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TMP007 for 3.3V I2C line

Satoshi
Guru 19495 points
Other Parts Discussed in Thread: TMP007, TMP006, TCA9617B

TMP007's VIL is too low(0.4V), and I didn't find match I2C bus IC on 3.3Vcc only board.

I think that TMP007 is difficult to use I2C interface for general 3.3Vcc board.

Please see below.

【Question】

①What background is low VIL spec?

②Can TMP007 use Vcc:3.3V only solution?

③If there reference design for match TMP007 and I2C bus solution, please let me know.

④Is there solution of matched 0.4VIL I2C line?

⑤Isn't TMP007's VIL(0.4V) typo?

※TMP006 is no problem, but customer is interested in TMP007's math engine.

Best regards,

Satoshi

  • 0
    TI__Mastermind 35895 points

    Hi Satoshi,

    These products are all compatible. The differences are a matter of extra margin. Please see attachment.

    Ren

  • 0 in reply to Ren Schackmann
    Guru 19495 points

    Ren-san

    Thank you for reply.

    And, sorry for my typo.

    Modified figure is below, please see it. (Modified point: I2C bus's VIL ⇒ VOL)

         

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Mastermind 35895 points

    Hi Satoshi,

    These products were built on a process technology that cannot support a 1.8V supply. In order to support customer demand for 1.8V I2C interface, TMP006B and TMP007 were designed with 1.8V compliant inputs. These inputs do not track supply, because it is necessary to supply the device with at least 2.5V. Other I2C products have VIH and VIL specs which track supply. If you require a VIL that tracks supply, then TMP006 is the only option.

    Normally, the VOL spec is a worst case voltage rise under high load. Under normal load, a typical driver should still pull very close to 0V. In this case, it would be up to customer to ensure their driver is not loaded to the point that it will violate VIL. 

    However, the translators you have listed contain a VOL MIN as well as a VOL MAX. Other translators I've looked up also have this MIN voltage. This leads me to believe that these devices are designed to not pull all the way to 0V as part of their bidirectional operation. It is actually the VOL MIN which is not compliant with TMP006B and TMP007. 

    May I ask what is the host voltage level? Is it necessary to use a translator at all?

    Thanks,

    Ren

  • 0 in reply to Ren Schackmann
    Guru 19495 points

    Ren-san

    Thank you for reply.

    Voltage level is 3.3V only.

    Customer is necessary to use translator because long cable range(6～7m).

    Addition, is below idea match TMP007 and 3.3Vcc solution?

    Or, is there better idea than below?

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Mastermind 35895 points
    Satoshi-san,

    The A side of the TCA9617B has a VOL that is compliant with TMP007. The B side has a VOL that is not compliant. Yes, I think what you have drawn is suitable.

    Ren