Register

Address

Read/

Write

Register

Name

Bit 7

(MSB)

Bit 6

Bit 5

Bit 4 Bit 3

Bit 2

Bit 1

Bit 0

(LSB)

Default

Value

Lock?

63h

R/W

Zone2, Zone3 Spike Smoothing

ZN2E

ZN2-2 ZN2-1 ZN2-0 ZN3E ZN3-2 ZN3-1 ZN3-0 00h

U

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.

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.

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.

TABLE 7. Spike Smoothing

ZN-X[2:0]

Spike Smoothed Over

000

35 seconds

001

17.6 seconds

010

11.8 seconds

011

7.0 seconds

100

4.4 seconds

101

3.0 seconds

110

1.6 seconds

111

.8 seconds

TABLE 8. PWM Output Below Limit Depending on Value of Off/Min

Off/Min

PWM Action

0

At 0% duty below LIMIT

1

At Min PWM Duty below LIMIT

20084607

FIGURE 2. What LM96000 Auto Fan Control Sees With and Without Spike Smoothing

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