ADF5000

Rev. 0 | Page 8 of 12

APPLICATION CIRCUIT

The ADF5000 can be connected either single-ended or differ-

entially to any of the Analog Devices PLL family of ICs. It is

recommended that a differential connection be used for best

performance and to achieve maximum power transfer. The

application circuit shown in Figure 10 shows the ADF5000

used as the RF prescaler in a microwave 12 GHz PLL loop. The

ADF5000 divides the 12 GHz RF signal down to 6 GHz, which

is input differentially into the ADF4156 PLL. An active filter

topology, using the OP184 op amp, is used to provide the wide

tuning ranges typically required by microwave VCOs.

The positive input pin of the OP184 is biased at half the ADF4156

simple resistor divider, ensuring sufficient decoupling close to

the +IN A pin of the OP184. This configuration, in turn, allows

the use of a single positive supply for the op amp. Alternatively,

to optimize performance by ensuring a clean bias voltage, a low

noise regulator such as the ADP150 can be used to power the

resistor divider network or the +IN A pin directly.

ADF5000

PRESCALER

VDD1

RFOUT

RFOUT

VDD2

ADF4156

PLL

GND

10pF

0.1µF

CP

820pF

220

Ω

330

Ω

1.8nF

47nF

1k

Ω

1.8nF

MICROWAVE

VCO

RFOUT

VTUNE

RFIN

37

Ω

150

Ω

150

Ω

1µF

18

Ω

6dB ATTENUATION PAD

18

Ω

12GHz OUT

DECOUPLING

INTEGRATED

OP184

OP AMP

Figure 10. ADF5000 Used as the RF Prescaler in a Microwave 12 GHz PLL Loop