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PCA9517: PCA9517/TCA9517 Level-Translating I2C Bus solution asking

user4979899
Expert 3080 points
Part Number: PCA9517
Other Parts Discussed in Thread: TCA9517

Hi Sir,

We are looking for a solution which can meet below requirement,

Could you please help to suggest any solution can meet it?

Thank you

--------------------------------------------------------------------------------------------------------------------------

VCCA=V3V3_AUX

VCCB=V3V3

IOL condition for port B connection : under 0.4V is the requirement

Attachment  is MUX LTC4306 spec for PORT B connection.

https://www.analog.com/media/en/technical-documentation/data-sheets/4306.pdf

Below is the spec for port A connection…….under 0.8V is the requirement  

  • 0
    TI__Guru 72521 points

    Hey Anne,

    "IOL condition for port B connection : under 0.4V is the requirement"

    I'm not quite sure what you mean by IoL condition and state a voltage. IoL is measured in A (or milliamps). Are you saying you need something that generates a VoL of 0.4V or less when IoL is 3mA? <-- this is I2C standard.

    "Below is the spec for port A connection…….under 0.8V is the requirement  "

    You need ViL to be 0.8V? To me it sounds like you just need VoL to be less than 0.8V not ViL.

    Are you trying to do a P2P replacement without doing layout changes? From how you specify an A side and a B side, it leads me to think you can't redesign the layout. TCA9517 does not meet the 0.4V requirement on B side because of it's static voltage offset.

    The only device we have that does is TCA980x. It's ViL is 30%*Vcc but it does have a "ViLc" requirement.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 3080 points

    Hi Bobby,

    Thanks for your replying,

    So I need to clarify more details from you,

    1. The VCCA and VCCB will both be 3.3V, is there any concern on it?

    2. I2C master on A port VIL max will be 0.8V and slave on B port VIL will be 0.4V, and I see TCA980x datasheet mention that VOL is 0.22,

    is it suitable to meet both A port & B port requirement? is there any concern on it?

  • 0 in reply to user4979899
    TI__Guru 72521 points

    Hey Anne,

    "1. The VCCA and VCCB will both be 3.3V, is there any concern on it?"

    This device's recommended operating Vcc is rated for up to 3.6V on VccA and VccB .

    I don't see an issue, this device can have VccA=VccB

    "2. I2C master on A port VIL max will be 0.8V and slave on B port VIL will be 0.4V, and I see TCA980x datasheet mention that VOL is 0.22"

    As you pointed out VoLA is about 0.04V which is lower than 0.8V and VoLB is 0.22V which is less than 0.4V.

    "is it suitable to meet both A port & B port requirement?"

    VoL of our device is less than ViL of the master and slave, I don't see the concern.

    "is there any concern on it?"

    My only two concerns about using this device is the I2C master/slave on B side must have RiLc of less than 150 ohms and B side must not have any pull up resistors or be tied to an I2C switch/buffer on the static offset side.

    Thanks,

    -Bobby