AD7008
AD7008/PCB DDS EVALUATION BOARD
The AD7008/PCB DDS Evaluation Board allows designers to
evaluate the high performance AD7008 DDS Modulator with a
minimum amount of effort.
necessary software. This data sheet provides information on
operating the evaluation board; additional details are available
from the ADI technical assistance line 1-800-ANALOGD.
Prototyping Area
To prove this DDS will meet the user’s waveform synthesis re-
quirements, the only things needed are the AD7008/PCB DDS
Evaluation Board, +5 V power supply, an IBM-compatible PC,
and a spectrum analyzer. The evaluation setup is shown below.
An area near one edge of the board is intentionally left void of
components to allow the user to add additional circuits to the
evaluation test set. Users may want to build custom analog fil-
ters for the outputs, or add buffers and operational amplifiers
used in the final applications.
The DDS evaluation kit includes a populated, tested AD7008/
PCB board; software which controls the AD7008 through the
parallel printer port in a DOS or Windows environment and an
AD7008P.
XO vs. External Clock
The reference clock of the AD7008/PCB is normally provided
by a 50 MHz CMOS oscillator. This oscillator can be removed
and an external CMOS clock connected to CLOCK. If an ex-
ternal clock is used, a 50 Ω resistor R6 should be installed.
The AD7008 direct digital synthesis chip is a numerically
controlled oscillator employing a 32-bit phase accumulator, sine
and cosine look-up tables, and a l0-bit D/A converter integrated
on a single CMOS chip. Modulation capabilities are provided
for phase modulation, frequency modulation, and both in-phase
and quadrature amplitude modulation suitable for SSB
generation.
Power Supply
Power for the AD7008/PCB must be provided externally
through the pin connections, as described in the Inputs/Outputs.
The power leads should be twisted to reduce ground loops.
Clock rates up to 20 MHz and 50 MHz are supported. Fre-
quency accuracy can be controlled to one part in four billion.
AD7008/PCB BILL OF MATERIAL
Quantity Reference
Description
EXTERNAL
POWER
SUPPLY
1
8
C1
Tag – Tant Cap, 10 µF, 35 V, 20%
C2–C9
Cer Chip Cap, 0.1 µF, Murata
Grm42
OPTIONAL
POWER
CLOCK
TTL CLOCK
REFERENCE
GENERATOR
+5V
6
CLOCK, FSEL SMB – Submin Snap-on (Male)
SUPPLY
OSCILLATOR
INTERFACE
I
OUT, IOUTN
PCB MT Plug
SCLK, SDATA
AD7008
50MHz
CMOS DDS
INTERFACE
LOGIC
1
1
1
1
FSADJ
RN55 – Res Met Film, 392
HDR SIP 3-Pin Male
Shunt 530153-2
STANDARD
PRINTER
CABLE
LK1
AD7008 DDS EVALUATION BOARD
50Ω CABLE
P1
P2
36-Pin D Conn Rt Ang Pcmt
Fem AMP
SOFTWARE
PROVIDED
1
PC Voltage Ter Blk w/Screws
Augat RDI
IBM-COMPATIBLE PC
SPECTRUM ANALYZER
3
2
1
R1–R3
R4, R5
RZ1
RN55 – Res Met Film, 10k
RN55 – Res Met Film, 49.9
10P Bussed Res Ntwk, 10k
CSC10A01103G
Figure 35. AD7008 DDS Evaluation Board Setup
Table IV. AD7008/PCB Typical Electrical Characteristics
(Nominal power supplies, CLK = 50 MHz)
1
1
RZ2
U1
6P Bussed Res Ntwk, 4.7k
CSC06A01472G
AD7008 JP50 CMOS DDS
Typical
Characteristics
Value
Units
Modulator
1
U2
74HC74 – Dual D-type Pos-Ed-
Trigd Flip-Flop
+5.0 V Supply Current
125
0 to +1.0
mA
V
AD7008 Output Voltage
(Terminated into 50 Ω Externally)
CMOS clock input HIGH
CMOS clock input LOW
1
1
VREF
Pin Terminal, Testpoint
4.1 to 5
0.0 to 0.5
V
V
XTAL
OSC XTAL, Fox F1100H
50 MHz
1
Socket, Methode 213-044-501
USING THE AD7008/PCB DDS EVALUATION BOARD
4
Support, Nylon
The AD7008/PCB evaluation kit is a test system designed to
simplify the evaluation of the AD7008 50 MHz Direct Digital
Synthesizer. Provisions to control the AD7008 from the printer
port of an IBM-compatible PC are included, along with the
1
PCB, 48295(-)
26
Pin Sockets, Closed End
REV. B
–15–
ADI [ ADI ]
