LINEAR TECHNOLOGY LTC3455 Technical data

LOAD CURRENT (mA)

60

EFFICIENCY (%)

80

75

70

65

85

90

95

100

3455 TA01b

V

BAT

= 3.6V

SWITCHER 1
V

OUT1

= 1.8V

SWITCHER 2
V

OUT2

= 3.3V

1 10 100 1000

查询LTC3411供应商

LTC3455

Dual DC/DC Converter

with USB Power Manager

FEATURES

■

Seamless Transition between Input Power Sources:
Li-Ion Battery, USB, and 5V Wall Adapter

■

Accurate USB Current Limiting (500mA/100mA)

■

Two High Efficiency DC/DC Converters: Up to 96%

■

Thermal Regulation Maximizes Battery Charge
Rate without Risk of Overheating*

■

Full-Featured Li-Ion Battery Charger

■

Hot Swap™ Output for SDIO and Memory Cards

■

Pin-Selectable Burst Mode® Operation

■

Output Disconnect: All Outputs Discharged to
Ground During Shutdown

■

Available in a 4mm × 4mm × 0.8mm 24-Pin
QFN Package

U

APPLICATIO S

■

Handheld Computers

■

Digital Cameras

■

MP3 Players

and Li-Ion Battery Charger

U

DESCRIPTIO

The LTC®3455 is a complete power management solution
for a variety of portable applications. The device contains
two synchronous step-down DC/DC converters, a USB
power controller, a full-featured Li-Ion battery charger, a
Hot Swap output, a low-battery indicator, and numerous
internal protection features. The LTC3455 provides a
small, simple solution for obtaining power from three
different power sources: a single-cell Li-Ion battery, a USB
port, and a wall adapter. Current drawn from the USB bus
is accurately limited under all conditions. Whenever a USB
or a wall adapter is present, the battery charger is enabled
and all internal power for the device is drawn from the
appropriate external power source. All outputs are dis­charged to ground during shutdown to provide complete
output disconnect. The device is available in a
4mm × 4mm 24-pin exposed-pad QFN package.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Hot Swap is a trademark of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent 6,522,118

TYPICAL APPLICATIO

USB 5V

1Ω

4.7µF

WALL 5V

1Ω

1µF

SINGLE

CELL Li-ION

3.3V TO 4.2V

USB

CONTROLLER

10µF

3.32k

1.24k

1.8V

+

LBO

V

BAT

2.49M

806k

0.1µF

4.7µF

1k

2.49k

1M

10

11

17

16

8
6

5

4

3
2

9

USB
SUSPEND

USBHP

V

MAX

CHRG
WALLFB

TIMER
PROG

V

BAT

AO

AI

LTC3455

U

MODE
HSON

ON2

PWRON

RST

PBSTAT

HSO

HSI

SW2

FB2

SW1

FB1

GND

3455 TA01a

21
15
19
22
20
23

1M

24

ON

14

13

4.7µH

12

10pF

18

4.7µH

7

10pF

1

25

1M

ON/OFF

µC

1.8V

3.3V, HS

1µF

249k

80.6k

100k

80.6k

3.3V

0.5A

10µF

1.8V

0.4A

10µF

Efficiency

3455f

1

LTC3455

242523 22 21 20 19

7 8 9

TOP VIEW

UF PACKAGE

24-LEAD (4mm × 4mm) PLASTIC QFN

10 11 12

6

5

4

3

2

1

13

14

15

16

17

18

FB1

PROG

TIMER

CHRG

USBHP

SUSPEND

FB2
AO
AI
HSON
HSO
HSI

ON

PBSTAT

PWRON

MODE

RST

ON2

SW1

USB

V

BAT

V

MAX

WALLFB

SW2

ABSOLUTE AXI U RATI GS

(Note 1)

V

BAT

SW1, SW2 Voltages ....................–0.3V to (V

TIMER Voltage.............................–0.3V to (V

PWRON, ON, ON2, HSON Voltages .............–0.3V to 6V

PBSTAT, RST, CHRG, AO Voltages ..............– 0.3V to 6V

HSI, HSO Voltages.......................................–0.3V to 6V

MODE, USBHP, SUSPEND Voltages ............–0.3V to 6V

WALLFB, AI, PROG Voltages .......................–0.3V to 2V

FB1, FB2 Voltages........................................–0.3V to 2V

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

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

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

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. V
V

USB

PARAMETER CONDITIONS MIN TYP MAX UNITS

Battery Undervoltage Lockout Voltage V
Battery Undervoltage Lockout Hysteresis 450 mV
V

