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MOPLL IC for Terrestrial Digital and Analog Broadcast Tuner
CXA3725ER
While mainly supplying analog broadcast TV tuner ICs up to now,
Sony is now adding digital broadcast tuner ICs for use in terrestrial
digital broadcast reception equipment to its product line due to the
rapid increase in popularity expected for this equipment.
In addition to mixer, oscillator, and PLL circuits, the CXA3725ER also
integrates IF AGC, IF level detection, and RF AGC circuits on the same
chip and thus can support even further miniaturization in tuners. |
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CXA3725ER |
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* Image canceling mixer adopted
* Balanced oscillator provides superb
oscillator stability
* High-linearity IF AGC allows a fixed
gain mode to be selected
* IF level detection and RF AGC circuits
integrated on the same chip (voltage
control can be applied over an I2C bus) |
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Easier Image Trap Filter Design |
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While the frequency conversion block
adopts the same single conversion method
used in previous terrestrial analog broadcast
tuner ICs, the CXA3725ER also includes
a newly-developed image canceling
mixer.
Although the requirements for image rejection
performance during analog broadcast
reception are becoming more strict
due to increases in TV screen sizes, the
CXA3725ER achieves stable image rejection
performance without the addition of
a trap circuit or other external components
by integrating an image canceling mixer
on the same chip.
This also can lead to simplification of the
adjustment steps in the tuner manufacturing
line.
Furthermore, the use of an external tank
circuit in the VCO block makes it easier
to design the tracking filter. |
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Integration of the IF AGC, IF
Level Detection, and RF AGC
Circuits |
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The CXA3725ER integrates on the same
chip not only the IF level detection circuit
required during digital reception but
both the IF AGC amplifier and RF AGC
circuit that used to be a separate IC in conventional
designs.
The IF AGC circuit newly developed for
this device includes not only a low-distortion
low-noise AGC amplifier for digital
reception, but also an independent
fixed-gain amplifier for analog broadcast
reception. (A gain of either 25, 30, 35, or
40 dB can be selected.)
The IF level detection circuit’s detection
level can be set over the I2C bus.
The RF AGC circuit outputs either the
built-in IF level detection circuit’s output
signal or an external control signal, as
selected by the application.
The CXA3725ER also supports applications
that enable the defeat function in the
output circuit and limit the RF AGC’s
maximum gain. |
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Low Power (700 mW) and the
VQFN Miniature Package |
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In the CXA3725ER, Sony succeeded at
achieving both the low power consumption
of 700 mW and low-distortion/low-noise
characteristics in a device that integrates
image canceling mixer, oscillator,
PLL, IF AGC, and IF detection functions
on a single chip by taking full advantage
of Sony’s superlative SiGe BiCMOS process
and RF circuit technologies. Furthermore,
Sony adopted a 0.4 mm lead pitch
56-pin VQFN miniature package to contribute
to even further end product miniaturization. |
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•••• Mr. FUKUDA and Mr.KABASHIMA••••
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The market for equipment that
supports terrestrial digital broadcasting
is growing rapidly since
Japan has committed to switching
over completely to digital in 2011.
We worked together as a tightly
unified group during this development
effort due to our shared hope
that this device will be used in
many products, from TV sets
themselves to recorders, set top
boxes, and other products.
The image canceling mixer we
adopted in this device is effective
at improving its image rejection
performance. I strongly urge you
to try this device in your next design
so that you can see how attractive
its performance really is. |
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See
all articles with figures and tables.  |
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Vol.44 |
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