TMP1075DR datasheet(20/49 Pages) TI2

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7.4.4 Thermostat Mode (TM)

The thermostat mode bit indicates whether ALERT pin operates in comparator mode (TM = 0) or interrupt mode

(TM = 1). ALERT pin mode is controlled by TM (bit 9) of the configuration register. Any write to the TM bit

changes the ALERT pin to a none active condition, clears the faults count, and clears the alert interrupt history

on the TMP1075 non-N orderables. The ALERT pin can be disabled in both comparator and interrupt modes if

both limit registers are set to the rail values TLOW = –128°C and THIGH = +127.9375°C on the TMP1075 non-N

orderables.

7.4.4.1 Comparator Mode (TM = 0)

In comparator mode (TM = 0), the ALERT pin becomes active when the temperature equals or exceeds the

value in THIGH for a consecutive number of Fault Queue bits [F1:F0]. The ALERT pin remains active until the

temperature falls below the indicated TLOW value for the same number of faults.

The difference between the two limits acts as a hysteresis on the comparator output, and a fault counter

prevents false alerts as a result of system noise. The SMBus Alert response function is ignored in the

comparator mode.

7.4.4.2 Interrupt Mode (TM = 1)

In interrupt mode (TM = 1), the device starts to compare temperature readings with the high limit register value.

The ALERT pin becomes active when the temperature equals or exceeds THIGH for a consecutive number of

conversions as set by the Fault Queue bits [F1:F0]. The ALERT pin remains active until the pin is cleared by

one of three events: a read of any register, a successful SMBus Alert response, or a shutdown command. After

the ALERT pin is cleared, the device starts to compare temperature readings with the TLOW. The ALERT pin

becomes active again only when the temperature drops below TLOW for a consecutive number of conversions

as set by the Fault Queue bits. The ALERT pin remains active until cleared by any of the same three clearing

events. After the ALERT pin is cleared by one of the events, the cycle repeats and the device resumes to

compare the temperature to THIGH. The interrupt mode history is cleared by a change in the TM=0 bit, setting the

device to SD mode, or resetting the device on the TMP1075 non-N orderables.

7.4.4.3 Polarity Mode (POL)

The polarity bit allows the user to adjust the polarity of the ALERT pin output. If the POL bit is set to 0 (default),

the ALERT pin becomes active low. When POL bit is set to 1, the ALERT pin becomes active high and the state

of the ALERT pin is inverted. Figure 7-10 shows the operation of the ALERT pin in various modes.

Measured

Temperature

THIGH

TLOW

ALERT PIN

(ComparatorMode)

POL=0

ALERT PIN

(InterruptMode)

POL=0

ALERT PIN

(ComparatorMode)

POL=1

ALERT PIN

(InterruptMode)

POL=1

Rea d

Read

Time

Read

Figure 7-10. Output Transfer Function Diagrams

TMP1075

SBOS854F – MARCH 2018 – REVISED JUNE 2024

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