LINEAR TECHNOLOGY LTC3576, LTC3576-1 Technical data

LTC3576/LTC3576-1

Switching Power Manager

with USB On-the-Go + Triple

Step-Down DC/DCs

FEATURES

n

Bidirectional Switching Regulator with Bat-

Track™ Adaptive Output Control Provides Effi cient
Charging and

n

Bat-Track Control of External High Voltage Step-

a 5V Output for USB On-The-Go

Down Switching Regulator

n

Overvoltage Protection Guards Against Damage

n

“Instant-On” Operation with Discharged Battery

n

Triple Step-Down Switching Regulators with I2C

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

n

180mΩ Internal Ideal Diode + External Ideal Diode

OUT

)

Controller Powers the Load in Battery Mode

n

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

n

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

n

Compact (4mm × 6mm × 0.75mm) 38-pin QFN Package

CHG

)

APPLICATIONS

n

HDD-Based Media Players

n

GPS, PDAs, Digital Cameras, Smart Phones

n

Automotive Compatible Portable Electronics

DESCRIPTION

The LTC
management and battery charger ICs for Li-Ion/Polymer
battery applications. They each include a high effi ciency,
bidirectional switching PowerPath™ manager with auto­matic load prioritization, a battery charger, an ideal diode, a
controller for an external high voltage switching regulator
and three general purpose step-down switching regulators
with 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.
Both the USB and external switching regulator power paths
feature Bat-Track optimized charging to provide maximum
power to the application from supplies as high as 38V. An
overvoltage circuit protects the LTC3576/LTC3576-1 from
damage due to high voltage on the V
just two external components. The LTC3576/LTC3576-1 are
available in a low profi le 38-pin (4mm × 6mm × 0.75mm)
QFN package.

L, LT, LTC and LTM 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.

®

3576/LTC3576-1 are highly integrated power

2

C adjustable output voltages. The internal switch-

or WALL pins with

BUS

TYPICAL APPLICATION

High Effi ciency PowerPath Manager with Overvoltage Protection

and Triple Step-Down Regulator

AUTOMOTIVE

FIREWIRE, ETC.

USB OR

5V AC

ADAPTER

CONTROLS

ENABLE

CHARGE

6

OVERVOLTAGE

PROTECTION

USB COMPLIANT

BIDIRECTIONAL

SWITCHING
REGULATOR

LTC3576/LTC3576-1

HIGH EFFICIENCY

LT3653

EXTERNAL HIGH VOLTAGE

BUCK CONTROLLER

CC/CV

BATTERY

CHARGER

ALWAYS ON LDO

TRIPLE

STEP-DOWN

SWITCHING

REGULATORS

2

C PORT

I

0V

T

1

2

3

OPTIONAL

+

Li-Ion

3.3V/20mA

0.8V TO 3.6V/400mA

0.8V TO 3.6V/400mA

0.8V TO 3.6V/1A
RST

2

TO OTHER
LOADS

RTC/LOW
POWER LOGIC

MEMORY

I/O

CORE

µPROCESSOR

2

C

I

3576 TA01

PowerPath Switching Regulator Effi ciency

to System Load (P

100

90

80

BAT = 4.2V

70

60

50

40

EFFICIENCY (%)

30

20

V

BUS

I

BAT

10

10x MODE

0

10

= 5V

= 0mA

LOAD CURRENT (mA)

BAT = 3.3V

VOUT/PVBUS

100 1000

)

3576 TA01b

3576f

1

LTC3576/LTC3576-1

(Notes 1, 2, 3)

V

, WALL (Transient) t < 1ms,

BUS

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

, WALL (Static), BAT, V

V

BUS

, ENOTG, NTC, SDA, SCL, DVCC,

V

OUT

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

, I

I

LIM0

.........–0.3V to Max(V

ILIM1

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

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

I

OVSENS

I

CLPROG

I

CHRG

I

PROG

I

LDO3V3

I

SW1

I

SW

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

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

, I

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

RST3

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

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

, I

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

SW2

, I

, I

SW3

BAT

, I

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

VOUT

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

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

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

IN1

, V

IN2

BUS

, V

,

IN3

, V

, BAT) + 0.3V

OUT

OUT

INx

+ 0.3V
+ 0.3V

PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS

TOP VIEW

LIM1ILIM0

I

38 37 36 35 34 33 32

1CLPROG

LDO3V3

2

NTCBIAS

3

NTC

4

OVGATE

5

OVSENS

6

FB1

7

V

8

IN1

SW1

9

EN1

10

ENOTG

11

DV

12

CC

13 14 15 16

SCL

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

T

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

JMAX

BUSVBUSVOUT

SW

V

39

17 18 19

NC

SDA

UFE PACKAGE

= 125°C, θJA = 34°C/W

NC

IN3

V

SW3

BAT

EN3

31
30

29
28
27

26
25
24
23
22
21
20

IDGATE

CHRG

PROG

ACPR

WALL
V

C

FB2
V

IN2

SW2
EN2

RST3

FB3

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC3576EUFE#PBF LTC3576EUFE#TRPBF 3576
LTC3576EUFE-1#PBF LTC3576EUFE-1#TRPBF 35761
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.

Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/

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

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. V

BUS

38-Lead (4mm × 6mm) Plastic QFN
38-Lead (4mm × 6mm) Plastic QFN

= 5V, BAT = 3.8V, DVCC = 3.3V, R

CLPROG

otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

PowerPath Switching Regulator—Step-Down Mode

V

BUS

I

VBUS(LIM)

I

(Note 4) Input Quiescent Current

VBUSQ

Input Supply Voltage 4.35 5.5 V
Total Input Current

1× Mode
5× Mode
10× Mode
Low Power Suspend Mode
High Power Suspend Mode

1× Mode
5×, 10× Modes
Low/High Power Suspend Modes

l

82

l

440

l

800

l

0.32

l

1.6

–40°C to 85°C
–40°C to 85°C

= 3.01k, unless

90
472
880

0.39

2.05
7

17

0.045

100
500

1000

0.5

2.5

mA
mA
mA
mA
mA

mA
mA
mA

2

3576f

LTC3576/LTC3576-1

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

= 25°C. V

A

otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

h

CLPROG

(Note 4)

I

VOUT(POWERPATH)VOUT

V

CLPROG

V

UVLO

V

DUVLO

V

V

OUT

f

OSC

R

PMOS_

POWERPATH

R

NMOS_

POWERPATH

I

PEAK_POWERPATH

R

SUSP

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

V

BUS

V

OUT

I

VBUS

I

PEAK

I

OTGQ

V

CLPROG

V

OUT(UVLO)

t

SCFAULT

Bat-Track Switching Regulator Control

V

WALL

ΔV

WALL

V

OUT

I

WALLQ

R

ACPR

V

HACPR

V

LACPR

Ratio of Measured V
CLPROG Program Current

Current to

BUS

1x Mode
5x Mode
10x Mode
Low Power Suspend Mode
High Power Suspend Mode

Current Available Before

Discharging Battery

1x Mode, BAT = 3.3V
5x Mode, BAT = 3.3V
10x Mode, BAT = 3.3V
Low Power Suspend Mode
High Power Suspend Mode

CLPROG Servo Voltage in Current Limit Switching Modes

Suspend Modes

V

Undervoltage Lockout Rising Threshold

BUS

Falling Threshold 3.95

V

to BAT Differential Undervoltage

BUS

Lockout

Voltage 1x, 5x, 10x Modes, 0V < BAT < 4.2V,

OUT

Rising Threshold
Falling Threshold

I

VOUT

USB Suspend Modes, I
Switching Frequency 1.8 2.25 2.7 MHz
PMOS On-Resistance 0.18 

NMOS On-Resistance 0.30 

Peak Inductor Current Limit 1x Mode (Note 5)

5x Mode (Note 5)

10x Mode (Note 5)
Suspend LDO Output Resistance Closed Loop 10 

Output Voltage 0mA ≤ I
Input Voltage 2.9 5.5 V
Output Current Limit

V

Leakage Current in Shutdown On-the-Go Disabled, V

BUS

Peak Inductor Current Limit (Note 5) 1.8 A
V

Quiescent Current V

OUT

OUT

= 3.8V, I
Output Current Limit Servo Voltage 1.15 V
V

UVLO—V

OUT

V

UVLO—V

OUT

Short-Circuit Fault Delay V

OUT
OUT

Falling
Rising

< 4V and PMOS Switch Off 7.2 ms

BUS

Absolute WALL Input Threshold Rising Threshold

Hysteresis

Differential WALL Input Threshold WALL-BAT Falling

Hysteresis
Regulation Target Under VC Control 3.55 BAT + 0.3 V
WALL Quiescent Current 100 µA

ACPR Pull-Down Strength 100 
ACPR High Voltage V
ACPR Low Voltage 0V

= 5V, BAT = 3.8V, DVCC = 3.3V, R

BUS

= 0mA, Battery Charger Off

= 250µA

VOUT

≤ 500mA, V

VBUS

VBUS

= 0mA (Note 6) 1.38 mA

> 3.2V 4.75 5.25 V

OUT

< UVLO

BUS

= 3.01k, unless

CLPROG

210
1160
2200

9.6
56

121
667

1217

0.26

1.6

0.31
2

0.41

2.4

1.18

100

4.30

4.35 V

4.00

200

50

3.4

4.5

BAT + 0.3

4.6

4.7

4.7

1
2
3

l

550

–150

680

0 150

2.5 2.6

2.8 2.9

4.2 4.3

4.4 V

1.1

0306045 mV

OUT

mA/mA
mA/mA
mA/mA
mA/mA
mA/mA

mA
mA
mA
mA
mA

mV

mV
mV

mA

nA

mV

3576f

V

V

V
V

A
A
A

V
V

V

V

3

LTC3576/LTC3576-1

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

= 25°C. V

A

otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Overvoltage Protection

V

OVCUTOFF

V

OVGATE

t

RISE

Battery Charger

V

FLOAT

I

CHG

I

BAT

V

PROG

V

PROG_TRKL

V

C/10

h

PROG

I

TRKL

V

TRKL

ΔV

TRKL

ΔV

RECHRG

t

TERM

t

BADBAT

h

C/10

V

CHRG

I

CHRG

R

ON_CHG

T

LIM

NTC

V

COLD

Overvoltage Protection Threshold With 6.2k Series Resistor 6.1 6.35 6.7 V
OVGATE Output Voltage V

