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TI Home » TI E2E Community » Support Forums » Digital Signal Processors (DSP) » DaVinci™ Video Processors » DM814x and AM387x Processors Forum » DM8148 EVB VTT pull up capacitor
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DM8148 EVB VTT pull up capacitor

DM8148 EVB VTT pull up capacitor

This question is not answered
daniel sun
Posted by daniel sun
on Apr 15 2012 21:15 PM
Prodigy45 points

Dear Sir

Please check VTT terminal side In DM8148 EVB DDR address line
, why we need to tie these extra 0.1uf to VDDQ_1.5V between VTT rail ?

DM8148 EVB
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  • Steve Clynes
    Posted by Steve Clynes
    on Apr 16 2012 13:59 PM
    Mastermind23430 points

    These capacitors are there to ensure that transitions on the address lines do not cause noise on the VTT voltage.

    BR,

    Steve

    Please mark this post as answered via the Verify Answer button below if you think it answers your question.  Thanks!

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  • David Liang
    Posted by David Liang
    on Dec 04 2012 20:44 PM
    Prodigy10 points

    Dear Sir:

    Why not connect these capacitors to GND for noise issue?Thanks.

    David

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  • Biser Gatchev-XID
    Posted by Biser Gatchev-XID
    on Dec 05 2012 05:29 AM
    Mastermind27965 points
    Hi David,
     
    please check this thread for explanation: https://e2e.ti.com/support/dsp/davinci_digital_media_processors/int-dm814x/f/720/t/203543.aspx?Redirected=true
    Best Regards
    Biser

    Note:  If this answer solves your question please mark post as "Answered"

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  • Steve Clynes
    Posted by Steve Clynes
    on Dec 05 2012 08:52 AM
    Mastermind23430 points

    For AC signals it does not matter whether the capacitor is connected to GND or VCC since, for AC signals, VCC and GND provide the same impedance.

    It does not really have anything to do with sourcing the voltage hence needing VCC, it is really about impedance. The resistors source the charge but the capacitors store it.

    BR,

    Steve

    Please mark this post as answered via the Verify Answer button below if you think it answers your question.  Thanks!

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