LM93
16.0 Registers
16.8.6 Register C1h
Register
Address
C1h
Read/
Write
R/W
(Continued)
Fan Boost Hysteresis (Zones 3/4)
Register
Name
Fan Boost
Hysteresis
(Zones 3/4)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Default
Value
44h
H4
H3
Bit
3:0
7:4
Name
H3
H4
R/W
R/W
R/W
Description
Sets the fan boost hysteresis for zone 3
Sets the fan boost hysteresis for zone 4
If the temperature zone is above fan boost temperature and then drops below the fan boost temperature, the following occurs:
the PWM output remains at 100% until the temperature goes a certain amount below the fan boost temperature. These hysteresis
registers control this amount and can be set anywhere from 0˚C to 15˚C (unsigned).
16.8.7 Register C2h
Register
Address
C2h
Read/
Write
R/W
Zones 1/2 Spike Smoothing Control
Register
Name
Zones 1/2 Spike
Smoothing
Control
Bit
2:0
3
Name
ZN1
ZN1E
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Default
Value
00h
ZN2E
ZN2
ZN1E
ZN1
R/W
R/W
R/W
Description
Configures the spike smoothing characteristics for
zone 1
When set, the filtered temperature for zone 1 is used
for both limit checking and auto-fan control instead of
the unfiltered temperature. Even when this bit is
cleared, the filtered temperature can be read by
software from the filtered temperature register.
Configures the spike smoothing characteristics for
zone 2
When set, the filtered temperature for zone 2 is used
for both limit checking and auto-fan control instead of
the unfiltered temperature. Even when this bit is
cleared, the filtered temperature can be read by
software from the filtered temperature register.
6:4
7
ZN2
ZN2E
R/W
R/W
If the REMOTE1 or REMOTE2 pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled
by the LM93. If these spikes are not ignored, the PWM outputs may cause the fans to turn on prematurely and produce
unpleasant noise. Also, false error events may occur. For this reason, any zone that is connected to a chipset or processor may
need spike smoothing enabled. The spike smoothing provides additional filtering above and beyond any
Σ∆
A/D inherent
averaging.
When spike smoothing is enabled, the temperature reading registers still reflect the current value of the temperature — not the
filtered value. Only the filtered temperature registers reflect the filtered value.
ZN1 or ZN2
0h
1h
2h
3h
4h
5h
6h
7h
Spike Smoothed Over
11.8 seconds
7.0 seconds
4.4 seconds
3.0 seconds
1.6 seconds
0.8 seconds
0.6 seconds
0.4 seconds
65
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