16
dc2313af
DEMO MANUAL DC2313A
software controL with LtpowerpLay
Status register contents are cleared when the lTC2937
begins a new sequence-up operation, so allowing auto-
matic re-try after a fault eliminates the debug information
that might exist in the registers.
The only fault information that will persist beyond a
successful re-sequence initiation is in the EEPROM
MONITOR_BACKUP register, which stores the contents
of the MONITOR_STATUS_HISTORY register when the
first fault after power-up is detected.
The ALERTB pin will remain asserted low until the ALERT
condition is cleared with an I
2
C bus (ARA) operation.
Recovering from and Clearing Faults
The FAULTB pin and status registers respond to a fault
condition, but can be cleared when the LTC2937 re-
sequences the power supplies. Along with the status
information registers, the FAULTB pin is cleared when the
sequence starts. In the case where fault information and
the FAULTB pin need to be cleared manually, the CLEAR
(0x2E) command is available.
LTpowerPlay allows the user to issue the CLEAR command
(0x2E) that clears the fault and status registers. Issue the
CLEAR command by pressing the “CLEAR” button in the
toolbar:
Clearing the AlERTB Pin
The ALERTB pin conforms to the SMBus protocol for
the
SMBALERT
fault response. It is designed to act as
an interrupt for a controller on the I
2
C bus. The LTC2937
ALERTB pin asserts when a fault event occurs, and it can
only be cleared by an appropriate bus response from the
controller.
When the ALERTB pin asserts, a controller may either
execute an alert response through the Alert Response
Address (0x0C), which is a defined as the ARA in the
SMBus protocol, or the controller may read from register
CLEAR_ALERTB (0x28) to immediately de-activate the
ALERTB pin.
LTpowerPlay will include the CLEAR_ALERTB command
when sending a CLEAR_FAULTS command if the behavior
is selected in the Preferences menu. Pull-down View
→
Preferences…, then select “Issue CLEAR_ALERTB on
CLEAR” = TRUE. When you click the CLEAR_FAULTS
button in the GUI it will also clear ALERTB.
warning: avoid issuing a ClEAR command while the
lTC2937 is in the sequenced-up state. The registers and
state-machines that get cleared have an immediate ef-
fect on the part, and will cause the supplies to fault and
re-sequence, which is usually an undesired behavior.
Sequence-down before issuing a ClEAR command.
If the LTC2937 is waiting, not re-trying, after a fault, turn
it off (press the “SEQUENCE UP/DOWN” button to turn-
off the PB_EN and GLOBAL_ON LEDs). The LTC2937 will
retain state, but will be ready to sequence-up. Press the
“SEQUENCE UP/DOWN” button again to sequence-up
normally and clear the latched fault status and the FAULTB
pin. The ALERT pin will remain asserted until cleared.