Linear Technology DC2028A Manual page 9

DEMO MANUAL DC2028A
common Demo BoArD operAtions
The LTC2977 has a feature which allows supply rails to
sequence off in a controlled manner in response to a fault
condition, as opposed to turning all rails off immediately.
The SequenceOffOnFault bit in the MFR_CONFIG_LTC2977
register sets this behavior on each channel. The DC2028A
demo board has been configured to sequence off all channels
when a fault occurs. Pressing the SHORT pushbutton causes
the Fault pin to be asserted low which triggers all rails to
power down based on the TOFF_DELAY times.
Figure 4 shows FAULTB asserting low, and each of the channels sequencing off per the TOFF_DELAY settings. Figure 5
shows the same except that the 3.0V rail (CH4) does not have its SequenceOffOnFault bit set. The 3.0V rail powers
down immediately as defined by the fault response setting.
Figure 4. Sequencing Off (SeqOffOnFault=1)
CLEARING A FAULT
To clear a fault, the user may click the CF icon in the GUI or simply push the RESET pushbutton on the
demo board. In both cases, the red (+) on the CF icon and alert LED on the board will be cleared. You will
notice that all rails are automatically re-enabled after a programmable retry period. The alert LED may be
cleared by clicking the clear faults (CF) icon in the GUI. After clearing faults, the system tree may remain yellow if any
non-volatile fault logs are present. For further information, see the Working with the Fault Log section.
RESETTING THE DC2028A
A reset pushbutton is provided on the board. To reset all devices on the DC2028A board and reload the EEPROM
contents into operating memory (RAM), press RESET (SW2) on the DC2028A.
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Figure 5. Sequencing Off (SeqOffOnFault=0)
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