LINEAR TECHNOLOGY LTC3555, LTC3555-X Technical data

LTC3555/LTC3555-X

High Effi ciency USB Power

Manager + Triple

Step-Down DC/DC

FEATURES

Power Manager

n

High Effi ciency Switching PowerPath™ Controller

with Bat-Track™ Adaptive Output Control

n

Programmable USB or Wall Current Limit

(100mA/500mA/1A)

n

Full Featured Li-Ion/Polymer Battery Charger

n

1.5A Maximum Charge Current

n

Internal 180mΩ Ideal Diode + External Ideal Diode

Controller Powers Load in Battery Mode

n

Low No-Load Quiescent Current when Powered from

BAT (<32µA)

DC/DCs

n

Triple High Effi ciency Step-Down DC/DCs

(1A/400mA/400mA I

n

All Regulators Operate at 2.25MHz

n

Dynamic Voltage Scaling on Two Outputs

n

I2C or Independent Enable, V

n

Low No-Load Quiescent Current: 20µA

n

28-Pin (4mm × 5mm × 0.75mm) QFN Package

OUT

)

Controls

OUT

APPLICATIONS

n

HDD-Based MP3 Players, PDAs, GPS, PMPs

n

Portable Medical Products

n

Handheld Instrumentation

n

Other USB-Based Handheld Products

DESCRIPTION

The LTC®3555 family are highly integrated USB com­patible power management and battery charger ICs for
Li-Ion/Polymer battery applications. They include a high
effi ciency current limited switching PowerPath manager
with automatic load prioritization, a battery charger, an ideal
diode and three general purpose synchronous step-down
switching regulators.

The LTC3555 family limits input current to either 100mA
or 500mA for USB applications or 1A for adapter-powered
applications. Unlike linear chargers, the LTC3555 family’s
switching architecture transmits nearly all of the power avail­able from the USB port to the load with minimal loss and
heat which eases thermal constraints in small spaces.

Two of the three general purpose switching regulators can
provide up to 400mA and the third can deliver 1A. The
entire product can be controlled via I
LTC3555-1/LTC3555-3 versions offer “instant-on” power
delivery to the portable product even with a very low battery
voltage. The LTC3555-3 version also has a reduced charger
fl oat voltage of 4.100V for battery safety and longevity.

The LTC3555 family is available in the low profi le 28-pin
(4mm × 5mm × 0.75mm) QFN surface mount package.

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. PowerPath
and Bat-Track are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 6522118 and 6404251.

2

C or simple I/O. The

TYPICAL APPLICATION

High Effi ciency PowerPath Manager and Triple Step-Down Regulator

USB/WALL

4.35V TO 5.5V

CHARGE

ENABLE

CONTROLS

5

USB COMPLIANT

STEP-DOWN
REGULATOR

CURRENT
CONTROL

LTC3555/LTC3555-X

HIGH EFFICIENCY

STEP-DOWN

SWITCHING

REGULATORS

2

I

TRIPLE

C PORT

CC/CV

BATTERY

CHARGER

ALWAYS ON LDO

0V

1

2

3

OPTIONAL

+

T

0.8V TO 3.6V/400mA

0.8V TO 3.6V/400mA

0.8V TO 3.6V/1A

RST

2

Li-Ion

TO OTHER
LOADS

3.3V/25mA

RTC/LOW
POWER LOGIC

MEMORY

I/O

CORE

µPROCESSOR

2

C

I

3555 TA01

Switching Regulator Effi ciency to

System Load (P

100

90

80

BAT = 4.2V

70

60

50

40

EFFICIENCY (%)

30

20

V

= 5V

BUS

= 0mA

I

10

BAT

10x MODE

0

0.01

OUT/PBUS

BAT = 3.3V

0.1 1

I

(A)

OUT

)

3555 TA01b

3555fd

1

LTC3555/LTC3555-X

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Notes 1, 2, 3)