BAT

Burst Mode,
PWM Mode, Battery Powered V
USB Powered V
Wall Powered V
Shutdown V

ON Pin Threshold 0.8 1.0 V
PWRON Pin Threshold 0.8 1.0 V
ON2 Pin Threshold 0.8 1.0 V
MODE Pin Threshold 0.8 1.0 V
WALLFB Pin Threshold Voltage WALLFB Rising ● 1.20 1.23 1.26 V
WALLFB Pin Hysteresis 60 mV
ON Pin Pullup Current VON = 1V 2.5 µA
PWRON Pin Pulldown Current V
ON2 Pin Pulldown Current V
MODE Pin Pullup Current V
WALLFB Pin Input Bias Current V
PBSTAT Pin Low Voltage VON = 0V, I

RST Pin Low Voltage I

RST Pulse Duration After FB1 and FB2 in Regulation 200 ms

2

, V

, USB Voltages ...........................–0.3V to 6V

MAX

= 0V, V

Pin Quiescent Current (Note 3)

= 0V unless otherwise noted.

WALLFB

Battery Powered V

WW

W

U

UUW

PACKAGE/ORDER I FOR ATIO

ORDER PART

+0.3V)

MAX

+0.3V)

MAX

T

= 125°C, θJA = 36°C/W, θJC = 2.5°C/W

JMAX

EXPOSED PAD (PIN 25) IS GND

MUST BE SOLDERED TO PCB

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

The ● denotes the specifications which apply over the full operating

= 3.6V, V

BAT

Rising 2.9 3.0 3.2 V

BAT

= V

ON2

= 1V, V

ON2

= 5V, Charger Off 10 20 µA

USB
WALL
PWRON

PWRON

= 1V 2.5 µA

ON2

MODE

WALLFB

= 0V, I

V

ON

= 100µA 0.02 0.10 V

RST

= 1mA 0.20 0.35 V

I

RST

= 1V, Not Switching 110 160 µA

MODE

= 1.5V, V

= 0V, V

= 0V, Not Switching 500 800 µA

MODE

= 4.5V, Charger Off 10 20 µA

MAX

= 0V 2 4 µA

MAX

= 1V 2.5 µA

= 1V 2.5 µA

= 1.35V ● ±1 ±30 nA

= 100µA 0.02 0.10 V

PBSTAT

= 1mA 0.20 0.35 V

PBSTAT

= 3.6V, V

MAX

PWRON

= 2V, V

is open, V

ON

NUMBER

LTC3455EUF

UF PART

MARKING

3455

ON2

= 0V,

3455f

LTC3455

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. V
V

USB

= 0V, V

= 0V unless otherwise noted.

WALLFB

The ● denotes the specifications which apply over the full operating

= 3.6V, V

BAT

= 3.6V, V

MAX

PWRON

= 2V, V

is open, V

ON

ON2

= 0V,

PARAMETER CONDITIONS MIN TYP MAX UNITS
Battery-V

V

MAX

V

MAX

V

MAX

PMOS

MAX

PMOS Switch On-Resistance 0.15 Ω
Switch Current Limit 2.5 4.0 A
Switch Current Limit at Startup With V

MAX

Rising, V

MAX

= 3V, V

= 3.6V 0.4 0.9 A

BAT

Gain Block

AI Pin Threshold Voltage ● 0.784 0.805 0.826 V
AI Pin/FB2 Pin Voltage Difference V

FB2

– V

AI

–8 0 8 mV
AI Pin Input Bias Current VAI = 0.85V ● ±1 ±25 nA
AO Pin Sink Current VAI = 0.6V, VAO = 1.5V 1.0 1.8 2.5 mA
AO Pin Voltage VAI = 0.6V, IAO = 1mA 0.8 1.2 V

Switching Regulators

FB1, FB2 Voltage ● 0.784 0.805 0.826 V
FB1, FB2 Voltage Line Regulation V
FB1, FB2 Voltage Burst Mode Hysteresis V
FB1, FB2 Pin Input Bias Current V

