• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 205 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

PCM1754-Q1: VCOM cap

PCM1754-Q1: minimum capacitance on Vcc

Shinji Tsuji
Genius 12738 points
Part Number: PCM1754-Q1

Hi team,

Could you advise the minimum required capacitance for Vcc bypass?

It is specified as 10uF electrolytic cap, but I plan to use ceramic cap and considering DC bias effect. 

regards, 

  • 0
    TI__Mastermind 21660 points

    Hello ,

    DS  recommends a 10u electrolytic cap . Electrolytic capacitors have good low-frequency characteristics and are mostly used in low-frequency circuits. They can filter out low-frequency ripples. Having said,  you still should be okay with ceramic caps but might not get the full benefit of filtering that you get from electrolytic caps specially if you are planning to use a lower value than the recommended value.  Here are two papers that might give you an idea on how low you can go on these bypass caps.

    https://www.ti.com/lit/an/scba007a/scba007a.pdf

    https://www.edn.com/bypass-capacitors-no-black-magic-here/  by an ex-TIer

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    TI__Genius 12738 points

    Hi Arash,

    Thank you for your comment.

    Could you advise how to estimate the minimum capacitance(ceramic) particularly for this device?

    I also would like to know the background theory of how did you determine 10uF electrolytic for this device.

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Mastermind 21660 points

    Hello ,

    The two articles that I sent should give you an idea how the calculations can be done in general. Having said that, usually as a rule of thumb we put a 10uF and 0.1uF.  as you can find many articles and even videos explaining it.  It boils down to how big of spikes  you would want to dampen down. I believe the original designer of the board used a rule of thumb estimate as it is the common value for many of our boards.

    Regards,

    Arash