THMC50

REMOTE/LOCAL TEMPERATURE MONITOR AND

FAN CONTROLLER WITH SMBus INTERFACE

SLIS090 – JULY 1999

20

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

THERM operation (continued)

Temperature

5

°C

FAN_SPD/NTEST_IN

0xFF

0xFF

Programmed

value

External

THERM

input

THERM

FAN_OFF

FAN_OFF

commanded

low by user

5

°C Hysteresis

THERM goes low after three

consecutive readings that exceed

the trip point, and stays low until

three consecutive readings that

are at least 5

°C below the trip

point.

Default or

Programmable

THERM Limit

FAN_SPD/NTEXT_IN goes to full

scale (0xFF) whenever THERM is

asserted internally or externally,

returns to previously programmed

value once THERM is cleared.

FAN_OFF floats

high due to THERM

Figure 16. Examples of THMC50 THERM Event Behavior

temperature data format

Temperature data can be read from the remote diode temperature register or the ambient temperature register

in the value RAM (locations 0x26 and 0x27, respectively). Temperature data is represented by an 8-bit, 2s

complement word with an LSB equal to 1

°C as shown in Table 2.

Table 2. T

emperature Data Format

TEMPERATURE

DIGITAL OUTPUT

TEMPERATURE

BINARY

HEX

125

°C

0111 1101

0x7D

25

°C

0001 1001

0x19

1

°C

0000 0001

0x01

0

°C

0000 0000

0x00

–1

°C

1111 1111

0xFF

–25

°C

1110 0111

0xE7

–55

°C

1100 1001

0xC9