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TLV320AIC3268: VNEG in paralel

Tihomir Stoyanov
Prodigy 65 points
Part Number: TLV320AIC3268

Dear All, good day, 

I would like to consider using 8 to 10 pcs of TLV320AIC3268 in my project. As I am in need of a negative rail supply of about 50mA, could I connect all the VNEG together to form a lane with negative voltage? As per MSDS the device uses a charge pump to generate its own needed negative power rail, using a 2.2uF capacitor. I am planning to increase it to 10uF (which is anyway suggested in the MSDS) and connect all VNEG together via 1mH inductances (to reduce any ripples) in order to form a negative supply rail. Any design considerations? How much would be the maximum current draw per device?

  • 0
    TI__Guru 57800 points

    Hi, Tihomir,

    The intended application is not recommended. The VNEG pin of the AIC3268 is used as a decoupling point for the internal charge pump and should be connected only to the recommended decoupling capacitor. We don't have detailed test data for a use case like this as the VNEG supply is specifically designed for the AIC3268's requirements and it is not intended to be used as external supply. Using this pin as power supply for external components may lead into device issues. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 65 points

    I understand completely that such application of VNEG is not intended, indeed. Otherwise it would be mentioned explicitly in the MSDS. Two simple questions: 

    1) nevermind the intentions, is it possible to work (for a drain of no more than 5mA)?

    2) what is the actual voltage that is suposed to be there? (we still don't have the EVAL board in possession to measure it)

  • 0 in reply to Tihomir Stoyanov
    TI__Guru 57800 points

    Hi, Tihomir,

    It may work but the device performance may be affected as the charge pump is specifically designed to operate within certain limits set for the codec. 

    The voltage seen at VNEG pin is about -1.8V.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer