LTC4253AIGN-ADJ datasheet(13/32 Pages) LINER

13 / 32 page

LTC4253A-ADJ

4253a-adjf

OPERATIO

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 VACL/RS current

limit loop then takes over, and servos the current as

previously described. As before, TIMER runs and shuts

down LTC4253A-ADJ when CT reaches 4V.

If CT reaches 4V, the LTC4253A-ADJ latches off with a 5µA

pull-up current source. The LTC4253A-ADJ circuit breaker

latch is reset by either pulling the RESET pin active high for

>20

µs, pulling UVL/UV momentarily low, dropping the

input voltage VIN below the internal 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 CT rejects these events allowing the LTC4253A-ADJ

to “ride out” temporary overloads and disturbances that

could trip a simple current comparator and, in some

cases, blow a fuse.

LTC4253AIGN-ADJ 데이터시트(PDF) 13 Page - Linear Technology