LTC2972 datasheet(64/112 Pages) LINER

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LTC2972

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Clearing Latched Faults

Latched faults are reset by toggling the CONTROL pin, using the OPERATION command, or removing and reapplying

the bias voltage to the VIN_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. The CLEAR_FAULTS does not clear a faulted off state nor allow a

channel to turn back on.

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 LTC2972 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 tS_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).

PMBus COMMAND DESCRIPTION

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