SMH4044 Datasheet, PDF (9/20 Pages) Summit Microelectronics, Inc. – Compact PCI Hot-Swap Controller With IPMI Support

SMH4044
Preliminary
DEVICE OPERATION
POWER UP SEQUENCE
The SMH4044 is an integrated power controller for any hot
swappable add-in card. It provides all the signals and
control functions to be compatible with CompactPCI Hot
Swap requirements for basic hot swap systems, full hot
swap boards, and high availability systems.
Insertion Process
As the add-in board is inserted into the backplane,
physical connections are made with the chassis in order
to properly discharge any voltage potentials to ground.
The board will first contact the long pins on the backplane
that provide early power (5V, 3.3V and ground). Depend-
ing upon the board configuration, early power and ground
should be routed to the SMH4044. As soon as power is
applied the SMH4044 will assert the reset outputs to the
card side circuits, turn off the VGATE3 and VGATE5
outputs (disabling the external power FETs) and assert
1VREF. This signal can be used to pre-charge the I/O pins
before they begin to mate with the bus signals. The open
collector HEALTHY# output will be de-asserted. It should
be actively pulled high by an external pull-up resistor
(minimum 10kΩ).
The next pins to mate are the I/Os, and the balance of the
power pins if they are not already mated. The I/Os will
have been pre-charged by the 1VREF output.
The BD_SEL# pins are the last inputs to be driven to their
true state. In most systems these will most likely be
driven to ground when the short pins are mated. This
would indicate the card is fully inserted and the power-up
sequence can begin. If, however, the design is based on
high availability requirements, the two pins can be ac-
tively driven by the host or combined with a switch input
indicating the ejector handles are fully engaged.
Sequencing
Once the proper card insertion has been assured the
SMH4044 will check the status of the Power Enable signal
from the host. This input can be used to power down
individual cards on the bus via software control. It must
by held high in order for the SMH4044 to enable power
sequencing to the card.
When these conditions have been met, the SMH4044 will
drive the VGATE3 and VGATE5 outputs to turn on the
external 3 volt and 5 volt power FETs. The slew rate of
these outputs is controlled to 250V/s. Different slew rates
can be accommodated by either adding an additional
capacitor between the MOSFET gate and ground or by
injecting current into the ISLEW input. All circuitry on the
card is held in a reset condition until the 5V (or 3.3V)
supply is stable and the reset interval timer has timed out.
At this point, the reset signals are de-asserted, and proper
operation of the card commences. See Figure 1, Table
1, and Flow Chart 1.
The SMH4044 will monitor the card’s backend voltages.
Once they are at or above the card VTRIP levels the
SMH4044 will drive the HEALTHY# output low.
Card Removal Process
The card removal process operates in the opposite
sequence. For non-high-availability cards the action of
card removal disconnects the BD_SEL# (short pins) from
ground and the SMH4044 will instantly shutdown the
VGATE outputs, change the HEALTHY# status, and
assert the LOCAL_PCI_RST and LOCAL_PCI_RST#
outputs.
Because connectors to the host backplane employ stag-
gered pins, power will still be applied to the SMH4044 and
the I/O interface circuits. The LOCAL_PCI_RST and
LOCAL_PCI_RST# signals will place the interface cir-
cuits into a high impedance condition. The pre-charge
voltage will be applied to the I/Os enabling a graceful
disengagement from the active bus. Once the I/O pins are
free of the backplane, power can be removed from the
SMH4044 and other early power devices by releasing the
long pins.
The removal process is slightly different for a high-
availability system. As the ejector handle is rotated the
ejector switch will open, causing a change of state that will
activate the ENUM# signal to the host. In response to this
notification the host will de-assert a hardware controlled
BD_SEL# signal. This action will turn on an indicator LED
on the card, notifying the operator it is now safe to proceed
with the removal of the card. The sequence will then follow
that outlined for the non-high-availability removal pro-
cess.
Power Configurations
The SMH4044 can be used in 5V only, 3.3V-only and
mixed voltage systems. For systems with a single power
supply, connect VCC and HST_3V_MON together to the
bus power line. Also connect CARD_3V_MON and
CARD_5V_MON together to the card side power. Now the
state of VSEL determines the reset level that will be used
to signal valid power. For 3.3V systems tie VSEL to VCC,
for 5V systems tie VSEL to ground.
SUMMIT MICROELECTRONICS, Inc.
2057 1.x 8/16/01
9