STCN75 datasheet(10/35 Pages) STMICROELECTRONICS

10 / 35 page

Operation

STCN75

10/35

Operation

After each temperature measurement and analog-to-digital conversion, the STCN75 stores

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

selection summary on page 16) in the 2-byte temperature register (see Table 7 on page 17).

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 register

at any time. Since temperature conversions are performed in the background, 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 14 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/INT 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 STCN75 is used in a noisy environment (see Table 2 on page 13).

The active state of the OS/INT 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 STCN75, the

OS/INToutput 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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