EVAL-AD9838SDZ Analog Devices Inc, EVAL-AD9838SDZ Datasheet - Page 14

• Manufacturer Part Number: EVAL-AD9838SDZ
• Description: EVALUATION BOARD
• Manufacturer: Analog Devices Inc
• Series: -r

Specifications of EVAL-AD9838SDZ

• Main Purpose: Timing, Direct Digital Synthesis (DDS)
• Embedded: No
• Utilized Ic / Part: AD9838
• Primary Attributes: USB Powered or External Supply
• Secondary Attributes: SPI Interface
• Kit Application Type: Clock & Timing
• Application Sub Type: Clock Generator
• Kit Contents: Software CD, USB Cable
• Silicon Manufacturer: Analog Devices
• Silicon Core Number: AD9838
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

AD9838
THEORY OF OPERATION
Sine waves are typically thought of in terms of their magnitude
form: a(t) = sin(ωt). However, sine waves 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 = 2π f .
2
+1
–1
28
0
0
Figure 20. Sine Wave
2π
2π
MAGNITUDE
PHASE
4π
4π
6π
6π
Rev. A | Page 14 of 32
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 as follows:
Solving for ω,
Solving for f and substituting the reference clock frequency for
the reference period (1/f
The AD9838 builds the output based on this simple equation. A
simple DDS chip can implement this equation with three major
subcircuits: numerically controlled oscillator (NCO) plus phase
modulator, SIN ROM, and digital-to-analog converter (DAC).
Each subcircuit is described in the Circuit Description section.
ΔPhase = ω Δ t
ω = Δ Phase/ Δ t = 2 πf
f = Δ Phase × f
MCLK
∕2 π
MCLK
= Δt),
(1)
(2)
(3)