V

(Transient) t < 1ms,

BUS

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

, V

, V

, V

V

IN1

IN2

IN3

(Static), DVCC,

BUS

FB1, FB2, FB3, NTC, BAT, EN1, EN2, EN3,

, I

I

LIM0

I

CLPROG

I

RST3

I

PROG

I

LDO3V3

I

SW1

, I

I

SW

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

LIM1

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

, I

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

CHRG

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

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

, I

............................................................600mA

SW2

, I

, I

SW3

BAT

...................................................2A

VOUT

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

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

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

LDO3V3

CLPROG

NTC

FB2

V

IN2

SW2

EN2

DV

CC

28-LEAD (4mm × 5mm) PLASTIC QFN

EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB

TOP VIEW

LIM1ILIM0

I

SW

28 27 26 25 24

1

2

3

4

5

6

7

8

T

JMAX

29

9 10

11 12 13

IN3

SCL

SDA

V

UFD PACKAGE

= 125°C, θJA = 37°C/W

BUSVOUT

V

EN3

SW3

BAT

23

22

GATE

21

CHRG

20

PROG

19

FB1

18

V

IN1

17

SW1

16

EN1

15

RST3

14

FB3

ORDER INFORMATION

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

LTC3555EUFD#PBF LTC3555EUFD#TRPBF 3555 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

LTC3555IUFD#PBF LTC3555IUFD#TRPBF 3555 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

LTC3555EUFD-1#PBF LTC3555EUFD-1#TRPBF 35551 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

LTC3555IUFD-1#PBF LTC3555IUFD-1#TRPBF 35551 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

LTC3555EUFD-3#PBF LTC3555EUFD-3#TRPBF 35553 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

LTC3555IUFD-3#PBF LTC3555IUFD-3#TRPBF 35553 28-Lead (4mm x 5mm) Plastic QFN –40°C to 85°C

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
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

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

BUS

PROG

= 1k, R

CLPROG

= 3k,

unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

PowerPath Switching Regulator

V

BUS

I

BUSLIM

I

VBUSQ

Input Supply Voltage 4.35 5.5 V

Total Input Current 1x Mode, V

V

Quiescent Current 1x Mode, I

BUS

5x Mode, V
10x Mode, V
Suspend Mode, V

5x Mode, I
10x Mode, I
Suspend Mode, I

OUT
OUT

OUT
OUT

OUT

= BAT
= BAT

OUT

= 0mA
= 0mA

= 0mA

= BAT

OUT

OUT

= BAT

= 0mA

l

87

l

436

l

800

l

0.31

95
460
860

0.38
7

15
15

0.044

100
500

1000

0.50

mA
mA
mA
mA

mA
mA
mA
mA

3555fd

2

LTC3555/LTC3555-X

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

unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

h

CLPROG

(Note 4)

