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Altera_Forum's avatar
Altera_Forum
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12 years ago

Drive leds with CPLD

Hello, sorry form my little question about currents.

I'm trying to reduce the components usage of an board using a CPLD.

I wan't to control buttons, leds and logic with a MAXV, but I'm not sure how many led's can I drive using it.

I have read from the device manual that it can drive +-25mA, but it's the absolute ratings, I have found the document "an286.pdf" where they mencion limits based on a table of "Maximum Source Current Per VCCIO Group" and "Maximum Sink Current Per GNDIO Group" but I cannot find this for the MAX V CPLD in the table netither in the dc caracteristic nor the website.

I hoped to put the CPLD output, an resistor and the LED to ground, ensuring that it drives 10mA and use like 20 leds, but i'm not sure if I going out of spec or not, and I'm not sure if it best this or connect to +3.3V and sink the current.

Hopping that you could give me some points, thanks

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Use sinking configuration. MaxV can handle 20mA per pin sinking without problem

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    --- Quote Start ---

    Use sinking configuration. MaxV can handle 20mA per pin sinking without problem

    --- Quote End ---

    Have any limits per bank in that configuration? In an286.pdf they tell 130mA per GNDIO Bank for the MAXII, but i can't find any information about this.

    Certanly I will not use too much leds, less than 20 so even that especification will be correct, but I would love to known the limits, if there is any, since in the MAXII they existed like is said in the an286.pdf
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    I have a MAXII board with 8 LEDs. They are from the same bank. I believe sinking current should not be problem at all.

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    As a first guess, I would assume that the AN286 specifications apply for MAX V as well.