Connect several PCM1808 to ADAU1701

Hello everyone,

I'm trying to connect several PCM1808 AD converters to an ADAU1701. Can anybody tell me how the connections have to be made? And can the MCLK of the PCM1808 directly connected to the ADAU1701 clock? I have tried several combinations, but for some reason i get only static noise. Thank you!

  • 0
    •  Analog Employees 
    on Jun 17, 2021 9:12 PM

    Hello Audiodude,

    You have to connect the serial data output of the PCM1808 to the MP0 pin 

    You have to connect the LRCLK ( sample rate clock) to MP4 pin.

    You have to connect the Bit Clock to the MP5 pin.

    Either both the PCM1808 and the ADAU1701 are running off of the same master clock or the PCM1808 has to send out the master clock. 

    The master clock needs to be at the correct frequency and the PLL Mode pins need to be properly setup. Look at table 12 in the datasheet. 

    The PCM1808 needs to be the clock master for the LRCLK and the BITCLK. 

    It is easiest at first to just use standard I2S signals. Go to TDM later if you need more than two channels. 

    I2S is the following:

    50/50 duty cycle LRCLK

    32 bit wide channel slots so there are 64 bits for each sample period. This means that the bitclock MUST be 64 x fs. ( fs being the LRCLK)

    If you are using fly-wires to connect the two you will have more luck and less clicks and pops if you run a ground wire with each of these clock signals. If you use a ribbon cable this is a bit easier to do. Then keep the wires as short as possible. 

    Use 48kHz sample rate at first. Do not try to use 192kHz or even 96kHz at first especially. Learn to walk before you run. 

    Dave T