Internet Modem Using iChip CO561AD-S/20PC-3

Internet Modem Using iChip CO561AD-S/20PC-3
Reference Design 105
Internet Modem Using iChip CO561AD-S/20PC-3
Introduction
Features
•
The Internet Modem is based on the iChipTM
CO561AD-S Internet ControllerTM and a MultiTech dial-up SocketModemTM (see:
http://www.multitech.com/PRODUCTS/SocketModem/).
The design is intended to connect to a host
device through a standard EIA RS232 serial
port. Modem AT commands and iChip AT+iTM
commands are accepted at baud rates of 2400
through 115200 bits/sec. The Internet modem
may be used as a normal external dial-up
modem, due to iChip’s default Transparent
mode, as well as for communicating over highlevel Internet protocols.
•
•
•
•
•
Standard RS232, serial input
channel via 9 pin ‘D’ connector.
Data and Internet connection
through standard PSTN dial-up
SocketModem.
Full hardware flow control.
CD, RING and PWR LED
indicators.
Supports the full SocketModem
AT commands.
Supports iChip AT+i commands
for Internet connectivity.
Reference Design
This reference design outlines the required
connections to link a 3.3V CO561AD-S
iChip Internet Controller with an
embedded SocketModem, based on the
block diagram in Figure 1. Changes
required for a 5V design are also provided.
The reference design is intended to clarify
iChip signal connections. It may be used
as a general reference with guidelines for
hooking up an iChip CO561AD-S to any
standard external landline or cellular
modem.
Block Diagram
iChip
Serial
Data
Modem
RJ11
9pin D
Serial
Figure 1: Internet Modem Block Diagram
Connect One Ltd.
Copyright © 2003
16-1350-01
RD105
iChip Signal Connections
Table 1 defines the required iChip signal connections
X2
CLKO
VCC
GND
-RTSH
-DTRH
-DSRH
-CDH
-RIH
41
31
52
68
21
14
62
61
40
64
Must be Not Connected.
Must be Not Connected.
Must be Not Connected.
Must be Not Connected.
Must be Not Connected.
Must be Not Connected.
Should be connected to ground.
Must be Not Connected.
Should be Pulled-up to VCC.
Should be Pulled-up to VCC. May be connected to GND through a
mode select switch.
12 Reset input. Should be connected to reset circuit.
42 Crystal input. May be connected to crystal with X2 or connected
directly to external clock source.
43 Crystal input. May be connected to crystal with X1 or Not
Connected when operating on external clock source.
44 CLK OUT. May be connected as external clock.
1
Power pin. Connect to power supply. Add at least two bypass
filters of 0.1uF and 1nF.
55, Power pin. Connect to circuit ground.
67
30 Connect to output of host (Host TXD signal).
26 Connect to input of host (Host RXD signal).
59 H/W Flow Ctl.: Connect to input of host (Host -RTS signal).
No H/W Flow Ctl.: Connect to –RTSH (Pin 58).
58 H/W Flow Ctl.: Connect to output of host (Host -CTS signal).
No H/W Flow Ctl.: Connect to –CTSH (Pin 59).
63 Connect to input of host (Host -DSR signal).
15 Connect to output of host (Host -DTR signal).
Connect -DSRH to GND when not in use.
60 Connect to input of host (Host -CD signal).
20 Connect to input of host (Host -RI signal).
© 2003 Connect One Ltd.
Page 2
Host Interface Signals
RXDH
TXDH
-CTSH
Connection
Must be Not Connected.
Must be Not Connected.
Miscellaneous Signals
-RES
X1
#
Local Bus Signals
Pin Name
A0 – A19
AD0 –
AD15
ALE
-BHE
-WR
-RD
-LCS
-UCS
HOLD
HLDA
URTINT
MMSEL
RD105
-RTSM
32
-DTRM
-DSRM
18
65
-CDM
66
Connection
Connect to output of modem (Modem RXD signal).
