ADM1168 Analog Devices, ADM1168 Datasheet - Page 20

• Manufacturer Part Number: ADM1168
• Description: Super Sequencer and Monitor with Nonvolatile Fault Recording
• Manufacturer: Analog Devices

Specifications of ADM1168

• # Supplies Monitored: 8
• Volt Monitoring Accuracy: 1%
• # Output Drivers: 8
• Fet Drive/enable Output: Both
• Package: 32 ld LQFP

ADM1168
COMMUNICATING WITH THE ADM1168
CONFIGURATION DOWNLOAD AT POWER-UP
The configuration of the ADM1168 (undervoltage/overvoltage
thresholds, glitch filter timeouts, and PDO configurations) 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 Configuration section.
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:
1.
2.
3.
4.
5.
6.
Note that any attempt to communicate with the device prior to
the completion of the download causes the ADM1168 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 ADM1168, 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 ADM1168 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.
With no power applied to the device, the PDOs are all high
impedance.
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 EEPROM
into the SE.
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Option 1
Update the configuration in real time. The user writes to
the RAM across the SMBus, and the configuration is updated
immediately.
Option 2
Update the Latch As without updating the Latch Bs. With this
method, the configuration of the ADM1168 remains unchanged
and continues to operate in the original setup until the instruction
is given to update the Latch Bs.
Option 3
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
ADM1168 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 the Option 3
section 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 the Option 1
section. 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 the Option 3
section, restoring the ADM1168 to its original configuration.
The topology of the ADM1168 makes this type of operation
possible. The local, volatile registers (RAM) are all double-
buffered latches. Setting Bit 0 of the UPDCFG register to leaves the
double buffered latches open at all times, allowing the registers
to be updated continuously as they are written to. 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 this bit is set 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
for download at power-up and subsequent configuration updates is
shown in Figure 24.
AN-721 Application
Note. A flow diagram