LTC2977 datasheet(57/138 Pages) AD

57 / 138 page

LTM4664A

Rev. 0

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PMBus COMMAND SUMMARY

PMBus COMMANDS

Table 7 lists supported PMBus commands and manu-

facturer specific commands. A complete description of

these commands can be found in the “PMBus Power

System Mgt Protocol Specification – Part II – Revision

1.2”. Users are encouraged to reference this specifica-

tion. Exceptions or manufacturer specific implementations

are listed in Table 7. Floating point values listed in the

“DEFAULT VALUE” column are either Linear 16-bit Signed

(PMBus Section 8.3.1) or Linear_5s_11s (PMBus Section

7.1) format, whichever is appropriate for the command.

All commands from 0xD0 through 0xFF not listed in

Table 7 are implicitly reserved by the manufacturer. Users

should avoid blind writes within this range of commands

to avoid undesired operation of the part. All commands

from 0x00 through 0xCF not listed in Table 7 are implicitly

not supported by the manufacturer. Attempting to access

non-supported or reserved commands may result in a

CML command fault event. All output voltage settings and

measurements are based on the VOUT_MODE setting of

0x14. This translates to an exponent of 2–12.

If PMBus commands are received faster than they are

being processed, the part may become too busy to handle

new commands. In these circumstances the part follows

the protocols defined in the PMBus Specification v1.2,

Part II, Section 10.8.7, to communicate that it is busy.

The part includes handshaking features to eliminate busy

errors and simplify error handling software while ensur-

ing robust communication and system behavior. Please

refer to the subsection titled PMBus Communication

and Command Processing in the Dual 25A/30A PSM

Applications Information section for further details.

COMMAND NAME

CMD

CODE DESCRIPTION

TYPE

PAGED

DATA

FORMAT UNITS NVM

DEFAULT

VALUE

PAGE

0x00 Provides integration with multi-page

PMBus devices.

R/W Byte

Reg

0x00

OPERATION

0x01 Operating mode control. On/off, margin

high and margin low.

R/W Byte

Reg

0x80

ON_OFF_CONFIG

0x02 RUN pin and PMBus bus on/off command

configuration.

R/W Byte

Reg

0x1E

CLEAR_FAULTS

0x03 Clear any fault bits that have been set.

Send Byte

119

PAGE_PLUS_WRITE

0x05 Write a command directly to a

specified page.

W Block

PAGE_PLUS_READ

0x06 Read a command directly from a

specified page.

Block R/W

WRITE_PROTECT

0x10 Level of protection provided by the device

against accidental changes.

R/W Byte

Reg

0x00

STORE_USER_ALL

0x15 Store user operating memory to EEPROM. Send Byte

130

RESTORE_USER_ALL

0x16 Restore user operating memory from

EEPROM.

Send Byte

130

CAPABILITY

0x19 Summary of PMBus optional communication

protocols supported by this device.

R Byte

Reg

0xB0

118

SMBALERT_MASK

0x1B Mask ALERT activity

Block R/W

Reg

See CMD

119

VOUT_MODE

0x20 Output voltage format and exponent (2–12).

R Byte

Reg

2–12

0x14

100

VOUT_COMMAND

0x21 Nominal output voltage set point.

R/W Word

L16

1.0

0x1000

101

VOUT_MAX

0x24 Upper limit on the commanded output

voltage including VOUT_MARGIN_HI.

R/W Word

L16

1.8

0x1CCD

100

Table 7. PMBus Commands Summary (Note: The Data Format Abbreviations are Detailed in Table 8)

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