The MAX5946 dual hot-plug controller is designed for
PCI Express® applications. The device provides hotplug
control for 12V, 3.3V, and 3.3V auxiliary supplies of
two PCI Express slots. The MAX5946's logic inputs/outputs
allow interfacing directly with the system hot-plug
management controller or through an SMBus™ with an
external I/O expander. An integrated debounced attention
switch and present-detect signals are included to
simplify system design.
The MAX5946 drives four external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V auxiliary
outputs are controlled through internal 0.3
n-channel MOSFETs. Internal charge pumps provide
gate drive for the 12V outputs while the gate drive of
the 3.3V output is driven by the 12V input supply. The
3.3V auxiliary outputs are completely independent from
the main outputs with their own charge pumps.
At power-up, the MAX5946 keeps all of the external
MOSFETs off until the supplies rise above their respective
undervoltage lockout (UVLO) thresholds. The
device keeps the internal MOSFETs off only until the
auxiliary input supply rises above its UVLO threshold.
Upon a turn-on command, the MAX5946 enhances the
external and internal MOSFETs slowly with a constant
gate current to limit the power-supply inrush current.
The MAX5946 actively limits the current of all outputs at
all times and shuts down if an overcurrent condition
persists for longer than a programmable overcurrent
timeout. Thermal-protection circuitry also shuts down all
outputs if the die temperature exceeds +150°C. After an
overcurrent or overtemperature fault condition, the
MAX5946L latches off while the MAX5946A automatically
restarts after a restart time delay. The device is available
in a 36-pin (6mm x 6mm) thin QFN package and
operates over the -40°C to +85°C temperature range.
Key Features
Applications/Uses
PCI Express Compliant
Hot Swaps 12V, 3.3V, and 3.3V Auxiliary for 2
PCI-E Slots
Integrated Power MOSFET for Auxiliary Supply
Rails
Controls dI/dt and dV/dt
Active Current Limiting Protects Against
Overcurrent/Short-Circuit Conditions
Programmable Current-Limit Timeout
PWRGD-bar Signal Outputs with Programmable
Power-On Reset (POR) (160ms Default)
Latched FAULT-bar Signal Output after Overcurrent
or Overtemperature Fault
Notes: *This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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n-channel MOSFETs. Internal charge pumps provide
gate drive for the 12V outputs while the gate drive of
the 3.3V output is driven by the 12V input supply. The
3.3V auxiliary outputs are completely independent from
the main outputs with their own charge pumps.