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TLV320ADC3101: How to select parameters of PLL

Ruixin Feng
Intellectual 2445 points
Part Number: TLV320ADC3101


Hi team,

Accroding to datasheet ,PLL in TLV320ADC3101 has corresponding parameters as NADC, MADC, P, K(J,D), R.

1. What means of  ADC MAC engine clock referring to NADC (divider for the ADC MAC engine clock) ?

2. What are P,K,R representing for?

3. How can I make sure what number to selece as NADC, MADC, P, K(J,D), R besides its range?

4.How can I make sure IADC when filter mode equals to zero?

Thanks a lot!

Rayna

  • 0
    TI__Mastermind 30220 points

    Rayna,

    The PLL can seem a bit complicated at first.  There are PLL constraints to be aware of:

    Then Figure 28 (pg 24) pretty much gives you the information you are asking for. 

    PLL_CLK = PLL_CLKIN * (RxJ.D)/P

    ADC_FS *AOSR *MADC*NADC = ADC_CLKIN

    The major constraints to be aware of I've highlighted in red. 

    As you pointed out there is also the constraint for IADC:

    This constraint merely ensures that your clock is fast enough to run all of the instructions in the DSP. 

    you will know how many instructions you need by checking the Table:

    It is likely that you already know what your MCLK is and what your desired Fs is.  So work backwards from Fs to MCLK. observing the constraints. 

    best regards,

    -STeve Wilson

  • 0 in reply to Steve-Wilson
    TI__Intellectual 2445 points

    Hi Steve,

    Several questions:

    1. So after reaching the constraints above, NADC, MADC, P,K,R can be selected any value among their respective range?

    2. Could you please tell me what ADC MAC engine is?

    3. If I didn't choose processing blocks, what will the number of instructions be?

    Thanks

    Rayna

  • 0 in reply to Ruixin Feng
    TI__Mastermind 30220 points

    Rayna, 

    1. After meeting the constraints, the values cannot be ANY value.  They must be a value that allows that meets the constraints AND Generates the proper clock frequency from a specific MCLK.  

    2. MAC means the "Multiplier - Accumulator " this is a standard part of any processor.  Not sure why the Datasheet wanted to call this out rather than just saying the ADC DSP engine or something like that.  

    3. Even if you don't "choose" a processing block,  you choose the default one (processing block 1), OR if you are using Purepath studio then it gives you the number of instructions you are using in the resources window.  That being said PPS also takes care of setting up the clocks.

    best regards,

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    TI__Intellectual 2445 points

    Hi Steve

    Understood! Thanks a lot!

    Rayna