RPM-Based Fan Controller with Multiple Temperature Zones & Hardware Thermal Shutdown
Datasheet
transition of the actual fan operation as the desired fan speed changes. The Update Time is set as
shown in Table 7.35.
Table 7.35 Update Time
UPDATE[2:0]
2
1
0
UPDATE TIME
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
100ms
200ms
300ms
400ms (default)
500ms
800ms
1200ms
1600ms
7.25
Fan Configuration 2 Register
Table 7.36 Fan Configuration 2 Register
ADDR
R/W
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Fan
Configuration 2
TEMP_
RR
EN_
RRC
GLITCH_
EN
43h
DER_OPT [1:0] ERR_RNG:0]
-
28h
The Fan Configuration 2 Register controls the tachometer measurement and advanced features of the
RPM-based Fan Speed Control Algorithm.
Bit 7 - TEMP_RR - Overrides max step controls for the FSC algorithm when any temperature exceeds
its respective high limit.
‘0’ (default) - All ramp rate control circuitry works at all times for the FSC algorithm or as determined
by the EN_RRC bit for manual mode.
‘1’ - If any measured temperature or the PWM Input Duty cycle meets or exceeds its respective
high limit, then the Fan Max Step register settings are not used and the FSC algorithm acts as if
the Max Step settings were at 3Fh. The device will continue to operate in this way until all
temperatures (and the PWM input duty cycle) have dropped below the respective high limit.
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.
‘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 Table 7.35.
Revision 1.2 (10-08-09)
SMSC EMC2113
DATA6S0HEET
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