EVAL-AD9838SDZ Analog Devices Inc, EVAL-AD9838SDZ Datasheet - Page 6

• 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

UG-268
SELECT EXTERNAL MCLK FREQUENCY
Having selected the digital interface specifics, next use the
EXTERNAL MCLK box to choose which frequency to use. The
boards are supplied with a 75 MHz general oscillator. If a different
clock source is required, the CLK1 SMB connector can be used
to supply a different MCLK value.
Two options for the general oscillator include the AEL3013
oscillators from AEL Crystals and the SG-310SCN oscillators
from Epson Electronics.
PROGRAMMING METHOD: HARDWARE OR
SOFTWARE
Functions that select frequency and phase registers, reset
internal registers, and power down the DAC can be implemented
using either software or hardware. Figure 7 shows how to select
the source of control for these functions. PIN/SW = 1 implies
that the functions are being controlled using the appropriate
hardware control pins. PIN/SW = 0 implies that the functions
are being controlled using the appropriate software control bits.
LOADING FREQUENCY AND PHASE REGISTERS
The desired output frequency and output phase can be loaded
using the inputs shown in Figure 8. Either the FREQ 0 register or
the FREQ 1 register can be loaded with frequency data. The
frequency data is loaded in megahertz, and the equivalent hex code
is shown to the right once data is entered; click Enter to load
data. Once data is loaded, the output appears on the IOUT1 and
IOUT2 pins. Similarly, either the PHASE 0 register or PHASE 1
register can be selected, and the phase data is loaded in degrees.
Figure 6. EXTERNAL MCLK Input
Figure 7. Programming Method
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The analog output frequency from the
where FREQREG is the value loaded into the selected frequency
register in decimals. This signal is phase shifted by
where PHASEREG is the value contained in the selected phase
register in decimals.
FSK AND PSK FUNCTIONALITY
In software mode, the AD9838 can be set up for FSK or PSK
functionality by simply entering the bit rate in milliseconds
and selecting the push-button option (see Figure 9).
WAVEFORM OPTIONS
The output waveform can be selected as a sinusoidal waveform
or a ramp waveform. The internal comparator in the AD9838
can be disabled or enabled (see Figure 10). The MSB or the
MSB/2 of the phase accumulator can be selected as the output
on the SIGN BIT OUT pin.
f
2π/4096 × PHASEREG
MCLK
/2
28
Figure 10. Waveform Profile and SIGN BIT OUT Pin
× FREQREG
Figure 8. Frequency and Phase Load
Figure 9. FSK and PSK Functionality
Evaluation Board User Guide
AD9838
is defined by