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    Driving 15 LEDs with AT89C4051

    The datasheet says I can drive LEDs directly on the ports but I'm not sure if it really supports driving 8 LEDs per port at the same time. Do both drivers cut off as soon as a peak of 100mA (per port) are reached? I haven't found any notice on the total power consumption in the datasheet.

    As this is my first post I'm not allowed to post links. Google for AT89C4051 if you wanna have a look in that datasheet.

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  2. #2
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    Re: Driving 15 LEDs with AT89C4051

    As far as I can see you can drive 8 LEDs at the same time but should stick to 20mA per LED. Also, you need a current limiting resistor on each LED. The power will be dissipated in the LED and resistor, not the micro, so there shouldn't be an issue with maximum current/power of the micro.

    Keith.



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    Re: Driving 15 LEDs with AT89C4051

    I've just seen the note "Maximum total I for all output pins: 80 mA" so it won't work for this type of controller. Looking for another one.



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    Re: Driving 15 LEDs with AT89C4051

    @reimer why you are sourcing current try sinking



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    Re: Driving 15 LEDs with AT89C4051

    Quote Originally Posted by reimer View Post
    I've just seen the note "Maximum total I for all output pins: 80 mA" so it won't work for this type of controller. Looking for another one.
    Personally I don't see that as an "absolute maximum rating". It is Note 1. to the VOL specification. So, my interpretation would be that if you drew more than 80mA total the output would not meet the guaranteed 0.5V at 20mA.

    Keith.



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  6. #6
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    Re: Driving 15 LEDs with AT89C4051

    why not time multiplex led( turn on one led at a time for a very short duration ) this way you save power and never exceed the chip/port driving capability

    Asimov



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