ADF5709

Data Sheet

Rev. A | Page 8 of 9

APPLICATIONS INFORMATION

The ADF5709 serves as the local oscillator (LO) in microwave

synthesizer applications. The primary applications for this

device are point to point and multipoint radios, military radars,

test and measurement, industrial and medical equipment, and

wireless communication infrastructure. The low phase noise

allows higher orders of modulation and offers improved bit

error rates in communication systems. The linear, monotonic

tuning sensitivity allows a stable loop filter design. The higher

output power minimizes the gain required to drive subsequent

stages. The cascode output buffer amplifier stage guarantees

stability over a wide range of output load conditions and

improves the pulling performance of the VCO.

To achieve optimal performance of the VCO, high power

supply rejection ratio (PSRR) and low dropout (LDO) regulators

are recommended to minimize any spurious frequencies from the

power supply and to achieve the lowest phase noise native to

the VCO. The ADM7150 and the LT3042 meet these

requirements and are acceptable LDO regulators to use.

The wide frequency range of the VCO suggests the use of a low

noise, PLL synthesizer, such as the ADF41513. The wide input

bandwidth of this synthesizer (1 GHz to 26.5 GHz) makes the

ADF41513 an ideal synthesizer for use with the ADF5709. The

variable charge pump current allows compensation for VCO

sensitivity variation by allowing charge pump currents to be

increased or decreased as required. Ensure that optimal RF

layout practices are used for the layout of the interconnecting

circuits. Give first priority to the microwave power splitter

network from the output buffer of the VCO to the RF input pin

the ADF41513 CP output pin as possible, and the final RC pole

The wide tuning range of the ADF5709 requires the use of a

high voltage, low noise, op amp. The ADA4625-1 is acceptable

to use for such applications.

The suggested PCB stack up consists of a high quality dielectric

material, such as Rogers 4003. The transmission lines carrying

the high frequency signal must be carefully controlled, 50 Ω

characteristic impedances.

ADF41513

CE

CLK

DATA

LE

1nF

1pF

CP

MUXOUT

DLD

220Ω

1pF

NOTES

THIS IS A SIMPLIFIED SCHEMATIC, DECOUPLING CAPACITORS AND SPI CONNECTION DETAILS HAVE BEEN OMITTED FOR CLARITY.

LOCK

DETECT

RFIN

GND

RFOUT1

4.7kΩ

2

6

22

10

24

17

5

4

23

18

100nF

13

14

15

16

62Ω

36Ω

RFOUT

15nF

240pF

19

1

EP

DC1

DC2

75nF

2200pF

RFOUT2

RFOUT1

7

8

9

+

–

ADA4625-1

20

21

LOCK

DETECT

11

POWER

SPLITTER

ADF5709

3

2

3

4

5

6

1

13

14

15

16

17

18

19

20

21

22

23

24

78

9

10 11 12

Figure 17. Typical Application Diagram