2795T [BEL]
HIGH FREQUENCY MAGNETICS Application Note for Miniature Pulse Transformers; 对于小型脉冲变压器高频磁性元件应用笔记
| 型号： | 2795T |
| 厂家： | 
BEL FUSE INC. |
| 描述： | HIGH FREQUENCY MAGNETICS Application Note for Miniature Pulse Transformers |
| 文件： | 总4页 (文件大小：58K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
HIGH FREQUENCY MAGNETICS
Application Note for Miniature Pulse Transformers
TM00145B
2795T and 2795YTransformers Application Note
The 2795T and 2795Y transformers provide two transformation ratios to match both 75Ω and
120Ω line impedances with Lucent 3.3 V transceivers using a single terminating network design.
These dual-ratio transformers can also be used for 100Ω lines with a change in resistor values.
The 2795T is optimized for the receive function, while the 2795Y is optimized for the transmit
function.The 2795T can be used for both receive and transmit operation; the 2795Y is designed
for transmit operation only. Suggested applications for a single-transformer design solution (two
2795T transformers) are shown in Figure 1.The recommended two-transformer design solution
(2795T and 2795Y) is shown in Figure 2. For 2795T and 2795Y data sheet refer to document
TM00145.
Single-Transformer Design and CommonTermination Network
A typical line termination network using the 2795T transformer for both the receive interface
and the transmit interface is shown below for a single channel.The termination network consists
of capacitors and resistors arranged to provide the proper voltage gain and impedance matching
to the characteristic impedance of the various transmission lines. The network is designed to
operate with both E1 cable impedances (75Ω and 120Ω) with no change in components. For
DS1 applications (100Ω), only the resistor values need to be changed.The same transformer
can be used for all three cable impedances in both receive and transmit operation. Figure 1
below shows the proper connections for each cable impedance. Connections for cable selection
are made on the line side for the receive interface and on the device side for the transmit interface.
The components and suggested values are listed in Table 1. Capacitor CS provides high-frequency
return loss enhancement.
©2000 Bel Fuse Inc. Specifications subject to change without notice. 07.00
Bel Fuse Inc. 198 Van Vorst Street, Jersey City, NJ 07302 • Tel 201-432-0463 • Fax 201-432-9542 • www.belfuse.com
T1-103
HIGH FREQUENCY MAGNETICS
Application Note for Miniature Pulse Transformers
TM00145B
2795T and 2795YTransformers Application Note
2795T
Transformer
RR
4
Receive Data
3
RTIP
2
Z
O
CC
RS
(Line)
5
1
75
RR
6
RRING
120
100
T1
Device
(1 Channel)
2795T
Transformer
RT
Transmit Data
3
4
TTIP
2
120
CS
RT
Z
O
100
5
(Line)
TRING
1
6
75
T2
Figure 1. Connections for two 2795T transformers
Symbol
Name
Value
75Ω (E1) 120Ω (E1)
Zo
Characteristic impedance
Center tap capacitor
100Ω (DS1)
0.1 µF
132Ω
CC
RR
RS
RT
CS
T1
0.1 µF
158Ω
114Ω
6.2Ω
0.1 µF
158Ω
Receive series resistor
Receive shunt resistor
Transmit series resistor
Shunt capacitor
114Ω
95.3Ω
6.2Ω
1.2Ω
470 pF
2795T
2795T
470 pF
2795T
2795T
470 pF
2795T
2795T
Bel part number—receive
Bel part number—transmit
T2
Table 1. Components and values for two 2795T transformers
©2000 Bel Fuse Inc. Specifications subject to change without notice. 07.00
Bel Fuse Inc. 198 Van Vorst Street, Jersey City, NJ 07302 • Tel 201-432-0463 • Fax 201-432-9542 • www.belfuse.com
T1-104
HIGH FREQUENCY MAGNETICS
Application Note for Miniature Pulse Transformers
TM00145B
2795T and 2795YTransformers Application Note
Two-Transformer Design and CommonTermination Network
A typical line termination network using the 2795T transformer for the receive interface and
the 2795Y transformer for the transmit interface is shown below for a single channel.The
termination network consists of capacitors and resistors arranged to provide the proper voltage
gain and impedance matching to the characteristic impedance of the various transmission lines.
The network is designed to operate with both E1 cable impedances (75Ω and 120Ω) with no
change in components. For DS1 applications (100Ω), only the resistor values need to be changed.
The 2795T transformer is used for all three cable impedances at the receive interface. The 2795Y
transformer is used for all three cable impedances at the transmit interface. Figure 2 below shows
the proper connections for each cable impedance. Connections for cable selection are made on
the line side for both receive and transmit interfaces. The components and suggested values
are listed in Table 2. Capacitor CS provides high-frequency return loss enhancement.
2795T
Transformer
RR
Receive Data
4
3
RTIP
2
Z
O
CC
RS
(Line)
5
1
75
RR
6
RRING
120
100
T1
Device
(1 Channel)
2795Y
Transformer
RT
4
Transmit Data
2
3
TTIP
Z
O
CS
(Line)
5
1
75
RT
6
TRING
120
100
T2
Figure 2. Connections for one 2795T transformer and one 2795Y transformer
©2000 Bel Fuse Inc. Specifications subject to change without notice. 07.00
Bel Fuse Inc. 198 Van Vorst Street, Jersey City, NJ 07302 • Tel 201-432-0463 • Fax 201-432-9542 • www.belfuse.com
T1-105
HIGH FREQUENCY MAGNETICS
Application Note for Miniature Pulse Transformers
TM00145B
2795T and 2795YTransformers Application Note
Symbol
Name
Value
Zo
Characteristic impedance
Center tap capacitor
Receive series resistor
Receive shunt resistor
Transmit series resistor
Shunt capacitor
75Ω (E1) 120Ω (E1)
100Ω (DS1)
0.1 µF
132Ω
CC
RR
RS
RT
CS
T1
0.1 µF
158Ω
0.1 µF
158Ω
114Ω
114Ω
95.3Ω
7.15Ω
330 pF
2795T
2795Y
7.15Ω
330 pF
2795T
2795Y
1.8Ω
330 pF
2795T
2795Y
Bel part number—receive
Bel part number—transmit
T2
Table 2. Components and values for one 2795T transformer and one 2795Y transformer
©2000 Bel Fuse Inc. Specifications subject to change without notice. 07.00
CORPORATE
FAR EAST
EUROPE
Bel Fuse Inc.
Bel Fuse Ltd.
Bel Fuse Europe Ltd.
198 Van Vorst Street
Jersey City, NJ 07302
Tel 201-432-0463
Fax 201-432-9542
www.belfuse.com
8F / 8 Luk Hop Street
San Po Kong
Kowloon, Hong Kong
Tel 852-2328-5515
Fax 852-2352-3706
www.belfuse.com
PrestonTechnology Management Centre
Marsh Lane, Suite G7, Preston
Lancashire, PR1 8UD, U.K.
Tel 44-1772-556601
Fax 44-1772-888366
www.belfuse.com
T1-106
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