I

OUT(POWERPATH)VOUT

V

CLPROG

V

UVLO_VBUS

V

UVLO_VBUS-BAT

V

OUT

f

OSC

R

PMOS_POWERPATH

R

NMOS_POWERPATH

I

PEAK_POWERPATH

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

Ratio of Measured V
CLPROG Program Current

Current to

BUS

1x Mode
5x Mode
10x Mode
Suspend Mode

Current Available Before

Loading BAT

1x Mode, BAT = 3.3V
5x Mode, BAT = 3.3V
10x Mode, BAT = 3.3V
Suspend Mode

CLPROG Servo Voltage in Current
Limit

V

Undervoltage Lockout Rising Threshold

BUS

1x, 5x, 10x Modes
Suspend Mode

Falling Threshold 3.95

V

to BAT Differential Undervoltage

BUS

Lockout
V

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

OUT

Rising Threshold
Falling Threshold

I

= 0mA, Battery Charger Off

OUT

USB Suspend Mode, I

Switching Frequency 1.8 2.25 2.7 MHz

PMOS On Resistance 0.18 

NMOS On Resistance 0.30 

Peak Switch Current Limit 1x, 5x Modes

10x

BAT Regulated Output Voltage LTC3555/LTC3555-1

LTC3555/LTC3555-1
LTC3555-3
LTC3555-3

Constant Current Mode Charge
Current

Battery Drain Current V

R
R

V

PROG
PROG

BUS
BUS

= 1k
= 5k

> V

= 0V, I
LTC3555
LTC3555-1/LTC3555-3

PROG Pin Servo Voltage 1.000 V

PROG Pin Servo Voltage in Trickle

BAT < V

Charge
C/10 Threshold Voltage at PROG 100 mV

Ratio of I

to PROG Pin Current 1022 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 Timer Starts when BAT = V

Bad Battery Termination Time BAT < V

End of Charge Indication Current Ratio (Note 5) 0.088 0.1 0.112 mA/mA

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

BUS

= 250µA 4.5 4.6 4.7 V

VOUT

, Battery Charger Off, I

UVLO

= 0µA (Ideal Diode Mode)

VOUT

TRKL

TRKL

FLOAT

FLOAT

TRKL

VOUT

= 0µA

PROG

= 1k, R

CLPROG

= 3k,

224
1133
2140

11.3
135

672

1251

0.32

1.188
100

4.30

4.35 V

4.00
200

50

3.4 BAT + 0.3 4.7 V

2
3

4.179

l

4.165

4.079

l

4.065
980

185

4.200

4.200

4.100

4.100
1022

204

2 3.5

27
32

4.221

4.235

4.121

4.135
1065

223

5

38
44

0.100 V

100 mA

–75 –100 –125 mV

3.3 4 5 Hour

0.42 0.5 0.63 Hour

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

mA
mA
mA
mA

mV

mV
mV

mA
mA

µA

µA
µA

V

V

A
A

V
V
V
V

3555fd

3

LTC3555/LTC3555-X

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

unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CHRG

I

CHRG

R

ON_CHG

T

LIM

NTC

V

COLD

V

HOT

V

DIS

I

NTC

Ideal Diode

V

FWD

R

DROPOUT

I

MAX_DIODE

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

, SDA, SCL Input High Threshold 70 %DV

V

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

CHRG Pin Output Low Voltage I
CHRG Pin Leakage Current V

= 5mA 65 100 mV

CHRG

= 5V 1 µA

CHRG

Battery Charger Power FET On
Resistance (Between V

and BAT)

OUT

Junction Temperature in Constant
Temperature Mode

Cold Temperature Fault Threshold
Voltage

Hot Temperature Fault Threshold
Voltage

Rising Threshold
Hysteresis

Falling Threshold
Hysteresis

NTC Disable Threshold Voltage Falling Threshold

Hysteresis

NTC Leakage Current V

Forward Voltage V

Internal Diode On Resistance, Dropout V

= V

NTC

= 0V, I

BUS

I

= 10mA

VOUT

= 0V 0.18 

BUS

Internal Diode Current Limit 1.6 A

Regulated Output Voltage 0mA < I

Closed-Loop Output Resistance 4 

Dropout Output Resistance 23 

, I

, EN1, EN2, EN3)

LIM1

Logic Low Input Voltage 0.4 V

Logic High Input Voltage 1.2 V

I

, I

LIM0

, EN1, EN2, EN3

LIM1

Pull-Down Currents

Input Supply Voltage 1.6 5.5 V

DVCC Current SCL/SDA = 0kHz 0.5 µA

DVCC UVLO 1.0 V

2

C Address 0001 001[0]