OVSENS

V

OVSENS

OVGATE Time to Reach Regulation OVGATE C

BAT Regulated Output Voltage LTC3576

LTC3576-1

Constant Current Mode Charger Current R

Battery Drain Current V

PROG

R

PROG

BUS

I

VOUT

V

BUS

> V

= 0µA

= 0V, I

(Ideal Diode Mode)
PROG Pin Servo Voltage 1.000 V
PROG Pin Servo Voltage in Trickle Charge BAT < V
C/10 Threshold Voltage at PROG 100 mV
Ratio of I

to PROG Pin Current 1030 mA/mA

BAT

Trickle Charge Current BAT < V
Trickle Charge Threshold Voltage BAT Rising 2.7 2.85 3.0 V
Trickle Charge Hysteresis Voltage 135 mV
Recharge Battery Threshold Voltage Threshold Voltage Relative to V
Safety Timer Termination Period Timer Starts When V
Bad Battery Termination Time BAT < V
End of Charge Current Ratio (Note 7) 0.085 0.1 0.112 mA/mA

CHRG Pin Output Low Voltage I
CHRG Pin Leakage Current V

= 5mA 65 100 mV

CHRG

CHRG

Battery Charger Power FET On­Resistance (Between V

and BAT)

OUT

Junction Temperature in Constant
Temperature Mode

Cold Temperature Fault Threshold Voltage Rising Threshold

Hysteresis

= 5V, BAT = 3.8V, DVCC = 3.3V, R

BUS

< V

OVCUTOFF

> V

OVCUTOFF

= 1nF 1.25 ms

LOAD

4.179

l

4.165

4.079

l

4.065

= 1k
= 5k

, Suspend Mode,

UVLO

VOUT

TRKL

, R

TRKL

PROG

TRKL

= 0µA

= 1k 100 mA

FLOAT

= V

BAT

FLOAT

980
185

–75 –100 –125 mV

3.3 4 5 Hour

0.4 0.5 0.6 Hour

= 3.01k, unless

CLPROG

1.88•V

OVSENS

12 V

0

4.200

4.200

4.100

4.100
1030

206

4.221

4.235

4.121

4.135
1065

223

3.6 6 µA

28 45 µA

0.100 V

mA
mA

= 5V 1 µA

0.18 

110 °C

75 76.5

1.5

78 %NTCBIAS

%NTCBIAS

V

V
V

V
V

V

HOT

V

DIS

I

NTC

Ideal Diode

V

FWD

R

DROPOUT

I

MAX_DIODE

4

Hot Temperature Fault Threshold Voltage Falling Threshold

Hysteresis

NTC Disable Threshold Voltage Falling Threshold

Hysteresis

33.4 34.9

1.5

0.7 1.7
50

36.4 %NTCBIAS
%NTCBIAS

2.7 %NTCBIAS
mV

NTC Leakage Current NTC = NTCBIAS = 5V –50 50 nA

Forward Voltage I
Internal Diode On-Resistance Dropout I

= 10mA 15 mV

VOUT

= 200mA 0.18 

VOUT

Diode Current Limit 2 A

3576f

LTC3576/LTC3576-1

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

= 25°C. V

A

otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Always On 3.3V LDO Supply

V

LDO3V3

R

CL_LDO3V3

R

OL_LDO3V3

Logic (I

LIM0

V

IL

V

IH

I

PD1

2

C Port

I

DV

CC

I

DVCC

V

DVCC(UVLO)

ADDRESS I
V

, SDA, SCL Input High Threshold 70 %DV

IH

VIL, SDA, SCL Input Low Threshold 30 %DV
I

, SDA, SCL Pull-Down Current 2µA

PD2

V

OL

f

SCL

t

BUF

t

HD_STA

t

SU_STA

t

SU_STO

t

HD_DAT(O)

t

HD_DAT(I)

t

SU_DAT

t

LOW

t

HIGH

t

f

t

r

t

SP

General Purpose Switching Regulators 1, 2 and 3

V

IN1,2,3

V

OUT(UVLO)

f

OSC

I

FB1,2,3

D1,2,3 Maximum Duty Cycle 100 %
R

SW1,2,3_PD

Regulated Output Voltage 0mA < I
Closed-Loop Output Resistance 2.7 
Dropout Output Resistance 23 

, I

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

LIM1

Logic Low Input Voltage 0.4 V
Logic High Input Voltage 1.2 V
I

, I

LIM0

, EN1, EN2, EN3, ENOTG, SCL,

LIM1

SDA Pull-Down Current

Input Supply 1.6 5.5 V
DVCC Current SCL/SDA = 0kHz, DVCC = 3.3V 0.5 µA
DVCC UVLO 1.0 V

2

C Address 0001001[0]

Digital Output Low (SDA) I

= 3mA 0.4 V

SDA

Clock Operating Frequency 400 kHz
Bus Free Time Between Stop and Start

Condition
Hold Time After (Repeated) Start

Condition
Repeated Start Condition Setup Time 0.6 µs
Stop Condition Setup Time 0.6 µs
Data Hold Time Output 0 900 ns
Data Hold Time Input 0 ns
Data Setup Time 100 ns
SCL Low Period 1.3 µs
SCL High Period 0.6 µs
SDA/SCL Fall Time 20 300 ns
SDA/SCL Rise Time 20 300 ns
Input Spike Suppression Pulse Width 50 ns

Input Supply Voltage (Note 8) 2.7 5.5 V
V

OUT

V

OUT

UVLO—V
UVLO—V

OUT
OUT

Falling
Rising

V

IN1,2,3

Low Impedance. Switching

Regulators are Disabled in UVLO
Switching Frequency 1.8 2.25 2.7 MHz
FBx Input Current V

FB1,2,3

SWx Pull-Down in Shutdown 10 k

= 5V, BAT = 3.8V, DVCC = 3.3V, R

BUS

< 20mA 3.1 3.3 3.5 V

LDO3V3

= 3.01k, unless

CLPROG

2µA

1.3 µs

0.6 µs

Connected to V

Through

OUT

2.5 2.6

2.8 2.9

= 0.85V –50 50 nA

CC

CC

V
V

3576f

5

LTC3576/LTC3576-1

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

= 25°C. V

A

otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

VIN1,2,3

V

FBHIGH1,2,3

V

FBLOW1,2,3

V

LSB1,2,3

R

LDO_CL1,2,3

R

LDO_OL1,2,3

General Purpose Switching Regulator 1 and 2

I

LIM1,2

I

OUT1,2

R

P1,2

R

N1,2

General Purpose Switching Regulator 3

I

LIM3

I

OUT3

R

P3

R

N3

t

RST3

Burst Mode is a registered trademark of Linear Technology Corporation.

