STTS2002 datasheet(22/52 Pages) STMICROELECTRONICS

22 / 52 page

Temperature sensor registers

STTS2002

22/52

Doc ID 15389 Rev 5

4.2.5

Event output pin functionality

The STTS2002 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 23 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 12 on page 24) 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 16 on page 26).

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 21 and Table 10 on page 21 for details.

Similarly, when using the “below alarm window” bit (temperature register bit 13, see Table 12

on page 24) 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 17 on page 26). 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 21 and Table 10 on page 21 for details.

The device will retain the previous state when entering the shutdown mode. If the device

enters the shutdown mode while the EVENT pin is low, the shutdown current will increase

due to the additional event output pull-down current.

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