STTS2004 datasheet(24/58 Pages) STMICROELECTRONICS

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Temperature sensor registers

STTS2004

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DocID024229 Rev 3

4.2.5

Event output pin functionality

The STTS2004 EVENT pin is an open drain output that requires a pull-up to VDD on the

system motherboard or integrated into the master controller. EVENT has three operating

modes, depending on configuration settings and any current out-of-limit conditions. These

modes are interrupt, comparator or critical.

In interrupt mode the EVENT pin will remain asserted until it is released by writing a ‘1’ to

the “Clear Event” bit in the status register. The value to write is independent of the EVENT

polarity bit.

In comparator mode the EVENT pin will clear itself when the error condition that caused the

pin to be asserted is removed.

In the critical mode the EVENT pin will only be asserted if the measured temperature

exceeds the critical limit. Once the pin has been asserted, it will remain asserted until the

temperature drops below the critical limit minus hysteresis. Figure 9 on page 25 illustrates

the operation of the different modes over time and temperature.

When the hysteresis bits (bits 10 and 9) are enabled, hysteresis may be used to sense

temperature movement around trigger points. For example, when using the “above alarm

window” bit (temperature register bit 14, see Table 13 on page 26) and hysteresis is set to

3 °C, as the temperature rises, bit 14 is set (bit 14 = 1). The temperature is above the alarm

window and the temperature register contains a value that is greater than the value set in

the alarm temperature upper boundary register (see Table 17 on page 28).

If the temperature decreases, bit 14 will remain set until the measured temperature is less

than or equal to the value in the alarm temperature upper boundary register minus 3 °C (see

Figure 8 on page 23 and Table 11 on page 23 for details.

Similarly, when using the “below alarm window” bit (temperature register bit 13, see

Table 13 on page 26) will be set to '0'. The temperature is equal to or greater than the value

set in the alarm temperature lower boundary register (see Table 18 on page 28). As the

temperature decreases, bit 13 will be set to '1' when the value in the temperature register is

less than the value in the alarm temperature lower boundary register minus 3 °C (see

Figure 8 on page 23 and Table 11 on page 23 for details.

If the device enters the shutdown mode with the EVENT output asserted, the output will be

de-asserted.

Once the shutdown bit is cleared, the EVENT output will do the following, based on whether

the device is configured for comparator or interrupt modes:

Comparator mode

The EVENT output will remain de-asserted until after the first temperature conversion

(tCONV) is completed. After this initial temperature conversion, TA must satisfy the TUPPER or

TLOWER boundary conditions in order for the EVENT output to be asserted.

Interrupt mode

The EVENT output will remain de-asserted until after the first temperature conversion

(tCONV) is completed. If the Clear event bit (bit 5 of configuration register) is never set, then

the EVENT output will re-assert after the first temperature conversion.

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