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TMP423: The communication distance is 10m. Is there attenuation? How to achieve it?

Part Number: TMP423
Other Parts Discussed in Thread: TMP421, TMP464, TMP468, TMP107, TMP104

Hi

We use it on the base of the charging pile, the distance between the main body and the split of the charging pile is 10m, the temperature of the charging socket is measured, the accuracy is less than ± 2 ° C, and the contact type can be used because of the cost requirements; the packaging is not required, mainly the communication line distance Long; interface type is not required;

We used to use TMP421, but now we need to detect more points, there are a total of 11, in order to save costs, I want to choose TMP423, so 4pcs / set is enough;
I don't know if the communication distance is appropriate. The communication distance is 10m. Is there attenuation? How to achieve it?

Is there any other more suitable chip recommendation?

Thank you.

Elsa Duan

  • Hi Elsa,

    There is also the 8 channel TMP468 and 4 channel TMP464.

    It's not clear if you are wanting to use 10m of cable for the TMP4x to remote junction connection or 10m of cable for the I2C communication between TMP4x and host. The limitation is going to be capacitance of the wire in both cases.

    For the TMP4x to remote junction wire, the TMP4x device can't handle much more than 1nF of total capacitance. Depending on the wire, this could be 30m or more. Series resistance is automatically corrected by the algorithm, but excessive resistance will have the same effect as excessive capacitance; resistance and capacitance will both contribute to loss of bandwidth. The loss of bandwidth will have the same effect as excessive capacitance as shown in Figure 6 of TMP421 datasheet. Temperature error will become increasingly negative. 

    The I2C specification limits bus capacitance to 400pF, depending on bus mode/frequency. 

    thanks,

    ren

  • Hi Ren

    Thanks for your advice.

    After check the Typical application schematic, I want to ask if it can achieve? I Intended to use tmp468 to test 8 points and TMP423 to test other 3 points.

    From Remote Zone to Tmp468 is about 10m, and Remote Zone 1 to Remote Zone 2 is about 1m, And so on;

    The block is as below:

    Thank you

    Elsa Duan

  • Elsa,

    I would not recommend using a remote sensor with 10m of cable. The D+/D- lines are not well suited to it. Your application is better suited to TMP107. UART is much more robust, and TMP107 has been proven on 300m of cable.

    thanks,

    ren

  • Hi Ren

    So nice to you.

    Thank you very much.

    But TMP107 is too expensive, can you recommend other cheap temperature sensor with UART?

    Thanks again.

    Elsa Duan

  • Elsa,

    The only other UART device we have is TMP104, but the interface is slightly different from TMP107.

    thanks,

    ren