Board description
AN2744
20/56
5.1
Line coupling interface
The line coupling interface is composed of three different filters: the dual channel Tx passive
filter, the dual channel Rx passive filter and the dual channel Rx active filter. The coupling
interface structure is represented in
.
All three filters are described in
,
and
For each
filter, calculations and measured frequency responses are given.
The filters are quite sensitive to the components' value tolerance. Actual components used
in the ST7538Q dual channel reference design have the following tolerances:
●
+/- 10% for coils and for the X2 capacitor
●
+/- 1% for SMD resistors
●
+/- 5% for SMD ceramic capacitors
To evaluate sensitivity to the tolerances indicated above, the following sections include
simulated responses of the filters with Montecarlo statistical analysis. Statistical simulation
helps to understand the relationship between tolerance of components' value and variations
Figure 9.
Schematic of Rx and Tx filters
Tx PASSIVE FILTER
Rx
PASSIVE
FILTER
Rx ACTIVE FILTER
CMINUS
5V
C15
100nF
COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
ACT_IN
CH2
P
N
3
1
2
Q2
2N7002
CH2
R8
330
RAI
3
1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6
4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
Q4
2N7002
R16
1M
3
1
2
D7
ESDA6V1L
3
1
2
JP3
CLOSE 2-3
C16
4.7nF
C20
10nF
L7
330uH
R18
330
C29
150 nF
D6
SM6T6V8CA
1
8
4
5
T2
LINE TRANSFORMER
C28
100nF X2
L6
68 uH
C27
56 nF
R21
3.3
C14
10 nF
Tx PASSIVE FILTER
Rx
PASSIVE
FILTER
Rx ACTIVE FILTER
CMINUS
5V
C15
100nF
COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
ACT_IN
CH2
P
N
3
1
2
Q2
2N7002
CMINUS
5V
C15
100nF
COUT
R15
5K1
R14
5K1
ACT_IN
CPLUS
ATOP1
ATOP2
ACT_IN
CH2
P
N
3
1
2
Q2
2N7002
CH2
R8
330
RAI
3
1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6
4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
CH2
R8
330
RAI
3
1
2
JP2
CLOSE 2-3
NEG_CH2
JP1
LEAVE OPENED
1
2
6
4
U2
LCA710
R17
1M
L5
100 uH
R10
100K
C11
270pF
R13
5K1
R9
1K2
R12
680
C12
270pF
3
1
2
Q4
2N7002
R16
1M
3
1
2
D7
ESDA6V1L
3
1
2
JP3
CLOSE 2-3
C16
4.7nF
C20
10nF
L7
330uH
R18
330
C29
150 nF
D6
SM6T6V8CA
1
8
4
5
T2
LINE TRANSFORMER
C28
100nF X2
L6
68 uH
C27
56 nF
R21
3.3
C14
10 nF
Содержание ST7538Q
Страница 3: ...AN2744 Contents 3 56 Appendix A Board layout 53 10 Revision history 55...
Страница 15: ...AN2744 Board description 15 56 Figure 7 Modem and coupling interface schematic...
Страница 16: ...Board description AN2744 16 56 Figure 8 Power supply schematic HIGH VOLTAGE SECTION...
Страница 53: ...AN2744 Board layout 53 56 Appendix A Board layout Figure 50 PCB layout top view...
Страница 54: ...Board layout AN2744 54 56 Figure 51 PCB layout bottom view...