no PLL for the ESS DAC?

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Ivalentic
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no PLL for the ESS DAC?

Postby Ivalentic » Fri Jul 06, 2018 7:41 pm

Is it possible to create USB interface for the ESS DAC without PLL, using only 24MHz oscillator for the main processor clock?
The ESS DAC uses BCLK input to regenerate it's own MCLK, so it does not need external MCLK?
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mon2
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Postby mon2 » Sat Jul 07, 2018 1:08 am

Hi. Not an audio developer but can you be more specific about the reference design you are reviewing? Which PLL?

If you are referencing the xCORE-AUDIO Hi-Res 2 which is based on the Si5351A-B04486-GT then the short answer is no. The reason is that this PLL with this exact p/n was defined by XMOS and offers 3 output clocks and each such clock is of a unique value.

CLK2 is being fed into the ESS DAC and is of a value of 45.158400000 Mhz which is not an easy value to generate from 24 Mhz with precision. For the sake of your audio quality (bit rate sampling), use the clock value as defined by XMOS. Have seen some offshore products use fixed clocks to avoid using the PLL so that may be an option for you to consider but the more flexible idea is to consider the PLL so that you may change the clock values to suit using software (ie. XMOS is the I2C master). Best to review the source code of the XMOS IP to confirm if you can hard define the clock sources but 24 Mhz for the USB and audio dac does not sound practical.

Example of fixed clocks with XMOS audio solutions:

https://www.aliexpress.com/item/New-XU2 ... autifyAB=0
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Ivalentic
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Postby Ivalentic » Sat Jul 07, 2018 7:31 am

Hi! Thank you for the answer.
Our ESS DAC uses dedicated 100MHz clock. We don't need MCLK at all.
Ivalentic
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Postby Ivalentic » Sat Jul 07, 2018 8:01 am

We are referencing to xCORE-200-Multichannel-Audio-Platform.
We need only I2S output to ESS DAC, which uses BCLK input to regenerate it's own MCLK and has dedicated 100MHz low jitter oscillator.
Question is; does XCORE neccesery need MCLK clock MCLK_XCORE as in schematic on page 23, CORE-200-Multichannel-Audio-Platform-2V0-Hardware-Manual(1.4)?

Thank you in advance

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