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Multi frequency Generation (40KHz to 48KHz) problem

Moinuddin Syed
Prodigy 30 points

I want to generate 40Hz to 48KHz sweep  for robotic car navigation . The codec TLC320AIC3204 supports these freuquencies, unfortunately The kit has 12MHz crystal               CB3LV-3C-12.0000-T which can support maximum 48KHZ  sampling frequency which turns out that maximum i can generate 22.1KHz safely (technically 24KHz but due to aliasing and filtering 22.1 is spectrally safe). One way is to change the crystal to higher frequency i.e MCLK of AIC3204 = 256*fs  which in my case comes out to be 25MHzcrystal sampling rate 96KHz . Since the 12Mhz clock is also fed to USB Controller in schematics, Is it possible to change the crystal . Does USB function correctly if we change crystal to higher frequency 25MHz or 50MHz

The Maximum clock internal pll can generate is 20Mhz which corresponds to 78KHz sampling rate.

 

 

Regards

Syed Moinuddin

 

 

 

  • 0
    TI__Prodigy 310 points

    Quite an interesting scenario. Which development board are you using?

    If you are using a C5515 or C5505 board, you should be able to generate a 25MHz or 50MHz (or other any other frequency up to 50MHz) from the DSP at the I2Sn_CLK signal using the CLKDIV bit field in the I2Sn Sample Rate Generator Register (I2SSRATE) and/or changing the System Clock. Then set your TLC320AIC3204 codec to use BCLK as clock source. 

    About the frequency sweep, the portable audio group should be able to help you out. Let me know how this goes and good luck!

  • 0 in reply to Nelson Vazquez
    Prodigy 30 points

    I am using C5505 EzDSP board