Is the schematic correct ?  the two outputs are connected  and the two inputs

Where do I find the other end of "FILTER OUT" ?

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  • 0
    •  Analog Employees 
    on Jun 15, 2021 4:21 PM in reply to izhmel

    Hello izhmel,

    Yes, they are pin and software compatible. 

    The ADAU1452 was produced first and so the ADAU1466 was designed to be compatible with the 1452. So any 1452 program will run with no changes and the pinouts are the same. 

    The 1466 has a few features and specs that are different. So if a 1466 program is using features that are not in the 1452 then it will be an issue. 

    Many of the added features of the Sigma350 parts are in the 88 pin versions like the 1467.

    Here is  list of the top of my head. Always refer to the datasheet if there are questions.

    The 1466 has more data and program memory.

    The SPDIF ports can run up to 192kHz fs

    The I2C port can operate up to 1MHz. 

    These are the most significant changes. 

    The 88 pin parts have even more differences but this is not what you are asking about. 

    Dave T

  • Where do I find OP_AMP_REF in the data sheet for the ADAU1466 ? the ADAU1452 shows the other end connected to an opamp , but the data sheet dos not show this EVAL-ADAU1466Z User Guide (Rev. 0) ( 

    Thanks in advance

  • 0
    •  Analog Employees 
    on Jun 18, 2021 3:26 PM in reply to izhmel

    Hello Izhmel,

    I may be confused as to what you are asking about? The ADAu1452 or the ADAU1466 datasheets will not show any of this because it has to do with interfacing with the codec so it will not be mentioned in the DSP datasheet. The AD1938 datasheet will show the op amps referenced to the CM (common Mode) pin of the codec. That is one way to do it but the other way to do it is to setup a divider between the the AVDD and ground. The purpose is to setup a virtual ground between the single ended power rail so you can use an op amp that uses differential power supplies. As long as the filter is cap coupled you do not have to have this reference voltage be exactly the CM voltage. 

    The Opamp you see in your screenshot is the virtual ground source.

    The way it is drawn does not make it obvious that the two 1K resistors are a divider to setup the voltage mid way then the op amps are setup as voltage followers to provide a low impedance drive. It is a dual op amp so each section drives different input filters which helps keep crosstalk to a minimum. 

    When you ask " where do I find OP_AMP_REF" do you mean on the actual hardware in front of you or in the schematic?

    Dave T

  • Yes the schematic . In the schematic data sheet of the ADAU1466  dose not show this in the schematic . The data sheet of the ADAU1452 shows this . I cant find the opamp ADA48412YRMZ for OP_AMP_REF in the  ADAU1466 data sheet . Are you saying I don't need this as shown in the image ?

    Thanks in advance