Pulse Skip Mode Input Current I
Burst Mode

®

Input Current I
LDO Mode Input Current I
Shutdown Input Current Limit I

OUT1,2,3

OUT1,2,3

OUT1,2,3

OUT1,2,3

Maximum Servo Voltage Full Scale (1,1,1,1) (Note 10)
Minimum Servo Voltage Zero Scale (0,0,0,0) (Note 10) 0.405 0.425 0.445 V
V

Servo Voltage Step Size 25 mV

FB1,2

LDO Mode Closed-Loop R
LDO Mode Open-Loop R

OUT

OUT

V

FB1,2,3

(Note 11) 2.5 

PMOS Switch Current Limit Pulse Skip/Burst Mode Operation

(Note 5)
Available Output Current LDO Mode 50 mA
PMOS R

DS(ON)

NMOS R

DS(ON)

PMOS Switch Current Limit Pulse Skip/Burst Mode Operation

(Note 5)
Available Output Current LDO Mode 50 mA
PMOS R

DS(0N)

NMOS R

DS(ON)

Power-On Reset Time for Switching
Regulator

V

Within 92% of Final Value to

FB3

RST3 Hi-Z

= 5V, BAT = 3.8V, DVCC = 3.3V, R

BUS

= 3.01k, unless

CLPROG

= 0µA (Note 9) 90 µA
= 0µA (Note 9) 20 35 µA
= 0µA (Note 9) 15 25 µA
= 0µA, FB1,2,3 = 0V 1 µA

l

0.78 0.80 0.82 V

= V

= 0.8V 0.25 

OUT1,2 3

600 900 1300 mA

0.6 

0.7 

1300 1800 2800 mA

0.18 

0.3 

230 ms

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 2: The LTC3576E/LTC3576E-1 are guaranteed to meet performance
specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.

Note 3: 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 specifi ed maximum
operating junction temperature may impair device reliability.

Note 4: Total input current is the sum of quiescent current, I
measured current given by V

CLPROG

/R

CLPROG

• (h

CLPROG

VBUSQ

+ 1).

, and

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 specifi ed pin current rating may result in device
degradation or failure.

Note 6: The bidirectional switcher’s supply current is bootstrapped to V
and in the application will refl ect back to V

OUT

by (V

BUS/VOUT

) •

BUS

1/effi ciency. Total quiescent current is the sum of the current into the
V

pin plus the refl ected current.

OUT

Note 7: h

is expressed as a fraction of the measured full charge

C/10

current with indicated PROG resistor.
Note 8: V

not in UVLO.

OUT

Note 9: FBx above regulation such that regulator is in sleep. Specifi cation
does not include resistive divider current refl ected back to V

INx

.

Note 10: Applies to pulse skip and Burst Mode operation only.
Note 11: Inductor series resistance adds to open-loop R

OUT

.

3576f

6

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

Ideal Diode Resistance

Ideal Diode V-I Characteristics

1.0

0.8

0.6

0.4

CURRENT (A)

0.2

INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS

0

0.04

0

INTERNAL IDEAL
DIODE ONLY

0.12

0.08

FORWARD VOLTAGE (V)

V

0.16

BUS

USB Limited Load Current vs Battery
Voltage (Battery Charger Disabled)

900

800

700

600

500

400

300

LOAD CURRENT (mA)

200

100

0

2.7

3.0 3.6
BATTERY VOLTAGE (V)

3.3

V

BUS

5x MODE

3.9

= 5V

0.20

3576 G01

= 5V

4.2

3576 G04

vs Battery Voltage

0.25

0.20
INTERNAL IDEAL

0.15

0.10

RESISTANCE ()

0.05

0

3.0

2.7

Battery and V
vs Load Current

750

500

250

0

CURRENT (mA)

V

= 5V

BUS

BAT = 3.8V

–250

5x MODE
R

CLPROG

= 1k

R

PROG

–500

100 200 300

0

DIODE

INTERNAL IDEAL DIODE

WITH SUPPLEMENTAL

EXTERNAL VISHAY

Si2333 PMOS

3.6

3.3

BATTERY VOLTAGE (V)

Currents

BUS

V

CURRENT

BUS

BATTERY CURRENT
(CHARGING)

= 3.01k

BATTERY CURRENT

(DISCHARGING)

600 700 900

400 500

LOAD CURRENT (mA)

TA = 25°C unless otherwise specifi ed.

