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Thread: Audio Board Voltage Regulator?

  1. #1
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    Audio Board Voltage Regulator?

    Hi all,

    I happened to be looking at the schematic for the audio board and got curious about the voltage regulator. I had a look at one of the ones I have handy and based on the markings I believe it's a 1.8V regulator. This also matches some of the other anecdotal info I've seen around.

    So my question is...why a 1.8V supply to the SGTL5000? Is it to better match it to line level signals?

  2. #2
    Member houtson's Avatar
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    As far as I know, the 1.8V supply is for VDDD, text below from the Datasheet, the max for VDDD is 2.0V-

    The SGTL5000 requires 2 external power supplies: VDDA and VDDIO. An optional third external power supply VDDD may be provided externally to achieve lower power. This external VDDD power supply is required for new designs. A description for the different power supplies is as follows:
    VDDA: This external power supply is used for the internal analog circuitry including ADC, DAC, LINE inputs, MIC inputs, headphone outputs and reference voltages. VDDA supply ranges are shown in Maximum Ratings. A decoupling cap should be used on VDDA, as shown in the typical application diagrams in Typical Applications.
    VDDIO: This external power supply controls the digital I/O levels as well as the output level of LINE outputs. VDDIO supply ranges are shown in Maximum Ratings. A decoupling cap should be used on VDDIO as shown in the typical application diagrams in Typical Applications.
    Note that if VDDA and VDDIO are derived from the same voltage, a single decoupling capacitor can be used to minimize cost. This capacitor should be placed closest to VDDA.
    VDDD: This is a digital power supply that is used for internal digital circuitry. An external VDDD power supply is required for new designs. For lowest power, this supply can be driven at the lowest specified voltage given in Maximum Ratings. If an external supply is used for VDDD, a decoupling capacitor is recommended, as shown in the typical applications diagram. VDDD supply ranges are shown in Maximum Ratings for when externally driven. If the system drives VDDD externally, an efficient switching supply should be used or no system power savings is realized.

  3. #3
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    Interesting, thank you for that!

  4. #4
    Senior Member PaulStoffregen's Avatar
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    I've never quite understood what they meant by "required for new designs" in the datasheet. But it said that back in 2014 when I designed the audio shield, so I put that regulator chip on the PCB.

  5. #5
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    Hah, I was wondering about that too! Given that the voltage range is different for that vs the VDDIO, I can't imagine what would happen if you didn't power it.

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