Datasheet

6-Channel Intelligent Fan Controller
MAX31785
14
Table 1. PMBus Command Codes
Detailed Description
The MAX31785 is a closed-loop fan controller. Automatic
closed-loop fan control saves system power by operat-
ing the fans at the lowest possible speeds. Added ben-
efits of slower fan speeds include lower audible noise,
longer fan life, and reduced system maintenance. Based
on a user-programmable lookup table (LUT), the device
automatically adjust the speeds of the six independent
fans based on one or more of the 11 available tem-
perature sensors. Temperature offset can be added to
individual sensors to compensate for thermal differences
in a system. Alternately, an external host can manually
command the fan speeds and the device automatically
adjusts the fan speeds. The device can also monitor up
to six remote voltages.
The device provides ALERT and FAULT output sig-
nals. Host communications are conducted through a
PMBusK-compatible communications port. Address
input connections are also provided to allow up to four
MAX31785 devices to reside on the system’s I/O bus.
PMBus is a trademark of SMIF, Inc.
CODE COMMAND NAME TYPE
PAGE
0–5
PAGE
6–16
PAGE
17–22
PAGE
255
NO. OF
BYTES
FLASH
STORED
(NOTE 2)
DEFAULT
VALUE
(NOTE 2)
(NOTE 1)
00h PAGE R/W Byte R/W R/W R/W R/W 1 N 00h
03h CLEAR_FAULTS Send Byte W W W W 0 N —
10h WRITE_PROTECT R/W Byte R/W R/W R/W R/W 1 N 00h
11h STORE_DEFAULT_ALL Send Byte W W W W 0 N —
12h RESTORE_DEFAULT_ALL Send Byte W W W W 0 N —
19h CAPABILITY Read Byte R R R R 1 N 00h/10h
20h VOUT_MODE Read Byte R R R R 1 FIXED 40h
2Ah VOUT_SCALE_MONITOR R/W Word — — R/W — 2 Y 7FFFh
3Ah FAN_CONFIG_1_2 R/W Byte R/W — — — 1 Y 00h
3Bh FAN_COMMAND_1 R/W Word R/W — — — 2 Y FFFFh
40h VOUT_OV_FAULT_LIMIT R/W Word — — R/W — 2 Y 7FFFh
42h VOUT_OV_WARN_LIMIT R/W Word —
— R/W — 2 Y 7FFFh
43h VOUT_UV_WARN_LIMIT R/W Word — — R/W — 2 Y 0000h
44h VOUT_UV_FAULT_LIMIT R/W Word — — R/W — 2 Y 0000h
4Fh OT_FAULT_LIMIT R/W Word — R/W — — 2 Y 7FFFh
51h OT_WARN_LIMIT R/W Word — R/W — — 2 Y 7FFFh
78h STATUS_BYTE Read Byte R R R R 1 N 00h
79h STATUS_WORD Read Word R R R R 2 N 0000h
7Ah STATUS_VOUT Read Byte — — R — 1 N 00h
7Eh STATUS_CML Read Byte R R R R 1 N 00h
80h STATUS_MFR_SPECIFIC Read Byte — R — — 1 N 00h
81h STATUS_FANS_1_2 Read Byte R — — — 1 N 00h
8Bh READ_VOUT Read Word — — R — 2 N 0000h
8Dh READ_TEMPERATURE_1 Read Word — R — — 2 N 0000h
90h READ_FAN_SPEED_1 Read Word R — — — 2
N 0000h
98h PMBUS_REVISION Read Byte R R R R 1 FIXED 11h
99h MFR_ID Read Byte R R R R 1 FIXED 4Dh
9Ah MFR_MODEL Read Byte R R R R 1 FIXED 53h
9Bh MFR_REVISION Read Word R R R R 2 FIXED 3030h
9Ch MFR_LOCATION Block R/W R/W R/W R/W R/W 8 Y (Note 3)