LM93 datasheet(30/92 Pages) NSC

30 / 92 page

15.0 Using The LM93 (Continued)

Zone 1/2 (CPU1 and CPU2) Table

In this example: Zones 1 and 2 are bound to the PWM1 output and the PWM1 frequency set to a value in the low range;

Hysteresis is set to 2˚C; Toffset and hysteresis resolution is set to 0.5˚C; minPWM register set to 05h for Zones 1/2. Note,

the duty cycle assignment depends on the zone to PWM output binding and the frequency setting of that PWM output.

Lookup

Table

Duty Cycle

Zone 1/2

Toffset

table

Tbase

CPU1,

Zone1

CPU1 Thermal Diode, Zone 1

Tbase

CPU2,

Zone2

CPU2 Thermal Diode, Zone 2

(%)

(˚C)

28.57

32.14

35.71

39.29

42.86

0.5

≤T

70.5

≤T

60.5

46.43

1.5

70.5

≤T

60.5

≤T

53.57

57.14

≤T

71.43

1.5

≤T

76.5

≤T

66.5

85.71

1.5

76.5

≤T

66.5

≤T

100

≤T

Zone 3/4 (LM93 Ambient and External Ambient) Table

In this example: Zone 3 and Zone 4 are bound to the PWM 2 output and the PWM2 output frequency set to 22.5kHz; Hys-

teresis is set to 1˚C; Toffset and hysteresis resolution set to 0.5˚C; minPWM for Zones 3/4 register is set to 06h. Note, the

duty cycle assignment depends on the zone to PWM output binding and the frequency setting of that PWM output.

Lookup

Table

Duty Cycle

Zone 3/4

Toffset

table

Tbase

LM93

Ambient

LM93 Ambient, Zone 3 (T

Tbase

External

Ambient

External Ambient, Zone 4 (T

(%)

(˚C)

31.25

37.5

43.75

56.25

62.5

≤T

68.75

≤T

81.25

0.5

≤T

33.5

≤T

38.5

87.5

0.5

33.5

≤T

38.5

≤T

93.75

0.5

≤T

34.5

≤T

39.5

100

34.5

≤T

39.5

≤T

15.10.2 Fan Control Temperature Resolution

As shown in the example the auto fan control algorithm can

operate in a mode that allows 0.5˚C of temperature resolu-

tion instead of the normal 1˚C. When this mode is enabled,

the temperature offset registers that make up the lookup

table are interpreted differently. One LSB represents 0.5˚C,

and the available range between each datapoint is 0˚C to

7.5˚C instead of 0˚C to 15˚C. In addition, the hysteresis

registers for auto fan control are interpreted in the same way

(one LSB equals 0.5˚C).

Zones 1, 2 and 3 all have 9-bits of internal resolution, which

makes this feature useful. Zone 4 is written in from the

SMBus and only has 8-bits of resolution. The LM93 left

justifies the value into a 9-bit field before using it, if the 0.5˚C

mode is enabled.

LM93 Datasheet(PDF) 30 Page - National Semiconductor (TI)

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