ADL5811ACPZ-R7 datasheet(22/28 Pages) AD

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ADL5811

Rev. 0 | Page 22 of 28

APPLICATIONS INFORMATION

BASIC CONNECTIONS

The ADL5811 mixer is designed to downconvert radio

frequencies (RF) primarily between 700 MHz and 2800 MHz

to lower intermediate frequencies (IF) between 30 MHz and

450 MHz. Figure 59 depicts the basic connections of the mixer.

It is recommended to ac couple RF and LO input ports to

prevent nonzero dc voltages from damaging the RF balun or LO

input circuit. A RFIN capacitor value of 22 pF is recommended.

IF PORT

The mixer differential IF interface requires pull-up choke inductors

to bias the open-collector outputs and to set the output match.

The shunting impedance of the choke inductors used to couple

dc current into the IF amplifier should be selected to provide

the desired output return loss.

The real part of the output impedance is approximately 200 Ω,

as seen in Figure 31, which matches many commonly used SAW

filters without the need for a transformer. This results in a voltage

conversion gain that is approximately 6 dB higher than the power

conversion gain. When a 50 Ω output impedance is needed, use a

4:1 impedance transformer, as shown in Figure 59.

BIAS RESISTOR SELECTION

An external resistor, R1, is used to adjust the bias current of the

integrated amplifier at the IF terminal. It is necessary to have a

sufficient amount of current to bias both the internal IF amplifier to

optimize dc current vs. optimum input IP3 performance. Figure 42

and Figure 43 provide the reference for the bias resistor selection

when lower power consumption is considered at the expense of

conversion gain and input IP3 performance.

VGS PROGRAM

MING

The ADL5811 allows programmability for internal gate-to-source

voltages for optimizing mixer performance over the desired

frequency bands. The ADL5811 defaults the VGS setting to 0.

Power conversion gain, input IP3, NF, and input P1dB can be

optimized, as shown in Figure 39 and Figure 40.

LOIP

LOIN

DATA

CLK

RFCT

RFIN

ADL5811

PAD

VCC

RED

BLK

VCC

C23

10pF

C17

22pF

100pF

22pF

120pF

C18

10pF

0.1µF

120pF

0.1µF

VCC

C19

10pF

VCC

C20

10pF

VPOS

AGND

LOIP

RFIN

IFON

IFOP

DATA

CLK

R20

OPEN

R21

0Ω

910Ω

TC4-1W+

470nH

Figure 59. Basic Connections

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