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LM5064 SMBus pin connection

K. Sasaki14
Guru 10200 points
Other Parts Discussed in Thread: ISO1540, LM5064

Does SDAI pin have to be connected to SDAO pin?

 

My customer confirmed following phenomenons,

[Case 1]  Ack signal from SDAO enters to SDAI

It is possible to normal communication.

 

[Case 2]  Ack signal from SDAO doesn't enter to SDAI

It is impossible to write protocol. Writed data  is not reflected in the register.

  • 0
    TI__Prodigy 320 points

     

    Hi Kohei,

    The reason the SDAO and SDAI lines are separated out is to facilitate the use of discrete opto-isolators.  Master controllers typically only have one SDA line so at some point the SDAO and SDAI line must be connected together for the ACK and NACK process.  The opto-isolator circuit must also ensure a latch-up free implementation.

    An example of a discrete circuit can be found in the following app note>  http://www.ti.com/lit/an/slva229/slva229.pdf

    However, to simplify i2C/SMBUS isolation, TI has a an i2C opto-isolator that can be used that will facilitate proper isolation and communication. In this case, SDAI and SDAO should be connected together.  The part number is ISO1540. The datasheet  can be found here>  http://www.ti.com/lit/ds/sllseb6a/sllseb6a.pdf.

    Also, please reference the LM5064 evaluation module app-note which has opto-isolation> http://www.ti.com/lit/ug/snva481/snva481.pdf

    Best Regards,

    Dan