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OPA2673 De-coupling question.

Russell Smith1
Prodigy 50 points
Other Parts Discussed in Thread: OPA2673

The OPA2673 datasheet page 31 recommends that the power supply pin be decoupled with a 0.1uF cap right at the pin, with a larger cap (2.2uF to 6.8uF) farther away.


I am using the OPA2673 in single supply mode (Vcc=11.5V) and have a 4.7uF/35V tantalum cap providing the larger decoupling.


For the 4.7uF cap, is there any preference for a tantalum vs. ceramic, or will both provide the same performance?

In particular, I am concerned about the stability of the device.

  • 0
    TI__Genius 13935 points

    Hi Russel,

    Tantalum would be better for the larger value capacitor. I think fir the smaller cap (0.1uF) capacitor that ceramic is better due to the lower ESR and smaller size. 

    Here is a presentation prepared by a tantalum cap manufacturer:

    http://www.avx.com/tantalum/presentations/tantalum_vs_ceramic.pdf

    Regards,

    Loren

  • 0
    TI__Genius 12631 points

    Hello Russell,

      Historically we have used Tanatalums on our Evaluation Modules to provide the large power supply bypass cap. In the past Tantalums have shown higher ESR and ESL vs ceramics, however recently their performance has improved.

    Also, the ceramics tend to have a voltage coefficient associated with them , for e.g a 4.7uF/16V ceramic may actually have a much lower capacitance when the full 16V is applied across it. I dont believe the tantalums suffer from a similar performance degradation. The voltco of the ceramic can be mitigated by derating it and using one that is rated for a higher voltage than what you actually use in the application.

    From a cost and board space perspective however you may find the ceramic to be a better fit for your application.

    Now with regards to the smaller capacitor close to the Vcc pin it is highly recommended to use a COG/NPO ceramic cap.

    Samir