B902.C (2/02)
For More Information :
Performance warranty of products offered on this data sheet is limited to the parameters specified. Data is subject to change without notice. Other brand and product
names mentioned herein may be products and/or registered trademarks of their respective owners.
Printed on recycled paper. 2002, Pulse Engineering, Inc.
INDUCTORS AND
COMMON MODE CHOKES
For Use in ADSL POTS Low Pass Filters
Performance Description
The series of coupled inductors shown on this data sheet are
ideal for use in Asymmetrical Digital Subscriber Line (ADSL)
applications where a low pass filter is required to separate the
voice frequencies from the data frequencies that are carried on
an ADSL line. In spite of their small footprint and low profile,
these coupled inductors provide excellent electrical
performance. They have stable inductance with varying DC
current and temperature, high self-resonant frequency, low
coupling capacitance, and excellent balance.
The common mode chokes were developed to reduce common
mode voltages in the low frequency range that is used for voice
transmission. The chokes are also designed to accommodate
DC currents up to 100 mA.
Application Circuit
The following schematic depicts a typical LC filter that
incorporates the use of a common mode choke in addition to
the LC network. As shown in the frequency response graph
below, at low frequencies, the amplitude of the output signal is
roughly equal to the amplitude of the input signal. At higher
frequencies the amplitude of the output decreases. Thus, the
network passes low frequency voice signals with only a small
degree of attenuation, while it suppresses high frequency
signals and acts as a low pass filter.
Frequency Response
Choke
Inductor
Inductor
Inductor
Capacitor
Capacitor
Capacitor
Input
ADSL & POTS
Signals
Output
POTS Signal
Only
100 Hz
1 KHz
10 KHz
100 KHz
10 dB/REF 0 dB
-100 dB
0 dB
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