= 3V to 5V 0.01 %/V

MAX

= 2V 8 mV

MODE

= V

FB1

= 0.85V ● ±1 ±25 nA

FB2

Switching Frequency Both Switchers 1.2 1.5 1.8 MHz
PMOS Switch On-Resistance Both Switchers 0.35 Ω
NMOS Switch On-Resistance Both Switchers 0.45 Ω
PMOS Switch Current Limit Switcher 1 450 600 850 mA

Switcher 2 700 900 1200 mA

USB Power Manager

USB Undervoltage Lockout Voltage From Low to High 3.75 3.90 4.10 V
USB Undervoltage Lockout Hysteresis 150 mV
USB Minimum Voltage to Charge Battery 4.0 V
USB PMOS Switch On-Resistance V
USB Current Limit V

USB Suspend Mode Bias Current V

= 5V 0.5 Ω

USB

V

USB
USB

USB

= 5V, V
= 5V, V

= 5V, V

= 2V ● 440 475 500 mA

USBHP

= 0V ● 60 80 100 mA

USBHP

= 2V 4 20 µA

SUSPEND

SUSPEND Pin Threshold 0.8 1.1 V
USBHP Pin Threshold 0.8 1.1 V
SUSPEND Pin Pulldown Current V
USBHP Pin Pulldown Current V

= 0.5V 2.5 µA

SUSPEND

= 0.5V 2.5 µA

USBHP

Hot Swap Output

Hot Swap PMOS Switch On-Resistance V
Hot Swap PMOS Switch Current Limit V

= 3.3V 0.9 Ω

HSI

= 3.3V, V

HSI

= 2.5V 120 160 mA

HSO

HSON Pin Threshold 0.8 1.1 V
HSON Pin Pulldown Current 2.5 µA

3455f

3

LTC3455

TEMPERATURE (°C)

–50

QUIESCENT CURRENT (µA)

5

4

3

2

1

0

25 75

3455 G03

–25 0

50 100 125

V

BAT

= 3.6V

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. V
V

USB

= 0V, V

= 0V unless otherwise noted.

WALLFB

The ● denotes the specifications which apply over the full operating

= 3.6V, V

BAT

= 3.6V, V

MAX

PWRON

= 2V, V

is open, VON = 0V,

ON

PARAMETER CONDITIONS MIN TYP MAX UNITS
Battery Charger

Regulated Charger V
Charger Current Limit (USB Powered) R

Charger Current Limit (Wall Powered) R
Recharge Battery Voltage Threshold V

Voltage 0°C ≤ TA ≤ 85°C 4.158 4.200 4.242 V

BAT

=2.49kΩ, V

PROG

=2.49kΩ, V

R

PROG

=2.49kΩ, V

PROG

BAT(REGULATED)

= 2V, V

USBHP

= 0V, V

USBHP

= 4.5V, 0°C ≤ TA ≤ 85°C 425 500 575 mA

MAX

– V

RECHARGE

= 5V, 0°C ≤ TA ≤ 85°C 400 470 mA

USB

= 5V, 0°C ≤ TA ≤ 85°C5090mA

USB

150 mV
Trickle Charge Trip Threshold Battery Voltage Rising 2.85 V
Trickle Charge Trip Hysteresis 60 mV
Trickle Charge Current R
PROG Pin Current Internal Pull-Up Current, No R
PROG Pin Voltage R
CHRG Pin Output Low Voltage I
Timer Accuracy C

=2.49kΩ, V

PROG

=2.49kΩ 1.23 V

PROG

= 5mA 0.75 V

CHRG

= 0.1µF ±10 %

TIMER

= 2V 65 mA

BAT

PROG

2 µA

Junction Temperature in 105 °C
Constant Temperature Mode

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: The LTC3455 is guaranteed to meet specified performance from

Note 3: Quiescent current is pulled from the V

wall power is present, and from the V

pin when either USB or Wall

MAX

power is present.

pin when neither USB or

BAT

0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at –40°C and 85°C

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Burst Mode Quiescent Current PWM Mode Quiescent Current Shutdown Quiescent Current

120

100

80

60

40

QUIESCENT CURRENT (µA)

20

V

= 3.6V

BAT

NOT SWITCHING

0

–50

–25 0

BOTH SWITCHERS ENABLED

ONLY SWITCHER 1 ENABLED

50 100 125

25 75

TEMPERATURE (°C)

3455 G01

600

500

400

300

200

QUIESCENT CURRENT (µA)

