LM96000CIMT National Semiconductor, LM96000CIMT Datasheet - Page 21

• Manufacturer Part Number: LM96000CIMT
• Description: IC,Data Acquisition System,7-CHANNEL,8-BIT,TSSOP,24PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM96000CIMT

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Register
Address
63h
Functional Description
The Off/Min Bits [7:5] specify whether the duty cycle will be 0% or Minimum Fan Duty when the measured temperature falls below
the Temperature LIMIT register setting (see table below). OFF1 applies to fan 1, OFF2 applies to fan 2, and OFF3 applies to fan
3.
If the Remote1 or Remote2 pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled by
the LM96000. If these spikes are not ignored, the CPU fan (if connected to LM96000) may turn on prematurely and produce
unpleasant noise. For this reason, any zone that is connected to a chipset or processor should have spike smoothing enabled.
When spike smoothing is enabled, the temperature reading registers will still reflect the current value of the temperature — not
the ‘smoothed out’ value.
These registers become ready only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to
these registers shall have no effect.
ZN1E, ZN2E, and ZN3E enable temperature smoothing for zones 1, 2, and 3 respectively.
ZN1-2, ZN1-1, and ZN1-0 control smoothing time for Zone 1.
ZN2-2, ZN2-1, and ZN2-0 control smoothing time for Zone 2.
ZN3-2, ZN3-1, and ZN3-0 control smoothing time for Zone 3.
Read/
Write
R/W
Register
Name
Zone2, Zone3 Spike Smoothing
FIGURE 2. What LM96000 Auto Fan Control Sees With and Without Spike Smoothing
TABLE 8. PWM Output Below Limit Depending on Value of Off/Min
Off/Min
0
1
ZN-X[2:0]
000
001
010
011
100
101
110
111
(Continued)
PWM Action
At 0% duty below LIMIT
At Min PWM Duty below LIMIT
TABLE 7. Spike Smoothing
Bit 7
(MSB)
ZN2E
Spike Smoothed Over
35 seconds
17.6 seconds
11.8 seconds
7.0 seconds
4.4 seconds
3.0 seconds
1.6 seconds
.8 seconds
Bit 6
ZN2-2 ZN2-1 ZN2-0 ZN3E ZN3-2 ZN3-1 ZN3-0 00h
21
Bit 5
Bit 4 Bit 3
20084607
Bit 2
Bit 1
Bit 0
(LSB)
Default
Value
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Lock?
U