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  1. #1
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    Pulse width modulation

    I have problem to make a pwm with high frequency and high resolution. I´m using a internal clock of 160 MHz and I get a pwm of 1.25 MHz and a resolution of 4 bits. I have made my pwm by using a comparator a ROM-table and 2 counters.

    How do I do to make a pwm with higher resolution och higher frequency?

    How is this made for example for pwm for audio, are they using more outputs to make more resolution?

    /Robin

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  2. #2
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    Pulse width modulation

    160 MHz to 1.25 MHz is a factor of 128 (7 bits). Why do you have only 4 bits?

    Audio outputs commonly use delta-sigma DAC techniques (not simple PWM) to get high amplitude resolution from a modest clock rate. Here's an introduction:
    http://www.beis.de/Elektronik/DeltaS...eltaSigma.html



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  3. #3
    Newbie level 4
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    Re: Pulse width modulation

    To create a 4 bit pwm with a compartor to compare a counter with a ROM-table it will be 7 bits lower frequency (if detecting on both falling and rising edge on the clk else it will be 8 bits). Se attachment "pwm_scheme" on the scematic.

    I hope it can be done in another way.

    I´m going to create a sinus (5-10 MHz) with as high resolution a possible.

    My internal clk alternative is max. 500-600 MHz.

    It seem that sigma delta modulation is for lower frequency, and by that it is possible to get higher resolution?

    /Robin



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