adf4351 Analog Devices, Inc., adf4351 Datasheet - Page 13

• Manufacturer Part Number: adf4351
• Description: Wideband Synthesizer With Integrated Vco Preliminary Technical Data Adf4351
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
The VCO shows variation of K
band and from band-to-band. It has been shown for wideband
applications covering a wide frequency range (and changing
output dividers) that a value of 33 MHz/V provides the most
accurate K
how K
average value for the frequency band. Users may prefer this
figure when using narrowband designs.
–0000
–0000
–0000
–0000
–0000
V
–000
varies with fundamental VCO frequency along with an
V
as this is closest to an average value. Figure shows
–000
Figure 21. K
TBD
ALL CAPS (Initial cap)
V
V
vs. Frequency
as the V
–000
TUNE
varies within the
–000
–000
Rev. PrC | Page 13 of 28
OUTPUT STAGE
The RF
to the collectors of an NPN differential pair driven by buffered
outputs of the VCO, as shown in Figure . To allow the user to
optimize the power dissipation vs. the output power requirements,
the tail current of the differential pair is programmable by
Bits [D2:D1] in Register 4 (R4). Four current levels of 8 mA, 11
mA , 15 mA and 21 mA may be set. These levels give output
power levels of −4 dBm, −1 dBm, +2 dBm, and +5 dBm,
respectively, using a 50 Ω resistor to AV
a 50 Ω load. Alternatively, both outputs can be combined in a 1
+ 1:1 transformer or a 180° microstrip coupler (see the Output
Matching section). If the outputs are used individually, the
optimum output stage consists of a shunt inductor to V
unused complementary output must
be terminated with a similar circuit to the used output.
An auxiliary output stage exists on Pins RF
providing a second set of differential outputs which can be
used to drive another circuit, or which can be powered down
if unused. The auxiliary output stage can only be used if the
primary outputs are enabled.
Another feature of the ADF4351 is that the supply current to
the RF output stage can be shut down until the part achieves
lock as measured by the digital lock detect circuitry. This is
enabled by the mute till lock detect (MTLD) bit in Register 4 (R4).
VCO
OUT
A+ and RF
1/2/4/8/16/32/64
DIVIDE-BY
BUFFER/
OUT
Figure 22. Output Stage
A− pins of the ADF4351 are connected
RF
OUT
DD
A+
and ac coupling into
OUT
RF
B+ and RF
OUT
ADF4351
A–
VCO
OUT
. The
B−