LTC4214-1CMS#PBF Linear Technology, LTC4214-1CMS#PBF Datasheet - Page 12

• Manufacturer Part Number: LTC4214-1CMS#PBF
• Description: IC CTRLR HOTSWAP NEGVOLT 10MSOP
• Manufacturer: Linear Technology
• Type: Hot-Swap Controllerr

Specifications of LTC4214-1CMS#PBF

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 6 V ~ 16 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Linear Misc Type: Negative Low Voltage
• Family Name: LTC4214-1
• Package Type: MSOP
• Operating Supply Voltage (min): -6V
• Operating Supply Voltage (max): -16V
• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Product Depth (mm): 3mm
• Product Height (mm): 0.86mm
• Product Length (mm): 3mm
• Mounting: Surface Mount
• Pin Count: 10
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATIO
LTC4214-1/LTC4214-2
turn on gradually so that the inrush into the load capaci-
tance remains a low value. The output will simply ramp to
–12V and the LTC4214 will fully enhance the MOSFET. A
second possibility is that the load current exceeds the
soft-start current limit threshold of [V
In this case the LTC4214 will ramp the output by sourcing
soft-start limited current into the load capacitance. If the
soft-start voltage is below 1.2V, the circuit breaker TIMER
is held low. Above 1.2V, TIMER ramps up. It is important
to set the timer delay so that, regardless of which start-up
mode is used, the TIMER ramp is less than one circuit
breaker delay time. If this condition is not met, the
LTC4214-1 may shut down after one circuit breaker delay
time whereas the LTC4214-2 may continue to autoretry.
Board Removal
If the board is withdrawn from the card cage, the UV/OV
divider is the first to lose connection. This shuts off the
MOSFET and commutates the flow of current in the
connector. When the power pins subsequently separate,
there is no arcing.
Current Control
Three levels of protection handle short-circuit and over-
load conditions. Load current is monitored by SENSE and
resistor R
50mV for a timed circuit breaker function; 70mV for an
analog current limit loop; and 200mV for a fast, feedforward
comparator which limits peak current in the event of a
catastrophic short-circuit.
If, owing to an output overload, the voltage drop across
R
eventually charges to a 3V threshold and the LTC4214
shuts off. If the overload goes away before C
and SENSE measures less than 50mV, C
charges (5 A). In this way the LTC4214’s circuit breaker
function responds to low duty cycle overloads and ac-
counts for fast heating and slow cooling characteristics of
the MOSFET.
12
S
exceeds 50mV, TIMER sources 40 A into C
S
. There are three distinct thresholds at SENSE:
U
SS
(t)/20 – V
T
T
slowly dis-
reaches 3V
OS
T
]/R
. C
S
T
.
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 70mV/R
mode, V
heating. If V
resistor, R
timing cycle to be shortened by accelerating the charging
of the TIMER capacitor. The TIMER pull-up current is
increased by 8 • I
TIMER charges C
eventually shut down.
Low impedance failures on the load side of the LTC4214
can produce high current slew rates. Under these condi-
tions, 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 70mV/R
then takes over and servos the current as previously
described. As before, TIMER runs and shuts down the
LTC4214 when C
If C
pull-up current source whereas the LTC4214-2 starts a
shutdown cooling cycle. The LTC4214-1 circuit breaker
latch is reset by either pulling UV momentarily low or drop-
ping the input voltage V
old of 4.8V or pulling TIMER momentarily low with a switch.
The LTC4214-2 retries after its shutdown cooling cycle.
Although short-circuits are the most obvious fault type,
several operating conditions may invoke overcurrent pro-
tection. Noise spikes from the backplane or load, transient
currents caused by faults on adjacent circuit boards shar-
ing the same power bus or the insertion of non-hot-
swappable products could cause higher than anticipated
input current and temporary detection of an overcurrent
condition. The action of TIMER and C
allowing the LTC4214 to “ride out” temporary overloads and
disturbances that could trip a simple current comparator
and, in some cases, blow a fuse.
T
reaches 3V, the LTC4214-1 latches off with a 5 A
OUT
D
, between V
OUT
typically rises and this increases MOSFET
> V
DRN
T
T
reaches 3V.
during this time and the LTC4214 will
DRNCL
. Note that because SENSE > 50mV,
IN
OUT
below the internal UVLO thresh-
(4.2V), connecting an external
S
and DRAIN allows the fault
reaches 70mV, the current
T
rejects these events
S
S
. In current limit
current limit loop
421412f