Digital Output Low (SDA) I

= 3mA 0.4 V

PULLUP

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

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

BUS

PROG

= 1k, R

CLPROG

= 3k,

0.18 

110 °C

75.0 76.5

78.0 %V

1.5

33.4 34.9

36.4 %V

1.5

0.7 1.7

2.7 %V

50

= 5V –50 50 nA

BUS

VOUT

= 10mA

2

15

< 25mA 3.1 3.3 3.5 V

LDO3V3

2µA

1.3 µs

0.6 µs

%V

%V

BUS
BUS

BUS
BUS

BUS

mV

mV
mV

CC

CC

3555fd

4

LTC3555/LTC3555-X

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

unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

t

SU_STD

t

HD_DAT(OUT)

t

HD_DAT(IN)

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

OUTUVLO

f

OSC

I

FB1,2,3

D

1,2,3

R

SW1,2,3_PD

General Purpose Switching Regulator 1

I

VIN1

I

LIMSW1

I

OUT1

V

FB1

R

P1

R

N1

R

LDO_CL1

R

LDO_OL1

General Purpose Switching Regulator 2

I

VIN2

I

LIMSW2

I

OUT2

Stop Condition Time 0.6 µs

Data Hold Time 225 ns

Input Data Hold Time 0 900 ns

Data Setup Time 100 ns

Clock Low Period 1.3 µs

Clock High Period 0.6 µs

Clock Data Fall Time 20 300 ns

Clock Data Rise Time 20 300 ns

Spike Suppression Time 50 ns

Input Supply Voltage 2.7 5.5 V

V

OUT

V

OUT

UVLO—V
UVLO—V

OUT
OUT

Falling
Rising

Connected to V

V

IN1,2,3

Impedance. Switching Regulators are Disabled in
UVLO

Oscillator Frequency 1.8 2.25 2.7 MHz

FBx Input Current V

= 0.85V –50 50 nA

FB1,2,3

Maximum Duty Cycle 100 %

SWx Pull-Down in Shutdown 10 k

Pulse Skip Mode Input Current
Burst Mode Input Current
Forced Burst Mode

®

Input Current
LDO Mode Input Current
Shutdown Input Current

= 0µA (Note 6)

I

OUT1

I

= 0µA (Note 6)

OUT1

I

= 0µA (Note 6)

OUT1

I

= 0µA (Note 6)

OUT1

I

= 0µA, FB1 = 0V

OUT1

PMOS Switch Current Limit Pulse Skip/Burst Mode Operation 600 800 1100 mA

Available Output Current Pulse Skip/Burst Mode Operation (Note 7)

Forced Burst Mode Operation (Note 7)
LDO Mode (Note 7)

V

Servo Voltage (Note 8)

FB1

PMOS R

DS(ON)

NMOS R

DS(ON)

LDO Mode Closed-Loop R

LDO Mode Open-Loop R

Pulse Skip Mode Input Current
Burst Mode Input Current
Forced Burst Mode Input Current
LDO Mode Input Current
Shutdown Input Current

OUT

OUT

(Note 9) 2.5 

I

= 0µA (Note 6)

OUT2

I

= 0µA (Note 6)

OUT2

I

= 0µA (Note 6)

OUT2

I

= 0µA (Note 6)

OUT2

I

= 0µA, FB2 = 0V

OUT2

PMOS Switch Current Limit Pulse Skip/Burst Mode Operation 600 800 1100 mA

Available Output Current Pulse Skip/Burst Mode Operation (Note 7)

Forced Burst Mode Operation (Note 7)
LDO Mode (Note 7)

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

BUS

Through Low

OUT

PROG

= 1k, R

CLPROG

= 3k,

2.5 2.6

2.8 2.9

225

35
20
20

60
35
35

1

400

60
50

l

0.78 0.80 0.82 V

0.6 

0.7 

0.25 

225

35
20
20

60
35
35

1

400

60
50

µA
µA
µA
µA
µA

mA
mA
mA

µA
µA
µA
µA
µA

mA
mA
mA

V
V

Burst Mode is a registered trademark of Linear Technology Corporation.

