ADL5330

Rev. A | 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 impedances of 50 Ω. Agilent’s free

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

Input

Output

Center

Frequency

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