Datasheet

LTC2978A
38
2978afa
For more information www.linear.com/LTC2978A
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: The unit continues operating for the delay time specified which for this type of fault corresponds to an
immediate shutdown. After shutting off, the device responds according to the retry settings in bits [5:3].
1Xb: The device shuts down and responds according to the retry setting 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 continuously, without limitation, using Mfr_retry_delay,
until it is commanded OFF (by the CONTROLn 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.
Clearing Latched Faults
When a channel shuts down due to a fault, the off state is latched. This is referred to as a latched fault condition. Latched
faults
are reset by toggling the CONTROL pin, using the OPERATION or ON_OFF_CONFIG command, or removing and
reapplying the bias voltage to the V
IN_SNS
pin. All fault and warning conditions result in the ALERTB pin being asserted
low and the corresponding bits being set in the status registers. The CLEAR_FAULTS command resets the contents
of the status registers and de-asserts the ALERTB output, but it does not clear a faulted off state nor allow a channel
to turn back on.
After resetting the faults, ALERTB will be de-asserted. If using a CONTROL pin toggle that does not affect all channels,
a non-global OPERATION or ON_OFF_CONFIG command, or a CLEAR_FAULTS command, check the Status_word of
all other channels to make sure no additional faults are reported.
STATUS COMMANDS
STATUS_BYTE
The STATUS_BYTE command returns the summary of the most critical faults or warnings which have occurred, as
shown in the following table. STATUS_BYTE is a subset of STATUS_WORD and duplicates the same information.
STATUS_BYTE Data Contents
BIT(S) SYMBOL OPERATION
b[7] Status_byte_busy Same as Status_word_busy
b[6] Status_byte_off Same as Status_word_off
b[5] Status_byte_vout_ov Same as Status_word_vout_ov
b[4] Status_byte_iout_oc Same as Status_word_iout_oc
b[3] Status_byte_vin_uv Same as Status_word_vin_uv
b[2] Status_byte_temp Same as Status_word_temp
b[1] Status_byte_cml Same as Status_word_cml
b[0] Status_byte_high_byte Same as Status_word_high_byte
PMBus COMMAND DESCRIPTION