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am335x ADPLLS formulas

David Monts
Prodigy 30 points

In the TRM, Table 8-17 shows the formula for CLKDCOLDO = 2 * [M / (N + 1)] * CLKINP. However, in the diagram (Figure 8-8), I can not find out where the (x2) comes from. The x2 is also why for CLKOUT, we don't divide by 2 as Figure 8-8 shows happening before CLKOUT enters the mux. It is really just for informational purposes, but it would be great to know where the x2 comes from.

Thanks.

David

  • 0
    TI__Guru*** 125430 points

    Here's a markup showing where it comes from:

    Note that since this "1/2" is in the feedback path of the PLL, it has the end effect of making the resulting frequency twice as fast.  The 1/M2 and and 1/2 following it are NOT in the feedback path and so those are functioning as frequency dividers.