SMM764 SUMMIT Microelectronics, Inc:, SMM764 Datasheet - Page 15

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

A pulse of current either sourced or sunk for 5µs every
1.7ms, to the capacitors connected to the TRIM_CAP
pins adjusts the voltage output on the TRIM
The voltages on the TRIM_CAP
and applied to the TRIM
adjustments on the TRIM
less than 1mV on the power supply voltages. The
amplitude of this ripple is a function of the TRIM_CAP
capacitor and the trim gain of the converter.
Application Note 37 details the calculation of the
TRIM_CAP
ripple.
Each channel can be programmed to either enable or
disable the ADOC function.
active, the TRIM
impedance inputs. If disabled and not used, they can
be connected to ground. The voltages on the TRIM
pins are buffered and applied to the TRIM_CAP
charging the capacitors.
transition from the converter powering up to its
nominal voltage, to the SMM764 controlling that
voltage, and to the ADOC nominal setting.
The pulse of current can be increased to a 10X pulse
of current until the power supply voltages are at their
nominal settings by selecting the programmable Fast
Margin option.
decreases the time required to bring a supply voltage
from the converter’s nominal output voltage to the
ADOC nominal, high, or low voltage setting.
POWER-ON CASCADE SEQUENCING
The SMM764 can be programmed to sequence on 32
supplies occupying up to 29 sequence positions. This
is accomplished using the SEQ_LINK pin. Each of the
4 channels (A-D) on a SMM764 has an associated
open drain PUP output that, when connected to a
converter’s enable pin, controls the turn-on of the
converter.
positions to determine the order of the sequence. The
polarity of each of the PUP
for use with various types of converters.
Power-on sequencing is initiated on the rising edge of
the PWR_ON pin.
The SMM764 can be programmed to wait until any or
all
Temperature) ADC readings are within their respective
voltage threshold or temperature limits before power-
on sequencing is allowed to begin. This ensures that
the converters have reached their full supply voltage
before they are enabled.
Summit Microelectronics, Inc
APPLICATIONS INFORMATION (CONTINUED)
VDD,
X
12VIN,
The channels are assigned sequence
capacitor to achieve a desired minimum
X
As the name implies, this option
pins on the SMM764 are high
and
X
pins cause a slight ripple of
X
Internal
outputs is programmable
X
This allows a smooth
When disabled or not
pins.
X
pins are buffered
Temp
The voltage
(Internal
X
X
pins.
pins
2098 1.1 6/29/2005
X
X
X
On the rising edge of the PWR_ON pin the SMM764
will wait a power-on delay time (t
channels in the first sequence position (position 1) and
then activate the PUP
The
programmable for each channel. The SMM764 will
then wait until all VM
to the first sequence position are above their user
programmable UV1 thresholds, which is called
cascade sequencing.
sequence position (position 2) and begin to timeout
the power-on delay times for the associated channels.
This process continues until all of the channels
assigned to participate in the sequence have turned
on and are above their UV1 threshold. Once the
sequence has completed the status register indicates
that all sequenced power supply channels have turned
on. After the sequence has completed the SMM764
will begin the ADOC of the enabled channels. The
power-on sequencing mode ends when the ADOC
channels are at their nominal voltage setting.
“Ready” bit in the status register signifies that the
voltages are at their set points.
The programmable sequence termination timer can be
used to protect against a stalled power-on sequence.
This timer resets itself at the beginning of each
sequence position.
position must go above their UV1 threshold before the
sequence termination timer times out (t
sequence will terminate by pulling the FS# pin low,
initiating a Force Shutdown. The status register
contains bits indicating in which sequence position the
timer timed out. This sequence termination timer has
four settings of OFF, 100ms, 200ms and 400ms.
While the SMM764 is in the power-on sequencing
mode the RST# output is held active and the
HEALTHY output is held inactive regardless of trigger
sources (Figure 8). The power-off and force-shutdown
trigger options are also disabled while in this mode.
Furthermore, the SMM764 will not respond to activity
on the PWR_ON pin or to a power-off I
during power-on sequencing mode.
The SMM764 permits multiple supplies to occupy the
same sequence position. When a sequence position is
shared, each channel will be enabled after its
respective power-on delay. When the last channel
occupying a shared sequence position exceeds its
UV1 setting the SMM764 will increment to the next
At this point, the SMM764 will enter the second
power-on
delay
X
All channels in the sequence
inputs of the channels assigned
X
outputs for those channels.
times
Preliminary Information
are
SMM764
DPON
2
C command
STT
individually
) for any
) or the
The
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