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TMP441: Problem with the temperature measurement with a Xilinx FPGA XC7A50T-1FGG484C internal diode and the TMP441

Robert Thomas21
Prodigy 160 points
Part Number: TMP441
Other Parts Discussed in Thread: DXP

Hello TI Team,

we have a problem with the TMP441 and a Xilinx FPGA:

We connected the DXP and DXN tothe FPGAs DXP and DXN.

It works real good with the XC7A35T-1FGG484C and we get a temperature value through the diode of the FPGA.

Now we change the FPGA: XC7A50T-1FGG484C , and now the temperature measurement do not work. We gelt always 0°C              

Do you have an idear, whats going wrong with this kind of FPGA?

Thank you in advance for answering my question.

Kind Regards

R. Thomas

  • 0
    TI__Mastermind 35895 points
    Hi Robert,

    Did the pinout change between FPGAs?
    How many samples have you tested?
    Do you power the FPGA during the measurement? Sometimes there are ESD structures on the diode pins that prevent normal operation without proper supply biasing.

    There can be a temperature error due to difference in semiconductor process, but it should not cause total failure as you've described.

    Ren
  • 0 in reply to Ren Schackmann
    Prodigy 160 points

    Hi Ren

    thank you for your quick reply.

    The FPGA is pin compatible and we checked the pinning: its ok.

    We power the FPGA and he gets his binary from his flash. He works perfect.

    We have been tested all boards and its always the same:

    Register 01: 00

    Register 11: the open bit is1, the /PVLD Bit is 0.

    So I think we have a problem wih FPGA.

    What are you thinking about this?

    Thank you in advance answering my question.

    Kind Regards

    Robert

  • 0 in reply to Robert Thomas21
    TI__Mastermind 35895 points
    Hi Robert,

    If the Open bit is 1, it means the remote diode is not connected.

    The TMP device must source current to bias the remote diode. It then samples the voltage developed across the diode drop. If there is no connection, the current source will swing to the upper voltage rail. The device is designed to detect a voltage at the rail, and flag this as OPEN.

    It's possible that other conditions could cause the TMP device to swing to rail and flag OPEN. If you can't resolve the issue in your system design, it may be that the structure of the diode on the FPGA is not compatible with the voltage range of TMP441.

    Ren
  • 0 in reply to Ren Schackmann
    Prodigy 160 points

    Hello Ren

    Thank you for your answer and explanation.

    We had no connection to the diode, because the via was to close to the pad. There was no solder resist between

    th pad and the via, so the solder flow in the hole of the via when it melted.

    Please close the ticket, there was no problem with your IC.

    Best Regards

    Robert