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参数资料
| 型号： | LTC4251-1IS6#TRM |
| 厂商： | Linear Technology |
| 文件页数： | 10/24页 |
| 文件大小： | 266K |
| 描述： | IC CTRLR HOTSWAP NEGVOLT SOT23-6 |
| 标准包装： | 500 |
| 类型： | 热交换控制器 |
| 应用： | 通用 |
| 内部开关： | 无 |
| 电源电压： | -36 V ~ -72 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 供应商设备封装： | SOT-23-6 |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC4251-1IS6 LTC4251-1IS6-ND LTC42511IS6 |
10
425112fd
LTC4251/LTC4251-1/
LTC4251-2
For more information www.linear.com/4251
Two modes of operation are possible during the time the
MOSFET is first turning on, depending on the values of
external components, MOSFET characteristics and nomi-
nal design current. One possibility is that the MOSFET
will turn on gradually so that the inrush into the load
capacitance remains a low value. The output will simply
ramp to 48V and the MOSFET will be fully enhanced.
A second possibility is that the load current exceeds the
current limit threshold of 100mV/R
S
. In this case, the
LTC4251/LTC4251-1/LTC4251-2 will ramp the output by
sourcing 100mV/R
S
current into the load capacitance.
It is important to set the timer delay so that, regardless
of which start-up mode is used, the start-up time is less
than the TIMER delay time. If this condition is not met,
the LTC4251/LTC4251-1/LTC4251-2 may shutdown after
one TIMER delay.
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If the board is withdrawn from the card cage, the UV/OV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 con-
nector. 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
S
. There are three distinct thresholds at SENSE:
50mV for a timed circuit breaker function; 100mV for an
analog current limit loop; and 200mV for a fast, feedfor-
ward comparator which limits peak current in the event
of a catastrophic short-circuit.
If, owing to an output overload, the voltage drop across R
S
exceeds 50mV , TIMER sources 230礎 into C
T
. C
T
eventually
charges to a 4V threshold and the LTC4251/LTC4251-1/
LTC4251-2 latchoff. If the overload goes away and SENSE
measures less than 50mV , C
T
slowly discharges (5.8礎).
OPERATION
In this way the circuit breaker function will also respond
to low duty cycle overloads, and accounts for fast heating
and slow cooling characteristic of the MOSFET .
Higher overloads are handled by an analog current limit
loop. If the drop across R
S
reaches 100mV , the current
limiting loop servos the MOSFET gate and maintains a
constant output current of 100mV/R
S
. Note that because
SENSE > 50mV , TIMER charges C
T
during this time and the
LTC4251/LTC4251-1/LTC4251-2 will eventually shut down.
Low impedance failures on the load side of the LTC4251/
LTC4251-1/LTC4251-2 coupled with 48V or more driving
potential can produce current slew rates well in excess of
50A/祍. 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 can the weaker current limit loop. The
100mV/R
S
current limit loop then takes over, and servos
the current as previously described. As before, TIMER
runs and latches the LTC4251/LTC4251-1/LTC4251-2 off
when C
T
reaches 4V .
The LTC4251/LTC4251-1/LTC4251-2 circuit breaker latch
is reset by either pulling UV/OV momentarily low, or
dropping the input voltage V
IN
below the internal UVLO
threshold of 8.2V .
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 detection of an
overcurrent condition. The action of TIMER and C
T
rejects
these events allowing the LTC4251/LTC4251-1/LTC4251-2
to ride out temporary overloads and disturbances that
would trip a simple current comparator and in some cases,
blow a fuse.
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| LTC4251-2CS6#TRM | 功能描述:IC CTRLR HOTSWP NEG VOLT SOT23-6 RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 标准包装:50 系列:- 类型:热交换控制器 应用:-48V 远程电力系统，AdvancedTCA ? 系统，高可用性 内部开关:无 电流限制:可调 电源电压:11.5 V ~ 14.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-MSOP 包装:管件 |
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