STLM75 datasheet(10/37 Pages) STMICROELECTRONICS

10 / 37 page

Operation

STLM75

10/37

Operation

After each temperature measurement and analog-to-digital conversion, the STLM75 stores

the temperature as a 16-bit two’s complement number (see Table 5: Register pointers

selection summary on page 17) in the 2-byte Temperature register (see Table 7 on

page 18). The most significant Bit (S) indicates if the temperature is positive or negative:

●

for positive numbers S = 0, and

●

for negative numbers S = 1.

The most recently converted digital measurement can be read from the Temperature

reading the Temperature register does not affect the operation in progress.

The temperature data is provided by the 9 MSBs (Bits 15 through 7). Bits 6 through 0 are

unused. Table 3 on page 15 gives examples of the digital output data and corresponding

temperatures. The data is compared to the values in the TOS and THYS registers, and then

the OS is updated based on the result of the comparison and the operating mode.

The alarm fault tolerance is controlled by the FT1 and FT0 Bits in the Configuration register.

They are used to set up a fault queue. This prevents false tripping of the OS/INT pin when

the STLM75 is used in a noisy environment (see Table3 on page15).

The active state of the OS output can be changed via the Polarity Bit (POL) in the

Configuration register. The power-up default is active-low.

If the user does not wish to use the thermostat capabilities of the STLM75, the OS output

should be left floating.

Note:

If the thermostat is not used, the TOS and THYS registers can be used for general storage of

system data.

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