LTC3882-1
37
Rev A
PMBus COMMAND SUMMARY
Table 6. Abbreviations of Supported Data Formats
PMBus
TERMINOLOGY
SPECIFICATION
REFERENCE
LTC
TERMINOLOGY DEFINITION
EXAMPLE
L11 Linear
Part II ¶7.1
Linear_5s_11s Floating point 16-bit data: value = Y • 2
N
,
where N = b[15:11] and Y = b[10:0], both
two’s compliment binary integers.
b[15:0] = 0x9807 = 10011_000_0000_0111
value = 7 • 2
–13
= 854E-6
L16 Linear VOUT_MODE
Part II ¶8.2
Linear_16u
Floating point 16-bit data: value = Y • 2
–12
,
where Y = b[15:0], an unsigned integer.
b[15:0] = 0x4C00 = 0100_1100_0000_0000
value = 19456 • 2
–12
= 4.75
CF
DIRECT
Part II ¶7.2
varies
16-bit data with a custom format
defined in the detailed PMBus command
description.
Often an unsigned or two’s compliment
integer.
Reg register bits
Part II ¶10.3
Reg
Per-bit meaning defined in detailed PMBus
command description.
PMBus STATUS_BYTE command.
ASC text characters
Part II ¶22.2.1
ASCII
ISO/IEC 8859-1 [A05]
LTC (0x4C5443)
PMBus Commands
Table 7 lists supported PMBus commands and manufac-
turer specific commands. Additional information about
these commands can be found in Revision 1.2 of Part II of
the PMBus Power System Management Protocol Specifica-
tion that can be found at
http://www.pmbus.org/specs.html
.
Users are encouraged to reference that manual. Exceptions
or manufacturer-specific implementations are detailed in
the tables below. All standard PMBus commands from
0x00 through 0xCF not listed in this table are implicitly
not supported by the LTC3882-1. All commands from
0xD0 through 0xFF not listed in this table are implicitly
reserved by the manufacturer. The LTC3882-1 may execute
additional commands not listed in this table, and these
can change without notice. Reading these unlisted com-
mands is harmless to the operation of the IC. Writes to any
unsupported or reserved command should be avoided, as
they may result in a CML fault and/or undesired operation
of the part.
If PMBus commands are received faster than they are be-
ing processed, the part may become too busy to handle
new commands. In these cases the LTC3882-1 follows the
protocols defined in the PMBus Specification V1.2, Part
II, Section 10.8.7, to communicate that it is busy. This
device includes handshaking features to eliminate busy
responses, simplify error handling software and ensure
robust communication and system behavior. Please refer
to PMBus Communication and Command Processing in
the Applications Information section for further details.
LTC has made an effort to establish PMBus command
compatibility and functional uniformity among its family
of parts. However, differences may occur due to specific
product requirements. Compatibility of PMBus commands
among any ICs should not be assumed based simply on
command name. Always refer to the manufacturer’s data
sheet of each device for a complete definition of a com-
mand function.
Data Formats
PMBus supports specific floating point number formats
and allows for a wide range of other data formats.
Table 6 describes the data formats used by the LTC3882-1.
Abbreviations of these formats appear throughout this
document.