3555fd

5

LTC3555/LTC3555-X

ELECTRICAL CHARACTERISTICS

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

FBHIGH2

V

FBLOW2

V

LSB2

R

P2

NMOS R

R

N2

R

LDO_CL2

R

LDO_OL2

General Purpose Switching Regulator 3

I

VIN3

I

LIMSW3

I

OUT3

V

FBHIGH3

V

FBLOW3

V

LSB3

R

P3

R

N3

R

LDOCL3

R

LDOOL3

t

RST3

Maximum Servo Voltage Full Scale (1, 1, 1, 1) (Note 8)

Minimum Servo Voltage Zero Scale (0, 0, 0, 0) (Note 8) 0.405 0.425 0.445 V

V

Servo Voltage Step Size 25 mV

FB2

PMOS R

DS(ON)

DS(ON)

LDO Mode Closed-Loop R

LDO Mode Open-Loop R

OUT

OUT

Pulse Skip Mode Input Current
Burst Mode Input Current
Forced Burst Mode Input Current
LDO Mode Input Current
Shutdown Input Current

PMOS Switch Current Limit Pulse Skip/Burst Mode Operation 1500 2000 2800 mA

Available Output Current Pulse Skip/Burst Mode Operation (Note 7)

Maximum Servo Voltage Full Scale (1, 1, 1, 1) (Note 8)

Minimum Servo Voltage Zero Scale (0, 0, 0, 0) (Note 8) 0.405 0.425 0.445 V

VFB Servo Voltage Step Size 25 mV

PMOS R

DS(ON)

NMOS R

DS(ON)

LDO Mode Closed Loop R

LDO Mode Open Loop R

OUT

OUT

Power On Reset Time for Switching
Regulator

= 25°C. V

A

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

BUS

= 1k, R

PROG

l

0.78 0.80 0.82 V

CLPROG

= 3k,

0.6 

0.7 

0.25 

(Note 9) 2.5 

I

= 0µA (Note 6)

OUT3

I

= 0µA (Note 6)

OUT3

I

= 0µA (Note 6)

OUT3

I

= 0µA (Note 6)

OUT3

I

= 0µA, FB3 = 0V

OUT3

Forced Burst Mode Operation (Note 7)
LDO Mode (Note 7)

1000

150

50

l

0.78 0.80 0.82 V

225

35
20
20

60
35
35

1

mA
mA
mA

0.18 

0.30 

0.25 

(Note 9) 2.5 

V

Within 92% of Final Value to RST3 Hi-Z 230 ms

FB3

µA
µA
µA
µA
µA

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 LTC3555E/LTC3555E-X 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. The LTC3555I/LTC3555I-X are
guaranteed to meet performance specifi cations over the full –40°C to 85°C
operating temperature range.

Note 3: The LTC3555/LTC3555-X 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.

6

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

VBUSQ

, and

measured current given by:
V

CLPROG/RCLPROG

Note 5: h

C/10

• (h

CLPROG

+1)

is expressed as a fraction of measured full charge current

with indicated PROG resistor.
Note 6: FBx above regulation such that regulator is in sleep. Specifi cation

does not include resistive divider current refl ected back to V

INx

.

Note 7: Guaranteed by design but not explicitly tested.
Note 8: Applies to pulse skip, Burst Mode operation and forced Burst

Mode operation only.
Note 9: Inductor series resistance adds to open-loop R

OUT

.

3555fd

TYPICAL PERFORMANCE CHARACTERISTICS

LTC3555/LTC3555-X

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

0.08

FORWARD VOLTAGE (V)

USB Limited Battery Charge
Current vs Battery Voltage

700

600

500

400

300

200

CHARGE CURRENT (mA)

100

5x USB SETTING,
BATTERY CHARGER SET FOR 1A

0

2.7

LTC3555

LTC3555-1/
LTC3555-3

3.0 3.3 3.6 4.2

V

= 5V

BUS

R

PROG

R

CLPROG

BATTERY VOLTAGE (V)

