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Original question:

TMP464: Temperature less than zero problem

TMP464: Temperature less than zero problem

Rhea Gao
Expert 2350 points
Part Number: TMP464

Hi，

1. Customer waveform is attached.

   

2.  The customer's problem recurred again. The I2C waveform was measured, and the data read was indeed 256℃.

When the problem recurred, all the remote channels read 256 ° C, and only the local channel was normal.

In addition, do you need to add delay between channel reads? How much is appropriate?

When the problem is repeated, register 0x23 is read with the value 0x0f00, indicating that all four remote channels are OPEN.

Thanks~

  • 0
    TI__Mastermind 41235 points

    Hi Rhea,

    Meredith requested an oscilloscope picture of D+ zoomed in on the conversion activity. What you posted previously shows two conversions, but we specifically need to see the voltage levels during conversion to identify any noise problems. Noise will cause the ADC to report an abnormally high reading, but can also make the ADC rail. The noise may be intermittent, so the customer may need to confirm they have captured the oscilloscope activity during a moment the device is reporting an erroneous temperature. RC filtering can alleviate some noise issues, but ultimately extreme noise can only be prevented by appropriate shielding in the layout or cabling.

    thanks,

    ren

  • 0 in reply to Ren Schackmann
    Expert 2350 points

    Hi Ren,

    Once there is a problem with TMP464, the temperature we read later is always 256℃, which can only be restored after the device is powered off and restarted. Not the probability that something will go wrong.

    If the problem is repeated later, the customer will grab the D+ waveform of one channel for feedback according to the following example.

    Thanks~