AD7008

REV. B

–15–

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.

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.

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.

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.

Clock rates up to 20 MHz and 50 MHz are supported. Fre-

quency accuracy can be controlled to one part in four billion.

+5V

SOFTWARE

PROVIDED

POWER

SUPPLY

INTERFACE

EXTERNAL

POWER

SUPPLY

STANDARD

PRINTER

CABLE

IBM-COMPATIBLE PC

AD7008

50MHz

CMOS DDS

INTERFACE

LOGIC

50

Ω CABLE

SPECTRUM ANALYZER

AD7008 DDS EVALUATION BOARD

OPTIONAL

TTL CLOCK

REFERENCE

GENERATOR

CLOCK

OSCILLATOR

Figure 35. AD7008 DDS Evaluation Board Setup

Table IV. AD7008/PCB Typical Electrical Characteristics

(Nominal power supplies, CLK = 50 MHz)

Typical

Characteristics

Value

Units

+5.0 V Supply Current

125

mA

AD7008 Output Voltage

0 to +1.0

V

(Terminated into 50

Ω Externally)

CMOS clock input HIGH

4.1 to 5

V

CMOS clock input LOW

0.0 to 0.5

V

USING THE AD7008/PCB DDS EVALUATION BOARD

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

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

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.

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.

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.

AD7008/PCB BILL OF MATERIAL

Quantity

Reference

Description

1

C1

Tag – Tant Cap, 10

µF, 35 V, 20%

8

C2–C9

Cer Chip Cap, 0.1

µF, Murata

Grm42

6

CLOCK, FSEL SMB – Submin Snap-on (Male)

PCB MT Plug

SCLK, SDATA

1

FSADJ

RN55 – Res Met Film, 392

1

LK1

HDR SIP 3-Pin Male

1

Shunt 530153-2

1

P1

36-Pin D Conn Rt Ang Pcmt

Fem AMP

1

P2

PC Voltage Ter Blk w/Screws

Augat RDI

3

R1–R3

RN55 – Res Met Film, 10k

2

R4, R5

RN55 – Res Met Film, 49.9

1

RZ1

10P Bussed Res Ntwk, 10k

CSC10A01103G

1

RZ2

6P Bussed Res Ntwk, 4.7k

CSC06A01472G

1

U1

AD7008 JP50 CMOS DDS

Modulator

1

U2

74HC74 – Dual D-type Pos-Ed-

Trigd Flip-Flop

Pin Terminal, Testpoint

1

XTAL

OSC XTAL, Fox F1100H

50 MHz

1

Socket, Methode 213-044-501

4

Support, Nylon

1

PCB, 48295(-)

26

Pin Sockets, Closed End