LM90

SNIS126A – MAY 2004 – REVISED MARCH 2013

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Fault Queue

In order to suppress erroneous ALERT or T_CRIT triggering the LM90 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 14. The fault

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

“1”.

Figure 14. Fault Queue Temperature Response Diagram

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.

LM90 REGISTERS

COMMAND REGISTER

Selects which registers will be read from or written to. Data for this register should be transmitted during the

Command Byte of the SMBus write communication.

P7

P6

P5

P4

P3

P2

P1

P0

Command Select

P0-P7: Command Select

Command Select Address

Power On Default State

Register

Register Function

Name

Read Address

Write Address

<D7:D0> binary

<D7:D0> decimal

<P7:P0> hex

<P7:P0> hex

00h

NA

0000 0000

0

LT

Local Temperature

01h

NA

0000 0000

0

RTHB

Remote Temperature High Byte

02h

NA

0000 0000

0

SR

Status Register

03h

09h

0000 0000

0

C

Configuration

04h

0Ah

0000 1000

8 (16 conv./sec)

CR

Conversion Rate

05h

0Bh

0100 0110

70

LHS

Local HIGH Setpoint

06h

0Ch

0000 0000

0

LLS

Local LOW Setpoint

07h

0Dh

0100 0110

70

RHSHB

Remote HIGH Setpoint High Byte

08h

0Eh

0000 0000

0

RLSHB

Remote LOW Setpoint High Byte

16

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