Datasheet

LTC2974
58
2974fc
For more information www.linear.com/LTC2974
pMbus coMManD DescripTion
TON_MAX_FAULT_RESPONSE
This command defines the LTC2974 response to a TON_MAX_FAULT. It may be used to protect against a short-circuited
output at startup. After startup use VOUT_UV_FAULT_RESPONSE to protect against a short-circuited output.
The device also:
• Sets the HIGH_BYTE bit in the STATUS_BYTE,
• Sets the VOUT bit in the STATUS_WORD,
• Sets the TON_MAX_FAULT bit in the STATUS_VOUT register, and
• Notifies the host by asserting ALERTB.
TON_MAX_FAULT_RESPONSE Data Contents
BIT(S) SYMBOL OPERATION
b[7:6] Ton_max_fault_response_action Response action:
00b: The unit continues operation without interruption.
01b-11b: The unit shuts down immediately or sequences off after TOFF_DELAY (See Mfr_config_track_enn).
After shutting down, the device responds according to the retry settings in bits [5:3].
b[5:3] Ton_max_fault_response_retry Response retry behavior:
000b: A zero value for the retry setting means that the unit does not attempt to restart. The output remains
disabled until the fault is cleared.
001b-111b: The PMBus device attempts to restart the number of times specified by the global Mfr_retry_
count[2:0] until it is commanded OFF (by the CONTROL pin or OPERATION command or both), bias power is
removed, or another fault condition causes the unit to shut down.
Changing the value might not take effect until the next off-then-on sequence on that channel.
b[2:0] Ton_max_fault_response_delay Hard coded to 000b: There is no additional deglitch delay applied to fault detection.
MFR_RETRY_DELAY
This command determines the retry interval when the LTC2974 is in retry mode in response to a fault condition. This
delay is counted using SHARE_CLK only. This delay is internally limited to 13.1 seconds, and rounded to the nearest
200µs. The read value of this command always returns what was last written and does not reflect internal limiting.
MFR_RETRY_COUNT
The MFR_RETRY_COUNT is a global command that sets the number of retries attempted when any channel faults off
with its fault response retry field set to a non zero value.
In the event of multiple or recurring retry faults on the same channel the total number of retries equals MFR_RETRY_
COUNT. If a channel has not been faulted off for 6 seconds, its retry counter is cleared. Toggling a channel’s CONTROL
pin off then on or issuing OPERATION off then on commands will synchronously clear the retry count.
MFR_RETRY_COUNT Data Contents
BIT(S) SYMBOL OPERATION
b[7:3] Reserved Always returns zero.
b[2:0] Mfr_retry_count [2:0] 0: No retries:
1-6: Number of retries.
7: Infinite retries.
Changing the value might not take effect until the next off-then-on sequence on that channel.