INTERNAL IDEAL
DIODE ONLY

V

BUS

V

BUS

0.12

0.16

= 1k

= 3k

LTC3555-3

3.9

= 0V
= 5V

3555 G01

3555 G04

0.20

Ideal Diode Resistance
vs Battery Voltage

0.25

0.20

INTERNAL IDEAL

0.15

0.10

RESISTANCE (Ω)

0.05

0

2.7

DIODE

INTERNAL IDEAL DIODE

WITH SUPPLEMENTAL

EXTERNAL VISHAY

Si2333 PMOS

3.0

3.3

BATTERY VOLTAGE (V)

USB Limited Battery Charge
Current vs Battery Voltage

150

125

100

75

50

CHARGE CURRENT (mA)

25

1x USB SETTING,
BATTERY CHARGER SET FOR 1A

0

2.7

LTC3555

LTC3555-1/
LTC3555-3

3.0 3.3 3.6 3.9

V

BUS

R

PROG

R

CLPROG

BATTERY VOLTAGE (V)

3.6

= 5V

= 1k

= 3k

LTC3555-3

3.9

3555 G02

3555 G05

4.2

4.2

Output Voltage vs Output Current
(Battery Charger Disabled)

4.50

BAT = 4V

4.25

4.00

BAT = 3.4V

3.75

OUTPUT VOLTAGE (V)

3.50

3.25
200

0

OUTPUT CURRENT (mA)

400

600

Battery Drain Current
vs Battery Voltage

25

= 0µA

I

VOUT

BUS

V

= 5V

3.6

20

15

10

BATTERY CURRENT (µA)

5

0

2.7

V

(SUSPEND MODE)

3.0

3.3

BATTERY VOLTAGE (V)

BUS

V

= 5V

BUS

5x MODE

800

3555 G03

= 0V

3.9

3555 G06

1000

4.2

PowerPath Switching Regulator
Effi ciency vs Output Current

100

BAT = 3.8V

90

80

70

EFFICIENCY (%)

60

50

40

0.01

1x MODE

0.1 1

OUTPUT CURRENT (A)

5x, 10x MODE

3555 G07

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

100

R

CLPROG

R

PROG

= 0mA

I

VOUT

90

80

EFFICIENCY (%)

70

60

2.7

BAT/PBUS

= 3k

= 1k

3.0

)

LTC3555-1/
LTC3555-3

LTC3555-3

1x CHARGING EFFICIENCY

5x CHARGING EFFICIENCY

3.6

3.3

BATTERY VOLTAGE (V)

3.9

3555 G08

50

40

30

20

QUIESCENT CURRENT (µA)

10

4.2

Current vs V

V

BUS

(Suspend)

BAT = 3.8V
I

VOUT

0

0

= 0mA

1

Voltage

BUS

3

2

BUS VOLTAGE (V)

4

5

3555 G09

3555fd

7

LTC3555/LTC3555-X

TYPICAL PERFORMANCE CHARACTERISTICS

Output Voltage vs Load Current in
Suspend

5.0

4.5

4.0

3.5

OUTPUT VOLTAGE (V)

3.0

V

= 5V

BUS

BAT = 3.3V

= 3k

R

CLPROG

2.5

0.1

0

LOAD CURRENT (mA)

0.2

0.3

Battery Charge Current vs
Temperature

600

500

400

300

200

CHARGE CURRENT (mA)

100

R

PROG

10x MODE

0

–40

–20 20

THERMAL REGULATION

= 2k

040

TEMPERATURE (°C)

60

V

Current vs Load Current in

BUS

Suspend

0.5
V

= 5V

BUS

BAT = 3.3V

= 3k

R

CLPROG

0.4

0.3

CURRENT (mA)

0.2

BUS

V

0.1

0.4

0.5

3555 G10

0

0.1

0

LOAD CURRENT (mA)

