EMC2105 Datasheet, PDF (61/90 Pages) SMSC Corporation – RPM-Based High Side Fan Controller with Hardware Thermal Shutdown

RPM-Based High Side Fan Controller with Hardware Thermal Shutdown
Datasheet
6.21
Table 6.29 Derivative Options
DER_OPT[1:0]
1
0
OPERATION
0
0
No derivative options used
Basic derivative. The derivative of the error from
0
1
the current drive setting and the target is added
to the iterative Fan Drive Register setting (in
addition to proportional and integral terms)
Step derivative. The derivative of the error from
1
0
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
1
1
are used effectively causing the derivative term to
have double the effect of the derivative term
(default).
Bit 2 - 1 - ERR_RNG[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 6.30 Error Range Options
ERR_RNG[1:0]
1
0
0
0
0
1
1
0
1
1
OPERATION
0 RPM (default)
50 RPM
100 RPM
200 RPM
Gain Register
ADDR
45h
R/W
REGISTER
R/W Gain Register
Table 6.31 Gain Register
B7
B6 B5
B4
B3
B2
-
-
GAIND[1:0]
GAINI[1:0]
B1 B0
GAINP[1:0]
DEFAULT
2Ah
The Gain Register stores the gain terms used by the proportional and integral portions of each of the
RPM based Fan Speed Control Algorithms. These gain terms are used as the KD, KI, and KP gain
terms in a classic PID control solution.
SMSC EMC2105
61
DATASHEET
Revision 1.72 (11-01-07)