Multiple RPM-Based PWM Fan Controller
Datasheet
Table 5.13 Update Time (continued)
UPDATEX[2:0]
2
1
1
1
1
0
1
1
0
1
0
1
UPDATE TIME
800ms
1200ms
1600ms
5.10
Fan Configuration 2 Registers
Table 5.14 Fan Configuration 2 Registers
ADDR
33h
43h
53h
R/W
R/W
R/W
R/W
REGISTER
Fan 1
Configuration 2
Fan 2
Configuration 2
Fan 3
Configuration 2
B7
-
-
-
B6
EN_
RRC1
EN_
RRC2
EN_
RRC3
B5
GLITCH_
EN1
GLITCH_
EN2
GLITCH_
EN3
B4
B3
B2
B1
B0
-
-
-
DEFAULT
28h
28h
28h
DER_OPT1 [1:0]
DER_OPT2 [1:0]
DER_OPT3 [1:0]
ERR_RNG1[1:0]
ERR_RNG2[1:0]
ERR_RNG3[1:0]
The Fan Configuration 2 register control the tachometer measurement and advanced features of the
RPM-based Fan Speed Control Algorithm.
Bit 6 - EN_RRCx - Enables ramp rate control when the corresponding fan driver is operated in the
Direct Setting Mode.
‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode,
the fan setting will instantly transition to the next programmed setting.
‘1’ - Ramp rate control is enabled. When the fan driver is operating in Direct Setting mode, the fan
drive setting will follow the ramp rate controls as determined by the Fan Step and Update Time
settings. The maximum fan drive setting step is capped at the Fan Step setting and is updated
based on the Update Time as given by
Bit 5 - GLITCH_ENx - Disables the low pass glitch filter that removes high frequency noise injected
on the TACHx pin.
‘0’ - The glitch filter is disabled.
‘1’ (default) - The glitch filter is enabled.
Bits 4 - 3 - DER_OPTx[1:0] - Control some of the advanced options that affect the derivative portion
of the RPM-based Fan Speed Control Algorithm as shown in
SMSC EMC2303
35
Revision 1.1 (10-12-09)
DATASHEET
SMSC [ SMSC CORPORATION ]
