EMC2103 Standard Microsystems Corporation, EMC2103 Datasheet - Page 57

• Manufacturer Part Number: EMC2103
• Description: Rpm-based Fan Controller with HW Thermal Shutdown
• Manufacturer: Standard Microsystems Corporation

RPM-Based Fan Controller with HW Thermal Shutdown
Datasheet
SMSC EMC2103
The Fan Configuration 2 Register controls the tachometer measurement and advanced features of the
RPM based Fan Speed Control Algorithm.
Bit 6 - EN_RRC - Enables ramp rate control when the fan driver is operated in the Direct Setting mode
or the Direct Setting with LUT mode.
Bit 5 - GLITCH_EN - Disables the low pass glitch filter that removes high frequency noise injected on
the TACH pin.
Bits 4 - 3 - DER_OPT[1:0] - Control some of the advanced options that affect the derivative portion of
the RPM based Fan Speed Control Algorithm as shown in
options disable the ramp rate control maximum step settings. To take advantage of the full ramp rate
control, limit derivative options to the disabled or basic derivative settings.
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.
1
0
0
1
1
‘0’ (default) - Ramp rate control is disabled. When the fan driver is operating in Direct Setting mode
or Direct Setting with LUT mode, the PWM 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 PWM setting will follow the ramp rate controls as determined by the
Fan Step and Update Time settings. The maximum PWM step is capped at the Fan Step setting
and is updated based on the Update Time as given by
‘0’ - The glitch filter is disabled.
‘1’ (default) - The glitch filter is enabled.
DER_OPT[1:0]
Table 6.34 Derivative Options
0
0
1
0
1
DATASHEET
57
are used effectively causing the derivative term to
Basic derivative. The derivative of the error from
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 setting (in addition to
have double the effect of the derivative term
capped by the maximum Fan Step Register
to the iterative Fan Drive setting and is not
Table
Table
proportional and integral terms)
No derivative terms used
6.34. Note that the default derivative
6.32.
OPERATION
(default).
setting.
Revision 0.85 (01-29-08)