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Supply voltage for ADV7125 and decoupling of VREF pin

y_suzuki
on Apr 23, 2015

Hello,

I have two questions about ADV7125.

1. The VAA pin is described "Analog Power Supply(5V +/-5%)." in table-6 ,datasheet.

   But VAA is allowed 3.3V in Table-2. I think the "Analog Power Supply" contains not only 5V but also 3.3V.

   Is it true ?

2. About decoupling for VREF pin.

   In the ADV7123 datasheet(Rev.D), I can see following description in P.18 reference input section.

     "The VREF pin is normally terminated to VAA through a 0.1uF capacitor"

   ADV7125 should be same connection ?

   ADV7125 should not be connected to GND through 0.1uF capacitor ?

   I saw "https://ez.analog.com/message/165693#165693" and there is following comment.

     "The compensation loop is referenced to Vaa so the comp cap needs to be tied to Vaa."

   I assume that this comment describes about VREF pin.

   It is true ?

Regards,

ysuzuki

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  • 0
    •  Analog Employees 
    on Dec 17, 2015 5:22 AM

    Hi

    This might be repeated question.

    What is ADI recommended chircuit about ADV7123/7125 VREF pin when internal reference used?

    0.1uF decoulping to VAA was mentioned in the schematic of old datasheet and P18/24 of the latest datasheet

    but 1uF decoulping to GND when external ref(AD1580) used.

    Latest datasheet saying

    REFERENCE INPUT

    The ADV7123 contains an on-board voltage reference. The VREF pin is normally terminated to VAA through a 0.1 μF capacitor. Alternatively, the part can, if required, be overdriven by an external 1.23 V reference (AD1580).

    Regards,

    Tomoto

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  • 0
    •  Analog Employees 
    on Dec 17, 2015 5:22 AM

    Hi

    This might be repeated question.

    What is ADI recommended chircuit about ADV7123/7125 VREF pin when internal reference used?

    0.1uF decoulping to VAA was mentioned in the schematic of old datasheet and P18/24 of the latest datasheet

    but 1uF decoulping to GND when external ref(AD1580) used.

    Latest datasheet saying

    REFERENCE INPUT

    The ADV7123 contains an on-board voltage reference. The VREF pin is normally terminated to VAA through a 0.1 μF capacitor. Alternatively, the part can, if required, be overdriven by an external 1.23 V reference (AD1580).

    Regards,

    Tomoto

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