LTC3455EUF#TRPBF Linear Technology, LTC3455EUF#TRPBF Datasheet - Page 14

• Manufacturer Part Number: LTC3455EUF#TRPBF
• Description: IC CONV DC/DC DUAL USBBATT 24QFN
• Manufacturer: Linear Technology

Specifications of LTC3455EUF#TRPBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 3 V ~ 6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

LTC3455/LTC3455-1
APPLICATIONS INFORMATION
Using the V
The V
devices within the system. This pin is connected to the
battery when no external power is available, and it is
connected to either the USB bus or the wall adapter when
either are available. This ensures that all devices powered
from V
input power source.
The internal PMOS connecting V
limited to 900mA at startup (to minimize in-rush current)
and to 4A once V
Because of the reduced startup current limit, the turn-on
of other devices powered from V
delayed to minimize the currrent initially needed from the
V
either switcher output, since the turn-on of both switch-
ers is always delayed until the V
V
when the LTC3455/LTC3455-1 are shut down, so that
any device supplied by V
during shutdown. This ensures output disconnect for all
supply voltages within the system.
14
MAX
BAT
pin voltage. The V
pin. The best choice is to enable these devices from
MAX
MAX
pin can be used to provide power for other
will always draw power from the best available
MAX
MAX
Pin to Power Other Devices
has risen close to the battery voltage.
MAX
MAX
pin is discharged to ground
will have its input grounded
MAX
μC
MAX
MAX
to the battery is current
pin has reached the
BUTTON
PUSH
should always be
Figure 2. Momentary Push-Button Operation
PWRON
PBSTAT
ON2
ON
23
24
22
19
Startup and Shutdown when Battery-Powered
When only battery power is available, the LTC3455/
LTC3455-1 turn on when either the ON pin is pulled low
or the PWRON pin is pulled high. Either of these pins will
keep the device running, but typically the ON and PWRON
pins are used together to provide turn-on and turn-off us-
ing a single momentary-on push-button switch. Figure 2
shows the method for using a momentary-on pushbutton
to turn the LTC3455/LTC3455-1 off and on.
When the momentary-on switch is fi rst pressed, short-
ing the ON pin to ground, PBSTAT goes low and the
LTC3455/LTC3455-1 fi rst bring up the V
enables Switcher 1 to power the microcontroller. Once
up and running, the microcontroller provides the PWRON
signal to keep the LTC3455/LTC3455-1 turned on after the
push-button is released. When the push-button is pressed
again to turn off the device, the PBSTAT pin is pulled low
to notify the microcontroller that the push-button has been
pressed. The microcontroller prepares for shutdown then
pulls the PWRON signal low. When the push-button is re-
leased, the ON pin goes high and the LTC3455/LTC3455-1
turn off. The ON and PWRON pins enable Switcher 1 (along
with all the internal circuits needed for normal operation),
and the ON2 pin enables Switcher 2. Switcher 2 can only
operate when Switcher 1 is also enabled. The turn-on of
both switchers is always delayed until the V
reached the V
BAT
LTC3455/LTC3455-1
pin voltage.
SWITCHER 1
ENABLED
SWITCHER 2
ENABLED
3455 F02
MAX
MAX
pin, then
pin has
3455fc