20 p 0.05

0.40 BSC

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE

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

3576fb

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

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

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

47

LTC3576/LTC3576-1

TYPICAL APPLICATION

Firewire/Automotive Battery Charger with Automatic USB On-the-Go and Overvoltage Protection

AUTOMOTIVE

FIREWIRE, ETC.

7.5V TO 36V

TRANSIENTS TO 60V

7

8

1

L1

4.7μH

V

IN

BOOST

SW

0.47μF

D1

4.7μF

LT3653

22μF

34.2k

6

5

3

I

SENSE

LIM

V

OUT

V

GND HVOK

C

9

2

4

USB

ON-THE-GO

M1

26

28

27

J1

L2

MICRO-AB

3.3μH

ACPR WALL

C

35

34

36

33

TO OTHER

LOADS

V

BUS

V

SW

BUS

C1

22μF

0805

–

D

V

BUS

OUT

C2

22μF

0805

+

D

32

5

6

ID

OVGATE

OVSENS

BAT

6.2k

+

GND

Li-Ion

3.01k

LTC3576/LTC3576-1

TO USB

TRANSCEIVER

29

1

2

LDO3V3

PROG

1μF

CLPROG

300k

C3

M2

1k

0.1μF

0402

11

ENOTG

3576 TA06

V

BUS

POWERS UP WHEN ID PIN HAS LESS THAN 10ꢀ TO GND (MICRO-A PLUG CONNECTED)

C1, C2: TAIYO YUDEN JMK212BJ226MG L2: COILCRAFT LPS4018-332LM

D1: DIODES INC. DFLS140

J1: HIROSE ZX62-AB-5PA

L1: COILCRAFT MSS6132-472MLC

M1: FAIRCHILD FDN372S

M2: SILICONIX Si2333DS

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

Power Management

Switching USB Power Manager with Li-Ion/Polymer

Chargers Plus Triple Buck DC/DC

Maximizes Available Power from USB Port, Bat-Track, 1.5A Max Charge

Current, 180mꢀ Ideal Diode with <50mꢀ Option, 3.3V/25mA Always-On

LDO, Two 400mA and One 1A Buck Regulators, Instant-On Operation

(LTC3555-1), Instant-On Operation and 4.1V Float Votlage (LTC3555-3),

4mm × 5mm 28-Pin QFN Package

LTC3555/LTC3555-1

LTC3555-3

Switching USB Power Manager with Li-Ion/Polymer

Charger Plus Dual Buck Plus Buck-Boost DC/DC

Maximizes Available Power from USB Port, Bat-Track, Instant-On

Operation, 1.5A Max Charge Current, 180mꢀ Ideal Diode with <50mꢀ

Option, 3.3V/25mA Always-On LDO, Two 400mA Buck Regulators,

One 1A Buck-Boost Regulator, 4mm × 5mm 28-Pin QFN Package

LTC3556

LTC3586

Switching USB Power Manager with Li-Ion/Polymer

Charger Plus Dual Buck Plus Buck-Boost Plus Boost

DC/DC

Maximizes Available Power from USB Port, Bat-Track, Instant-On

Operation, 1.5A Max Charge Current, 180mꢀ Ideal Diode with <50mꢀ

Option, 3.3V/25mA Always-On LDO, Two 400mA Synchronous Buck

Regulators, One 1A Buck-Boost Regulator, One 600mA Boost Regulator,

4mm × 6mm 38-Pin QFN Package

Switching USB Power Manager and Battery Chargers

with Overvoltage Protection

Maximizes Available Power from USB Port, Bat-Track, Instant-On

Operation, 1.5A Max Charge Current, 180mꢀ Ideal Diode with <50mꢀ

Option, Controller for External High Voltage Buck Regulator, Protection

Against Transients of Up to 60V, 3.3V/25mA Always-On LDO,4.1V Float

Voltage (LTC4098-1), 4mm × 3mm 14-Pin DFN Package

LTC4098/LTC4098-1

3576fb

LT 0809 REV B • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

48

●

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


型号：	LTC3576-1_15
厂家：	Linear
描述：	Switching Power Manager with USB On-the-Go Triple Step-Down DC/DCs
文件：	总48页 (文件大小：593K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC3576-1_15 [Linear]

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