SMH4814
Preliminary Information 1 (See Last Page)
Dual Feed Active-ORing Programmable Hot Swap Controller
FEATURES AND APPLICATIONS
INTRODUCTION
ꢀ
Eliminates Passive ORing Diodes for Reduced
The SMH4814 is an integrated power controller
designed to control the hot-swapping of plug-in cards
in a distributed power environment. The SMH4814
drives external power MOSFET switches that connect
the supply to the load while reducing in-rush current
and providing over-current protection. When the
source and drain voltages of the external MOSFETs
are within specification the SMH4814 asserts the four
PUP logic outputs in a programmable cascade
sequence to enable the DC/DC converters.
The SMH4814 also monitors two independent –48V
feeds. The redundant power supplies allow for high
availability and reliability. The traditional method of
supplying power from these feeds is via ORing power
diodes, which consume a significant amount of power.
The SMH4814 allows low-RDSON FETs to be used in
place of ORing diodes to reduce power consumption.
The SMH4814 determines when at least one of the
–48V feeds is within an acceptable voltage range and
switches on the appropriate FET path while providing
slew rate control. The SMH4814 continuously monitors
the incoming feeds and switches to the most negative
feed as necessary. The SMH4814 is programmed and
controlled using the I2C bus as required in ATCATM
applications.
Power Consumption
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High Noise Immunity on All Logic Inputs
Soft Starts Main Power Supply on Card
Insertion or System Power Up with Slew Rate
Control
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•
•
Programmable Differential Current Sense
Programmable Inrush Current Limiting
Master Enable to Allow System Control of
Power-Up or -Down
ꢀ
Programmable Independent Enabling of up to
4 DC/DC Converters
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ꢀ
Programmable Circuit Breaker Level and Mode
Programmable Quick-Trip™ Value, Current
Limiting, Duty Cycle Times, Over-Current Filter
Programmable Host Voltage Fault Monitoring
Programmable UV/OV Filter and Hysteresis
Programmable Fault Mode: Latched or Duty
Cycle
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ꢀ
ꢀ
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Internal Shunt Regulator Allows for a Wide
Supply Range
Applications
ꢀ
ꢀ
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Telecom Hot-Swap Card - AdvancedTCATM
Network Processors
Power-on Ethernet, IEEE 802.3af
SIMPLIFIED APPLICATIONS DRAWING
–48V Ret.
I2C
RD
VOUT
DC-to-DC
Converter A
ON/OFF
+
VIN+
Pin
PD1
Detect
UV
PUPA
PUPB
PUPC
PUPD
VOUT
-
VIN-
OV
SMH4814
VSS
PD0
Pin
Detect
RA
TM
dvanced
A
TCA
RS
–48V A
–48V B
RB
Primary
Secondary
Figure 1. The SMH4814 Controller hot-swaps and cascade sequences up to 4 DC/DC Converters and actively
controls the A and B –48V feeds eliminating the need for ORing diodes and the associated voltage drop.
Note: This is an applications example only. Some pins, components and values are not shown.
© SUMMIT Microelectronics, Inc. 2005 • 1717 Fox Drive • San Jose CA 95131 • Phone 408 436-9890 • FAX 408 436-9897
The Summit Web Site can be accessed by “right” or “left” mouse clicking on the link: http://www.summitmicro.com/
2080 2.0 07/21/05
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