n

n+1

n+2

n+3

n+4

n+5

SAMPLE NUMBER

RDTS Measurement

Status Register: RTDS High

25

27

29

31

33

35

37

39

41

43

45

0

50

100

150

200

SAMPLE NUMBER

LM89

with

Filter On

LM89

with

Filter Off

LM89

SNIS128D – AUGUST 2002 – REVISED JUNE 2014

www.ti.com

A.

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

9.3.11 Fault Queue

In order to suppress erroneous ALERT or T_CRIT triggering the LM89 incorporates a Fault Queue. The Fault

Queue acts to insure a remote temperature measurement is genuinely beyond a HIGH, LOW or T_CRIT setpoint

by not triggering until three consecutive out of limit measurements have been made, see Figure 15. The fault

queue defaults off upon power-up and may be activated by setting bit D0 in the Configuration register (09h) to

“1”.

Figure 15. Fault Queue Temperature Response Diagram

9.3.12 One-Shot Register

The One-Shot register is used to initiate a single conversion and comparison cycle when the device is in standby

mode, after which the device returns to standby. This is not a data register and it is the write operation that

causes the one-shot conversion. The data written to this address is irrelevant and is not stored. A zero will

always be read from this register.

9.4 Device Functional Modes

9.4.1 Power-On-Default States

LM89 always powers up to these known default states. The LM89 remains in these states until after the first

conversion.

1. Command Register set to 00h

18

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