25

27

29

31

33

35

37

39

41

43

45

0

50

100

150

200

SAMPLE NUMBER

LM99

with

Filter On

LM99

with

Filter Off

LM99

www.ti.com

SNIS129D – JANUARY 2003 – REVISED MARCH 2013

DIGITAL FILTER

D2

D1

Filter

0

0

No Filter

0

1

Level 1

1

0

Level 1

1

1

Level 2

In order to suppress erroneous remote temperature readings due to noise, the LM99 incorporates a user-

configured digital filter. The filter is accessed in the FILTER and ALERT CONFIGURE REGISTER at BFh. The

filter can be set according to the table shown.

Level 2 sets maximum filtering.

Filter Output Response to a Step Input depict the filter output to in response to a step input and an impulse input.

Figure 14 depicts the digital filter in use in a Pentium 4 processor system. Note that the two curves, with filter and

without, have been purposely offset so that both responses can be clearly seen. Inserting the filter does not

induce an offset as shown.

Filter Output Response to a Step Input

Figure 12. Step Response

Figure 13. Impulse Response

The filter on and off curves were purposely offset to better show noise performance.

Figure 14. Digital Filter Response in a Pentium 4 processor System

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