External SPI Delay on ADAU1452

I'm looking to design 4 channel DSP with the ADAU1452. I want/need 400ms of Delay per channel, sampling at 96kHz. 

Can I use the internal delay for 1 channel and add an external SPI SRAM for the other 3 channels of delay?

I've seen comments to other questions in the forum that SigmaStudio only supports 1 instance of external delay, has there might be a software update to fix that?

and can I use an external delay that's 4Mb (512Kx8), or is it only designed to work with the microchip 23LC1024?

Thanks!

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  • +1
    •  Analog Employees 
    on Mar 19, 2019 9:51 PM

    Hello wachtman,

    The SPI delay has been updated/fixed to support multiple SPI memories (multiple instances) and also multiple channels for each instance. It will be released with the Rev 4.3 which I think now is stated to release in April. But don't quote me on that. (I am often the last to know) 

    To handle four channels of data at 96kHz fs will require a SPI speed that is above the max. I roughly calculated over 21MHz and the max is 20MHz. It will probably work but there might be issues with some parts. Also your PCB layout will be important and make sure there is plenty of current for the IOVDD. There is a note in the datasheet about it. Although, it does say to run at 1.8V for less current but then the timing margins will suffer so I would not go to 1.8V in my opinion. Stick with 3.3V and keep transmission lines short so you can keep the drive strengths low. 

    So if you can keep one of them internal, like you said, then you will be fine. The 1452 has 800ms at 48kHz. but this is if you use hardly any of the memory for the program and parameters. So depending on how much you are doing in the DSP you will probably not have enough memory for 400ms of delay at 96kHz. The solution would be to go up to the ADAU1466 which has twice the memory and also have more program memory that can be used for delays. So with that part I think you will be good. The 1466 is pin compatible with the 1452. This is really pushing the envelope and testing the delay capabilities. Keep us informed on how the project is progressing!  

    Thanks,

    Dave T

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