LTM4677 datasheet(103/110 Pages) AD

103 / 110 page

LTC3888-1

103

Rev. 0

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Table 14. Data Byte Contents for the Following _FAULT_RESPONSE Commands: VIN_OV, OT and TON_MAX

BITS

DESCRIPTION

VALUE

MEANING

[7:6]

For all values of bits [7:6], the LTC3888-1:

• Sets the corresponding fault bits in the status commands.

• Notifies the host by asserting ALERT, unless masked.

The fault, once set, is cleared only when one or more of the

following events occurs:

• The device receives a CLEAR_FAULTS command.

• The corresponding fault bit is written to a one.

• The output is commanded off, then on, by the RUN pin or

OPERATION command.

• The device receives a RESTORE_USER_ALL command.

• The device receives an MFR_RESET command.

• IC supply power is cycled.

The LTC3888-1 continues operating without interruption.

Not supported. Writing this value will generate a CML fault.

The LTC3888-1 shuts down immediately (disables the

output) and responds according to the retry setting in bits

[5:3].

Not supported. Writing this value will generate a CML fault.

[5:3]

Retry setting.

000-110

The LTC3888-1 does not attempt to restart. The output

remains disabled until the fault is cleared, the device is

commanded off and then on, or IC supply power is cycled.

111

The LTC3888-1 attempts to restart continuously without

limitation with an interval set by MFR_RETRY_DELAY.

This response persists until the unit is commanded off, IC

supply power is removed, or another fault response forces

shutdown without retry.

[2:0]

Delay time.

xxx

Not supported. Values ignored.

MFR_RETRY_DELAY

The MFR_RETRY_DELAY command sets the time, in milliseconds, between restart attempts for all retry fault responses.

Retry delay starts once the fault is no longer detected by the LTC3888-1 or its FAULT pin is externally released. Legal

values run from 120ms to 32.7 seconds.

This command has two data bytes in Linear_5s_11s format.

SMBALERT_MASK

The SMBALERT_MASK command can be used to prevent a particular status bit or bits from pulling ALERT low as

they are asserted.

Figure 50 shows an example of the Write Word format used to set an ALERT mask, in this case without PEC. The bits in

the mask byte align with bits in the specified status register. For example, if the STATUS_TEMPERATURE command code

is sent in the first data byte, and the mask byte contains 0x40, then a subsequent External Overtemperature Warning

would still set bit 6 of STATUS_TEMPERATURE but not assert ALERT. All other supported STATUS_TEMPERATURE

bits would continue to assert ALERT if set.

Figure 51 shows an example of the Block Write – Block Read Process Call protocol used to read back the present state

of the ALERT mask for any supported status register, again without PEC.

SMBALERT_MASK cannot be applied to STATUS_BYTE, STATUS_WORD, MFR_COMMON or MFR_PADS_LTC3888-1.

Factory default masking for applicable status registers is shown below. Providing an unsupported command code to

SMBALERT_MASK will generate a CML for Invalid/Unsupported Data.

PMBus COMMAND DETAILS (Fault Response and Communication)

LTM4677 Datasheet(PDF) 103 Page - Analog Devices

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