Multiple RPM-Based PWM Fan Controller
Datasheet
Table 5.15 Derivative Options
DER_OPTX[1:0]
1
0
0
0
OPERATION
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)
(default)
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.
0
1
1
0
1
1
Bit 2 - 1 - ERR_RNGx[1:0] - Control some of the advanced options that affect the error window. When
the measured fan speed is within the programmed error window around the target speed, then the fan
drive setting is not updated. The algorithm will continue to monitor the fan speed and calculate
necessary drive setting changes based on the error; however, these changes are ignored.
Table 5.16 Error Range Options
ERR_RNGX[1:0]
1
0
0
1
1
0
0
1
0
1
OPERATION
0 RPM (default)
50 RPM
100 RPM
200 RPM
5.11
Gain Registers
Table 5.17 Gain Registers
ADDR
35h
45h
55h
R/W
R/W
R/W
R/W
REGISTER
Gain 1
Register
Gain 2
Register
Gain 3
Register
B7
-
-
-
B6
-
-
-
B5
B4
B3
B2
B1
B0
DEFAULT
2Ah
2Ah
2Ah
GAIND1[1:0]
GAIND2[1:0]
GAIND3[1:0]
GAINI1[1:0]
GAINI2[1:0]
GAINI3[1:0]
GAINP1[1:0]
GAINP2[1:0]
GAINP3[1:0]
Revision 1.1 (10-12-09)
36
SMSC EMC2303
DATASHEET
SMSC [ SMSC CORPORATION ]
