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PCA9517: PCA9517 application

Nanfang Liao
Intellectual 2085 points
Part Number: PCA9517
Other Parts Discussed in Thread: TCA9803, PCA9548A, TCA9548A, TCA9517, TCA9509, TCA9406

Hello Team,

My customer one board use two I2C solutions below, please help to give your comments, thanks

1. Can PCA9545/PCA9548 connect to B port of PCA9517? if they are not OK, do you have other solution to replace PCA9517?

2. Can you delete PCA9517 and connect PCA9545/PCA9548 directly? The slaves are 1.8V level

  • 0
    TI__Guru 62920 points
    Hi Nanfang,

    We are looking into this one and will get back to you soon.

    Regards,
    Max
  • 0
    TI__Genius 16450 points

    Hello Nanfang,

    I would actually recommend a product from the TCA980x family (such as the TCA9803) for this use case, and here is why:

    You have the B side of the PCA9517s connected to the PCA9548A. If you have multiple channels connected on the switch, you will have multiple B-sides connected together, which is not recommended. The buffers are not able to pass a signal from B-side to B-side. This should not affect communication between the master and a single slave device, but this configuration is not recommended since it could possibly cause a slave device to do something weird since it won't be able to see any traffic from another slave device.

    I would recommend using a TCA9803, and using the opposite A and B sides shown here (B side connected to slave, a side to switch). The TCA980x does not have a VCCA < VCCB dependency and VCCB can go down to 1.65 V (VCCA down to 0.8 V). The TCA980x also features integrated current source on the B-side, so you do not need external pull up resistors (and they are not recommended on the B-side). The A-side of the TCA980x still requires pull-ups.

    Also, I would recommend a switch to a TCA9548 and TCA9546 instead of the PCA variants. Power on reset circuit is much improved and more robust. 

  • 0 in reply to Jonathan Valdez
    TI__Intellectual 2085 points

    Hello Jonathan,

    Thanks for your good suggestions, can we PCA9517, and use PCA9545/PCA9548 connect to slaves directly?

    Regards,

    Nanfang

  • 0 in reply to Nanfang Liao
    TI__Genius 16450 points

    Nanfang,

    I believe you are asking if you can have it go (Master) ----- (B) TCA9517 (A) ----- TCA9548A ------ Slave

    Yes, you can do this. The TCA9548A/PCA9548 is able to do voltage translation.

  • 0 in reply to Jonathan Valdez
    TI__Intellectual 2085 points
    Hello Jonathan,

    Thanks, TCA9803 has no AVL code in my customer, so they want to use PCA9509 to replace PCA9517 in below two applications, it is OK?

    Regards,
    Nanfang
  • 0 in reply to Nanfang Liao
    TI__Genius 16450 points

    The PCA9509 cannot be used to replace PCA9517 in both applications. I can be used to replace the TCA9406, but NOT the top tca9517. The reason is the TCA9509 does not allow vcca = vccb. There must be a 1 v difference.