Cascade ADUM1250 I2C 400kHz

Can I cascade the ADUM1250 on a 400kHz I2C bus?

MCU - ADUM1250 - I2C slave1 - ADUM1250 - I2C slave2 - ...

If so, how many times?

Thanks, Koen.

  • Hi Koen,

    It sounds like you're think about making a really long chain. If you line them up in series with opposites sides of the ADuM1250 facing each other they will transmit data through a chain. The trouble with a longer chain would eventually be timing. Every time a signal goes through an ADuM1250 a max prop delay would need to be accounted for. With every stage the timing will shift further. You would need to figure out how much of a shift the design can tolerate.     

    Maybe it can be set up with the MCU connected to a bus and have each ADuM1250 tap into the bus. In that case the secondary sides of the ADuM1250 would face the bus. Like this the prop delays at each stage won't add to each other. The secondary side of the ADuM1250 can sink up to 30mA.  

    Regards,

    Jason

  • Thanks for the reply.

    As I understand correctly, for a short chain I can cascade, for a longer chain I need to implement like this:

    MCU ─┬─ ADUM1250 - I2C Slave 1     ├─ ADUM1250 - I2C Slave 2
         ├─ ...

     

     

    Br, Koen.

  • Hello Koen,

    Something else to keep in mind is that side 1 of the ADuM1250 can not communicate with  side 1 of another ADuM1250.  They would ignore each others output low.  To ensure correct operation in a star configuration as shown above, make sure that side 1 faces the slave, and side 2 faces the common node.

    Best Regards,

    MSCantrell

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