0.2

0.3

0.4

0.5

3555 G11

Normalized Battery Charger Float
Voltage vs Temperature

1.001

1.000

0.999

0.998

0.997

NORMALIZED FLOAT VOLTAGE

80

100

120

3555 G13

0.996
–40

–15

10

TEMPERATURE (°C)

35

60

85

3555 G14

3.3V LDO Output Voltage vs Load

3.4

3.2

3.0

OUTPUT VOLTAGE (V)

2.8

2.6

Current, V

BAT = 3.9V, 4.2V

BAT = 3V

BAT = 3.1V

BAT = 3.2V

0

= 0V

BUS

BAT = 3.4V

BAT = 3.3V

5

10

LOAD CURRENT (mA)

BAT = 3.5V

15

Low-Battery (Instant-On) Output
Voltage vs Temperature

3.68
BAT = 2.7V

= 100mA

I

VOUT

5x MODE

3.66

3.64

OUTPUT VOLTAGE (V)

3.62

3.60

–40

–15

10

TEMPERATURE (°C)

35

BAT = 3.6V

20

3555 G12

60

3555 G15

25

85

Oscillator Frequency vs
Temperature

2.6

2.4

2.2

FREQUENCY (MHz)

2.0

1.8
–40

–15

8

V

= 5V

BUS

BAT = 3V

= 0V

V

BUS

BAT = 2.7V

= 0V

V

BUS

35

10

TEMPERATURE (°C)

BAT = 3.6V

= 0V

V

BUS

60

3555 G16

15

12

QUIESCENT CURRENT (mA)

85

Quiescent Current vs

V

BUS

Temperature

V

= 5V

BUS

= 0µA

I

VOUT

9

6

3

–40

1x MODE

–15

TEMPERATURE (°C)

V

Quiescent Current in

BUS

Suspend vs Temperature

70

I

= 0µA

VOUT

5x MODE

35

60

10

85

3555 G17

60

50

40

QUIESCENT CURRENT (µA)

30

–40

–15

10

TEMPERATURE (°C)

35

60

85

3555 G18

3555fd

TYPICAL PERFORMANCE CHARACTERISTICS

LTC3555/LTC3555-X

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)

0

1

0

RST3, CHRG PIN VOLTAGE (V)

R

for Switching Regulator

DS(ON)

3

2

Power Switches vs Temperature

1.0

0.8

0.6

0.4

ON-RESISTANCE (Ω)

0.2

0

–40

NMOS SWITCH

PMOS SWITCH

NMOS SWITCH

PMOS SWITCH

–15

REGULATORS 1, 2

REGULATOR 3

35

10

TEMPERATURE (°C)

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

I

LDO3V3

5mA/DIV

0mA

V

LDO3V3

20mV/DIV

AC COUPLED

20µs/DIVBAT = 3.8V

4

5

3555 G19

3555 G20

Switching Regulator Current Limit
vs Temperature

2.0

REGULATOR 3

1.5

1.0

CURRENT LIMIT (A)

0.5

V

IN1,2,3

60

85

3555 G22

0

–40

REGULATORS 1, 2

= 3.8V

–15

10

TEMPERATURE (°C)

35

60

85

3555 G23

Battery Drain Current vs
Temperature

50

BAT = 3.8V

= 0V

V

BUS

BUCK REGULATORS OFF

40

30

20

BATTERY CURRENT (µA)

10

0

–40

–15

TEMPERATURE (°C)

35

10

Switching Regulator Low Power
Mode Quiescent Currents

50

V

= 3.8V

IN1,2,3

= 2.5V

V

OUT1,2,3

40

30

20

INPUT CURRENT (µA)

10

0

–40

FORCED

Burst Mode

OPERATION

–15

10

TEMPERATURE (°C)

35

60

Burst Mode

OPERATION

LDO MODE

60

85

3555 G21

85

3555 G24

Switching Regulators 1, 2 Pulse
Skip Mode Quiescent Currents

325

V

= 3.8V

IN1,2

300

V

= 2.5V

275

250

INPUT CURRENT (µA)

