Commercialization of Microchip Transformers
(Balun Transformers) for Digital TV Tuners
-DXW21BN, DXP18BN Series-
[Text]
Murata Manufacturing Co., Ltd. has commercialized microchip transformers (balun transformers),
which are used to convert between unbalanced-balanced signals in the antenna inputs of TV tuner
circuits for terrestrial digital broadcast compatible compact mobile devices.
Up to now balun transformers for TV tuners have been made by winding wire around a
spectacle-shaped ferrite core, and are widely used in large-scale devices such as TVs and desktop
PCs. However, these kinds of transformers are about 5 x 5 mm in size, and therefore unsuited for
usage in compact mobile devices such as mobile phones, notebook PCs, and portable gaming
devices. Murata’s newly developed balun transformers represent the industry’s smallest m icrochip
transformers, featuring an ultra small, ultra low-profile design achieved through optimized
internal circuits, utilizing wire wound and film forming technologies developed by Murata. The
wire wound type model is 2.0 x 1.2 mm (EIA Code: 0805), and the film type is 1.6 x 0.8 mm (EIA
Code: 0603). Note that since the film type does not connect externally to the transformer and has a
conversion rate of 1:4, it is suited to a variety of circuits.
Compared to conventional balun transformers made with wire wound around a spectacle-shaped
ferrite core, the wire wound type reduces the required mounting space by approximately 75%, and
height by approximately 40%, while the film type can cut mounting space by 95%, and height by
80%. Thus, these microchip transformers can contribute significantly to enabling sm aller, slimmer
mobile device for terrestrial digital broadcasts, which are expected to become increasingly
popular.
This new product line can make a major contribution to space savings in tuner block circuits as
balun transformers for unbalance-balance conversion of antenna inputs, for products such as tuner
ICs for terrestrial digital broadcasts. In addition, these components can also be used as balun
transformers for analog TV tuner circuits.
These new products are free of all substances controlled by RoHS regulations.
Mass production of the wire wound type commenced in November 2006 at the rate of 4 million
units per month, while mass production of the film type is set to commence in December 2006, at
3 million units per month. Sample price is set at 20 yen per unit for each type.
[Background]
The antenna inputs of tuner ICs use balanced input signals, but the output of the antenna is
unbalanced. For this reason, balun transformers are generally used to convert unbalanced signals
to balanced signals. However, due to their construction, conventional balun transformers are
large—approximately 5 mm x 5 mm. Since this has presented a hindrance to enabling more
compact, space-saving tuner modules, it became necessary to develop more compact balun
transformers.
Tuner Module
DXW21B DXP18B
For VHF / UHF / DVB-T / ISDB-T etc.
IF signal
processor IC
Microchip transformer (balun) for unbalance-balance conversion
Balanced
One-chip
tuner IC
Unbalance
Antenna
or
[Terminology]
• Balun transformer
A part that converts signals between balanced and unbalanced. It is also known as a
balanced-unbalanced converter. The name “balun” is derived from the first letters of the two
words, “balanced” and “unbalanced.”
• Balanced
A method of transmitting signals using two signal lines. One line carries the source signal; the
other carries a signal of opposite phase (antiphase).
• Unbalanced
A method of transmitting signals using one signal line, with a ground line providing a reference
potential.
[Features]
1. Greatly reduced mounting space (compared to conventional balun transform ers), enabling far
more compact, slimmer mobile devices to be fitted with TV tuners
2. The DXW21BN Series is a wire wound type microchip transformer of size 2.0 x 1.2 x 1.2 m m
(1:1 balun)
3. The DXP18BN Series is a film type microchip transformer featuring an impedance
conversion function, of size 1.6 x 0.8 x 0.45 mm (1:4 balun)
4. Low insertion loss and high output balance over a wide frequency band
5. Compatible with reflow soldering for surface mounting
6. Totally free of all RoHS-regulated substances
[Applications]
・TV Tuner, Cable Tuner which needs to convert between unbalanced-balanced signals
・Terrestrial digital broadcast tuner ICs, Tuner Module
[Parts Number]
・DXW21BN Series wire wound type: DXW21BN7511T
・DXP18BN Series film type: DXP18BN5014H / DXP18BN5014T / DXP18BN7514T
[External Dimensional Diagram]
・DXW21BN wire wound type ・DXP18BN
film type
[Equivalent Circuit]
・DXW21BN wire wound type ・DXP18BN
film type
Unbalanced NC GND
GND Balanced 2Balanced 1
[Part Number and Specification]
Part Number Freq.Range
(MHz)
Unbalanced
Impedance(ohm)
Balanced
Impedance(ohm)
Insertion Loss
(dB)
CMRR
(dB)
DXW21BN7511T 50 to 860 75 75 1.0max 20min
DXP18BN5014H 470 to 790 50 200 1.2max 25min
DXP18BN5014T 50 to 870 50 200 1.5max 25min
DXP18BN7514T 50 to 870 75 300 1.5max 25min
Operating Temp. Range: -40～85℃
[Characteristics]
・DXW21BN IL Insertion Loss Characteristics
Frequency (MHz)
50
1
00
1
000
2
000
0
-2
-4
-
6
Insertion Loss (dB)
・DXP18BN IL Insertion Loss Characteristics
DXP18 Insertion Loss
0
0.5
1
1.5
2
2.5
3
10 100 1000
Frequency (MHz)
Insertion Loss
DXP18BN7514T
DXP18BN5014T
DXP18BN5014H
[Sample Price]
・DXW21BN Series : 20YEN per unit
・DXP18BN Series : 20YEN per unit
[Production]
DXW21BN Series: 4 million units per month in November 2006
DXP18BN Series: 3 million units per month in December 2006
[Patents]
Three patents pending
