LTC4355 datasheet(5/16 Pages) LINER

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LTC4355

4355fa

pin FuncTions

EXPOSED PAD (Pin 15, DE Package Only): Exposed pad

may be left open or connected to GND.

FUSEFLTx (Pins 11,12/13,14): Fuse Fault Outputs.

Open-drain output that pulls to GND when VINx < 3.5V,

indicating that the fuse has blown open. Otherwise, this

output is high-impedance. Connect to GND if unused.

GATEx (Pins 2,4/2,6): Gate Drive Outputs. The GATE

pins pull high, enhancing the N-channel MOSFET when

the load current creates more than 25mV of voltage drop

across the MOSFET. When the load current is small,

the gates are actively driven to maintain 25mV across

the MOSFET. If the reverse current develops more than

–25mV of voltage drop across a MOSFET, a fast pulldown

circuit quickly connects the GATE pin to the IN pin, turning

off the MOSFET. Limit the capacitance between the GATE

and IN pins to less than 0.1µF.

GND (7/9): Device Ground.

INx(Pins1,5/1,7):InputVoltagesandGATEFastPulldown

Returns. The IN pins are the anodes of the ideal diodes

and connect to the sources of the N-channel MOSFETs.

The voltages sensed at these pins are used to control the

source-drain voltages across the MOSFETs and are used

by the fault detection circuits that drive the PWRFLT,

FUSEFLT, and VDSFLT pins. The GATE fast pulldown cur-

rent is returned through the IN pins. Connect these pins

as close to the MOSFET sources as possible. Connect to

OUT if unused.

MONx (Pins 9,14/11,16): Input Supply Monitors. These

pins are used to sense the input supply voltages. Connect

these pins to external resistive dividers between the input

suppliesandGND.IfVMONxfallsbelow1.23V,thePWRFLTx

pin pulls to GND. Connect to GND if unused.

OUT (Pin 3/4): Drain Voltage Sense and Positive Sup-

ply Input. OUT is the diode-OR output of IN1 and IN2. It

connects to the common drain connection of the N-chan-

nel MOSFETs. The voltage sensed at this pin is used to

control the source-drain voltages across the MOSFETs

and is used by the fault detection circuits that drive the

PWRFLT and VDSFLT pins. The LTC4355 is powered from

the OUT pin.

PWRFLTx (Pins 10,13/12,15): Power Fault Outputs.

Open-drain output that pulls to GND when VMONx falls

below 1.23V or the forward voltage across the MOSFET

exceeds

DVSD(FLT). When VMONx is above 1.23V and

the forward voltage across the MOSFET is less than

DVSD(FLT), PWRFLTx is high-impedance. Connect to GND

if unused.

SET (Pin 8/10):

DVSD(FLT) Threshold Configuration In-

put. Tying SET to GND, to a 100k

W resistor connected

to GND, or leaving SET open configures the

DVSD(FLT)

forward voltage fault threshold to 250mV, 500mV, or 1.5V

respectively. When the voltage across a MOSFET exceeds

DVSD(FLT), the VSDFLT pin and at least one of the PWRFLT

pins pull to GND.

VDSFLT (Pin 6, DE Package Only): MOSFET Fault Output.

Open-drainoutputthatpullstoGNDwhentheforwardvolt-

age across either MOSFET exceeds

DVSD(FLT). PWRFLT1

or PWRFLT2 also pulls low to indicate which MOSFET’s

forward voltage drop exceeds

DVSD(FLT). Otherwise, this

pin is high-impedance. Connect to GND if unused.

(DE/S Packages)

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