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TMP102, Interrupt mode, ALERT pin

Lukasz Baranski58559
Prodigy 10 points
Other Parts Discussed in Thread: TMP102

Hi Matt,


I have a problem with TMP102 sensor. Specifically, the ALERT signal. After reading the entire directory SBOS397B note, I would like to set the TMP102 to work as follows.


Example 1:
We would like to receive the signal on pin ALERT.
Tmax = 29
Tmin = 26

(Temperature measurements at the next second)
1s - 25C    ALERT(pin) - 1
2s - 26C    ALERT(pin) - 1
3s - 27C    ALERT(pin) - 0
4s - 28C    ALERT(pin) - 0
5s - 30C    ALERT(pin) - 1
6s - 29C    ALERT(pin) - 1
7s - 27C    ALERT(pin) - 0
8s - 26C    ALERT(pin) - 1
9s - 25C    ALERT(pin) - 1

Of course I read the register after each occurrence of "1" on pin ALERT. I would like to make sure that such action is possible.
End of example.

Example 2
To be certain, I conducted a test in the following configuration.
ADD0 - is connected to VCC

1 - CR0
0 - CR1
1 - AL
0 - EM

0 - OS
1 - R1
1 - R0
0 - F1
0 - F0
x - POL
x - TM
0 - SD

We now have the following cases:
A) [POL, TM] - [0.0] - ALERT pin is working properly.
B) [POL, TM] - [1.0] - ALERT pin is working properly.
C) [POL, TM] - [1.1] - ALERT pin is not responding (constant signal level 0)
D) [POL, TM] - [0,1] - no response to the ALERT pin. (Constant signal level 1)
For cases C and D, I am unable to determine why the system does not work correctly.
End of example.

Please answer the following questions:
1. Is the performance of the system of Example 1 can be obtained?
2. What must be done in Example 2 to point C and D to work properly?

Best regards,
Luke

  • 0
    TI__Guru 62945 points

    Hi Luke,

    Unfortunately I don't believe that the TMP102 will operate in the behavior that you're looking for.  Since you haven't listed it, I'm going to assume that you've based the "Temperature Measurements vs. Alert" chart that you created in your thread with:  POL = 1, F1/F0 = 0/0, and TM = 1.  This will put the part in "Interrupt Mode" with the Alert pin active "HIGH" and no requirements for consecutive faults.

    On page 9 in the “High- and Low-Limit Registers” section, the full description of the ALERT pin activity is described.  In the Interrupt Mode, the ALERT pin first becomes active when the temperature equals or exceeds the value in the Thigh register (29C for your example).  Since you state that you will read the output after every occurrence where ALERT = 1, the ALERT signal will clear after the read is performed.  The ALERT signal will remain unasserted (ALERT = 0) until the temperature falls below the Tlow register at which point the signal will go high again.  This behavior can be seen in Figure 10 in the datasheet.  Based on this description of the pin, I’ve modified your table below.

    (Temperature measurements at the next second)
    1s - 25C    ALERT(pin) - 0
    2s - 26C    ALERT(pin) - 0
    3s - 27C    ALERT(pin) - 0
    4s - 28C    ALERT(pin) - 0
    5s - 30C    ALERT(pin) – 1      ß first occurrence where temperature equals or exceeds Thigh
    6s - 29C    ALERT(pin) – 0      ß Cleared because you read the register
    7s - 27C    ALERT(pin) - 0
    8s - 26C    ALERT(pin) - 0
    9s - 25C    ALERT(pin) – 1      ß first occurrence where the temperature falls below Tlow after ALERT was set

     

    Regarding your second example:


    Conversion Rate = 1Hz

    Extended Mode Disabled – 12 bit output

    1 consecutive fault


    We now have the following cases:
    A) [POL, TM] - [0.0] - ALERT pin is working properly.
    B) [POL, TM] - [1.0] - ALERT pin is working properly.
    C) [POL, TM] - [1.1] - ALERT pin is not responding (constant signal level 0)
    D) [POL, TM] - [0,1] - no response to the ALERT pin. (Constant signal level 1)
    For cases C and D, I am unable to determine why the system does not work correctly.
    End of example.

     

    Please note that in interrupt mode (the mode that you’re having issues with) the ALERT pin will follow the description listed in the datasheet  on page 9 and briefly restated above.  Therefore, the signal will remain inactive until the temperature meets or exceeds the value in the Thigh register.  Please verify that the ALERT signal does not become active after the temperature in the Thigh value is exceeded.  If it does not become active when the temperature meets or exceeds the value in Thigh then we will investigate further into the issue.

     

    Regards,

    Collin Wells
    Precision Analog

    Linear Applications