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ADM1069
Preliminary Technical Data
OUTPUTS
SUPPLY SEQUENCING THROUGH
CONFIGURABLE OUTPUT DRIVERS
Supply sequencing is achieved with the ADM1069 using the
programmable driver outputs (PDOs) on the device as control
signals for supplies. The output drivers can be used as logic
enables or as FET drivers.
Rev. PrB | Page 16 of 32
The sequence in which the PDOs are asserted (and, therefore,
the supplies are turned on) is controlled by the sequencing
engine (SE). The SE determines what action is to be taken with
the PDOs based on the condition of the inputs of the ADM1069.
Therefore, the PDOs can be set up to assert when the SFDs are
in tolerance, the correct input signals are received on the VXn
digital pins, no warnings are received from any of the inputs of
the device, and so on. The PDOs can be used for a variety of
functions. The primary function is to provide enable signals for
LDOs or dc/dc converters, which generate supplies locally on a
board. The PDOs can also be used to provide a POWER_GOOD
signal when all the SFDs are in tolerance, or a RESET output if
one of the SFDs goes out of specification (this can be used as a
status signal for a DSP, FPGA, or other microcontroller).
The PDOs can be programmed to pull up to a number of
different options. The outputs can be programmed as follows:
Open-drain (allowing the user to connect an external pull-up
resistor)
Open-drain with weak pull-up to V
DD
Push/pull to V
DD
Open-drain with weak pull-up to VPn
Push/pull to VPn
Strong pull-down to GND
Internally charge-pumped high drive (12 V, PDO1–6 only)
The last option (available only on PDO1–6) allows the user to
directly drive a voltage high enough to fully enhance an external
N-FET, which is used to isolate, for example, a card-side voltage
from a backplane supply (a PDO can sustain greater than 10.5 V
into a 1 μA load). The pull-down switches can also be used to
drive status LEDs directly.
The data driving each of the PDOs can come from one of three
sources. The source can be enabled in the PnPDOCFG con-
figuration register (see the AN-698 application note for details).
The data sources are
Output from the SE.
Directly from the SMBus. A PDO can be configured so that
the SMBus has direct control over it. This enables software
control of the PDOs. Therefore, a microcontroller can be
used to initiate a software power-up/power-down sequence.
On-Chip Clock. A 100 kHz clock is generated on the device.
This clock can be made available on any of the PDOs. It can
be used, for example, to clock an external device such as
an LED.
By default, the PDOs are pulled to GND by a weak (20 k) on-
chip pull-down resistor. This is also the condition of the PDOs
on power-up, until the configuration is downloaded from
EEPROM and the programmed setup is latched. The outputs
are actively pulled low once a supply of 1 V or greater is on VPn
or VH. The outputs remain high impedance prior to 1 V appear-
ing on VPn or VH. This provides a known condition for the
PDOs during power-up. The internal pull-down can be over-
driven with an external pull-up of suitable value tied from the
PDO pin to the required pull-up voltage. The 20 k resistor
must be accounted for in calculating a suitable value. For
example, if PDOn must be pulled up to 3.3 V, and 5 V is available
as an external supply, the pull-up resistor value is given by
3.3 V = 5 V × 20 k/(
R
UP
+ 20 k)
Therefore,
R
UP
= (100 k 66 k)/3.3 = 10 k
0
PDO
SE DATA
CFG4
CFG5
CFG6
SMBus DATA
CLK DATA
1
2
1
2
VP1
SEL
VP4
1
2
V
DD
VFET (PDO1-6 ONLY)
2
Figure 24. Programmable Driver Output