Voltage vs Load Current

V

OUT

(Battery Charger Disabled)

4.50
BAT = 4V

4.25

4.00

(V)

3.9

3576 G02

4.2

OUT

V

3.75

3.50

3.25

0

BAT = 3.4V

0.1 0.2 0.3

0.4 0.5

LOAD CURRENT (A)

Battery Charge Current vs
Temperature

600

R

= 2k

PROG

500

400

THERMAL REGULATION

040

TEMPERATURE (°C)

800

3576 G05

1000

300

200

CHARGE CURRENT (mA)

100

0

–40

–20 20

0.6 0.7 0.9

0.8

80

60

100

1.0

3576 G03

120

3576 G06

V

OUT

50mV/DIV

AC COUPLED

I

VOUT

500mA/DIV

0mA

PowerPath Switching Regulator
Transient Response

V

= 5V

BUS

= 3.65V

V

OUT

CHARGER OFF
10x MODE

20µs/DIV

3576 G07

PowerPath Switching Regulator
Effi ciency vs Load Current

100

90

1x MODE

80

70

60

EFFICIENCY (%)

50

40

30

10

5x, 10x MODE

100

LOAD CURRENT (mA)

3576 G08

1000

Battery Charging Effi ciency vs
Battery Voltage with No External
Load (P

95

R

CLPROG

R

90

PROG

85

80

75

70

EFFICIENCY (%)

65

5x MODE

60

55

50

2.7

BAT/PVBUS

= 3.01k

= 1k

3.0 3.6
BATTERY VOLTAGE (V)

)

1x MODE

3.3

3.9

4.2

3576 G09

3576f

7

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

V

Quiescent Current vs

BUS

V

Voltage (Suspend)

BUS

60

50

40

30

20

QUIESCENT CURRENT (µA)

10

0

0

1234

BUS VOLTAGE (V)

Battery Charge Current vs V
Voltage

600

R

= 3.01k

CLPROG

= 2k

R

PROG

500

5x MODE

400

300

200

BATTERY CURRENT (mA)

100

0

3.40

3.50 3.60

3.45 3.55
V

(V)

OUT

3.65

3.70

OUT

3.75

3576 G10

3576 G13

3.80

(V)

OUT

V

3.0

5

4.7

4.5

4.3

4.1

3.9

(V)

3.7

OUT

V

3.5

3.3

3.1

2.9

2.7

Voltage vs Load Current in

V

OUT

Suspend

5.0

4.5

3.5

2.5

4.0

0

V

HIGH POWER SUSPEND

LOW POWER SUSPEND

V

= 5V

BUS

BAT = 3.3V

= 3.01k

R

CLPROG

0.5
LOAD CURRENT (mA)

Voltage vs Battery Voltage

OUT

1.0

1.5

(Charger Overprogrammed)

V

= 5V

BUS

= 0V

I

VOUT

= 3.01k

R

CLPROG

= 1k

R

PROG

5x MODE

1x MODE

2.7

3.0

BATTERY VOLTAGE (V)

3.3

3.6

TA = 25°C unless otherwise specifi ed.

V

Current vs Load Current in

BUS

Suspend

2.5
V

= 5V

BUS

BAT = 3.3V

= 3.01k

R

CLPROG

2.0

1.5
HIGH POWER

SUSPEND

LOW POWER SUSPEND

0.5

0

1.0

LOAD CURRENT (mA)

2.0

3576 G11

2.5

CURRENT (mA)

1.0

BUS

V

0.5

0

Normalized Battery Charger Float
Voltage vs Temperature

1.001

1.000

0.999

0.998

0.997

NORMALIZED FLOAT VOLTAGE

3.9

3576 G14

4.2

0.996
–40

–15

10

TEMPERATURE (°C)

1.5

35

2.0

2.5

3576 G12

60

85

3576 G15

V

Quiescent Current vs

BUS

Temperature

25

V

= 5V

BUS

20

15

10

QUIESCENT CURRENT (mA)

5

0

–15

–40

8

5x MODE

1x MODE

35

10

TEMPERATURE (°C)

V

Quiescent Current in

BUS

Suspend vs Temperature

60

V

= 5V

BUS

50

40

30

20

QUIESCENT CURRENT (µA)

10

0

–40

60

85

3576 G16

–15 10 35 60

TEMPERATURE (°C)

85

3576 G17

Battery Drain Current vs
Temperature

35

30

25

20

15

10

BATTERY CURRENT (µA)

5

0

–15 10 35 85

–40

TEMPERATURE (°C)

BAT = 3.8V

= 0V

V

BUS

SWITCHING
REGULATORS OFF

60

3576 G18

3576f

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

OTG Boost Quiescent Current
vs V

Voltage

OUT

2.5

2.3

2.1

1.9

1.7

1.5

1.3

1.1

QUIESCENT CURRENT (mA)

0.9

0.7

0.5

2.90

3.55

4.20

V

(V)

OUT

OTG Boost Effi ciency
vs V

Voltage

OUT

95

500mA LOAD

90

85

80

EFFICIENCY (%)

75

100mA LOAD

4.85

3576 G19

5.50

OTG Boost V
vs Load Current

5.5

5.0

0 100

V

V

OUT

V

OUT

V

OUT

V

OUT

(V)

BUS

V

4.5

4.0

3.5

3.0

OTG Boost Start-Up Time into
Current Source Load vs V
Voltage

2.50

2.25

2.00

TIME (ms)

1.75

22µF ON V

22µF ON V
LOAD THROUGH OVP

Voltage

BUS

= 4.75V

BUS

I

= 500mA

VBUS

= 5V
= 4.4V
= 3.8V
= 3.2V

400

300

200

LOAD CURRENT (mA)

, 22µF AND

BUS

LOAD THROUGH OVP

22µF ON V

,

BUS

500

OUT

NO OVP

TA = 25°C unless otherwise specifi ed.

