Datasheet

ADF5002
Rev. 0 | Page 8 of 12
ADF5002
PRESCALER
VDD1
RFOUT
VDD2
ADF4156
PLL
RF
IN
A
10pF 0.1µF
CP
220Ω
330Ω
1.8nF
47nF
1kΩ
RFIN
APPLICATION CIRCUIT
The ADF5002 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 ADF5002
used as the RF prescaler in a microwave 16 GHz PLL loop. The
ADF5002 divides the 16 GHz RF signal down to 2 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
charge pump supply (V
P
). This can be easily achieved using a
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.
RFOUT RF
IN
B
GND
820pF
1.8nF
MICROWAVE
VCO
RFOUT VTUNE
37Ω
150Ω150Ω
1µF
V
P
/2
18Ω
6dB ATTENUATION PAD
18Ω
16GHz OUT
DECOUPLING
INTEGRATED
OP184
OP AMP
0
8753-010
Figure 10. ADF5002 Used as the RF Prescaler in a Microwave 16 GHz PLL Loop