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TCA9509: TCA9509 Supply Voltage

Prodigy 130 points

Replies: 3

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Part Number: TCA9509

I want to use I2C repeater to interface I2C bus signals between two boards of same voltage levels. Can I supply VCCA=VCCB=3.3V to TCA9509 part? please confirm or suggest a part that support thisrequirement.

  • Hey Manoj,

    TCA9509 can function while VccA=VccB=3.3V though the device's datasheet characteristics were designed for B side to be larger by 1V, so you may see some shifts to the datasheet parameters.

    Maybe TCA9511A/TCA9517 would work better for this application though. Are your two boards both going to be using an I2C buffer? If so, we need to make sure they do not include static voltage offsets connected to each other (like TCA9517 B side<---> B side TCA9517 or TCA9509 A side <---> A side TCA9509)<-- DO NOT DO THIS.

    -Bobby

  • In reply to BOBBY:

    Hi BObby,

    Thanks for your response.

    We are not using I2C buffers in both boards. We are planning to just have a repeater in processor board alone, so that it can drive the I2C devices in other sensor board. So is it better to use TCA9517 part for my application?

    Also you have mentioned "static voltage offsets connected to each other", could you please explain bit more on this.

    thanks

    Manoj.

  • In reply to manoj kumar kakireni muni:

    Hey Manoj,

    "So is it better to use TCA9517 part for my application?"

    From the information provided so far, yes.

    TCA9511A could also be a good choice because it has a built in rise time accelerator, hot swap insertion (seems like you are interfacing two board and if one board is being inserted unpowered while the other is powered then this may be a good solution), dynamic offset instead of a static voltage offset.

    "Also you have mentioned "static voltage offsets connected to each other", could you please explain bit more on this."

    I'll try to provide a short answer to this:

    I2C redrivers are both inputs and outputs. If you output a low and your input sees a low (they are connected) then you would get stuck low on both sides. Static voltage offset buffers get around this problem by having an offset when outputting low (say 0.54V) while having a ViL of 0.4V when this offset is turned on. If you have two of these kind of devices connected in series (or parallel) you may not be able to send lows through each other. TCA9517 has this offset on B side so two B sides of this device cannot be connected. A to B and A to A side connections are okay though.

    An app note which goes through this in more detail can be found here:

    Thanks,

    -Bobby

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