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OPA4872: OPA4872

Intellectual 575 points
Raheel Bari

Replies: 3

Views: 622

Part Number: OPA4872

Hi

I'm using OPA4872-EP as video multiplexer of 4*1.

I've two grounds.

1)- Digital ground.

2)- Analog Ground.

There are 04 inputs which are to be controlled by the microcontroller which is using digital ground. However, the video sources are with respect to Analog ground. Please confirm should the pins 2 (GND) and pin 4 (GND) are to be connected with the digital ground or analog ground? I think we need to connect with Digital ground and we don't need any connection with the analog ground.

Regards;

Intellectual 575 points
Raheel Bari
  • Expert 6865 points
    Jacob Freet

    Hi,

    the OPA4872 is designed to be used with split supply voltages on the V+ and V- pins with a ground reference to the GND pins. The GND pin is indeed for the digital logic, but it is important that you are using an actual negative supply for the V- pin. It will not work if you connect the V- and the GND pins to the same potential. 

    Regards,

    Jacob Freet 
    High Speed Amplifiers

  • Intellectual 575 points
    Raheel Bari

    In reply to Jacob Freet:

    Jacob

    Thankyou for the reply. I was on medical leave so couldn't reply you earlier.

    There is a part b of above question.

    As a microcontroller is running with DGND reference and analog signals are runnning with AGND reference, and to use OPA4872 as multiplexer it is necessary to short AGND and DGND. They can't be separated out. If i want separate ground, i have to use optocoupler between my control signals of microcontroller and analog multiplexer which is not possible as there are around 12 multiplexers in my design. What should be the best topology in mixing analog and digital ground in such case with reference to OPA4872?

    Regrds;
  • Expert 6865 points
    Jacob Freet

    In reply to Raheel Bari:

    HI,

    Just to understand, you are using a negative supply connected to V- correct? In that case you should be able to connect the DGND to the ground of the OPA4872 and I would expect you to not run into any issues unless you AGND is a significantly different potential than DGND.

    Regards,

    Jacob Freet 
    High Speed Amplifiers

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