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參數(shù)資料
| 型號： | SMH4811 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 元件分類： | 散熱片 |
| 英文描述： | Heat Sink; Package/Case:TO-220; Thermal Resistance:23 C/W; Mounting Type:Clip-On; Length:6.81mm; Height:25.4mm; Width:20.32mm; Body Material:Aluminum; Body Plating:Anodized; Color:Black; Leaded Process Compatible:Yes RoHS Compliant: Yes |
| 中文描述： | 分布式電源熱插拔控制器 |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 358K |
| 代理商： | SMH4811 |
8
SMH4811A
Preliminary
2044 6.1 2/8/01
SUMMIT MICROELECTRONICS, Inc.
charging the filter capacitance (normally required at the
input of the DC/DC controller) too quickly may generate
very high current. The VGATE output of the SMH4811A
is current limited to I
VGATE
, allowing the slew rate to be
easily modified using external passive components. The
slew rate may be found by dividing I
VGATE
by the gate-to-
drain capacitance placed on the external FET. A complete
design example is given in the Applications Section.
Load Control
—
Sequencing the Secondary Sup-
plies
Once power has been ramped to the DC/DC controllers,
two conditions must be met before the PG# output can be
enabled: the Drain Sense voltage must be below 2.5V,
and the VGATE voltage must be greater than V
–
V
.
The Drain Sense input helps ensure that the power MOS-
FET is not absorbing too much steady state power from
operating at a high V
. This sensor remains active at all
times (except during the current regulation period). The
VGATE sensor makes sure that the power MOSFET is
operating well into its saturation region before allowing the
load to be switched on. Once VGATE reaches V
DD
–
V
GT
this sensor is latched.
Once the external MOSFET is properly switched on the
PG# output may be enabled (if ENPG is high). The PG#
output has a 12V withstand capability, so high voltages
must not be connected to this pin. A bipolar transistor or
opto-isolator can be used to boost the withstand voltage to
that of the host supply.
Circuit Breaker Operation
The SMH4811A provides a number of circuit breaker
functions to protect against over current conditions. A
sustained over-current event could damage the host sup-
ply and/or the load circuitry. The board
’
s load current
passes through a series resistor (R
) connected between
the MOSFET source (which is tied to CBSENSE) and V
SS
.
The breaker trips whenever the voltage drop across R
is
greater than 50mV for more than t
(a factory program-
mable filter delay ranging from 10μs to 500μs).
Quick-Trip
TM
Circuit Breaker
Additionally, the SMH4811A provides a Quick-Trip feature
that will cause the circuit breaker to trip immediately if the
voltage drop across R
exceeds V
. The Quick-Trip
level may be factory set to 60mV, 100mV (default),
200mV, or the feature may be disabled.
Current Regulation
The current regulation mode is an optional feature that
provides a means to regulate current through the MOS-
FET for a programmable period of time. If enabled the
device will start the internal timer when the voltage at
CBSENSE exceeds 50mV. Also, it attempts to limit the
voltage at CBSENSE to 60mV by regulating the VGATE
output. The circuit breaker will trip if the over-current
condition remains after the time-out. However, if CB-
SENSE drops below 50mV before the timer ends, the
timer is reset and VGATE resumes normal operation. If
the Quick-Trip level is exceeded then the device will
bypass the current regulation timer and shut down imme-
diately. The Current Regulation feature is disabled in the
default configuration.
Non-Volatile Fault Latch
The SMH4811A also provides an optional nonvolatile fault
latch (NVFL) circuit breaker feature. The nonvolatile fault
latch essentially provides a programmable fuse on the
circuit breaker. When enabled the nonvolatile fault latch
will be set whenever the circuit breaker trips. Once set, it
cannot be reset by cycling power.
N
OTE
: T
HE
DEVICE
REMAINS
PERMANENTLY
DISABLED
UNTIL
IT
IS
REPROGRAMMED
AT
THE
FACTORY
.
As long as the NVFL is set the FAULT# output will be
driven active. The Non-Volatile Fault Latch feature is
disabled in the default configuration.
Resetting FAULT#
When the circuit breaker trips the VGATE output is turned
off and FAULT# is driven low. In the default condition the
breaker resets automatically after a time of t
. In the
latched condition cycling power to the board or toggling the
EN/TS input will also reset the circuit breaker. If the over
current condition still exists after the MOSFET switches
back on, the circuit breaker will re-trip.
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| SMH4811A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:DISTRIBUTED POWER HOT SWAP CONTROLLER |
| SMH4811A_09 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Programmable Distributed Power Hot-Swap Controller for High-Availability Systems |
| SMH4811AG | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:DISTRIBUTED POWER HOT SWAP CONTROLLER |
| SMH4811AS | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:DISTRIBUTED POWER HOT SWAP CONTROLLER |
| SMH4812 | 制造商:SUMMIT 制造商全稱:SUMMIT 功能描述:Distributed Power Hot-Swap Controller |
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