ADF4360-8 Data Sheet
Rev. D | Page 12 of 24
OUTPUT STAGE
The RF
OUT
A and RF
OUT
B pins of the ADF4360-8 are connected
to the collectors of an NPN differential pair driven by buffered
outputs of the VCO, as shown in Figure 20. To allow the user to
optimize the power dissipation vs. the output power require-
ments, the tail current of the differential pair is programmable
via Bits PL1 and PL2 in the control latch. Four current levels
may be set: 3.5 mA, 5 mA, 7.5 mA, and 11 mA. These levels give
output power levels of −9 dBm, −6 dBm, −3 dBm, and 0 dBm,
respectively, using the correct shunt inductor to V
DD
and ac
coupling into 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
DD
.
Another feature of the ADF4360-8 is that the supply current
to the RF output stage is shut down until the device achieves lock,
as measured by the digital lock detect circuitry. This is enabled by
the Mute-Till-Lock Detect (MTLD) bit in the control latch.
VCO
RF
OUT
ARF
OUT
B
BUFFER
04763-020
Figure 20. Output Stage ADF4360-8
