Datasheet

LTC2977
28
2977fa
For more information www.linear.com/LTC2977
ADDRESSING AND WRITE PROTECT
PAGE
The LTC2977 has eight pages that correspond to the eight 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
programming. 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 PURPOSE
b[7:0] Page Page operation.
0x00: All PMBus commands address channel/page 0.
0x01: All PMBus commands address channel/page 1.
•
•
•
0x07: All PMBus commands address channel/page 7.
0xXX: All nonspecified values reser
ved.
0xFF: A single PMBus write/send to commands that support this mode will simultaneously address all channels/pages with
MFR_PAGE_FF_MASK enabled.
WRITE_PROTECT
The WRITE_PROTECT command provides protection against accidental programming of the LTC2977 command
registers. 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 write 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.
WRITE_PROTECT Data Contents
BITS(S) SYMBOL OPERATION
b[7:0] Write_protect[7:0] 1000_0000b: Level 1 Protection - Disable all writes except to the WRITE_PROTECT, PAGE, MFR_EE_UNLOCK, and
STORE_USER_ALL commands.
0100_0000b: Level 2 Protection – Disable all writes except to the WRITE_PROTECT, PAGE, MFR_EE_UNLOCK, STORE_
USER_ALL, OPERATION, MFR_PAGE_FF_MASK and CLEAR_FAULTS commands.
0000_0000b: Enable writes to all commands.
xxxx_xxxxb: All other values reserved.
PMBus COMMAND DESCRIPTION