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INA233: Logic level threshold drift over temperature

Christopher Arntzen
Intellectual 590 points
Part Number: INA233

Hello,

I am using the INA233 in a noisy power supply application and am having trouble communicating with the INA233 at hot temperatures (85degC).  One aspect I noticed where the INA233 differs from other PMBus chips is the logic low threshold level.  The INA233 has a maximum 0.4V logic low threshold level whereas other PMBus chips may have a 0.8V maximum logic low level.  My hypothesis at this time is that the logic low level threshold is drifting over temperature and the noise in the system is exceeding that threshold, resulting in failed communication.  So, I have two questions:

  1. Are communication problems with the INA233 over temperature a known issue?
  2. Can you provide data / graphs of the logic level threshold drift over operating temperature?

Any insight would be helpful.  Thanks.

  • 0
    TI__Mastermind 29730 points

    Hi,

    1 Can you please be more specific with the communication problem? Whether you can’t establish communication at all, or communication is OK but measurements are off? I suggest capture the bus waveform, it should provide a lot of useful information. BTW, there have been no reported issues with this device related to communication at temperature.

    2 The logic input low of 0.4V does drift with temperature; however notice this is a “Max” specification, you should keep input level BELOW this level at all times. In reality it will tolerate 25% to 50% higher voltages for margin. At 85C, the threshold is around 0.6V under 3.3V supply. If your PMBus controller can’t drive this low, there is going to be reliability issues.

    Regards, Guang

  • 0 in reply to Guang Zhou
    Intellectual 590 points

    Hi Guang,

    For 1: We can't establish communication at all.

    For 2: We are using a 5V supply.  Is the logic level threshold higher at high temps or lower at high temps (does the line have a positive slope or negative slope)?

  • 0 in reply to Christopher Arntzen
    TI__Mastermind 29730 points

    Hi,

    Thanks for the clarification.

    The threshold has a negative TC, ie, decreasing as temp increases.

    With a 5V supply, the typical value at 150 degrees is about 0.59V and 0.72V at -50 degrees. You can draw a straight line between these two points. It should be noted that this is a typical number based on a handful of samples, and is FYI only. It shouldn’t be used as design guideline, for which the datasheet spec of 0.4V should be used.

    Regards, Guang