LM99

SNIS129D – JANUARY 2003 – REVISED MARCH 2013

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8. 70°C Local and Remote HIGH temperature setpoints

9. 0°C Local and Remote LOW temperature setpoints

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

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

SMBus INTERFACE

The LM99 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBData line is bi-

directional. The LM99 never drives the SMBCLK line and it does not support clock stretching. According to

SMBus specifications, the LM99 has a 7-bit slave address. All bits A6 through A0 are internally programmed and

can not be changed by software or hardware. The LM99 and LM99-1 have the following slave addresses:

Version

A6

A5

A4

A3

A2

A1

A0

LM99

1

0

0

1

1

0

0

LM99-1

1

0

0

1

1

0

1

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:

Table 1. Actual vs. LM99 Remote Temperature Conversion

Actual Remote Diode

LM99 Remote Diode

Binary Results in LM99 Remote

Hex Remote

Temperature,°C

Temperature Register, °C

Temperature Register

Temperature Register

120

+104

0110 1000 0000 0000

6800h

125

+109

0110 1101 0000 0000

6D00h

126

+110

0110 1110 0000 0000

7100h

130

+114

0111 0010 0010 0000

7200h

135

+119

0111 0111 0000 0000

7700h

140

+124

0111 1100 0000 0000

7200h

Table 2. Actual vs. Remote T_Crit Setpoint

Actual Remote Diode T_Crit

Factory-Programmed Remote

Binary Remote T_CRIT High

Hex Remote T_CRIT High

Setpoint,°C

T_CRIT High Setpoint, °C

Setpoint Value

Setpoint Value

126

+110

0110 1110

71h

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

Bit) equal to 1°C:

Local 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

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