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TMP275 Temperature Sense - distance specifications for monitoring temperature at multiple location..??

Dhara Pandya
Expert 1220 points
Other Parts Discussed in Thread: TMP275

Hi,

I want to sense temperature at 5 different location on my test set up which has different mechanical fictures and electronics card. Inerface between the temp. sensor and micro-controller is I2C..

At what distance from micro-controller, the temp. IC TMP275 can be assembled..?

Are there any such distance constraints to follow between the master device and TMP275 in case of I2C interface between them..??

Let me know if anybody can guide me with this..

Thanks.

Regards,

Dhara

  • 0
    TI__Mastermind 43715 points
    Hi Dhara,

    There isn't a specific limit for distance. The limiting factors for any communication bus will be the amount of resistance and capacitance that can be tolerated in the wiring. For I2C, a straight forward way to increase the effective drive strength is to reduce the size of the pull-up resistors. The value of the supply divided by the value of the resistor is how much current the devices on the bus will be expected to sink in order to create a logic low (or zero.) This current cannot exceed 3mA (see SDA Vol spec,) so the strongest pull-up you could use is probably about 1kOhm (dependent on supply.) We typically use pull-up resistors in the 5-10kOhm range, and we don't have any issues with 6-12" of 24-30awg wire in our lab.

    There are some best practices for wiring in NXP's I2C Specification, page 60. www.nxp.com/.../UM10204.pdf

    There's also some good information that may help you understand the functions and limitations of the I2C Bus in the TI application report "Understanding the I2C Bus." www.ti.com/.../slva704.pdf

    Thanks,
    Ren