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query regarding I2C address

Raghavendra S
Prodigy 40 points

Hi Team,

As per the requirement we are using LM75BIMX-3/NOPB temperature sensor, and Integrating with IMX8MM.

we have one query w.r.t I2C address. from data sheet it is clear that 

but in our design HW Engineer has kept first 4 MSB bits 1111 instead of 1001 as mentioned in datasheet. could you please help us answering below mentioned queries.

1. is it compulsory to maintain MSB bits as "1001"

2. does we face any issues with address as "1111011"

3. below is the temperature sensor circuit designed as per project requirement and mentioned I2C address below the circuit.

Thanks,

Raghavendra

  • 0
    TI__Guru* 91206 points

    Dear Raghavendra - 

    Welcome to E2E and thanks for the post! Please see below for answers to your questions.

    A1. Yes

    A2. Yes, you will face an issue where the part will NACK that address and you will not establish communication over the I2C bus as a result. All the possible I2C addresses for this part are in a table below that I put together for you, from description in the datasheet, and I included the conversion to 8 bit, for writes and reads, as that is what you will see coming from your processor on the I2C lines. In your schematic, the part is wired to have a 0x4E for the I2C address (7 bit) or 0x9C (8 bit), as A0 & A1 are pulled high and A2 is pulled low. It is best practice to connect these pins directly and avoid the pullup resistors on these lines. It is also best practice to show the pullup resistors for the I2C lines on the schematic and to ensure they are the proper value based on the bus capacitance your layout presents. The green highlighted band applies directly to your hardware.

    A3.  see A2 with regards to schematic.