100

0

–50

V

= 3.6V

BAT

NOT SWITCHING

–25 0

TEMPERATURE (°C)

BOTH SWITCHERS ENABLED

ONLY SWITCHER 1 ENABLED

50 100 125

25 75

3455 G02

3455f

4

UW

TEMPERATURE (°C)

–50

HSO PIN CURRENT LIMIT (mA)

200

150

100

50

0

25 75

3455 G09

–25 0

50 100 125

V

HSI

= 3.3V

V

HSO

= 2.5V

TEMPERATURE (°C)

–50

CURRENT LIMIT (mA)

1000

800

600

400

200

0

25 75

3455 G06

–25 0

50 100 125

SWITCHER 1

SWITCHER 2

TEMPERATURE (°C)

–50

WALLFB TRIP VOLTAGE (V)

1.26

1.24

1.22

1.20

1.18

1.16

1.14

1.12

1.10
25 75

3455 G12

–25 0

50 100 125

FALLING

RISING

TYPICAL PERFOR A CE CHARACTERISTICS

LTC3455

Feedback Pins (FB1, FB2)
and AI Pin Voltage

815

810

805

800

VOLTAGE (mV)

795

790

785

–50

–25 0

FB2

TEMPERATURE (°C)

AI

FB1

50 100 125

25 75

3455 G04

USB Pin Current Limit V

500

USBHP = 2V

400

300

200

USB PIN CURRENT (mA)

100

0

–50

V

USB

–25 0

= 5V

USBHP = 0V

50 100 125

25 75

TEMPERATURE (°C)

3455 G07

Switching Regulator Oscillator
Frequency Switching Regulator Current Limit

2.0

1.5

1.0

0.5

SWITCHING FREQUENCY (MHz)

0

–50

5.0

4.5

4.0

3.5

3.0

2.5

2.0

CURRENT LIMIT (A)

1.5

MAX

V

1.0

0.5
0

–50

FOR BOTH SWITCHERS

50 100 125

–25 0

Pin Current Limit HSO Pin Current Limit

MAX

STARTUP

–25 0

25 75

TEMPERATURE (°C)

NORMAL OPERATION

50 100 125

25 75

TEMPERATURE (°C)

3455 G05

3455 G08

Battery Undervoltage Lockout USB Undervoltage Lockout WALLFB Trip Voltage

4.00

3.75

3.50

3.25

3.00

BATTERY UVLO (V)

2.75

2.50
–50

–25 0

RISING

FALLING

50 100 125

25 75

TEMPERATURE (°C)

3455 G10

4.00

3.75

3.50

3.25

USB UVLO (V)

3.00

2.75

2.50
–50

–25 0

RISING

TEMPERATURE (°C)

FALLING

50 100 125

25 75

3455 G11

3455f

5

LTC3455

TEMPERATURE (°C)

–50

BATTERY CURRENT (µA)

15.0

10.0

5.0

12.5

7.5

2.5

0

25 75

3455 G18

–25 0

50 100 125

V

BAT

= 4.2V

CHARGER OFF

TEMPERATURE (°C)

–50

R

DS(ON)

1.4

1.2

1.0

0.8

0.6

0.2

0.4

0

25 75

3455 G21

–25 0

50 100 125

HSO

USB

V

MAX

V

HSI

= 3.3V

V

USB

= 5V

V

BAT

= 3.6V

TEMPERATURE (°C)

–50

TRICKLE CHARGE THRESHOLD (V)

3.0

2.9

2.8

2.7

2.6

2.5
25 75

3455 G15

–25 0

50 100 125

FALLING

RISING

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Battery Charger Regulation
Voltage

4.30

4.25

4.20

(V)

4.15

BAT

V

4.10

4.05

4.00
–50

–25 0

25 75

TEMPERATURE (°C)

Charge Current When
Wall-Powered

600

500

400

THERMAL CONTROL
LOOP IN OPERATION

300

50 100 125

3455 G13

Battery Charger Recharge
Threshold

4.30

4.25

4.20

(V)

4.15

RECHARGE

V

4.10

4.05

4.00
–50

–25 0

25 75

TEMPERATURE (°C)

