LM93 datasheet(67/95 Pages) TI1

67 / 95 page

LM93

www.ti.com

SNAS210E – DECEMBER 2003 – REVISED MARCH 2013

Bit

Name

R/W

Description

ZN2E

R/W

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

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

ΣΔ 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.

SPACER

ZN1 or ZN2

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

3.17.8.8 Register C3h

Zones 1/2 MinPWM and Hysteresis

Read/

Default

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Address

Write

Name

Value

Zones 1/2

FC_TH

MinPWM

C3h

R/W

and

MinPWM

N/D

Hysteresi

Bit

Name

R/W

Description

3:0

FC_TH

R/W

This field sets the amount of hysteresis (in degrees C) that is used by the auto-fan

control for zones 1 and 2. This should be set greater than 0 to avoid unwanted

oscillation between two steps in the look-up table.

7:4

MinPWM

R/W

This field determines the duty cycle that the auto-fan control requests for zones 1

and 2 if the temperature for the given zone falls below the programmed base

temperature for that zone. This field accepts 16 possible values that are mapped to

duty cycles according the table in the Auto-Fan Control section.

3.17.8.9 Register C4h

Zones 3/4 MinPWM and Hysteresis

Read/

Default

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Address

Write

Name

Value

Zones 3/4

FC_TH

MinPWM

C4h

R/W

and

MinPWM

N/D

Hysteresi

Functional Description

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