Operation

STLM75

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2.5

Fault tolerance

For both Comparator and Interrupt modes, the alarm “fault tolerance” setting plays a role in

determining when the OS output will be activated. Fault tolerance refers to the number of

consecutive times an error condition must be detected before the user is notified. Higher

fault tolerance settings can help eliminate false alarms caused by noise in the system. The

alarm fault tolerance is controlled by the bits (4 and 3) in the Configuration register. These

bits can be used to set the fault tolerance to 1, 2, 4, or 6 as shown in Table 2. At power-up,

these bits both default to logic '0'.

2.6

Shutdown mode

For power-sensitive applications, the STLM75 offers a low-power Shutdown mode. The SD

Bit in the Configuration register controls Shutdown mode. When SD is changed to logic '1,'

the conversion in progress will be completed and the result stored in the Temperature

register, after which the STLM75 will go into a low-power standby state. The OS output will

be cleared if the thermostat is operating in Interrupt mode and the OS will remain

unchanged in Comparator mode. The 2-wire interface remains operational in Shutdown

mode, and writing a '0' to the SD Bit returns the STLM75 to normal operation.

Table 2.

Fault tolerance setting

FT1

FT0

STLM75 (Consecutive Faults)

Comments

0

0

1

Power-up Default

01

2

10

4

11

6