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

4.17 Registers 64-66h: Minimum PWM Duty Cycle

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?

64h

R/W

Fan1 PWM Minimum

7

6543210

80h

U

65h

R/W

Fan2 PWM Minimum

7

6543210

80h

U

66h

R/W

Fan3 PWM Minimum

7

6543210

80h

U

These registers specify the minimum duty cycle that the PWM will output when the measured temperature reaches the

Temperature LIMIT register setting.

This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this

register shall have no effect. After power up the default value is used whenever the Ready/Lock/Start/Override register Start bit

is cleared even though modifications to this register are possible.

20035307

FIGURE 2. What LM85 Auto Fan Control Sees With and Without Spike Smoothing

www.national.com

20