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  Microchip Technology Semiconductor Electronic Components Datasheet  


MCP18480

Hot Swap Controller



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MCP18480 pdf
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M
MCP18480
-48V Hot Swap Controller
Features
• Allows safe board removal and insertion from a
live backplane
• Accurate (<1.5%) internal voltage reference for
fault detection and precision timing
• Programmable foldback current limiting
• Programmable circuit breaker current limiting
• Auto restart option for all faults
• Adjustable Undervoltage lockout thresholds
• Adjustable Overvoltage protection threshold
• Adjustable Power Good delay
• Configurable Power Good output polarity
• Low-side drive of an external N-channel FET
CMOS Technology
• High-Voltage Operation
• Temperature range: Industrial (I): -40°C to +85°C
Packaging
• 20-lead SSOP
Package Type
SSOP
VPOS
OVTH
UVTH
UVHYS
UVD
VREFOUT
VREFIN
CL
ISET
TIMER
1 20
2 19
3 18
4 17
5 16
6 15
7 14
8 13
9 12
10 11
RESTART
ENABLE
PWRGOOD
OVO
DRAINTH
VFB
GATE
SENSE
RDISCH
VNEG
Description
The MCP18480 is a Hot Swap controller that allows
boards to be safely removed or inserted from an active
backplane using -48V.
When PCBs are inserted into a live backplane, high-
peak or transient currents from the source are gener-
ated due to the charging of the bypass capacitors on
the supply. The high transient currents can destroy
connectors and capacitors. The high inrush current can
pull the input voltage BUS down and reset the system.
The MCP18480 solves this problem by controlling the
slew rate of the backplane voltage to the board so that
these transients are eliminated. This allows boards to
be removed and inserted without causing damage to
connector pins and input bulk capacitors, in addition to
preventing false resets to the other boards on the
backplane.
The MCP18480 can be used in applications in several
areas including:
• Telecom Line Cards
• Network Switches
• Network Routers and Servers
• Base Station Line Cards
• Power-Over-LAN
• Power-Over-MDI
• IP Phone Switches/Routers
• Mid-Span, Power-Over-MDI
Two forms of current limit are provided in the
MCP18480. These are:
• Foldback
• Circuit breaker
The foldback current-limiting circuit uses an external
sense resistor and a voltage that is proportional to the
external MOSFET’s drain voltage. These are used to
keep the MOSFET in its Safe Operating Area (SOA).
If the device remains in current limit for a programmed
time period, the external N-channel FET is turned off.
The option exists to configure the device to automati-
cally restart after a programmed time delay. A program-
mable catastrophic current limit threshold shuts down
the switch (circuit breaker) if excessive current is
sensed due to a short-circuit condition.
2003 Microchip Technology Inc.
DS20091B-page 1



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MCP18480 pdf
MCP18480
Internal comparators are incorporated to add hystere-
sis for adjusting the Undervoltage Lockout (UVLO)
threshold. The external N-channel MOSFET is turned
on when the input is below the user-programmable,
Overvoltage threshold and above the user-
programmable, Undervoltage threshold.
MCP18480 Block Diagram
VPOS
The PWRGOOD pin indicates the status of the
MCP18480 and is active when the device has com-
pleted power-up and the system is not in an Undervolt-
age, Overvoltage or current-limit condition.
PWRGOOD can be externally configured to either
active-high or active-low to accommodate external cir-
cuitry (power supplies) that have either enabling logic.
A block diagram of the MCP18480 is shown below.
DRAINTH
VNEG
VREFOUT
VREFIN
ISET
BIAS (Section 6.8.8)
12V
Regulator
12VOUT
5V
Reg.
5VOUT
Internal
Bias
Generation
FET Good
(Section 6.8.3)
VPOS
PWRGOOD
Output Block
(Section 6.8.9)
GATE
Drive
(Section 6.8.7)
SENSE
PWRGOOD (1)
GATE
OVTH
OVO
Overvoltage
(Section 6.8.2)
5VOUT
ENABLE
UVTH
UVHYS
UVD
Undervoltage
(Section 6.8.1)
Latch
(Section
6.8.6)
RESTART
VNEG
VFB
SENSE
CL
Current Limit
(Section 6.8.4)
Current Limit Timer
Circuit Breaker
Timer
(Section 6.8.5)
TIMER
RDISCH
MCP18480
Note 1:
The PWRGOOD output pin can be either active-high or active-low. This polarity is determined by the
voltage (either the level on the VREFIN pin or level on the VNEG pin) on the ISET pin:
- Connecting the external RISET resistor to VREFIN configures the PWRGOOD pin as active-low
- Connecting the external RISET resistor to VNEG configures the PWRGOOD pin as active-high
DS20091B-page 2
2003 Microchip Technology Inc.



Part Number MCP18480
Description Hot Swap Controller
Maker Microchip Technology - Microchip Technology
Total Page 30 Pages
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