SMM764 SUMMIT Microelectronics, Inc:, SMM764 Datasheet - Page 17

• Manufacturer Part Number: SMM764
• Description: Four-channel Active Dc Output Controller, Monitor, Marginer And Sequencer With Sequence-link
• Manufacturer: SUMMIT Microelectronics, Inc:

each channel that decode the commands to margin
high, margin low, or control to the nominal setting.
Therefore, any combination of margin high, margin
low, and nominal control is allowed in the margining
mode.
Once the SMM764 receives the command to margin
the supply voltages, it begins adjusting the supply
voltages to move toward the desired setting. When all
channels are at their voltage setting, a bit is set in the
margin status registers.
Note: Configuration writes or reads of registers 00
to 0F
margining.
POWER-OFF CASCADE SEQUENCING
The SMM764 performs power-off sequencing in the
reverse order of power-on sequencing.
Power-off cascade sequencing can be initiated by the
PWR_ON pin, via I
condition on any of the monitored inputs. Toggling the
PWR_ON pin low will initiate the power-off sequence.
To
sequencing feature, the SMM764 offers an I
command to initiate power-off sequencing while the
PWR_ON pin is asserted.
sequencing can be initiated by a fault condition on a
monitored input.
Once power-off sequencing begins, the SMM764 will
wait a power-off delay time (t
the last sequence position and then deactivate the
PUP outputs for those channels. The power-off delay
times are individually programmable for each channel.
The
VM
position are below the programmed OFF thresholds.
At this point, the SMM764 will move to the next
sequence position and begin to timeout the power-off
delay times for the associated channels. This process
continues until all of the channels in the sequence
have turned off and are below their OFF thresholds.
Summit Microelectronics, Inc
APPLICATIONS INFORMATION (CONTINUED)
X
HEX
inputs of the channels assigned to that sequence
enable
SMM764
should not be performed while the SMM764 is
software
2
will
C control or triggered by a fault
control
then
DPOFF
Furthermore, power-off
) for any channel in
of
wait
the
until
power-off
HEX
2
all
2098 1.1 6/29/2005
C
The status register reveals that all sequenced
channels have turned off. The power-off sequencing
mode ends when all sequenced supplies are below
their OFF thresholds.
The programmable sequence termination timer can be
used to protect against a stalled power-off sequence.
This timer resets itself at the beginning of each
sequence position.
position must go below their OFF threshold before the
sequence termination timer times out (t
sequence will terminate and all PUP outputs will be
switched to their inactive state. This timer has four
settings of OFF: 100ms, 200ms and 400ms.
sequence termination timer can be disabled separately
for power-off sequencing.
While the SMM764 is in the power-off sequencing
mode, the RST# output is held active and the
HEALTHY output is held inactive, regardless of trigger
sources (Figure 8). The force-shutdown trigger option
is also disabled while in this mode. Furthermore, the
SMM764 will not respond to activity on the PWR_ON
pin during power-off sequencing mode.
FORCE SHUTDOWN
The force-shutdown operation brings all PUP
to their inactive state. This operation is used for an
emergency shutdown when there is not enough time
to sequence the supplies off.
operation shuts off all sequenced channels pulls the
PWR_ON pin low, and waits for the supply voltages to
drop below their respective OFF thresholds before
beginning a restart sequence.
A force-shutdown operation can be initiated by any
one of four events. The first two methods for initiating
a force-shutdown are always enabled. Simply taking
the FS# pin low will initiate a force-shutdown operation
and maintain it until the pin is brought high again. An
I
shutdown operation to be initiated via software control.
This bit is cleared after all sequenced channels have
dropped
2
C force-shutdown command allows the force-
below
their
All channels in the sequence
OFF
Preliminary Information
The force-shutdown
voltage
SMM764
STT
threshold.
X
) or the
outputs
The
17