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ADM1069ASTZ Datasheet(PDF) 24 Page - Analog Devices
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ADM1069ASTZ Datasheet(HTML) 24 Page - Analog Devices
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Rev. C | Page 24 of 32
COMMUNICATING WITH THE ADM1069
CONFIGURATION DOWNLOAD AT POWER-UP
The configuration of the ADM1069 (undervoltage/overvoltage
thresholds, glitch filter timeouts, PDO configurations, and so on)
is dictated by the contents of the RAM. The RAM comprises
digital latches that are local to each of the functions on the device.
The latches are double-buffered and have two identical latches,
Latch A and Latch B. Therefore, when an update to a function
occurs, the contents of Latch A are updated first, and then the
contents of Latch B are updated with identical data. The advantages
of this architecture are explained in detail in the Updating the
The two latches are volatile memory and lose their contents at
power-down. Therefore, the configuration in the RAM must be
restored at power-up by downloading the contents of the EEPROM
(nonvolatile memory) to the local latches. This download occurs
in steps, as follows:
With no power applied to the device, the PDOs are all high
When 1.2 V appears on any of the inputs connected to the
VDD arbitrator (VH or VPx), the PDOs are all weakly pulled
to GND with a 20 kΩ resistor.
When the supply rises above the undervoltage lockout of
the device (UVLO is 2.5 V), the EEPROM starts to
download to the RAM.
The EEPROM downloads its contents to all Latch As.
When the contents of the EEPROM are completely
downloaded to the Latch As, the device controller signals
all Latch As to download to all Latch Bs simultaneously,
completing the configuration download.
At 0.5 ms after the configuration download completes, the
first state definition is downloaded from the EEPROM into
Note that any attempt to communicate with the device prior to
the completion of the download causes the ADM1069 to issue
a no acknowledge (NACK).
UPDATING THE CONFIGURATION
After power-up, with all the configuration settings loaded from
the EEPROM into the RAM registers, the user may need to alter
the configuration of functions on the ADM1069, such as
changing the undervoltage or overvoltage limit of an SFD,
changing the fault output of an SFD, or adjusting the rise time
delay of one of the PDOs.
The ADM1069 provides several options that allow the user to
update the configuration over the SMBus interface. The
following three options are controlled in the UPDCFG register.
Update the configuration in real time. The user writes to the RAM
across the SMBus, and the configuration is updated immediately.
Update the Latch As without updating the Latch Bs. With this
method, the configuration of the ADM1069 remains unchanged
and continues to operate in the original setup until the instruction
is given to update the Latch Bs.
Change the EEPROM register contents without changing the RAM
contents, and then download the revised EEPROM contents to the
RAM registers. With this method, the configuration of the
ADM1069 remains unchanged and continues to operate in the
original setup until the instruction is given to update the RAM.
The instruction to download from the EEPROM in Option 3 is
also a useful way to restore the original EEPROM contents if
revisions to the configuration are unsatisfactory. For example,
if the user needs to alter an overvoltage threshold, the RAM
register can be updated, as described in Option 1. However,
if the user is not satisfied with the change and wants to revert to
the original programmed value, the device controller can issue
a command to download the EEPROM contents to the RAM
again, as described in Option 3, restoring the ADM1069 to its
The topology of the ADM1069 makes this type of operation
possible. The local, volatile registers (RAM) are all double-
buffered latches. Setting Bit 0 of the UPDCFG register to 1
leaves the double-buffered latches open at all times. If Bit 0 is set
to 0 when a RAM write occurs across the SMBus, only the first
side of the double-buffered latch is written to. The user must
then write a 1 to Bit 1 of the UPDCFG register. This generates a
pulse to update all the second latches at once. EEPROM writes
occur in a similar way.
The final bit in this register can enable or disable EEPROM page
erasure. If this bit is set high, the contents of an EEPROM page
can all be set to 1. If low, the contents of a page cannot be erased,
even if the command code for page erasure is programmed across
the SMBus. The bit map for the UPDCFG register is shown in
the AN-721 Application Note at www.analog.com. A flow diagram
for download at power-up and subsequent configuration updates
is shown in Figure 35.
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