LT1640L datasheet(5/16 Pages) LINER

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LT1640L/LT1640H

1640lhfb

PIN FUNCTIONS

UV (Pin 3): Analog Undervoltage Input. When UV is

pulled below the 1.223V high to low threshold, an under-

voltage condition is detected and the GATE pin will be

immediately pulled low. The GATE pin will remain low

until UV rises above the 1.243 low to high threshold.

The UV pin is also used to reset the electronic circuit

breaker. If the UV pin is cycled low and high following the

trip of the circuit breaker, the circuit breaker is reset and

a normal power-up sequence will occur.

VEE (Pin 4): Negative Supply Voltage Input. Connect to

the lower potential of the power supply.

SENSE (Pin 5): Circuit Breaker Sense Pin. With a sense

resistor placed in the supply path between VEE and

SENSE, the circuit breaker will trip when the voltage

across the resistor exceeds 50mV. Noise spikes of less

than 2

µs are filtered out and will not trip the circuit

breaker.

If the circuit breaker trip current is set to twice the normal

operating current, only 25mV is dropped across the

sense resistor during normal operation. To disable the

circuit breaker, VEE and SENSE can be shorted together.

GATE (Pin 6): Gate Drive Output for the External

N-Channel. The GATE pin will go high when the following

start-up conditions are met: the UV pin is high, the OV pin

is low and (VSENSE – VEE) < 50mV. The GATE pin is pulled

high by a 45

µA current source and pulled low with a

50mA current source.

DRAIN (Pin 7): Analog Drain Sense Input. Connect this

pin to the drain of the external N-channel and the V – pin

of the power module. When the DRAIN pin is below VPG,

the PWRGD or PWRGD pin will toggle.

VDD (Pin 8): Positive Supply Voltage Input. Connect this

pin to the higher potential of the power supply inputs and

the V + pin of the power module. The input supply voltage

ranges from 10V to 80V.

BLOCK DIAGRA

–

DRAIN

1640 BD

GATE

SENSE

VEE

VPG

OUTPUT

DRIVE

PWRGD/PWRGD

50mV

VCC

VDD

REF

LOGIC

AND

GATE DRIVE

VCC AND

REFERENCE

GENERATOR

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