LT4356HDE-3-TRPBF Ver la hoja de datos (PDF) - Analog Devices

Número de pieza

componentes Descripción

Fabricante

LT4356HDE-3-TRPBF

Surge Stopper with Fault Latchoff

Analog Devices 

LT4356-3

PIN FUNCTIONS

AOUT (DFN and SO Packages Only): Amplifier Output. Open

collector output of the auxiliary amplifier. It is capable of

sinking up to 2mA from 80V. The negative input of the

amplifier is internally connected to a 1.25V reference.

EN: Open-Collector Enable Output. The EN pin goes high

impedance when the voltage at the OUT pin is above (VCC

– 0.7V), indicating the external MOSFET is fully on. The

state of the pin is latched until the OUT pin voltage resets

at below 0.5V and goes back up above 2V. The internal

NPN is capable of sinking up to 3mA of current from 80V

to drive an LED or opto-coupler.

Exposed Pad: Exposed pad may be left open or connected

to device ground (GND).

FB: Voltage Regulator Feedback Input. Connect this pin

to the center tap of the output resistive divider connected

between the OUT pin and ground. During an overvoltage

condition, the GATE pin is servoed to maintain a 1.25V

threshold at the FB pin. This pin is clamped internally to

7V. Tie to GND to disable the OV clamp.

FLT: Open-Collector Fault Output. This pin pulls low

after the voltage at the TMR pin has reached the fault

threshold of 1.25V. It indicates the pass transistor is

about to turn off because either the supply voltage has

stayed at an elevated level for an extended period of

time (voltage fault) or the device is in an overcurrent

condition (current fault). The internal NPN is capable of

sinking up to 3mA of current from 80V to drive an LED or

opto-coupler.

GATE: N-Channel MOSFET Gate Drive Output. The GATE

pin is pulled up by an internal charge pump current source

and clamped to 14V above the OUT pin. Both voltage and

current amplifiers control the GATE pin to regulate the

output voltage and limit the current through the MOSFET.

GND: Device Ground.

IN+ (DFN and SO Packages Only): Positive Input of the

Auxiliary Amplifier. This amplifier can be used as a level

detection comparator with external hysteresis or linear

regulator controlling an external PNP transistor. This pin

is clamped internally to 7V. Connect to ground if unused.

OUT: Output Voltage Sense Input. This pin senses the

voltage at the source of the N-channel MOSFET and sets

the fault timer current. When the OUT pin voltage reaches

0.7V away from VCC, the EN pin goes high impedance.

SHDN: Shutdown Control Input. Pulling the SHDN pin

low shuts the LTC4356-3 down to a low current mode. All

functions, including the GATE and the spare amplifier are

turned off. The SHDN input threshold is similar to a TTL

input. If the SHDN voltage goes below 2.1V, the voltage

must go below 0.4V for 100µs to properly shut down the

part. To turn the part back on, the SHDN voltage must

transition from below 0.4V to greater than 2.1V with a slew

rate faster than 10V/ms. An internal 7µA current source

is provided to pull the SHDN pin up. An external pull-up

device should be used if the leakage current to ground

might exceed 1µA. After a fault time-out which turns the

GATE off, the GATE can be restarted by shutting down and

restarting the part. The SHDN pin can be pulled up to 100V

or below GND by 60V without damage.

SNS: Current Sense Input. Connect this pin to the output of

the current sense resistor. The current limit circuit controls

the GATE pin to limit the sense voltage between VCC and

SNS pins to 50mV. At the same time the sense amplifier

also starts a current source to charge up the TMR pin.

This pin can be pulled below GND by up to 60V, though

the voltage difference with the VCC pin must be limited to

less than 30V. Connect to VCC if unused.

TMR: Fault Timer Input. Connect a capacitor between this

pin and ground to set the times for early warning and fault

periods. The current charging up this pin during fault

conditions depends on the voltage difference between the

VCC and OUT pins. When VTMR reaches 1.25V, the FLT pin

pulls low to indicate the detection of a fault condition. If

the condition persists, the pass transistor turns off when

VTMR reaches the threshold of 1.35V. The GATE pin remains

low even after the fault condition has disappeared and the

voltage at the TMR pin has reached 0.5V. A minimum of

10nF capacitor is needed to compensate the loop. A 10V

rated X7R capacitor is recommended for CTMR.

VCC: Positive Supply Voltage Input. The positive supply

input ranges from 4V to 80V for normal operation. It

can also be pulled below ground potential by up to 60V

during a reverse battery condition, without damaging the

part. The supply current is reduced to 7µA with all the

functional blocks off.

Rev D

For more information www.analog.com

7

Share Link: