ADAU1442 Power

I'm confused on what "DVDD" needs to be to the ADAU1442.  The data sheet says 1.8 volts.  So on my layout I have it connected to +1.8 volts.  But then I was going to connect some pullups on the "PLLx" and "CLKMODEx" pins.  The data sheet shows these connected to DVDD but 1.8 volts does not meet Vin High Min for the digital I/O.  Then I looked at the EVAL board schematic and they have DVDD and PVDD (+3.3V) tied together.  Also I measured DVDD on the EVAL board and it measures 3.3 volts????  Is the data sheet wrong?

Message was edited by: Roger Leopold I see what's confusing me now.  On the Eval. Board (UG-032) there is a supply labeled "DVDD" but this does not power the "DVDD" pins (Figure 45, page 24).  I measured the power on the "DVDD" supply and it's 3.3 volts.  I measured the "DVDD" pins and they measure 1.8 volts. On the Data Sheet the supply connected to the "DVDD" pins is labeled "DVDD" (Figure 64, page 89). So a little confusing but I see that these pins should be +1.8 volts now. One other point.  On the Data Sheet the "Selfboot" pin is pulled up to "DVDD" - which is +1.8 volts here.  This would not meet Vin High Min..  On the Eval Board this signal is pulled up to +3.3 volts which seems correct.

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    •  Analog Employees 
    on Jun 3, 2013 11:35 PM

    Hello, I'm moving this to the SigmaDSP forum since it is a question about SigmaDSP hardware.

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    •  Analog Employees 
    on Jun 3, 2013 11:46 PM

    The evaluation board unfortunately uses some slightly confusing nomenclature. For some reason, "DVDD" was selected as the name for the board supply of 3.3 V, which powers the ADAU1442's AVDD, PVDD, and IOVDD pins, as well as the other ICs on the board like the AD1938 CODECs. The DVDD pin on the ADAU1442, on the other hand, is the DSP core supply, which should be 1.8 V. We have been much more aware of net naming conventions on our newer evaluation boards, where we name nets by explicitly stating the associate IC (for example, AD1938_DVDD is the DVDD pin of an AD1938) or by labeling the exact voltage (for example, BOARD_3V3 = the 3.3 V board supply).

    In any case, let me try to answer your questions as clearly as possible.

    • The ADAU1442's DVDD (DSP core supply) pin should be connected to 1.8 V.
      • You can supply 1.8 V directly from an external supply if it is available; just ground the VDRIVE pin when doing so.
      • You can alternatively have the ADAU1442 derive 1.8 V from its own 3.3 V supply using an external pass transistor. Figure 12 in the datasheet shows how to do this.
    • The ADAU1442's AVDD, PVDD, and IOVDD pins should be connected to 3.3 V.
    • All digital inputs to the ADAU1442 (including the PLLx and CLKMODEx pins) should be connected to either ground or IOVDD (3.3 V).
  • Yes that's what was confusing me.  Thank you for your time.