Analog Circuits Cookbook

80 Analog Circuits Cookbook

from the accumulator to the sine look-up ROM is (say) 10, then F^/1024

is one of these good frequencies as is

F

c

[

ock

/5l2,

and 7^/7256, all three

frequencies falling in the binary submultiple series mentioned above. At

these frequencies, the phase passed to the ROM advances on each clock

cycle by

2n/2

p

,

by twice this amount and by four times this amount

respectively But likewise, the phase increment is constant on every clock

cycle when it advances by three, five or any other constant whole number

multiple of

2n/2

P

.

So potentially there are 2

P

frequencies free of phase

modulation spurs, less if you discount those