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LM75A: 4 LM75's over a single i2c interface to FPGA

naresh kumar2
Prodigy 200 points
Part Number: LM75A

In our modem design , we have 4 dsp's used for demodulation and 4 LM75 temperature sensors are used to monitor the temperature of those 4 DSP's respectively ,all these 4 lm75 modules are connected via single i2c interface to Cyclone FPGA which monitors the temperature of DSP.

Do we need to have an I2C buffer placed as mentioned in the above diagram ?? or since device has 3 address lines which means 8 such devices can be driven through single i2c interface?

Thnx in Advance.

Regards,

Naresh

  • 0
    TI__Expert 5695 points
    Hi Naresh,
    As described on section 7.3.1 of the LM75A Data sheet, up to 8 devices are supported on the same I2C bus. I captured the relevant part below:

    "The LM75A operates with a single supply from +2.7 V to +5.5 V. Communication is accomplished over a 2-wire
    interface which operates up to 400kHz. The LM75A has three address pins, allowing up to eight LM75A devices
    to operate on the same 2-wire bus"

    However the need of the buffer or not will depend on how long are the traces for the I2C bus connection points , meaning the overall capacitance in the bus.
  • 0
    TI__Mastermind 32100 points
    Hi Naresh,

    Thank you for choosing temperature sensor for your design. As long as you configure each LM75A to an unique address, you do not need any buffer.

    Hope this helps. Let me know if you have further question.

    Aaron