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PCA9306: PCA9306 and ISO1540 Design Question

Jim CHEN
Expert 4795 points
Part Number: PCA9306
Other Parts Discussed in Thread: ISO1540,

Dear Team,

Below is my customer's schematic design with PCA9306 and ISO1540.

Under some conditions, 3D3V_VCC, SDA and SCL would become floating when there is no connection at J2. But the enable pin of PCA9306 still has power(Remote_VCC). V_STBY has power also.

They would like to know is it possible SDA and SCL of J1 would have noise or drive to low?

Thank you.

Regards,

Jim    

  • 0
    TI__Guru 73591 points

    Hey Jim,

    The ISO device may be able to drive side 1 of PCA9306 low but since the PCA9306 is a pass FET device, if side 1 starts to dip lower than REMOTE_CC-Vth, side 1 may leak current into side to to push it back up a little. I don't think side 1 floating would drive side 2 low  and in return drive the ISO device low. Worse case is the bus may hang around REMOTE_VCC-0.6V if side 1 remains 'leaking'

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 4795 points

    Bobby,

    Thanks for your reply.

    Regards,

    Jim