emc2106 Standard Microsystems Corp., emc2106 Datasheet - Page 73

• Manufacturer Part Number: emc2106
• Description: Emc2106 Dual Rpm-based Linear Fan Controller With Hardware Thermal Shutdown
• Manufacturer: Standard Microsystems Corp.

Dual RPM-Based Linear Fan Controller with Hardware Thermal Shutdown
Datasheet
SMSC EMC2106
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.
Bit 0 - LOWDRIVEx - Determines whether the tachometer measurement circuit will use the Tach Period
Measurement method of fan speed measurement or the Tach Pulse Count Method of fan speed
measurement. Setting this bit allows the use of low side fan drive circuits as shown in
without requiring additional tachometer recovery circuitry.
1
0
0
1
1
1
0
0
1
1
‘0’ (default) - The tachometer signal must always be present when measuring the fan speed
regardless of the measurement method.
‘1’ - Low side PWM drive circuits are supported and the tachometer signal does not need to be
present at all times (which is common with such drive techniques). The tachometer measurement
circuitry will use the Tach Pulse Count Method to determine the fan speed (contact SMSC for
details on this operation). All tachometer related data is in the form of edge counts over a fixed
time period. This method is significantly slower and the tachometer updates are non-continuous.
ERR_RNGX[1:0]
DER_OPTX[1:0]
Table 6.37 Error Range Options
Table 6.36 Derivative Options
0
0
1
0
1
0
0
1
0
1
DATASHEET
73
are used effectively causing the derivative term to
Basic derivative. The derivative of the error from
to the iterative Fan Drive Register setting and is
Both the basic derivative and the step derivative
the current drive setting and the target is added
the current drive setting and the target is added
Step derivative. The derivative of the error from
to the iterative Fan Drive Register setting (in
have double the effect of the derivative term
addition to proportional and integral terms)
not capped by the Fan Step Register.
No derivative options used
0 RPM (default)
OPERATION
OPERATION
100 RPM
200 RPM
(default).
50 RPM
Revision 1.74 (05-08-08)
Figure 6.1