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LTC4414

4414fc

STAT (Pin 1): Open-Drain Output Status Pin. When the

SENSE pin is pulled above the VIN pin with an auxiliary

power source by VRTO or more, the reverse turn-off

threshold (VRTO) is reached. The STAT pin will then go

from an open state to a current sink (IS(SNK)). The STAT pin

current sink can be used, along with an external resistor,

to turn on an auxiliary P-channel power switch and/or

signal the presence of an auxiliary power source to a

microcontroller.

CTL (Pin 2): Digital Control Input. A logical high input (VIH)

on this pin forces the gate to source voltage of the primary

P-channel MOSFET power switch to a small voltage (VGOFF).

This will turn the MOSFET off and no current will flow from

the primary power input at VIN if the MOSFET is configured

so that the drain to source diode does not forward bias. A

high input also forces the Open-Drain STAT pin ON. If the

STAT pin is used to control an auxiliary P-channel power

switch, then a second active source of power, such as an

AC wall adaptor, will be connected to the load (see Appli-

cations Information). An internal current sink will pull the

CTL pin voltage to ground (logical low) if the pin is open.

GND (Pin 3): Ground. Provides a power return for all the

internal circuits.

PI FU CTIO S

SENSE (Pin 6): Power Sense Input Pin. Supplies power to

the internal circuitry and is a voltage sense input to the

internal analog controller (The other input to the controller

is the VIN pin). This input is usually supplied power from

an auxiliary source such as an AC adapter or back-up

battery which also supplies current to the load.

VIN (Pin 7): Primary Input Supply Voltage. Supplies power

to the internal circuitry and is one of two voltage sense

inputs to the internal analog controller (The other input to

the controller is the SENSE pin). This input is usually

supplied power from a battery or other power source

which supplies current to the load. This pin can be by-

passed to ground with a capacitor in the range of 0.1

µF to

µF if needed to suppress load transients.

GATE (Pin 8): Primary P-Channel MOSFET Power Switch

Gate Drive Pin. This pin is directed by the power controller

to maintain a forward regulation voltage (VFR) of 20mV

between the VIN and SENSE pins when an auxiliary power

source is not present. When an auxiliary power source is

connected, the GATE pin will pull up to the SENSE pin

voltage, turning off the primary P-channel power switch.

BLOCK DIAGRA

SOURCE

POWER

VOLTAGE/CURRENT

REFERENCE

0.5V

POWER

LINEAR GATE

DRIVER AND

VOLTAGE CLAMP

VIN

SENSE

ANALOG CONTROLLER

–

CTL

3.5

µA

ON/OFF

*DRAIN-SOURCE DIODE OF MOSFET

STATUS

OUTPUT

4414 BD

ON/OFF

STAT

VCC

GATE

GND

OUTPUT

TO LOAD

SELECTOR

PRIMARY

SUPPLY

AUXILIARY

SUPPLY

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