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INA231: INA231 / Data fall and rise time

S.Satoshi
Guru 21685 points
Part Number: INA231

Hi,

Please let me ask about the voltage to start/end of tR and tF as attached. I think that it should be 10% <-> 90% or VIL <-> VIH. 

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Mastermind 32395 points

    Hello Satoshi,

    According to the UM10204 I2C spec, tF and tR are measured as 70% -> 30% and 30% --> 70% respectively.

    Let me double check with our team though.

    Sincerely,

    Peter Iliya

    Current Sensing Applications

  • 0 in reply to Peter Iliya
    Guru 21685 points
    Hi Peter,

    Thank you for your response. I'm waiting for your update.

    Best Regards,
    Satoshi
  • 0 in reply to S.Satoshi
    TI__Mastermind 32395 points
    Hello Satoshi,

    We specify our rise and fall times using the standard 30%/70% marks of the full-scale signal. This is the same standard as the UM10204 specification. So if our I2C characterization of the INA231 was with a 5V full-scale signal, then we measured rise and fall times on the INA231 SCL and SDA lines as the times from 1.5V to 3.5V.

    Hope this help,
    Peter Iliya
    Current Sensing Applications
  • 0 in reply to Peter Iliya
    Guru 21685 points
    Hi Peter,

    Let me ask more about VIL and VIH of SCL/SDA.
    The VIL and VIH should be 0.99V and 2.31V at VDD=3.3V if it refer UM10204 specification. However the VIL and VIH in electrical characteristics is specified as 0.4V(max) and 1.4V(min). I think this should be VDDx30% and VDDx70%, is my understanding correct?

    Best Regards,
    Satoshi
  • 0 in reply to S.Satoshi
    TI__Mastermind 32395 points
    Hello Satoshi,

    There is a difference between how we measure rise and fall time versus how specify VIL/VIH.

    We measure rise/fall times based upon the 30% to 70% level of the full-scale signal.

    We specify VIL ("input-low") and VIH ("input-high") as the input specifications. If the master wants to communicate with our device, it must have a LOW digital logic level that is inside our VIL range (-0.5V to 0.4V) and it must have a HIGH digital logic level inside our VIH range (1.4V to 6V). We create these ranges so that no matter how the INA231 (or most of our digital current-sensing devices) is powered, the master can communicate with the device even if master device is operating on 1.8V, 3.3V, or 5V logic levels.

    The VOL ("output low") is an output specification of our device. This specifies what our device considers as a LOW digital logic level when it is transmitting data out to the master.

    I hope this helps.

    Sincerely,
    Peter Iliya
    Current Sensing Applications