ADA4304-3/ADA4304-4 Data Sheet
Rev. A | Page 10 of 11
APPLICATIONS
The ADA4304-3/ADA4304-4 active splitters are primarily
intended for use in the downstream path of television set-top
boxes (STBs) that contain multiple tuners. They are typically
located directly after the diplexer in a bidirectional CATV
customer premise unit. The ADA4304-3/ADA4304-4 provide a
single-ended input and three or four single-ended outputs that
allow the delivery of the RF signal to multiple signal paths. These
paths can include, but are not limited to, a main picture tuner,
the picture-in-picture (PIP) tuner, an out-of-band (OOB) tuner,
a digital video recorder (DVR), and a cable modem (CM).
The ADA4304-3/ADA4304-4 exhibit composite second-order
(CSO) and composite triple beat (CTB) products that are −62 dBc
and −72 dBc, respectively. The use of the SiGe bipolar process
also allows the ADA4304-3/ADA4304-4 to achieve a noise figure
(NF) of 4.6 dB at 550 MHz.
CIRCUIT DESCRIPTION
The ADA4304-3/ADA4304-4 consist of a low noise buffer
amplifier followed by a resistive power divider. This arrangement
provides 3.3 dB (ADA4304-3) or 2.9 dB (ADA4304-4) of gain
relative to the RF signal present at the input of the device. The
input and each output must be properly matched to a 75 Ω
environment for distortion and noise performance to match
the data sheet specifications. AC coupling capacitors of 0.01 μF
are recommended for the input and outputs.
A 1 μH RF choke (Coilcraft chip inductor 0805LS-102X) is
required to correctly bias the internal nodes of the ADA4304-3/
ADA4304-4. It should be connected between the 5 V supply and
the IL pin (Pin 14). The choke should be placed as close as possible
to the ADA4304-3/ADA4304-4 to minimize parasitic capacitance
on the IL pin, which is critical for achieving the specified
bandwidth and flatness.
