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Altera_Forum
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14 years ago

question about IO status while power up for MAX II EPM1270

for MAX II EPM1270

For the weak pull-up resistor during power up,IO will show a high voltage(3.3V).I want to make IO show a low voltage by adding a pull-down resistor.what is the appropriate resistor value for it? 5000ohm will be ok? Thank you.

上电时由于weak pull-up resistor ，IO输出很短的高电平。若通过加下拉电阻拉使之一直保持低，那需加多大的下拉电阻？

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  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    14 years ago

    Please do not multipost your question.

    The datasheet should give you the lowest possible value for the weak pull-up in the Max II. When you add a pull down you create a resistor divider, and depending on the voltage you want to reach (<0.8V for a TTL signal, as an example) it will give you the highest possible value for the pull down.