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Lpc84x PWM max source clock frequency and duty_cycle

Question asked by Peter Ma on Jun 1, 2019
Latest reply on Jun 3, 2019 by jeremyzhou

    Im using lpc845-BRK to generate a PWM pluse, which need 250KHz frequency with high dutycycle accuracy. But 845 max clock is 30MHz, after approximate calculation I find that the dutycycle accuracy is 0.83%(250K/30M * 100%) and affirmed by oscilloscope. I have no find any PWM clock frequency multiplica.

    According to Lpc84x user manual(UM11029, page 122),' The loop filter filters these control signals and drives the current controlled oscillator (CCO), which generates the CCO clock. The CCO frequency range is 156 MHz to 320 MHz. This clock is divided by 2xP by theprogrammable post divider to create the output clock. '

Does user manual means that  I can use a clock which is the output clock of the CCO as PWM clock source? Or the clock source max frequency only is 30M, the CCO is not availble?    

If CCO can't be the source, is there any way to get a higher PWM clock source to increase the dutycycle accuracy?

 

Thanks for your help

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