ADL5330 Analog Devices, Inc., ADL5330 Datasheet - Page 14

• Manufacturer Part Number: ADL5330
• Description: 10 Mhz To 3 Ghz Vga With 60 Db Gain Control Range
• Manufacturer: Analog Devices, Inc.

ADL5330
RF INPUT/OUTPUT INTERFACE
The ADL5330 is primarily designed for differential signals;
however, there are several configurations that can be
implemented to interface the ADL5330 to single-ended
applications. Figure 33 to Figure 35 show three options for
differential-to-single-ended interfaces. All three configurations
use ac-coupling capacitors at the input/output and RF chokes at
the output.
Figure 33 illustrates differential balance at the input and output
using a transformer balun. Input and output baluns are recom-
mended for optimal performance. Much of the characterization
for the ADL5330 was completed using 1:1 baluns at the input
and output for single-ended 50 Ω match. Operation using
M/A-COM ETC1-1-13 transmission line transformer baluns
is recommended for a broadband interface; however, narrow-
RFIN
RFIN
ETC1-1-13
Figure 33. Differential Operation with Balun Transformers
Figure 34. Single-Ended Drive with Balanced Output
100pF
100pF
100pF
100pF
INHI
INLO
INHI
INLO
ADL5330
RF VGA
RFIN
ADL5330
RF VGA
OPLO
OPHI
OPLO
OPHI
C
120nH
i
120nH
C
i
L
L
i
+5V
i
+5V
C
100pF
100pF
120nH
i
C
100pF
100pF
120nH
i
Figure 35. Differential Operation with Discrete LC Baluns
ETC1-1-13
ETC1-1-13
100pF
100pF
C
ip
RFOUT
RFOUT
INHI
INLO
Rev. A | Page 14 of 24
ADL5330
RF VGA
OPLO
OPHI
120nH
band baluns can be used for applications requiring lower
insertion loss over smaller bandwidths.
The device can be driven single-ended with similar
performance, as shown in Figure 34. The single-ended input
interface can be implemented by driving one of the input
terminals and terminating the unused input to ground. To
achieve the optimal performance, the output must remain
balanced. In the case of Figure 34, a transformer balun is used at
the output.
As an alternative to transformer baluns, lumped-element baluns
comprised of passive L and C components can be designed at
specific frequencies. Figure 35 illustrates differential balance at
the input and output of the ADL5330 using discrete lumped-
element baluns. The lumped-element baluns present 180° of
phase difference while also providing impedance
transformation from source to load, and vice versa. Table 4 lists
recommended passive values for various center frequencies
with single-ended impedances of 50 Ω. Agilent’s free
AppCAD
components for lumped-element baluns.
The lumped-element baluns offer ±0.5 dB flatness across
50 MHz for 900 MHz and 2200 MHz. At 2.7 GHz, the
frequency band is limited by stray capacitances that dominate
the passive components in the lumped-element balun at these
high frequencies. Thus, PCB parasitics must be considered
during lumped-element balun design and board layout.
Table 4. Recommended Passive Values for Lumped-Element
Balun, 50 Ω Impedance Match
Center
Frequency
100 MHz
900 MHz
2.2 GHz
2.7 GHz
+5V
100pF
100pF
C
120nH
op
TM
program allows for simple calculation of passive
C
27 pF
3.3 pF
1.5 pF
1.5 pF
C
i
o
C
o
L
o
L
L
82 nH
9 nH
3.3 nH
2.4 nH
o
Input
C
i
o
C
o
C
1 pF
16 nH
RFOUT
ip
C
33 pF
3.9 pF
1.5 pF
1.3 pF
o
Output
L
72 nH
8.7 nH
3.6 nH
2.7 nH
o
C
3.3 pF
0.5 pF
27 nH
33 nH
op