OTG Boost Effi ciency
vs Load Current

100

90

80

70

EFFICIENCY (%)

60

50

600

700

3576 G20

40

1

10 100 1000

LOAD CURRENT (mA)

OTG Boost Burst Mode Current

BUS

Threshold vs V

400

300

,

200

LOAD CURRENT (mA)

100

FALLING THRESHOLD

OUT

RISING THRESHOLD

Voltage

V

= 5V

OUT

= 4.4V

V

OUT

= 3.8V

V

OUT

= 3.2V

V

OUT

3576 G21

70

2.90

V

BUS

50mV/DIV

AC COUPLED

I

VBUS

200mA/DIV

0mA

3.55

1.50

2.9

4.20

V

OUT

(V)

4.85

5.50

3576 G22

3.4 3.9 4.4 4.9
V

(V)

OUT

5.4

3576 G23

0

2.90

3.55
V

4.20

OUT

(V)

4.85

5.50

3576 G24

OTG Boost Start-Up into Current
Source Load

50mV/DIV

I

VBUS

200mA/DIV

0mA

V

BUS

2V/DIV

0V

V

= 3.8V

OUT

20µs/DIV

3576 G25

V
I

LOAD

OUT

= 3.8V

= 500mA

200µs/DIV

AC COUPLED

3576 G26

V

BUS

V

1V/DIV

SW

OTG Boost Burst Mode OperationOTG Boost Transient Response

0V

OUT

I

LOAD

= 3.8V

= 10mA

50µs/DIVV

3576 G27

3576f

9

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

Battery Charging from USB-HV

USB OTG from BAT-HV BUCK-BAT

V

OUT

1V/DIV

V

BUS

I

BAT

0A

HVOK

5V/DIV

0V

V

V

BUS

5V/DIV

= 3.8V

BAT

= 285mA

I

BUS

= 12V

HV

IN

USING LT3653

500µs/DIV

V

OUT

1V/DIV

AC COUPLED

V

BUS

100mV/DIV

AC COUPLED

V

5V/DIV

HVOK

5V/DIV

V

BUS

5V/DIV

BUCK-USB

AC COUPLED

200mV/DIV

SW

0V

0V

V

BUS

HV
USING LT3653

IN

= 5V
= 12V

500µs/DIV

AC COUPLED

1A/DIV

3576 G28

OVP Connect Waveform OVP Disconnect Waveform

TA = 25°C unless otherwise specifi ed.

Oscillator Frequency vs
Temperature

2.30

2.25

2.20

2.15

FREQUENCY (MHz)

3576 G29

2.10

2.05
–40

–15

10

TEMPERATURE (°C)

Rising OVP Threshold vs
Temperature

6.280

6.275

V

= 5V

OUT

= 4.2V

V

OUT

= 3.6V

V

OUT

= 3V

V

OUT

= 2.7V

V

OUT

35

60

85

3576 G30

OVGATE

5V/DIV

OVP INPUT

VOLTAGE

0V TO 5V

STEP 5V/DIV

OVGATE vs OVSENS

12

OVSENS CONNECTED
TO INPUT THROUGH

6.2k RESISTOR

10

8

6

OVGATE (V)

4

2

0

0

OVP INPUT

STEP 5V/DIV

500µs/DIV

24 68

INPUT VOLTAGE (V)

3576 G31

3576 G34

OVGATE

5V/DIV

VOLTAGE

5V TO 10V

500µs/DIV

OVGATE Quiescent Current vs
Temperature

37

V

= 5V

OVSENS

35

33

31

QUIESCENT CURRENT (µA)

29

27

–40

–15

10

TEMPERATURE (°C)

6.270

6.265

OVP THRESHOLD (V)

3576 G32

6.260

6.255
–40

–15

10

TEMPERATURE (°C)

35

60

85

3576 G33

RST3, CHRG Pin Current vs
Voltage (Pull-Down State)

100

V

= 5V

BUS

BAT = 3.8V

80

60

40

20

RST3, CHRG PIN CURRENT (mA)

35

60

85

3576 G35

0

1

0

RST3, CHRG PIN VOLTAGE (V)

3

4

2

5

3576 G36

10

3576f

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

3.3V LDO Output Voltage vs
Load Current, V

3.4
BAT = 3.9V, 4.2V

3.2

3.0

OUTPUT VOLTAGE (V)

BAT = 3V

2.8

BAT = 3.1V

BAT = 3.2V

BAT = 3.3V

2.6

5

0

LOAD CURRENT (mA)

10

= 0V

BUS

BAT = 3.4V

15

Switching Regulator Soft-Start
Waveform

500mV/DIV

OUT

V

50µs/DIV

BAT = 3.5V

BAT = 3.6V

20

3576 G37

3576 G40

20mV/DIV

AC COUPLED

25

3.3V LDO Step Response
(5mA to 15mA)

I

LDO3V3

5mA/DIV

0mA

V

LDO3V3

20µs/DIVBAT = 3.8V

Switching Regulator Current Limit
vs Temperature

2.0
REGULATOR 3

1.5

1.0

CURRENT LIMIT (A)

0.5

V

IN1,2,3

0

–40

REGULATORS 1, 2

= 3.8V

–15

10

TEMPERATURE (°C)

35

TA = 25°C unless otherwise specifi ed.

