LTC3456_15 Datasheet, PDF(10/28 Page) Linear Technology – 2-Cell, Multi-Output DC/DC Converter with USB Power Manager

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LTC3456_15 Datasheet, PDF (10/28 Pages) Linear Technology – 2-Cell, Multi-Output DC/DC Converter with USB Power Manager

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LTC3456

PI FU CTIO S

HSO (Pin 17): Hot Swap Output. An internal 0.8â¦ current

limited PMOS switch connects this pin to the VINT pin

0.5ms after the core voltage comes into regulation. The

nominal voltage at this pin is 3.3V. It is short-circuit

protected and the current out of this pin is limited to

120mA (typ).

SUSPEND (Pin 18): USB Suspend Pin. Pull this pin high

to disable all USB functionality. The USB switch connected

between USB and VEXT behaves like a back-to-back diode

whenever SUSPEND is pulled high. In Suspend mode the

device limits the current drawn from the USB port to

100ÂµA (typ).

PWRKEY (Pin 19): Power ON/OFF Key. Connecting this

pin to GND will turn on the IC. This pin is typically used with

a momentary-on pushbutton switch to turn on the LTC3456.

This pin must be held low until the PWRON pin is pulled

high (usually from a microprocessor) in order to keep the

IC turned on. This pin has a 400k pull-up resistor to VMAX.

PBSTAT (Pin 20): Power ON/OFF Key Status Pin. This

open-drain output pin indicates the state of the PWRKEY

pin to the microcontroller. The pin output follows the state

of the PWRKEY pin (PBSTAT goes low when PWRKEY is

pulled low).

PWRON (Pin 21): Power On Pin. When pulled high this

microprocessor controlled pin turns on the IC. This pin

has a weak 1ÂµA pull-down current source.

MODE (Pin 22): Burst Mode Select Pin. Tie this pin high to

allow automatic Burst Mode operation. Burst Mode opera-

tion will provide superior efficiency when any of the

outputs are operating with very low output currents. Tie

this pin low to force PWM operation under all load current

conditions. The device operates in forced PWM mode

when powered from USB or wall input (irrespective of the

state of the MODE pin). Furthermore, at initial power-up,

the device operates in forced PWM mode during the

262ms internal delay timeout. This pin has a weak 1ÂµA

pull-down current source.

RESET (Pin 23): Fault Indicator Output Pin. This open-

drain output is active both at power-up and power-down.

RESET is held low at initial power up. When both the Core

and Main outputs come into regulation, an internal reset

delay timer is activated. RESET is released at the end of the

262ms timeout. If either Main or Core outputs fall out of

regulation during normal operation, RESET is pulled low.

Also, RESET is pulled low at power-off to prevent spurious

turn-on of the microprocessor.

FB1 (Pin 24): Feedback Pin for the Core Regulator. The

regulator drives the voltage at this pin to 0.8V. Connect the

resistor divider tap to this pin. The output voltage of the

core regulator can be adjusted from 0.8V to VBATT(MIN).

Exposed Pad (Pin 25): The Exposed Pad must be soldered

to the PCB system ground.

3456fa

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