EVAL-ADF4360-1EBZ1 Analog Devices Inc, EVAL-ADF4360-1EBZ1 Datasheet - Page 22

• Manufacturer Part Number: EVAL-ADF4360-1EBZ1
• Description: BOARD EVALUATION FOR ADF4360-1
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADF4360-1EBZ1

• Main Purpose: Timing, Frequency Synthesizer
• Embedded: No
• Utilized Ic / Part: ADF4360-1
• Primary Attributes: Single Integer-N PLL with VCO
• Secondary Attributes: 2.25GHz, 200kHz PFD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: Q4875592; Q5594761

ADF4360-1
PCB DESIGN GUIDELINES FOR CHIP-SCALE PACKAGE
The leads on the chip-scale package (CP-24) are rectangular.
The printed circuit board pad for these should be 0.1 mm
longer than the package lead length and 0.05 mm wider than
the package lead width. The lead should be centered on the pad
to ensure that the solder joint size is maximized.
The bottom of the chip-scale package has a central thermal pad.
The thermal pad on the printed circuit board should be at least
as large as this exposed pad. On the printed circuit board, there
should be a clearance of at least 0.25 mm between the thermal
pad and the inner edges of the pad pattern to ensure that short-
ing is avoided.
Thermal vias may be used on the printed circuit board thermal
pad to improve thermal performance of the package. If vias are
used, they should be incorporated in the thermal pad at a
1.2 mm pitch grid. The via diameter should be between 0.3 mm
and 0.33 mm, and the via barrel should be plated with 1 ounce
of copper to plug the via.
The user should connect the printed circuit thermal pad to
AGND. This is internally connected to AGND.
OUTPUT MATCHING
There are a number of ways to match the output of the
ADF4360-1 for optimum operation; the most basic is to use a
50 Ω resistor to V
nected in series, as shown Figure 21. Because the resistor is not
frequency dependent, this provides a good broadband match.
The output power in this circuit typically gives −6 dBm output
power into a 50 Ω load.
A better solution is to use a shunt inductor (acting as an RF
choke) to V
output power. Additionally, a series inductor is added after the
dc bypass capacitor to provide a resonant LC circuit. This tunes
the oscillator output and provides approximately 10 dB addi-
tional rejection of the second harmonic. The shunt inductor
needs to be a relatively high value (>40 nH).
VCO
Figure 21. Simple ADF4360-1 Output Stage
. This gives a better match and hence more
RF
VCO
V
VCO
OUT
. A dc bypass capacitor of 100 pF is con-
51Ω
100pF
50Ω
Rev. B | Page 22 of 24
Experiments have shown that Figure 22 provides an excellent
match to 50 Ω over the operating range of the ADF4360-1. This
gives approximately −4 dBm output power across the frequency
range of the ADF4360-1. Both single-ended architectures can be
examined using the EVAL_ADF4360-1EB1 evaluation board.
If the user does not need the differential outputs available on
the ADF4360-1, the user may either terminate the unused out-
put or combine both outputs using a balun. The circuit in
Figure 23 shows how best to combine the outputs.
The circuit in Figure 23 is a lumped-lattice-type LC balun. It is
designed for a center frequency of 2.2 GHz and outputs 1.0 dBm
at this frequency. The series 1 nH inductor is used to tune out
any parasitic capacitance due to the board layout from each
input, and the remainder of the circuit is used to shift the
output of one RF input by +90° and the second by −90°, thus
combining the two. The action of the 3.6 nH inductor and the
1.5 pF capacitor accomplish this. The 47 nH is used to provide
an RF choke in order to feed the supply voltage, and the 10 pF
capacitor provides the necessary dc block. To ensure good RF
performance, the circuits in Figure 22 and Figure 23 were im-
plemented with Coilcraft 0402/0603 inductors and AVX 0402
thin-film capacitors.
Alternatively, instead of the LC balun shown in Figure 23, both
outputs may be combined using a 180° rat-race coupler.
Figure 23. Balun for Combining ADF4360-1 RF Outputs
RF
RF
Figure 22. Optimum ADF4360-1 Output Stage
OUT
OUT
A
B
RF
V
VCO
OUT
1nH
1nH
V
VCO
47nH
1.5pF
3.6nH
1.5pF
3.6nH
1.5pF
3.9nH
47nH
50Ω
10pF
50Ω