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Original question:

INA237: VIL threshold confirmation

INA236: VIL threshold confirmation

Masami Akazawa
Intellectual 535 points
Part Number: INA236
Other Parts Discussed in Thread: ISO1643, INA237

Hi Team,

From the datasheet of VIL, can I understand the maximum 0.4V means the threshold that regard as low will not exceed 0.4V? We measured the SDA low voltage level is about 450 mV, and INA236 didn't actually return Ack. Does this mean that the low level of SDA/SCL is too high?

In this thread it was written that "The input voltage must be 0.4 V or lower for it to be guaranteed to be read as low. The actual switching threshold will be higher, near 0.8 V, but there is no guarantee", but does that also apply to INA236?

https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1242259/ina237-vil-threshold-confirmation?tisearch=e2e-sitesearch&keymatch=INA226%2525E3%252580%252580VIL

 

Currently, we are using ISO1643 for isolation. When we connect the microcontroller and INA236 directly, communication is fine.

The INA236 is connected to the SDA1/SCL1 side of the ISO1643.

Do you have any other recommended isolation ICs?

Best regards,

  • 0
    TI__Mastermind 35260 points

    Hi,

    I’ll forward your inquiry to experts in the ISO family of products for further assistance.

    Guang

  • 0 in reply to Guang Zhou
    Intellectual 535 points

    Hi Guang,

    Thank you for your reply.

    Let me partially correct what I said.
    When using ISO1643, the low voltage was just over 0.4V.

    In the above thread, it seems that the INA237 can communicate even when the low voltage is 0.5V or higher, so could you first tell me if there is a difference in the I2C functionality between the INA236 and INA237?

    Best regards

  • 0 in reply to Masami Akazawa
    TI__Mastermind 35260 points

    Hi,

    There are similarities, but adjustments are necessary in each product to meet the definition requirements. As long as the input voltage level is below VIL max spec, it will be interpreted as a logic low. This does not mean a voltage that is slightly higher won’t be. You'll be able find INA237's that won't work at 0.5V if the sample population is large enough, and over different production lots. 

    Guang

  • 0 in reply to Guang Zhou
    Intellectual 535 points

    Hi,

    Thank you for your answer!

    Is it correct to say that the INA236 does not have a particularly strict VIL requirement compared to the INA237?

    The VOL of ISO1643 (SIDE1) is 0.57 to 0.71V, so the actual low level may have been higher.

    If communication is not possible with ISO1643(SIDE1), is it likely that there is another factor than VIL?

    Best regards

  • +1 in reply to Masami Akazawa
    TI__Mastermind 35260 points

    Hi,

    It is incorrect to say that the INA236 does not have a particularly strict VIL requirement. We should interpret the datasheet spec as “VIL must be below 0.4V in order to guarantee reliable communication”.

    This does not mean you’ll not find parts that are able to communicate with VIL greater than 0.4V.    

    Guang