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TI Home » TI E2E Community » Support Forums » Power Management » Sequencers » Sequencers Forum » Wdi decoupling in TPS3823-33
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Wdi decoupling in TPS3823-33

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ofer nisan
Posted by ofer nisan
on Nov 15 2011 08:04 AM
Prodigy30 points

Hi

Can you clarify what do you mean by "

, do we need to decoupling it?edge connects to the CPU output and during reset can change at least once at the reset wdiWDI pin may be active (transitioning high and low) when the TPS3820/3/4/8 is asserting RESET" ,in the typical application

TPS3823-33 wdi decoupling
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  • Michael Day
    Posted by Michael Day
    on Nov 15 2011 08:44 AM
    Verified Answer
    Verified by Michael Day
    Mastermind36070 points

    I assume you are asking about the wording in the Description paragraph on page two of the datasheet.  This means that you can NOT apply a changing WDI signal to the TPS3820 if the IC is in reset.  You must disconnect the WDI signal to the IC when /RESET is low.  If you apply a changing WDI signal when /RESET is low, the /RESET pin can latch low even if VDD goes above the threshold to pull the IC out of reset.

      Note the existing question about the TPS3820 WDI pin.

    http://e2e.ti.com/support/power_management/svs_and_sequencers/w/design_notes/tps3820-watchdog-question.aspx

    TPS3820 WDI watchdog TPS3823 tps3825 TPS3826 TPS3824
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  • ofer nisan
    Posted by ofer nisan
    on Nov 15 2011 09:26 AM
    Prodigy30 points

    Hi Michael

    Thanks for the feedback

    Not clear what do you mean by the pin can latch low , do you mean latch for ever?

    My concern is that in typical application when the wdi input connects to a CPU IO output  on the reset edges the wdi signal might change, can this lead to an ever reset state?

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  • Michael Day
    Posted by Michael Day
    on Nov 15 2011 09:31 AM
    Mastermind36070 points

    Yes, latch low forever until you disconnect and reapply power to the IC.

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