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TMP422-EP: TMP422 LOCAL TEMPERATURE MEASUREMENT

ANBARASU SEMBANAN
Prodigy 20 points
Part Number: TMP422-EP
Other Parts Discussed in Thread: DXP, TMP422

Tool/software:

Hi All,

I am using the TMP422AMDCNTEP part for my design. Please clarify the below queries,

1) I am trying to use local temperature measurement alone not  for remote sensor (So no Transistors are connected in my current design), So all the DX1,DX2,DX3,DX4 pins connected to ground through 4.64K ohms resistor.

Question:

1) If i connect the DX1,2,3,4 through 4.64k to ground will have issue?

2) As per datasheet DX2 and DX4 is DXN for slave address 0x4C , And datasheet recommends to unconnected . But if i connect through 4.64k to GND will have issue?

3) By connecting 4.64k ohms to GND on DX1,2,3,4 pins shall i able to configure I2C address as 0x4C?

Regards,

ANBARASU S

  • 0
    TI__Expert 6240 points

    Hello Anbarasu,

    Please follow the datasheet recommendations in regarding to not using the remote junction. DXP should be grounded and DXN should be left not connected (floating). We measure the remote temperature measurement through pumping current through the device and measuring the Vbe across the junction. DX1 and DX3 are grounded. DX2 and DX4 are floating. This set up will not allow the current to flow through the device. Please do not add any resistors to the DX pins, GND pin, or address pins. Adding resistors will cause the device to consume more power than needed. 

    Best Regards,

    Meredith McKean

  • 0 in reply to Meredith McKean
    Prodigy 20 points

    Hi Meredith,

     Thanks for your response. As per your feedback if i add external resistor it consumes more power, but still, it works. Please confirm?

    I could see in two different statements in datasheet page 9/36 in TMP422 datasheet, here it says all unused pins to be connected to GND

    In page 19/36 it says both the pins connected to GND or OPEN,

    So please confirm which one is the right option for local temperature measurement for I2C address 0x4C,

    #1. DX1, DX2, DX3, DX4 pins to be connected to GND directly

    #2. DX1, DX2, DX3, DX4 pins left unconnected

    #3. DX1, DX3 pins to be connected to GND directly and DX2, DX4 pins to be unconnected 

    Waiting for your feedback!

  • 0 in reply to ANBARASU SEMBANAN
    TI__Expert 6240 points

    Hello Anbarasu,

    I would recommend repopulating the current resistors with 0 Olm resistors. Is there a reason why the customer is wanting to place resistors? Thank you for bringing the issue about the datasheet. I will need to test the device and confirm which statement is correct. I'm currently ordering some new parts for this test. I plan to provide an answer in the next week.

    Best Regards,

    Meredith McKean

  • 0 in reply to Meredith McKean
    Prodigy 20 points

    Hi Meredith,

      Thanks! I will wait for your test results. There is no specific reason for adding the external resistor (Just pull-down) .

    Regards,

    Anbarasu S

  • 0 in reply to ANBARASU SEMBANAN
    TI__Expert 6240 points

    Hello Anbarasu,

    Thank you for your patience.

    Best Regards,

    Meredith McKean

  • 0 in reply to Meredith McKean
    TI__Expert 6240 points

    Hello Anbarasu,

    I have test both ways:

    1)  DXP grounded, DXN floating

    2)  DXP and DXN grounded

    I was able to collect temperature through I2C in both ways. 

    Best Regards,

    Meredith McKean 

  • +1 in reply to Meredith McKean
    Prodigy 20 points

    Hi Meredith,

      Thanks for your quick results! This answer resolved my queries.

    Regards,

    Anbarasu S