Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown
Datasheet
6.23
Fan Configuration 2 Registers
Table 6.32 Fan Configuration 1 Registers
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Fan 1
Configuration
2
EN_
RRC1
GLITCH
_EN1
LOWD
RIVE1
43h
R/W
-
DER_OPT1 [1:0]
DER_OPT2 [1:0]
ERR_RNG[1:0]
ERR_RNG[1:0]
38h
Fan 2
Configuration
2
EN_
RRC2
GLITCH
_EN2
LOWD
RIVE2
83h
R/W
-
38h
The Fan Configuration 2 Register controls 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 or the Direct Setting with LUT mode.
‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode
or Direct Setting with LUT 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 or Direct
Setting with LUT 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 Table 6.31.
Bit 5 - GLITCH_ENx - Disables the low pass glitch filter that removes high frequency noise injected
on the TACHx pin. If the LOWDRIVE bit is set, this bit is ignored and the filter is automatically disabled.
‘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 Table 6.33.
Table 6.33 Derivative Options
DER_OPTX[1:0]
1
0
OPERATION
0
0
No derivative options used
Basic derivative. The derivative of the error from
the current drive setting and the target is added
to the iterative Fan Drive Register setting (in
addition to proportional and integral terms)
0
1
1
1
0
1
Step derivative. The derivative of the error from
the current drive setting and the target is added
to the iterative Fan Drive Register setting and is
not capped by the Fan Step Register.
Both the basic derivative and the step derivative
are used effectively causing the derivative term to
have double the effect of the derivative term
(default).
SMSC EMC2104
Revision 1.74 (05-08-08)
DATA6S7HEET
SMSC [ SMSC CORPORATION ]
