Datasheet

LTC2974
55
2974fc
For more information www.linear.com/LTC2974
pMbus coMManD DescripTion
VOUT_OV_FAULT_RESPONSE and VOUT_UV_FAULT_RESPONSE
The fault response documented here is for voltages that are measured by the high speed supervisor. These voltages
are measured over a short period of time and may require a deglitch period. Note that in addition to the response
described by these commands, the LTC2974 will also:
• Set the appropriate bit(s) in the STATUS_BYTE.
• Set the appropriate bit(s) in the STATUS_WORD.
• Set the appropriate bit in the corresponding STATUS_VOUT register, and
• Notify the host by pulling the ALERTB pin low.
VOUT_OV_FAULT_RESPONSE and VOUT_UV_FAULT_RESPONSE Data Contents
BIT(S) SYMBOL OPERATION
b[7:6] Vout_ov_fault_response_action,
Vout_uv_fault_response_action
Response action:
00b: The unit continues operation without interruption.
01b: The unit continues operating for the delay time specified by bits[2:0] in increments of t
S_VS
. See
Electrical Characteristics Table. If the fault is still present at the end of the delay time, 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].
10b-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] Vout_ov_fault_response_retry,
Vout_uv_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] Vout_ov_fault_response_delay,
Vout_uv_fault_response_delay
This sample count determines the amount of time a unit is to ignore a fault after it is first detected. Use this
delay to deglitch fast faults.
000b: There is no additional deglitch delay applied to fault detection.
001b-111b: The fault is deglitched for deglitch period of b[2:0] samples at a sampling period of tS_VS
(12.2µs typical).