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Zero IF Tuner IC for both Broadcast and Communication Satellite Digital TV
CXA3685ER
Along with the increasing popularity of terrestrial digital broadcast
receivers, the number of products such as TV sets and DVD recorders that
include tuners for broadcast satellite digital broadcasts is increasing.
Furthermore, due to the increasing functionality of these end products, the
number of products that include two or more tuner units is increasing.
Thus there are increasing demands not only for further miniaturization in
satellite broadcast tuners, but also for “hybrid tuners” that support both
terrestrial and satellite broadcast reception. To respond to these needs,
Sony has now developed the CXA3685ER miniature low-power satellite
broadcast tuner IC. |
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CXA3685ER |
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* Built-in VCO
* Low power consumption (400
mW)
* External ATT circuit control
output
* Superlative multipath and
adjacent channel interference
rejection characteristics
* Power saving mode |
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400 mW Power Consumption
in a Single 3.3 V Power
Supply Device |
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We are now in an age in which low power
consumption in products for use in the
home is simply expected, and in TV sets,
the rapid switchover to flat panel screens
such as LCD panels makes heat dissipation
a difficult problem. Thus there are
now strong demands for lower power consumption
in the individual components
used in these products. By using the latest
SiGe BiCMOS process in the
CXA3685ER, Sony succeeded in reducing
power consumption by one half compared
to earlier products while assuring
the performance required for broadcast
satellite reception. Furthermore, Sony
adopted a 48-pin VQFN miniature package
with a 0.4 mm lead pitch to contribute
to even further miniaturization in the tuner
block. |
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Superlative Distortion
Characteristics |
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The CXA3685ER includes an RF tracking
filter to prevent the characteristics
degradation due to interference signals at
frequencies twice or one half that of the
desired frequency, which is a problem with
the Zero IF (direct conversion) method.
The CXA3685ER also includes a seventh-order
elliptic function filter optimized for
broadcast satellite digital broadcasts to
minimize adjacent channel interference. |
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New Functions Optimal for
Double and Hybrid Tuners |
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The CXA3685ER provides a power saving
mode that can be controlled over the
I2C bus allowing power consumption
when not being used to be held to 180 mW.
The CXA3685ER also provides input and
output pins for a crystal oscillator reference
signal, and not only can it share a
crystal with another CXA3685ER, it can
also share a crystal with a CXA3725ER
terrestrial digital/analog broadcast tuner
IC. |
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Reduced Number of External
Components |
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In addition to integrating both low-pass
filter and VCO tank circuits on the same
chip, the CXA3685ER also includes the
control circuits required when an external
attenuator circuit is used. While this control
circuit is controlled by the AGC signal
from the demodulator IC, its slope
characteristics can be adjusted over the I2C
bus. |
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•••• Mr. SATO and Mr.YAMABE••••
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The main issue we faced in designing
the CXA3685ER was how to
reduce the voltage without sacrificing
the operating characteristics
of the device. The area that
was particularly difficult was the
baseband output circuit. Since
this device is fabricated in a
BiCMOS process, we were able to
achieve our goals by using circuits
that take advantage of the features
of both bipolar and CMOS devices.
While concern for performance
and power consumption go without
saying, we also targeted ease
of use in this design effort. We
strongly recommend that you consider
this device. |
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See
all articles with figures and tables.  |
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Vol.44 |
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