Datasheet

LTC3880/LTC3880-1
82
3880fc
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PMBus COMMAND DETAILS
Table 5. VOUT_OV_FAULT_RESPONSE Data Byte Contents
BITS DESCRIPTION VALUE MEANING
7:6 Response
For all values of bits [7:6], the LTC3880:
• Sets the corresponding fault bit in the status commands and
• Notifies the host by asserting ALERT pin
The fault bit, once set, is cleared only when one or more of the
following events occurs:
• The device receives a CLEAR_FAULTS command.
• The output is commanded through the RUNn pin, the
OPERATION command, or the combined action of the RUNn pin
and OPERATION command, to turn off and then to turn back on,
or
• Bias power is removed and reapplied to the LTC3880.
00 Part performs OV pull down only (i.e., turns off the top
MOSFET and turns on lower MOSFET while V
OUT
is >
VOUT_OV_FAULT)
01 The PMBus device continues operation for the delay time
specified by bits [2:0] and the delay time unit specified for that
particular fault. If the fault condition is still present at the end of
the delay time, the unit responds as programmed in the Retry
Setting (bits [5:3]).
10
The device shuts down immediately (disables the output) and
responds according to the retry setting in bits [5:3].
11 Not supported. Writing this value will generate a CML fault.
5:3 Retry Setting 000-110 The unit does not attempt to restart. The output remains
disabled until the fault is cleared until the device is commanded
OFF bias power is removed.
111 The PMBus device attempts to restart continuously, without
limitation, until it is commanded OFF (by the RUNn pin or
OPERATION command or both), bias power is removed, or
another fault condition causes the unit to shut down without
retry. Note: The retry interval is set by the MFR_RETRY_DELAY
command.
2:0 Delay Time XXX The delay time in 10µs increments. This delay time determines
how long the controller continues operating after a fault is
detected. Only valid for deglitched off state
VOUT_UV_FAULT_RESPONSE
The VOUT_UV_FAULT_RESPONSE command instructs the device on what action to take in response to an output
undervoltage fault. The data byte is in the format given in Table 6.
The device also:
• Sets the VOUT bit in the STATUS_WORD
• Sets the VOUT undervoltage fault bit in the STATUS_VOUT command
• Notifies the host by asserting ALERT pin
The UV fault and warn are masked until the following criteria are achieved:
1) The TON_MAX_FAULT_LIMIT has been reached
2) The TON_DELAY sequence has completed
3) The TON_RISE sequence has completed
4) The VOUT_UV_FAULT_LIMIT threshold has been reached
5) The IOUT_OC_FAULT_LIMIT is not present
The UV fault and warn are masked whenever the channel is not active.
The UV fault and warn are masked during TON_RISE and TOFF_FALL sequencing.
This command has one data byte.