LTC2977 datasheet(119/138 Pages) AD

119 / 138 page

LTM4664A

119

Rev. 0

For more information www.analog.com

PMBus COMMAND DETAILS

FAULT WARNING AND STATUS

COMMAND NAME

CMD CODE DESCRIPTION

TYPE

PAGED

FORMAT

UNITS

NVM

DEFAULT

VALUE

CLEAR_FAULTS

0x03

Clear any fault bits that have been set.

Send Byte

SMBALERT_MASK

0x1B

Mask activity.

Block R/W

Reg

See CMD

Details

MFR_CLEAR_PEAKS

0xE3

Clears all peak values.

Send Byte

STATUS_BYTE

0x78

One byte summary of the unit’s fault

condition.

R/W Byte

Reg

STATUS_WORD

0x79

Two byte summary of the unit’s fault

condition.

R/W Word

Reg

STATUS_VOUT

0x7A

Output voltage fault and warning

status.

R/W Byte

Reg

STATUS_IOUT

0x7B

Output current fault and warning

status.

R/W Byte

Reg

STATUS_INPUT

0x7C

Input supply fault and warning status.

R/W Byte

Reg

STATUS_ TEMPERATURE

0x7D

External temperature fault and warning

status for READ_TEMERATURE_1.

R/W Byte

Reg

STATUS_CML

0x7E

Communication and memory fault and

warning status.

R/W Byte

Reg

STATUS_MFR_ SPECIFIC

0x80

Manufacturer specific fault and state

information.

R/W Byte

Reg

MFR_PADS

0xE5

Digital status of the I/O pads.

R Word

Reg

MFR_COMMON

0xEF

Manufacturer status bits that are

common across multiple LTC chips.

R Byte

Reg

CLEAR_FAULTS

The CLEAR_FAULTS command is used to clear any fault bits that have been set. This command clears all bits in all

status commands simultaneously. At the same time, the device negates (clears, releases) its ALERT pin signal output

if the device is asserting the ALERT pin signal. If the fault is still present when the bit is cleared, the fault bit will remain

set and the host notified by asserting the ALERT pin low. CLEAR_FAULTS can take up to 10µs to process. If a fault

occurs within that time frame it may be cleared before the status register is set.

This write-only command has no data bytes.

The CLEAR_FAULTS does not cause a unit that has latched off for a fault condition to restart. Units that have shut

down for a fault condition are restarted when:

• The output is commanded through the RUN pin, the OPERATION command, or the combined action of the RUN pin

and OPERATION command, to turn off and then to turn back on, or

• MFR_RESET command is issued.

• Bias power is removed and reapplied to the integrated circuit

SMBALERT_MASK

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

are asserted.

Figure 33 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

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