Datasheet

LTC2974
28
2974fc
For more information www.linear.com/LTC2974
ADDRESSING AND WRITE PROTECT
COMMAND NAME
CMD
CODE DESCRIPTION TYPE PAGED FORMAT UNITS EEPROM
DEFAULT
VALUE
REF
PAGE
PAGE 0x00 Channel or page currently selected for any
command that supports paging.
R/W Byte N Reg 0x00
28
WRITE_PROTECT 0x10 Level of protection provided by the device
against accidental changes.
R/W Byte N Reg Y 0x00
28
MFR_I2C_BASE_ADDRESS 0xE6 Base value of the I
2
C/SMBus address byte. R/W Byte N Reg Y 0x5C 29
MFR_PAGE_FF_MASK 0xE4 Configuration defining which channels
respond to global page commands
(PAGE=0xFF).
R/W Byte N Reg Y 0xF
29
pMbus coMManD DescripTion
PAGE
The LTC2974 has four pages that correspond to the four DC/DC converter channels that can be managed. Each DC/DC
converter channel can be uniquely programmed by first setting the appropriate page.
Setting PAGE = 0xFF allows a simultaneous write to all pages for PMBus commands that support global page pro
-
gramming. The only commands that support PAGE = 0xFF are CLEAR_FAULTS, OPERATION and ON_OFF_CONFIG.
See MFR_PAGE_FF_MASK for
additional options. Reading any paged PMBus register with PAGE = 0xFF returns un-
predictable data and will trigger a CML fault. Writes to pages that do not support PAGE = 0xFF with PAGE = 0xFF will
be ignored and generate a CML fault.
PAGE Data Contents
BIT(S) SYMBOL OPERATION
b[7:0] Page Page operation.
0x00: All PMBus commands address channel/page 0.
0x01: All PMBus commands address channel/page 1.
0x02: All PMBus commands address channel/page 2.
0x03: All PMBus commands address channel/page 3.
0xXX: All non specified values reserved.
0xFF: A single PMBus write/send to commands that support this mode will simultaneously address all channel/pages with
MFR_PAGE_FF_MASK enabled.
WRITE_PROTECT
The WRITE_PROTECT command provides protection against accidental programming of the LTC2974 command reg-
isters. All supported commands may have their parameters read, regardless of the WRITE_PROTECT setting, and the
EEPROM contents can also be read regardless of the WRITE_PROTECT settings.
There are two levels of protection:
•
Level 1: Nothing can be changed except the level of write protection itself. Values can be read from all pages. This
setting can be stored to EEPROM.
• Level 2: Nothing can be changed except for the level of protection, channel on/off state, and clearing of faults. Values
can be read from all pages. This setting can be stored to EEPROM.