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LM49352

Gary Nacer
Prodigy 20 points

Hi,

I'm trying to use the LM49352 in Master mode (generates the clock and sync to my I2S interface).  From the documentation, it is not obvious how the port clocks and the converter clocks are related (or have to be configured).  Is there an app note on this?  Or some example?

For example:

I have a 6.144MHz Mclk, and I want an 8K sample rate, then I generate the clock for the DAC to be 2.048MHz (2*OSR*Fs).  Fine per document.

Now what should be the Port clock frequency?

I would expect the port output clock (master mode) to generate a frequency of 32*fs  (for 16-bit samples of L/R channels).  Does the port operating frequency = this or is it higher, or do I have apply interpolation,

Any help would be appreciated.

Thanks,

Gary

  • 0
    TI__Guru**** 189401 points

    Hi, Gary,

    Someone familiar with this device will be getting with you shortly. sorry for the delay.

    -d2

  • 0 in reply to Don Dapkus
    TI__Prodigy 380 points

    Hi Gary,

             I don't think we have an App Note in how to program the clocks for the Ports.  I'll double check and see what we have.  In the meantime, here is an example of how I set the clocks up on the bench using Fs=8kHz.

    Fs = 8kHz

    Sync = 2.048Mhz (Fs*256)

    Port Clock = 512khz (32 bits/channel; 16 bits data/ 16 bits padding)

  • 0 in reply to Gerardine S Ly
    Prodigy 20 points

    Hi Gerardine,

    Thanks.  It is exactly what I thought.  I programmed the port clock as per my original post:  that is, the clock rate on the port has to be equal to the sample rate * number of bits fetched.

    In my case, for 16 bits (stereo) @ 8K: port clock is 8K*16*2 = 256KHz

    Your case also works: 8K*32*2 = 512KHz.

    This, of course, is with Clock_Gen (0x52 or 0x62) @ 1/1.

    Hope this helps others.

    Thanks,

    Gary