LM90

SNIS126A – MAY 2004 – REVISED MARCH 2013

www.ti.com

3. Remote Diode Temperature set to 0°C until the end of the first conversion.

4. Status Register set to 00h.

5. Configuration register set to 00h; ALERT enabled, Remote T_CRIT alarm enabled and Local T_CRIT alarm

enabled

6. 85°C Local and Remote T_CRIT temperature setpoints

7. 70°C Local and Remote HIGH temperature setpoints

8. 0°C Local and Remote LOW temperature setpoints

9. Filter and Alert Configure Register set to 00h; filter disabled, ALERT output set as an SMBus ALERT

10. Conversion Rate Register set to 8h; conversion rate set to 16 conv./sec.

SMBus INTERFACE

The LM90 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBData line is bi-

directional. The LM90 never drives the SMBCLK line and it does not support clock stretching. According to

SMBus specifications, the LM90 has a 7-bit slave address. All bits A6 through A0 are internally programmed and

can not be changed by software or hardware.

The complete slave address is:

A6

A5

A4

A3

A2

A1

A0

1

0

0

1

1

0

0

TEMPERATURE DATA FORMAT

Temperature data can only be read from the Local and Remote Temperature registers; the setpoint registers

(T_CRIT, LOW, HIGH) are read/write.

Remote temperature data is represented by an 11-bit, two's complement word with an LSB (Least Significant Bit)

equal to 0.125°C. The data format is a left justified 16-bit word available in two 8-bit registers:

Temperature

Digital Output

Binary

Hex

+125°C

0111 1101 0000 0000

7D00h

+25°C

0001 1001 0000 0000

1900h

+1°C

0000 0001 0000 0000

0100h

+0.125°C

0000 0000 0010 0000

0020h

0°C

0000 0000 0000 0000

0000h

−0.125°C

1111 1111 1110 0000

FFE0h

−1°C

1111 1111 0000 0000

FF00h

−25°C

1110 0111 0000 0000

E700h

−55°C

1100 1001 0000 0000

C900h

Local Temperature data is represented by an 8-bit, two's complement byte with an LSB (Least Significant Bit)

equal to 1°C:

Temperature

Digital Output

Binary

Hex

+125°C

0111 1101

7Dh

+25°C

0001 1001

19h

+1°C

0000 0001

01h

0°C

0000 0000

00h

−1°C

1111 1111

FFh

−25°C

1110 0111

E7h

−55°C

1100 1001

C9h

12

Submit Documentation Feedback

Copyright © 2004–2013, Texas Instruments Incorporated

Product Folder Links: LM90