Battery Drain Current vs
Battery Voltage

35

I

= 0mA

VOUT

30

V

= 0V

BUS

25

20

15

10

3576 G38

BATTERY CURRENT (µA)

5

0

2.7

R

DS(ON)

V

BUS

(SUSPEND MODE)

3.0 3.3 3.6 4.2
BATTERY VOLTAGE (V)

for Switching Regulator

Power Switches vs Temperature

1.0

0.8
NMOS SWITCH

0.6

PMOS SWITCH

0.4

ON-RESISTANCE (Ω)

NMOS SWITCH

0.2
PMOS SWITCH

0

–15

60

85

3576 G41

–40

10

TEMPERATURE (°C)

= 5V

3.9

REGULATORS 1, 2

REGULATOR 3

35

60

3576 G39

85

3576 G42

Switching Regulator Low Power
Quiescent Currents vs Temperature

100

90

80

70

60

50

40

30

QUIESCENT CURRENTS (μA)

20

10

0

–40

PULSE-SKIP MODE

Burst Mode OPERATION

LDO MODE

–15

10

TEMPERATURE (°C)

35

Switching Regulators 1, 2
Pulse-Skip Mode Effi ciency

100

V

= 3.8V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

60

85

3576 G43

0.1 10 100 1000

V

= 2.5V

OUT1,2

V

OUT1,2

V

= 1.8V

OUT1,2

1

LOAD CURRENT (mA)

= 1.2V

3576 G44

Switching Regulators 1, 2
Burst Mode Effi ciency

100

V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

V

= 3.8V

OUT1,2

V

OUT1,2

1

LOAD CURRENT (mA)

= 2.5V

V

OUT1,2

= 1.8V

= 1.2V

3576 G45

3576f

11

LTC3576/LTC3576-1

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Regulator Constant
Frequency Quiescent Currents

8

7

6

5

4

3

2

QUIESCENT CURRENT (mA)

1

0

–40

SWITCHING

REGULATOR 3

SWITCHING

REGULATORS 1, 2

–15 10 60

TEMPERATURE (°C)

35

Switching Regulators 1, 2
Feedback Voltage vs Load Current

0.820

0.815

0.810

0.805

0.800

FEEDBACK VOLTAGE (V)

0.795

0.790

0.1 10 100 1000

Burst Mode
OPERATION

PULSE-SKIP

MODE

1

LOAD CURRENT (mA)

Switching Regulator 3 Feedback
Voltage vs Load Current

0.810

85

3576 G46

50mV/DIV

AC COUPLED

200mA/DIV

3576 G49

Switching Regulator 3
Pulse-Skip Mode Effi ciency

100

V

= 3.8V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

V

= 2.5V

OUT3

V

OUT3

V

= 1.2V

OUT3

1

LOAD CURRENT (mA)

= 1.8V

Switching Regulators 1, 2
Transient Response

V

OUT2

I

OUT2

0mA

V
V

IN2
OUT2

= 3.8V

= 3.4V

50µs/DIV

Switching Regulator 3
Transient Response

TA = 25°C unless otherwise specifi ed.

Switching Regulator 3
Burst Mode Effi ciency

100

V

3576 G47

= 3.8V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

V

OUT3

V

= 1.2V

OUT3

V

= 1.8V

OUT3

1

LOAD CURRENT (mA)

Switching Regulator Mode
Transition, Pulse Skip-LDO­Pulse Skip

V

OUT3

50mV/DIV

AC COUPLED

V

SW3

1V/DIV

0V

3576 G50

V
V
I

OUT3

IN3
OUT3

= 3.8V

= 1.8V

= 50mA

50µs/DIV

Switching Regulator Mode
Transition, Pulse Skip–Burst
Mode Operation–Pulse Skip

= 2.5V

3576 G48

3576 G51

0.805

0.800

FEEDBACK VOLTAGE (V)

0.795

0.790

0.1 10 100 1000

Burst Mode

OPERATION

PULSE SKIP MODE

1

LOAD CURRENT (mA)

12

3576 G52

V

OUT3

50mV/DIV

AC COUPLED

I

OUT3

500mA/DIV

0mA

V
V

IN3
OUT3

= 3.8V

= 1.8V

50µs/DIV

3576 G53

V

OUT3

50mV/DIV

AC COUPLED

V

SW3

1V/DIV

0V

V

IN3

V

OUT3

I

OUT3

= 3.8V

= 1.8V

= 100mA

50µs/DIV

3576 G54

3576f

PIN FUNCTIONS

LTC3576/LTC3576-1

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

pins. A precise fraction, h

V

BUS

CLPROG

, of the V

BUS

cur­rent 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.
Several V

current limit settings are available via user

BUS

input which will typically correspond to the 500mA and
100mA USB specifi cations. 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 fi ltering.

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

OUT

.

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.

NTC (Pin 4): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a negative temperature coeffi cient
thermistor, which is typically co-packaged with the battery,
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
resistor is required from NTCBIAS to NTC and a thermistor
is required from NTC to ground. To disable NTC operation,
connect NTC to GND and leave NTCBIAS open.

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

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
charge pump capable of creating suffi cient overdrive to fully
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.

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
pin exceeds

V

OVCUTOFF

,

the OVGATE pin will be pulled
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.

FB1 (Pin 7): Feedback Input for Switching Regulator 1.
When regulator 1’s control loop is complete, this pin servos
to 1 of 16 possible set points based on the commanded

2

value from the I

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

V

IN1

This pin will generally be connected to V

C serial port. See Table 4.

OUT

. A 1µF MLCC

capacitor is recommended on this pin.
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

2

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

I
current source.

