ADL5330

Data Sheet

Rev. B | Page 14 of 24

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.

RFIN

100pF

100pF

INHI

INLO

RFOUT

100pF

100pF

OPHI

OPLO

ADL5330

RF VGA

120nH

120nH

+5V

ETC1-1-13

ETC1-1-13

Figure 33. Differential Operation with Balun Transformers

100pF

100pF

INHI

INLO

RFOUT

RFIN

100pF

100pF

OPHI

OPLO

ADL5330

RF VGA

120nH

120nH

+5V

ETC1-1-13

Figure 34. Single-Ended Drive with Balanced 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-

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

for simple calculation of passive 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. Therefore,

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

Input

Output

100 MHz

27 pF

82 nH

1 pF

33 pF

72 nH

3.3 pF

900 MHz

3.3 pF

9 nH

3.9 pF

8.7 nH

0.5 pF

2.2 GHz

1.5 pF

3.3 nH

16 nH

1.5 pF

3.6 nH

27 nH

2.7 GHz

1.5 pF

2.4 nH

1.3 pF

2.7 nH

33 nH

INHI

INLO

RFOUT

100pF

100pF

OPHI

OPLO

ADL5330

RF VGA

120nH

120nH

+5V

RFIN

100pF

100pF

Figure 35. Differential Operation with Discrete LC Baluns