LTC2972 datasheet(65/112 Pages) LINER

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LTC2972

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OT_FAULT_RESPONSE, UT_FAULT_RESPONSE, VIN_OV_FAULT_RESPONSE and VIN_UV_FAULT_RESPONSE

The fault response documented here is for values that are measured by the ADC. 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_VIN or STATUS_TEMPERATURE register, and

• Notify the host by pulling the ALERTB pin low.

OT_FAULT_RESPONSE, UT_FAULT_RESPONSE, VIN_OV_FAULT_RESPONSE, VIN_UV_FAULT_RESPONSE Data Contents

BIT(S) SYMBOL

OPERATION

b[7:6] Ot_fault_response_action,

Ut_fault_response_action,

Vin_ov_fault_response_action,

Vin_uv_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] Ot_fault_response_retry,

Ut_fault_response_retry,

Vin_ov_fault_response_retry,

Vin_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] Ot_fault_response_delay,

Ut_fault_response_delay,

Vin_ov_fault_response_delay,

Vin_uv_fault_response_delay

Hard coded to 000b: There is no additional deglitch delay applied to fault detection.

TON_MAX_FAULT_RESPONSE

This command defines the LTC2972 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.

PMBus COMMAND DESCRIPTION

LTC2972 Datasheet(PDF) 65 Page - Linear Technology

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