5

LT1640L/LT1640H

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.

the lower potential of the power supply.

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

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

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

high by a 45

µA current source and pulled low with a

50mA current source.

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

the PWRGD or PWRGD pin will toggle.

pin to the higher potential of the power supply inputs and

ranges from 10V to 80V.

BLOCK DIAGRA

–

+

+

–

+

–

DRAIN

1640 BD

GATE

SENSE

OUTPUT

DRIVE

PWRGD/PWRGD

50mV

REF

REF

UV

OV

LOGIC

AND

GATE DRIVE

REFERENCE

GENERATOR