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ADM1069
Preliminary Technical Data
COMMUNICATING WITH THE ADM1069
CONFIGURATION DOWNLOAD AT POWER-UP
The configuration of the ADM1069 (UV/OV thresholds, glitch
filter timeouts, PDO configurations, and so on) is dictated by
the contents of RAM. The RAM is comprised of 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 this section.
Rev. PrB | Page 24 of 32
The 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:
1.
With no power applied to the device, the PDOs are all high
impedance.
2.
When 1 V appears on any of the inputs connected to the
VDD arbitrator (VH or VPn), the PDOs are all weakly
pulled to GND with a 20 k impedance.
3.
When the supply rises above the undervoltage lockout of
the device (UVLO is 2.5 V), the EEPROM starts to
download to the RAM.
4.
The EEPROM downloads its contents to all Latch As.
5.
Once 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.
6.
At 0.5 ms after the configuration download completes, the
first state definition is downloaded from EEPROM into
the SE.
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
EEPROM into the RAM registers, the user might need to alter
the configuration of functions on the ADM1069, such as chang-
ing the UV or OV 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 options are controlled in the UPDCFG register:
1.
Update the configuration in real time. The user writes to
RAM across the SMBus and the configuration is updated
immediately.
2.
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.
3.
Change EEPROM register contents without changing the
RAM contents, and then download the revised EEPROM
contents to the RAM registers. Again, 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 OV threshold, this can be done by
updating the RAM register as described in Option 1. However,
if the user is not satisfied with the change and wants to revert to
the original programmed value, then 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 original configuration.
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, then, 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, then the contents of a page
cannot be erased, even if the command code for page erasure is
programmed across the SMBus. The bitmap for the UPDCFG
register is shown in the AN-698 application note. A flow chart
for download at power-up and subsequent configuration
updates is shown in Figure 34.