ADM1169 Analog Devices, ADM1169 Datasheet - Page 21

• Manufacturer Part Number: ADM1169
• Description: Super Sequencer and Monitor with Margining Control and Non-Volatile Fault Recording
• Manufacturer: Analog Devices

Specifications of ADM1169

• # Supplies Monitored: 8
• Volt Monitoring Accuracy: 1%
• # Output Drivers: 8
• Fet Drive/enable Output: Both
• Voltage Readback: 12-bit ADC
• Supply Adj/margining: 12-bit ADC+4 DACs
• Package: 32 ld LQFP,40 ld LFCSP

Each fault record contains eight bytes, with each byte taking
typically about 250 μs to write to EEPROM, for a total write
time of about 2 ms. After the black box begins to write a fault
record into EEPROM, the ADM1169 ensures that is complete
before attempting to write any additional fault records. This
means that if consecutive sequencing engine states are designated
as black box write states, then a time delay must be used in the
first state to ensure that the fault record is written before moving to
the next state.
When the ADM1169 powers on initially, it performs a search to
find the first fault record that has not been written to. It does this by
checking the flag bit in each fault record until it finds one where
the flag bit is 1. The first fault record is stored at Address 0xF980,
and at multiples of eight bytes after that, with the last record
stored at Address 0xF9F8.
The fault recorder is only able to write in the EEPROM. It is
not able to erase the EEPROM prior to writing the fault record.
Therefore, to ensure correct operation, it is important that the fault
record EEPROM is erased prior to use. When all the EEPROM
locations for the fault records are used, no more fault records are
written. This ensures that the first fault in any cascading fault is
stored and not overwritten and lost.
To avoid the fault recorder filling up and fault records being lost, an
application can periodically poll the ADM1169 to determine if there
are fault records to be read. Alternatively, one of the PDOx outputs
can be used to generate an interrupt for a processor in the fault
record write state to signal the need to come and read one or more
fault records.
After reading fault records during normal operation, two things
must be done before the fault recorder is able to reuse the
EEPROM locations. First, the EEPROM section must be erased.
The fault recorder must then be reset so that it performs its search
again for the first unused location of EEPROM that is available to
store a fault record.
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BLACK BOX WRITES WITH NO EXTERNAL SUPPLY
In cases where all the input supplies fail, for example, if the card
has been removed from a powered backplane, the state machine
can be programmed to trigger a write into the black box EEPROM.
The decoupling capacitors on the rail that power the ADM1169
and other loads on the board form an energy reservoir. Depending
on the other loads on the board and their behavior as the supply
rails drop, there may be sufficient energy in the decoupling
capacitors to allow the ADM1169 to write a complete fault
record (eight bytes of data).
Typically, it takes 2 ms to write to the eight bytes of a fault record. If
the ADM1169 is powered using a 12 V supply on the VH pin, then
a UV threshold at 6 V can be set and used as the state machine
trigger to start writing a fault record to EEPROM. The higher the
threshold is, the earlier the black box write begins, and the more
energy available in the decoupling capacitors to ensure it completes
successfully.
Provided the VH supply, or another supply connected to a VPx pin,
remains above 3.0 V during the time to write, the entire fault record
is always written to the EEPROM. In many cases, there should be
sufficient decoupling capacitors on a board to power the ADM1169
as it writes into the EEPROM.
In cases where the decoupling capacitors are not able to supply
sufficient energy after the board is removed to ensure a complete
fault record is written, the value of the capacitor on VDDCAP
may be increased. In the worst case, assuming that no energy is
supplied to the ADM1169 by the external decoupling capacitors,
but that VDDCAP has 4.75 V on it, then a 47 μF is sufficient to
guarantee that a single complete black box record can be written
to the EEPROM.
ADM1169