225

200

(CONSTANT FREQUENCY)

–15

–40

OUT1,2

V

OUT1,2

(PULSE SKIPPING)

35

10

TEMPERATURE (°C)

= 1.25V

60

3555 G25

1.95

1.90
INPUT CURRENT (mA)

1.85

1.80

1.75

1.70

85

Switching Regulator 3 Pulse Skip
Mode Quiescent Currents

400

V

= 2.5V

OUT3

350

V

= 3.5V

(CONSTANT FREQUENCY)

300

INPUT CURRENT (µA)

250

200

–40

–15

TEMPERATURE (°C)

IN3

35

10

V

= 3.8V

IN3

(PULSE
SKIPPING)

60

3555 G26

11

INPUT CURRENT (mA)

10

9

8

7

85

Switching Regulator Soft-Start
Waveform

500mV/DIV

OUT

V

50µs/DIV

3555 G27

3555fd

9

LTC3555/LTC3555-X

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Regulators 1, 2
Pulse Skip Mode Effi ciency

100

90

V

= 2.5V

OUT1,2

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

1

10 100 1000

LOAD CURRENT (mA)

Switching Regulator 3
Pulse Skip Mode Effi ciency

100

V

= 3.8V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

1

V

= 2.5V

OUT3

10 100 1000

LOAD CURRENT (mA)

V

OUT1,2

V

OUT1,2

= 1.2V

= 1.8V

V

V

OUT3

V

OUT3

IN1,2

= 3.8V

= 1.2V

= 1.8V

3555 G28

3555 G31

Switching Regulators 1, 2
Burst Mode Effi ciency

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

V

= 2.5V

OUT1,2

V

OUT1,2

V

= 1.8V

OUT1,2

1

LOAD CURRENT (mA)

= 1.2V

V

IN1,2

Switching Regulator 3
Burst Mode Effi ciency

100

V

= 3.8V

IN3

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

1

V

= 2.5V

OUT3

V

= 1.2V

OUT3

V

= 1.8V

OUT3

LOAD CURRENT (mA)

= 3.8V

3555 G29

3555 G32

Switching Regulators 1, 2
Forced Burst Mode Effi ciency

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

0.1 10 100 1000

V

= 2.5V

OUT1,2

V

= 1.2V

OUT1,2

V

= 1.8V

OUT1,2

1

LOAD CURRENT (mA)

V

IN1,2

Switching Regulator 3
Forced Burst 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

1

LOAD CURRENT (mA)

OUT3

= 1.8V

V

V

OUT3

OUT3

= 2.5V

= 1.2V

= 3.8V

3555 G30

3555 G33

Switching Regulators 1, 2 Load
Regulation at V

1.230
V

= 3.8V

IN1,2

1.215

1.200

OUTPUT VOLTAGE (V)

1.185

1.170

PULSE SKIP

MODE

0.1 10 100 1000

OUT1,2

Burst Mode
OPERATION

Burst Mode
OPERATION

1

LOAD CURRENT (mA)

10

= 1.2V

FORCED

3555 G34

Switching Regulators 1, 2 Load
Regulation at V

1.845
V

= 3.8V

IN1,2

Burst Mode OPERATION

1.823
PULSE SKIP MODE

1.800

OUTPUT VOLTAGE (V)

1.778

1.755

FORCED

Burst Mode

OPERATION

0.1 10 100 1000

1

LOAD CURRENT (mA)

OUT1,2

= 1.8V

3555 G35

Switching Regulators 1, 2 Load
Regulation at V

2.56
V

= 3.8V

IN1,2

Burst Mode OPERATION

2.53

PULSE SKIP MODE

2.50

OUTPUT VOLTAGE (V)

2.47

2.44

FORCED
Burst Mode
OPERATION

0.1 10 100 1000

1

LOAD CURRENT (mA)

OUT1,2

= 2.5V

3555 G36

3555fd