AD9540/PCB Analog Devices Inc, AD9540/PCB Datasheet - Page 18

• Manufacturer Part Number: AD9540/PCB
• Description: BOARD EVAL CLK GEN SYNTH 48LFCSP
• Manufacturer: Analog Devices Inc

Specifications of AD9540/PCB

• Module/board Type: Evaluation Board
• For Use With/related Products: AD9540
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

AD9540
APPLICATION CIRCUIT DESCRIPTIONS
Dual Clock Configuration
In this loop, M = 1, N = 16, and R = 4. The DDS (direct digital
synthesizer) tuning word is also equal to ¼, so that the
frequency of CLOCK1’ equals the frequency of CLOCK 1.
Phase adjustments in the DDS provide 14-bit programmable
rising edge delay capability of CLOCK1’ with respect to
CLOCK1 (see Figure 32).
Optical Networking Clock
This is the AD9540 configured as an optical networking clock.
The loop can be used to generate a 622 MHz clock for OC12.
The DDS can be programmed to output 8 kHz to serve as a base
reference for other circuits in the subsystem (see Figure 33).
Fractional-Divider Loop This loop offers the precise frequency
division (48-bit) of the DDS in the feedback path as well as the
frequency sweeping capability of the DDS. Programming the
DDS to sweep from 24 MHz to 25 MHz sweeps the output of
the VCO from 2.7 GHz to 2.6 GHz. The reference in this case is
a simple crystal (see Figure 34).
CRYSTAL
25MHz
Figure 36. ISM Band Modulator (LO & Baseband Generation)
DRIVER
÷N
CML
REFIN
CLK2
CP_OUT
÷R
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DDS
AD9540
LPF
DAC
Direct Upconversion
The AD9540 is configured to use the DDS as a precision
reference to the PLL. Since the VCO is <655 MHz, it can be fed
straight into the phase frequency detector feedback.
LO and Baseband Modulation Generation
Using the AD9540 PLL section to generate LO and the DDS
portion to generate a modulated baseband, this circuit uses an
external mixer to perform some simple modulation at RF ISM
band frequencies (see Figure 36).
VCO
BPF
2.5GHz
TONE
(FC = 100MHz)
8-LEVEL FSK
BPF