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TLV320AIC3256: Filter coefficients calculation

Part Number: TLV320AIC3256

I'm trying to get the filter coefficients of the EQ filter,but can't get it right with the AIC document even with the examples in the appendix. I followed the instrustions and I'm sure I have understood the normzlization steps. But the problems seem to me I'm wrong after 1st step, i.e the equation in sec1.2 don't get to the result in the appendix. 

I'm confused and I need someone's help. Did I get something wrong or there is sth i should know?8358.Biquad Filters Application Note(1).pdf

  • 2shine, 

    You can use the TIBQ coefficient calculator tool, to help. 

    Also take a look at this document, It is written with the ADCx140 devices in mind, but the coefficient calculations should be the same although the coefficient resolution is 32Bit in the ADCx140 and I believe it is 24Bits in the AIC3256. 

    Note that the AIC3256EVM GUI,  or Purepath Studio also have Coefficient calculators

    best regards,

    -Steve Wilson

  • nope. I need to change the coefficients on the fly, so I cannot do it that way, either Matlab OR PpS. Is there anything I can do ?  Can I get the same coefficients without tools? Or at least make sure that the filter are the same as designed?

  • 2shine, 

    It sounds like you want to calculate the coefficients on the fly.  You could still change them on the fly using the method I've described with a look up table and a set number of options.  

    Can you show your steps?  note that the application note I linked to shows similar steps in section 3.2,  this assumes you already have the b0 b1 b2 a0 a1 a2 values, and it shows how to convert.  seeing another explanation may help. 

    best regards,

    -Steve Wilson

  • yes,on the fly. However, the table is a little 'big' to me . Yes, I know the normalization steps. the problem is I cannot get the correct b0 b1 b2 a1 a2 in the first place. The doc I refered to cannot get the result in its own appendix. I also tried filter equations from websites, but cannot get the pps results still, with normalizaton consideration of course.

    So, Is it true that  the only way to do this is to get all the combinations in simulations(tools) and get the coefficients in a table?  

  • 2shine, 

    The coefficients can be calculated on the fly,  the coefficient calculator isn't doing anything special,  it uses the calculations that are described in the document I linked to. 

    can you explain where your calculations are going wrong?

    best regards,

    -Steve wilson