LT4250H LINER [Linear Technology], LT4250H Datasheet - Page 5

• Manufacturer Part Number: LT4250H
• Description: Negative 48V Hot Swap Controller
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRA
PIN
OV (Pin 2): Analog Overvoltage Input. When OV is pulled
above the 1.255V threshold, an overvoltage condition is
detected and the GATE pin will be immediately pulled low.
The GATE pin will remain low until OV drops below the
1.235V threshold.
UV (Pin 3): Analog Undervoltage Input. When UV is
pulled below the 1.125V threshold, an undervoltage
condition is detected and the GATE pin will be immedi-
ately pulled low. The GATE pin will remain low until UV
rises above the 1.255 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 response
time for this pin is 1.5 s. Add an external capacitor to this
pin for additional filtering.
V
the lower potential of the power supply.
SENSE (Pin 5): Circuit Breaker Sense Pin. With a sense
resistor placed in the supply path between V
SENSE, the overcurrent condition will pull down the
GATE pin and regulate the voltage across the resistor to
be 50mV. If the overcurrent condition exists for more
than 500 s the electronic circuit breaker will trip and turn
off the external MOSFET.
EE
U
(Pin 4): Negative Supply Voltage Input. Connect to
FUNCTIONS
U
UV
OV
U
REF
W
–
+
–
+
V
EE
50mV
SENSE
–
+
–
+
UVLO
EE
and
DELAY
500 s
GENERATOR
REFERENCE
V
LOGIC
CC
V
DD
AND
If the current limit value is set to twice the normal
operating current, only 25mV is dropped across the
sense resistor during normal operation. To disable the
current limit feature, V
together.
GATE (Pin 6): Gate Drive Output for the External
N-Channel MOSFET. The GATE pin will go high when the
following start-up conditions are met: the UV pin is high,
the OV pin is low, (V
is greater than V
45 A current source and pulled low with a 50mA current
source. During current limit the GATE pin is pulled low
using a 100mA current source.
DRAIN (Pin 7): Analog Drain Sense Input. Connect this
pin to the drain of the external N-channel MOSFET and the
V
below V
the switch is on.
V
pin to the higher potential of the power supply inputs and
the V
circuit disables the chip until the V
the 16V V
DRIVER
GATE
GATE
DD
–
pin of the power module. When the DRAIN pin is
(Pin 8): Positive Supply Voltage Input. Connect this
+
pin of the power module. An undervoltage lockout
V
REF
CC
DL
V
+
+
–
EE
UVLOH
, the PWRGD/PWRGD pin will latch to indicate
V
DL
DRAIN
–
OUTPUT
DRIVE
UVLOH
threshold.
+
SENSE
. The GATE pin is pulled high by a
V
EE
–
+ –
GATE
LT4250L/LT4250H
– V
V
4250 BD
and SENSE can be shorted
GH
EE
PWRGD/PWRGD
) < 50mV and the V
DD
pin is greater than
DD
4250lhf
5
pin