AD9832_15 Datasheet, PDF (12/28 Pages) Analog Devices – 25 MHz Direct Digital Synthesizer

AD9832
THEORY OF OPERATION
Sine waves are typically thought of in terms of their magnitude
form a(t) = sin (ωt). However, these are nonlinear and not easy
to generate except through piecewise construction. On the
other hand, the angular information is linear in nature. That is,
the phase angle rotates through a fixed angle for each unit of
time. The angular rate depends on the frequency of the signal
by the traditional rate of ω = 2 πf.
MAGNITUDE
+1
0
–1
PHASE
2
0
Figure 23. Sine Wave
Data Sheet
Knowing that the phase of a sine wave is linear and given a
reference interval (clock period), the phase rotation for that
period can be determined by
ΔPhase = ωδt
Solving for ω,
ω = ΔPhase/δt = 2 πf
Solving for f and substituting the reference clock frequency for
the reference period (1/fMCLK = δt),
f = ΔPhase × fMCLK/2 π
The AD9832 builds the output based on this simple equation. A
simple DDS chip can implement this equation with three major
subcircuits.
Rev. E | Page 12 of 28