LTC2978A_15 Datasheet, PDF (36/82 Pages) Linear Technology – 8-Channel PMBus Power System Manager Featuring Accurate Output Voltage Measurement

LTC2978A
PMBus COMMAND DESCRIPTION
FAULT RESPONSE FOR VOLTAGES MEASURED BY THE HIGH SPEED SUPERVISOR
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 LTC2978A 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.
Data Contents
BIT(S) SYMBOL
b[7:6] Vout_ov_fault_response_action,
Vout_uv_fault_response_action
b[5:3] Vout_ov_fault_response_retry,
Vout_uv_fault_response_retry
b[2:0] Vout_ov_fault_response_delay,
Vout_uv_fault_response_delay
OPERATION
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 and responds as programmed in
the retry setting (bits [5:3]).
1Xb: The device shuts down and responds according to the retry setting in bits [5:3].
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, at intervals of Mfr_retry_
delay, 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.
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).
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