AD21489 and AD1937

Hi,

Is there any reference design of the Analog Devices DSP chip (AD21489) and Analog Devices CODEC (AD1937)?

By the way, I would like to confirm that the AD1937 can be configured so that the output is I2S. If can, how to set the serial data output to be I2S mode?

  • 0
    •  Analog Employees 
    on May 23, 2014 8:25 AM

    Hi,

    The ADSP-21489 EZ-Board design should be a good starting point, as it includes the AD1939 Audio CODEC. Although not an exact part match, it's essentially the same as what you are intending to implement.

    As for configuring the device for I2S serial transmission, the "Power On Self Test" code example provided with the ADSP-21489 Board Support Package should be of help.

    For more info, please refer to the evaluation board product page: http://www.analog.com/en/evaluation/21489-ezlite/eb.html

    Best regards,

    MKB

  • 0
    •  Analog Employees 
    on May 23, 2014 6:52 PM

    Hello cklooi,

    I am the applications engineer for the AD1937 family of parts so I can comment further on the use of this part. The AD1937 and the AD1939 is the same part with the only difference is that one is controlled via I2C and the other is SPI. The audio performance will be the same and the register settings will be the same.

    Setting up the ADC for I2S is actually quite easy. The default values upon power-up is for the ADC control registers 0,1 and 2 to be all zeros. This is for I2S stereo, 32/44.1/48kHz operation and in slave mode. So all that needs to be done is to power up the part, enable the ADC and DAC by writing 0x80 to PLL and Clock Control 0 Register, and supplying clocks to the ADC.

    Since you mentioned using the ADSP-21489 EZ board as a design reference I feel I need to mention a problem with the implementation of the board. The net that is named AD1939_VREF is used as a reference in many places in this design. The source of the VREF is shown on sheet 9 of the schematic and is two resistors dividing the 5V power rail. This is not a proper low impedance reference and so there is a lot of crosstalk present on this board. The best way to create a reference is to use the CM pin (common mode) of the AD1939 and feed that signal to a low noise JFET Op-Amp setup as a voltage follower to then be used as a voltage reference for the rest of the circuit. 

    Best Regards,

    Dave T.