Linear Technology LTC2977 Demo Board: Octal Power Supply Manager [Requires DC1613] DC2028A DC2028A Data Sheet

LTC2977

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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 LTC2977 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. 
Note: Odd numbered channels configured for high resolution ADC measurements (current measurements) will not 

respond to OV/UV faults or warnings.

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, Voltage Supervisor Characteristics section). 

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_chan_mode). After shutting down, the device responds according to the retry 

setting in bits [5:3].
1Xb: The unit shuts down immediately or sequences off after TOFF_DELAY (See Mfr_config_chan_mode). 

After shutting down, the device responds according to the retry setting 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.

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: The unit turns off immediately.
001b-111b: The unit turns off after b[2:0] samples at the sampling period of ts_vs (12.2µs typical).