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TCA9509 Connecting in Series

Sadanori Kato
Guru 36490 points
Other Parts Discussed in Thread: TCA9509, TCA9617A, TCA9517

Hi,

Could you please tell us whether TCA9509s can be connected in series ?
Is it possible to adopt as the following configurations if possible ?

Best regards,
Kato

  • 0
    TI__Genius 16430 points
    Kato-san,

    The TCA9509 is the exception to our normal buffered-translators.
    With the TCA9509, it is OK to connect B to B together. It is NOT OK to connect A side to A side.

    Please also note that with the TCA9509, the A side of the device MUST NOT have any external pull-up resistors, because it has an internal current source that it uses to determine which side is transmitting.

    If you need to do translation from 5V to 3.3 to 5V as you show in figure A, then you may look at the TCA9517 or TCA9617A/B, because with these devices, it is OK to connect A sides together, but it is NOT OK to connect B sides together.

    In short, the following devices can be used for your figures above in the configuration you show:
    A) TCA9517, TCA9617A/B and any of our other buffered translators (but NOT the TCA9509)
    B) TCA9509 is the only device which supports B to B connection, but has a requirement that A side bus must not have any external pull-up resistors.
  • 0 in reply to Jonathan Valdez
    Guru 36490 points

    Hi Jonathan-san,

    Thank you for explaining so politely.
    I understood your advice.
    So, could you please give me your advice regarding the device and the configuration which you recommend since we would need that the VOL for the master and slave side is less than 0.4V ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    TI__Genius 16430 points
    Kato-san,

    The TCA9509 will meet the 0.4V VOL requirement for scenario B.

    However, in Scenario A, the master and slave are both at 5V. I2C spec dictates that I2C valid VOL is 0.3 * VCC. This comes out to a VILmax of 1.5V according to I2C spec. Can you explain why in Scenario A, the master and slave would require a 0.4V VOL from a translator?

    If this 0.4V VOL is a hard requirement at 5V VCC, then we do not have any translators that will satisfy scenario A at 0.4V VOL. Our TCA9517 has a B-side VOL of ~0.5-0.6V, which falls well within the I2C spec requirement of 1.5V.
  • 0 in reply to Jonathan Valdez
    Guru 36490 points

    Hi Jonathan-san,

    Thank you for your response.
    As you said, our customer requests that the master and slave are both at 5V.
    I will suggest whether TCA9509 is able to be used in scenario B(Connecting B to B with TCA9509s) to our customer.
    I greatly appreciate your cooperation.

    Best regards,
    Kato