LT4356-1 Linear Technology Corporation, LT4356-1 Datasheet - Page 6

• Manufacturer Part Number: LT4356-1
• Description: Overvoltage Protection Regulator And Inrush Limiter
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
LT4356-1
A
output of the auxiliary amplifi er. It is capable of sinking
up to 2mA from 80V. The negative input of the amplifi er
is internally connected to a 1.25V reference.
EN (Pin 9/Pin 8): Open-Collector Enable Output. The EN
pin goes high impedance when the voltage at the OUT pin
is above (V
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 cur-
rent from 80V to drive an LED or opto-coupler.
Exposed Pad (Pin 13 DE Only): Exposed pad may be left
open or connected to device ground (GND).
FB (Pin 2/Pin 1): Voltage Regulator Feedback Input. Con-
nect 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 main-
tain a 1.25V threshold at the FB pin. This pin is clamped
internally to 7V. Tie to GND to disable the OV clamp.
FLT (Pin 8/Pin 7): 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 transis-
tor 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 (Pin 4/Pin 3): 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 amplifi ers control the GATE pin
to regulate the output voltage and limit the current through
the MOSFET.
GND (Pin 10/Pin 9): Device Ground.
IN+ (Pin 12 DE Only): Positive Input of the Auxiliary
Amplifi er. This amplifi er 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.
6
OUT
(Pin 11 DE Only): Amplifi er Output. Open collector
CC
– 0.7V), indicating the external MOSFET is
(DE/MS)
OUT (Pin 3/Pin 2): 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 volt-
age reaches 0.7V away from V
impedance.
SHDN (Pin 7/Pin 6): Shutdown Control Input. The LT4356-1
can be shutdown to a low current mode by pulling the
SHDN pin below the shutdown threshold of 0.6V. Pull this
pin above 1.7V or disconnect it and allow the internal cur-
rent source to turn the part back on. The leakage current
to ground at the pin should be limited to no more than
1μA if no pull up device is used to turn the part on. The
SHDN pin can be pulled up to 100V or below GND by 30V
without damage.
SNS (Pin 5/Pin 4): 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 V
sense amplifi er also starts a current source to charge up
the TMR pin. This pin can be pulled below GND by up to
30V, though the voltage difference with the V
be limited to less than 30V. Connect to V
TMR (Pin 1/Pin 10): Fault Timer Input. Connect a capaci-
tor between this pin and ground to set the times for early
warning, fault and cool down periods. The current charg-
ing up this pin during fault conditions depends on the
voltage difference between the V
V
detection of a fault condition. If the condition persists, the
pass transistor turns off when V
of 1.35V. The pull up current stops and a 2μA current
source starts to pull the TMR pin down as soon as the
fault condition disappears. When V
threshold of 0.5V, the GATE pin pulls high turning back
on the pass transistor.
V
positive supply input ranges from 4V to 80V for normal
operation. It can also be pulled below ground potential
by up to 30V during a reverse battery condition, without
damaging the part. The supply current is reduced to 5μA
with all the functional blocks off.
TMR
CC
(Pin 6/Pin 5): Positive Supply Voltage Input. The
reaches 1.25V, the FLT pin pulls low to indicate the
CC
and SNS pins to 50mV. At the same time the
TMR
CC
CC
, the EN pin goes high
TMR
reaches the threshold
and OUT pins. When
reaches the retry
CC
if unused.
CC
pin must
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