ADL5331

Rev. 0 | Page 10 of 16

APPLICATIONS INFORMATION

ADL5331

VPS1

COM1

INHI

INLO

COM1

VPS1

VPS2

COM2

OPHI

OPLO

COM2

VPS2

C7

100pF

L1

0.68µH L2

0.68µH

C5

10nF

C6

10nF

C13

10nF

C14

10nF

C9

10nF

C10

10nF

C8

0.1µF

C1

0.1µF

C16

100pF

C15

0.1µF

C11

100pF

C12

0.1µF

C2

100pF

C3

0.1µF

C4

100pF

VPOS

RFOUT

VPOS

VPOS

RFIN

VPOS

VPOS

GAIN

Figure 15. Basic Connections

BASIC CONNECTIONS

Figure 15 shows the basic connections for operating the

ADL5331. There are two positive supplies, VPS1 and VPS2,

which must be connected to the same potential. Connect COM1

and COM2 (common pins) to a low impedance ground plane.

Apply a power supply voltage between 4.75 V and 5.25 V to

VPS1 and VPS2. Connect decoupling capacitors with 100 pF

and 0.1 μF power supplies close to each power supply pin. The

VPS2 pins (Pins 13 and Pin 18 through Pin 22) can share a pair

of decoupling capacitors because of their proximity to each other.

The outputs of the ADL5331, OPHI and OPLO, are open

collectors that need to be pulled up to the positive supply

with 120 nH RF chokes. The ac-coupling capacitors and

the RF chokes are the principle limitations for operation at

low frequencies. For example, to operate down to 1 MHz,

use 0.1 μF ac coupling capacitors and 1.5 μH RF chokes. Note

that in some circumstances, the use of substantially larger

inductor values results in oscillations.

Because the differential outputs are biased to the positive

supply, ac-coupling capacitors (preferably 100 pF) are needed

between the ADL5331 outputs and the next stage in the system.

Similarly, the INHI and INLO input pins are at bias voltages of

about 3.3 V above ground.

The nominal input and output impedance looking into each

individual RF input/output pin is 25 Ω. Consequently, the

differential impedance is 50 Ω.

To enable the ADL5331, the ENBL pin must be pulled high.

Taking ENBL low puts the ADL5331 in sleep mode, reducing

current consumption to 250 μA at an ambient temperature.

The voltage on ENBL must be greater than 1.7 V to enable the

device. When enabled, the device draws 100 mA at low gain to

215 mA at maximum gain.

The ADL5331 is primarily designed for differential signals;

however, there are several configurations that can be imple-

mented to interface the ADL5331 to single-ended applications.

Figure 16 and Figure 17 show options for differential-to-single-

ended interfaces. Both configurations use ac-coupling capacitors

at the input/output and RF chokes at the output.

RFIN

10nF

10nF

INHI

INLO

RFOUT

10nF

10nF

OPHI

OPLO

ADL5331

RF VGA

120nH

120nH

+5V

ETC1-1-13

ETC1-1-13

Figure 16. Differential Operation with Balun Transformers

Figure 16 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 ADL5331 was completed using 1:1 baluns at the input

and output for a 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.