STDS75DS2F datasheet(12/37 Pages) STMICROELECTRONICS

12 / 37 page

Operation

STDS75

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2.2

Thermal alarm function

The STDS75 thermal alarm function provides user-programmable thermostat capability and

allows the STDS75 to function as a standalone thermostat without using the serial interface.

The OS/INT output is the alarm output. This signal is an open drain output, and at power-up,

this pin is configured with active-low polarity by default.

2.3

Comparator mode

In comparator mode, each time a temperature-to-digital (T-to-D) temperature conversion

occurs, the new digital temperature is compared to the value stored in the TOS and THYS

registers. If a fault tolerance number of consecutive temperature measurements are greater

than the value stored in the TOS register, the OS/INT output will be activated.

For example, if the FT1 and FT0 bits are equal to “10” (fault tolerance = 4), four consecutive

temperature measurements must exceed TOS to activate the OS/INT output. Once the

OS/INT output is active, it will remain active until the first time the measured temperature

drops below the temperature stored in the THYS register.

When the thermostat is in comparator mode, the OS/INT can be programmed to operate

with any amount of hysteresis. The OS/INT output becomes active when the measured

temperature exceeds the TOS value a consecutive number of times as defined by the FT1

and FT0 fault tolerance (FT) bits in the configuration register. The OS/INT then stays active

until the first time the temperature falls below the value stored in THYS. Putting the device

into shutdown mode does not clear OS/INT in comparator mode.

STDS75DS2F Datenblatt(PDF) 12 Page - STMicroelectronics