LTC4253AIGN#TR Linear Technology, LTC4253AIGN#TR Datasheet - Page 13

• Manufacturer Part Number: LTC4253AIGN#TR
• Description: MS-Hot Swap/High Voltage, Neg. 48V Hot Swap With 1% UV, Sequencer
• Manufacturer: Linear Technology

Specifications of LTC4253AIGN#TR

• Family Name: LTC4253A
• Package Type: SSOP N
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.99mm
• Product Height (mm): 1.5mm
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / Rohs Status: Not Compliant

OPERATIO
Higher overloads are handled by an analog current limit
loop. If the drop across R
limiting loop servos the MOSFET gate and maintains a
constant output current of V
V
and this increases MOSFET heating. If V
connecting an external resistor, R
DRAIN allows the fault timing cycle to be shortened by
accelerating the charging of the TIMER capacitor. The
TIMER pull-up current is increased by 8 • I
because SENSE > 50mV, TIMER charges C
time, and the LTC4253/LTC4253A eventually shut down.
Low impedance failures on the load side of the LTC4253/
LTC4253A, coupled with 48V or more driving potential,
can produce current slew rates well in excess of 50A/µs.
Under these conditions, overshoot is inevitable. A fast
SENSE comparator with a threshold of 200mV detects
overshoot and pulls GATE low much harder and hence
much faster than the weaker current limit loop. The V
R
rent as previously described. As before, TIMER runs and
shuts down the LTC4253/LTC4253A when C
OUT
S
current limit loop then takes over and servos the cur-
(MOSFET drain-source voltage drop) typically rises
U
ACL
S
reaches V
/R
S
. In current limit mode,
D
between V
ACL
OUT
DRN
, the current
T
T
reaches 4V.
during this
. Note that
> V
OUT
DRNCL
ACL
and
,
/
If C
5µA pull-up current source. The LTC4253/LTC4253A cir-
cuit breaker latch is reset by either pulling the RESET pin
active high until TIMER goes low, pulling UV momentarily
low, dropping the input voltage V
UVLO threshold or pulsing TIMER momentarily low with
a switch.
Although short-circuits are the most obvious fault type,
several operating conditions may invoke overcurrent
protection. Noise spikes from the backplane or load, input
steps caused by the connection of a second, higher
voltage supply, transient currents caused by faults on
adjacent circuit boards sharing the same power bus or the
insertion of non-hot swappable products could cause
higher than anticipated input current and temporary de-
tection of an overcurrent condition. The action of TIMER
and C
LTC4253A to “ride out” temporary overloads and distur-
bances that could trip a simple current comparator and,
in some cases, blow a fuse.
T
reaches 4V, the LTC4253/LTC4253A latch off with a
T
rejects these events allowing the LTC4253/
LTC4253/LTC4253A
IN
below the internal
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