ADAU1401 MCLK and BCLK

Question

I am currently working on a project with the adau1401. I going to be using an spdif receiver connected to an ASRC and then to the ADAU1401. The ADAU1401 will be doing some filtering and outputting i2s to a set of three DACs. I'm having an issue conceptually. So, if the ADAU1401 is the master, then the BCLK pin will be outputting the MCLK rather than the BCLK and I need to find a way to create the BCLK? Or, would it be better to have an external clock generator create the master clock and the ADAU1401 will not be the master device?

CopperMaze · Accepted Answer

ADAU1401 serial audio input => LRCLK and BCLK are "slave" only. (datasheet p.46). I see some options: 
 - Generate MCLK with a dedicated chip and push that into both the ASRC and the ADAU1401, and use the ASRC to generate BCLK and LRCLK. 
 - Generate all the clocks needed between ASRC and ADAU on a dedicated clock generator chip (including MCLK). 
 - Use an ASRC with PLL able to generate its own MCLK from BCLK, and get BCLK and LRCLK from the ADAU1401 output. ADAU is making MCLK with an Xtal in this case.)

DaveThib · Answer

Hello Scorch, 
 We have used the CS8416 and it has a clock output which is 128x fs or 256 x fs once the PLL locks to the incoming signal. It also will also switch to a system clock if the PLL is not locked. 
 This is what should drive the master clock input of the DSP. 
 I did not look at the CS8412 but it looks like CopperMaze did. The key is you have to have a master clock that is derived from the incoming clock on the SPDIF signal. Then you will not need a sample rate converter because the DSP will just follow the sample rate of the incoming SPDIF signal. 
 The only problem is if you are planning on using higher sample rates above 48kHz. Then it starts getting tricky. 
 I also recommend you move to the ADAU145x family of parts with SPDIF and ASRCs built in. They are so much more powerful and you can do a lot more with them without the need of a controller. 
 Dave T

Partner Forums

Partner Libraries

Products Mentioned

Associated Drivers

ADAU1401 MCLK and BCLK