Charge Current When
USB-Powered

600

V

= 3.6V

BAT

= 5V

V

USB

= 2.49k

R

500

PROG

400

THERMAL CONTROL
LOOP IN OPERATION

300

V

50 100 125

= 2V

USBHP

Battery Charger Trickle-Charge
Threshold

3455 G14

Battery Current When
USB- or Wall-Powered

200

V

= 3.6V

100

BAT

BATTERY CHARGE CURRENT (mA)

0

–50

V

MAX

R

PROG

–25 0

= 4.5V

= 2.49k

PROG Pin Voltage
vs Charge Current

1.50
V

= 3.6V

BAT

V

= 4.5V

MAX

= 2.49

R

1.25

PROG

= 25°C

T

A

1.00

(V)

0.75

PROG

V

0.50

0.25

0

0

100 200

50 100 125

25 75

TEMPERATURE (°C)

300

CHARGE CURRENT (mA)

3455 G16

400 500

3455 G19

200

100

BATTERY CHARGE CURRENT (mA)

0

–50

–25 0

R

DS(ON)

V

USBHP

25 75

TEMPERATURE (°C)

for Switching Regulator

Power Switches

0.7
V

= 3.6V

BAT

0.6

0.5

0.4

DS(ON)

R

0.3

0.2

0.1

0

–50

–25 0

NMOS

PMOS

25 75

TEMPERATURE (°C)

= 0V

50 100 125

3455 G17

50 100 125

3455 G20

R

for V

DS(ON)

MAX

PMOS Switches

, USB, and HSO

3455f

6

UUU

PI FU CTIO S

LTC3455

FB1 (Pin 1): Feedback Pin for Switcher 1. Set the output
voltage by connecting feedback resistors to this pin.

PROG (Pin 2): Charge Current Program and Charge Cur­rent Monitor Pin. Connect a resistor, R
to ground to program battery charge current.

I

= 1000 • 1.23V / R

BAT

In all modes the voltage on the PROG pin can be used to
measure charge current. PROG has a weak pull-up current
source to turn the charger off if the pin is left open.

TIMER (Pin 3): Timer Capacitor Pin. Connect a capacitor,
C
cycle termination time. The timer starts when USB or wall
power is first present. The timer period is:

Tie TIMER to ground to disable just the internal timer
function. Tie TIMER to V
constant-current-only mode (which disables the timer,
voltage amplifier and trickle charge function).

CHRG (Pin 4): Open-Drain Charge Status Pin. This pin is
pulled low with an internal N-channel MOSFET whenever
the battery charger is enabled, and is forced into a high
impedance state whenever it is disabled.

USBHP (Pin 5): USB High Power Mode Pin. This pin is
used to select the appropriate USB current limit (either
500mA or 100mA). Pull high to select 500mA (high power
mode); low to select 100mA (low power mode).

SUSPEND (Pin 6): USB Suspend Pin. When this pin is
pulled high, the internal USB power controller is disabled
and the USB pin current reduces to less than 20µA.

SW1 (Pin 7): Switch Pin for Switcher 1. Minimize the
length of the metal trace connected to this pin. Place the
inductor for Switcher 1 as close to this pin as possible.

USB (Pin 8): USB Supply Pin. Input current into this pin is
limited to either 100mA or 500mA based on the state of the
USBHP pin. The charger and Switcher 1 will remain alive
whenever USB power is present (when USB pin is above

3.9V and SUSPEND is low).

V

capacitor as close to the device as possible.

, between this pin and ground to set the charge

TIMER

T

(hours) = C

TIMER

(Pin 9): Battery Input Pin. Bypass this pin with a

BAT

PROG

• (3 hours) / (0.1µF)

TIMER

to use the charger in a

MAX

, from this pin

PROG

V

(Pin 10): Max Voltage Pin. This pin is used to power

MAX

the two internal step-down DC/DC converters and is
provided externally to power other devices (i.e. LDOs or
Switchers for LCD bias, white LED backlight drive, etc).
When the LTC3455 is on and neither USB or wall power are
available, an internal PMOS switch connects this pin to the
V

pin. When either USB or wall power is present, they

BAT

provide power to this pin, and the battery charger draws
power from this pin. In shutdown, this pin is discharged to
ground to provide output disconnect.

WALLFB (Pin 11): Wall Power Detection Pin. This pin is
the input to a comparator used to signal the presence of a
5V wall adapter. A resistor divider taken from the wall
adapter input is connected to this pin to tell the LTC3455
when the adapter voltage is high enough to provide power
to the LTC3455. When this pin is higher than 1.23V, the
battery charger is enabled. The 5V wall adapter is con­nected to the V
WALLFB to ground if a wall adapter is not used.