ENOTG (Pin 11): Logic Input. This logic input pin inde­pendently enables the bidirectional switching regulator to
step up the voltage on V

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

V

BUS

and provide a 5V output on

OUT

pin is logically ORed with its corresponding bit in the

2

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

I
current source.

3576f

13

LTC3576/LTC3576-1

PIN FUNCTIONS

DVCC (Pin 12): Logic Supply for the I2C Serial Port. If the
serial port is not needed, it can be disabled by grounding

. When DVCC is grounded, the I2C bits are set to their

DV

CC

default values. See Table 3.

2

SCL (Pin 13): Clock Input Pin for the I

2

C logic levels are scaled with respect to DVCC. If DVCC

I

C Serial Port. The

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
determine the operating modes of switching regulators 1,
2 and 3 when DV

is grounded. See Tables 3 and 5. Has

CC

a 2µA internal pull-down current source.

2

SDA (Pin 14): Data Input Pin for the I

2

C logic levels are scaled with respect to DVCC. If DVCC

I

C Serial Port. The

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

2

C7 bits in the I

C serial port. SDA in conjunction with SCL
determine the operating modes of switching regulators 1,
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

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

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

V

IN3

This pin will generally be connected to V

PCB trace wider.

IN3

. A 1µF MLCC

OUT

IN3

capacitor is recommended on this pin.
SW3 (Pin 17): Power Transmission Pin for Switching

Regulator 3.
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.

EN3 (Pin 19): Logic Input. This logic input pin indepen­dently enables switching regulator 3. Active high. This
pin is logically ORed with its corresponding bit in the

2

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

I
current source.

FB3 (Pin 20): Feedback Input for Switching Regulator 3.
When regulator 3’s control loop is complete, this pin servos

to 1 of 16 possible set points based on the commanded

2

value from the I

C serial port. See Table 4.

RST3 (Pin 21): Logic Output. This in an open-drain output
which indicates that switching regulator 3 has settled to
its fi nal value. It can be used as a power-on reset for the
primary microprocessor or to enable the other switching
regulators for supply sequencing.

EN2 (Pin 22): Logic Input. This logic input pin indepen­dently enables switching regulator 2. Active high. This
pin is logically ORed with its corresponding bit in the

2

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

I
current source.

SW2 (Pin 23): Power Transmission Pin for Switching
Regulator 2.

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

V

IN2

This pin will generally be connected to V

. A 1µF MLCC

OUT

capacitor is recommended on this pin.
FB2 (Pin 25): Feedback Input for Switching Regulator 2.

When regulator 2’s control loop is complete, this pin servos
to 1 of 16 possible set points based on the commanded

2

value from the I

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

V

C

Output. This pin drives the V

C serial port. See Table 4.

pin of an external Linear

C

Technology step-down switching regulator. An external P­channel MOSFET is sometimes required to provide power
to V

with its gate tied to the ACPR pin (see Applications

OUT

Information). In concert with WALL and ACPR, it will
regulate V

to maximize battery charger effi ciency

OUT

WALL (Pin 27): External Power Source Sense Input. 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 au­tomatically disabled. Pulling this pin above 4.3V enables

pin.

the V

C

14

3576f

PIN FUNCTIONS

LTC3576/LTC3576-1

ACPR (Pin 28): External Power Source Present Output
(Active Low). ACPR indicates that the output of the external
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
is connected to V
WALL. ACPR has a high level of V

and whose drain is connected to

OUT

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 Cur­rent Monitor Pin. Connecting a 1% resistor from PROG
to ground programs the charge current. If suffi cient input
power is available in constant-current mode, this pin servos
to 1V. The voltage on this pin always represents the actual
charge current by using the following formula:

V

I

BAT

PROG

= • 1030

R

PROG

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
indicate whether there is a short-circuit condition on 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.

IDGATE (Pin 31): Ideal Diode Amplifi er Output. This pin
controls the gate of an optional external P-channel MOSFET
used as an ideal diode between V

and BAT. The external

OUT

ideal diode operates in parallel with the internal ideal diode.
The source of the P-channel MOSFET should be connected
to V

and the drain should be connected to BAT. If the

OUT

external ideal diode MOSFET is not used, IDGATE should
be left fl oating.

BAT (Pin 32): Single Cell Li-Ion Battery Pin. Depending on
available V
deliver power to V
from V

V

OUT

(Pin 33): Output Voltage of the Bidirectional Pow-

OUT

power, a Li-Ion battery on BAT will either

BUS

through the ideal diode or be charged

OUT

via the battery charger.

erPath 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

and the internal bat-

OUT

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

ensures that V

OUT

the load exceeds the allotted power from V

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

V

BUS

pin delivers power to V

via the SW pin. V

BUS

is powered even if

OUT

or if the

BUS

should

OUT

be bypassed with a low impedance ceramic capacitor.

V

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

BUS

to V

via the SW pin by drawing controlled current from

OUT

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. Tie the two V

pins together at the part and bypass

BUS

with a low impedance multilayer ceramic capacitor.
SW (Pin 36): The SW pin transfers power between V

and V

via the bidirectional switching regulator. See

OUT

BUS

the Applications Information section for a discussion of
inductance value and current rating.

, I

I

LIM0

(Pins 37, 38): I

LIM1

LIM0

and I

control the current

LIM1

limit of the PowerPath switching regulator. See Table 1.
Both the I

LIM0

and I

corresponding bits in the I

pins are logically ORed with their

LIM1

2

C serial port. See Tables 3 and

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

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15