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AD1941 i2c with USBi programmer


Just wondered if the USBi programmer can supply the clock to the AD1940 / 1 to initialize the chip or if I need to supply an additional external mclk ? I see on the schematic of the USBi there is a 24mhz crystal but it doesn't quite divide into the 48khz or 96khz x FS clock speed I would select on the PLL pins of the IC.

I guess I'll hook another clock from a codec and see if that works. chip not initializing with USBi alone.

just thought someone might know the answer already ? the Eval boards are using the master clocks generated from Codecs it seams.

thanks , ben

  • Hello Ben,

    The USBi cannot and should not supply the clocks to run the part. The MCLK needs to be there always and so you do not want to run it from a board that will be disconnected. So yes, there should be MCLK on the board.

    I am not sure exactly which eval board you have but I just opened up the schematic to the latest revision and J1 is the selector for the MCLK source. You can select the 1939 codec as a source or you can select the SPDIF receiver as a source. There are also headers for external sources.

    So if you cannot initialize the part, then check that there is MCLK on TP1, then check to make sure all the power supplies are connected (jumped) because there are jumpers to allow you to use external sources or make current measurements. If all looks good then I will ask more questions.

    Dave T

  • Hi Dave, I'm not using an Eval board, just the 1941 chip on a proto board and the USBi as I2C master.. OK, so I just need to add a clock source I think and sleect the correct PLL multiplyer options with PLL_CTRL0 1 & 2.

    Thanks for reply,  BEN

  • Just to say the chip is now working. I set the PLL_CTRL with a 10k resistor to correct multiplyer for FS and added the master clock. now I can program the chip with the USBi board.