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.