SW2 (Pin 12): Switch Pin for Switcher 2. Minimize the
length of the metal trace connected to this pin. Place the
inductor for Switcher 2 as close to this pin as possible.

HSI (Pin 13): Hot Swap Input Pin. This pin is connected to
the HSO pin through a current-limited PMOS switch.

HSO (Pin 14): Hot Swap Output Pin. This output is used for
memory cards or other devices that would appear as a
short if they were hot-plugged directly to one of the
outputs (typically the 3.3V output). The current out of this
pin is limited to 160mA.

HSON (Pin 15): Hot Swap Enable Pin. This pin turns on the
PMOS that connects the HSI and HSO pins.

AI (Pin 16): Gain Block Input Pin. This pin is the inverting
input to an amplifier that can be used as a low-battery
detector or as an LDO with the addition of an external PNP
or PMOS. The non-inverting input of the gain block is
connected to the 0.8V internal reference.

AO (Pin 17): Gain Block Output Pin. This pin is an open­drain output, and is pulled low when the AI pin is less than
800mV. This output can be used as a low-battery detector,
or as an LDO with the addition of an external PNP or PMOS.
This pin can sink up to 1mA.

pin through a Schottky diode. Tie

MAX

3455f

7

LTC3455

PI FU CTIO S

UUU

FB2 (Pin 18): Feedback Pin for Switcher 2. Set the output
voltage by connecting feedback resistors to this pin.

ON2 (Pin 19): Enable Pin for Switcher 2. This pin turns on
Switcher 2 only if ON is low or PWRON is high. Switcher
2 cannot be turned on by itself.

RST (Pin 20): Reset Pin. This pin is an open-drain output
that provides a 200ms reset signal during power-up to
initialize a microcontroller.

MODE (Pin 21): Burst Mode Enable Pin. Tie this pin high
to allow Burst Mode operation for the LTC3455. Burst
Mode operation will provide superior efficiency when both
outputs are operating with very low output currents. Tie
this pin to ground to force PWM operation under all load
current conditions. Burst Mode is disabled initially at
startup (for 200ms) and also whenever external power is
available (even if MODE is pulled high).

PWRON (Pin 22): Power-On Pin. Pull this pin high to turn
on the LTC3455. This pin is typically used in conjunction

with the ON and PTSTAT pins, and a momentary-on
switch. Tie PWRON to ground if not used.

PBSTAT (Pin 23): Push-Button Status Pin. This pin is an
open drain output that indicates the state of the ON pin
(which is usually connected to a momentary-on push­button) to the microcontroller. This pin follows the state of
the ON pin (PBSTAT goes low when ON is pulled low).

ON (Pin 24): ON Pin. Pull this pin to ground to turn on the
LTC3455. This pin is typically used with a momentary-on
push-button switch to turn on the LTC3455. This pin
would be held low until the PWRON pin is pulled high by
a microcontroller to keep the LTC3455 turned on. If a
momentary-on switch is not used, this pin can be held to
ground to keep on the LTC3455. Leave ON open if not
used. This pin has a weak pull-up current source.

GND (Pin 25 – Exposed Pad): Ground Pin. The exposed
backside pad is the only ground pin for the LTC3455 and
must be soldered to the PC board ground plane for the
device to operate properly.

SI PLIFIEDWBLOCK DIAGRA

USB POWER

3.9V TO 5.3V

Li-Ion BATTERY

3.3V TO 4.2V

USE FOR LDO

OR LOW BATTERY

INDICATOR

USB POWER

MANAGER

BATTERY

PMOS SWITCH

BATTERY

CHARGER

GAIN BLOCK

W

V

IS CONNECTED TO THE BEST

MAX

AVAILABLE INPUT POWER SOURCE
(WALL ADAPTER, USB OR BATTERY)

SWITCHER 1

SWITCHER 2

HOT SWAP

3455 SBD

5V WALL ADAPTER

V

MAX

USE TO POWER OTHER
DC/DCs AND LDOs

V

OUT1

1.8V TYPICAL

V

OUT2

3.3V TYPICAL

HOT SWAP OUTPUT

3.3V TYPICAL

8

3455f