Connect to input of modem (Modem TXD signal).
H/W Flow Ctl.: Connect to output of modem (Modem -CTS signal)
No H/W Flow Ctl.: Connect to –RTSM (Pin 32).
H/W Flow Ctl.: Connect to input of modem (Modem -RTS signal)
No H/W Flow Ctl.: Connect to –CTSM (Pin 27).
Connect to input of modem (Modem -DTR signal).
Connect to output of modem (Modem -DSR signal).
Connect -DSRM to GND when not in use.
Connect to output of modem (Modem CD signal).
Serial Modem
Signals
Pin Name #
RXDM
28
TXDM
29
-CTSM
27
Table 1: iChip Signal Connections
© 2003 Connect One Ltd.
Page 3
RD105
Internet Modem Schematic
D
R3
2
8
F1
ZJYS51R5–2PT
L1
RXDM
TXDM
-CTSM
-RTSM
-DSRM
-DTRM
-CDM
R8
4.7K
R4
7
30
26
59
58
15
63
60
20
28
29
27
32
65
18
66
64
62
61
21
14
40
52
68
41
31
12
44
42
43
GND
C3
220PF/2KV
4
18.432MHZ
VCC
4.7K
VCC
RST-
Y1
TR600-150
GND
1
MC34164P-3
RST
C14
22PF
C16
22PF
U5
VIN
GND
GND
3
Telephone
Jack
J1
4
3
2
1
RJ11
+
GND
VCC
470
C18
10UF/16V
GND
R6
VCC
100K
S1
2
RXDH
TXDH
-CTSH
-RTSH
-DSRH
-DTRH
-CDH
-RIH
7
GND
GND
GND
U4
X1
X2
CLKO
RES
ALE
BHE
WR
RD
GND
RST-
C9
1NF
VCC
220PF/2KV
C4
LCS
UCS
URTINT
HOLD
HLDA
RXDM
TXDM
CTSM
RTSM
DSRM
DTRM
CDM
MMSEL
RXDH
TXDH
CTSH
RTSH
DSRH
DTRH
CDH
RIH
GND
1
2
24
26
U1
TIP
RING
RESET
DGND
6
7
6
5
4
3
2
24
9
22
17
16
13
23
11
10
25
57
19
34
35
36
46
33
37
38
54
56
53
48
51
47
49
45
8
39
50
GND
MT5600SMI
C10
0.1UF
A0
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
A13
A14
A15
A16
A17
A18
A19
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
AD8
AD9
AD10
AD11
AD12
AD13
AD14
AD15
CO561AD-S/20PC-3
6
64
63
61
41
40
39
38
37
36
35
34
33
SPKR
0.1UF
-DTRM
-CDM
-CTSM
-DSRM
TXDM
RXDM
-RTSM
GND
2
2
5
C2
GND
VCC
VCC
C11
+
330
R7
330
R5
10UF/16V
D3
LED
D4
LED
GND
VCC
C15
0.1UF
0.1UF
C5
LED
D2
R2
330
2
3
10UF/16V
GND
4
VIN
- V+
+
GND
C19
0.1UF
0.1UF
2
C8
C22
TXDH
-DTRH
-RTSH
-CDH
-RIH
RXDH
-DSRH
-CTSH
4
GND
LM386M-1
U2
5
G2
BP
+
GND
U3
R1
10
GND
1
+
VIN
GND
V-
V+
TOUT1
TOUT2
TOUT3
TOUT4
TOUT5
RIN1
RIN2
RIN3
INVALID
GND
3
+
GND
C6
10UF/16V
LS1
HPE1206
C13
0.1UF
D1
C20
1N4001
C21
GND
0.1UF
TX232
DTR232
RTS232
CD232
RI232
0.1UF
5
6
7
10
12
15
RX232
DSR232
CTS232
3
8
9
11
4
27
C17
0.1UF
C12
1000UF/16V
VCC
MAX3238CAI
FORCEOFF
FORCEON
ROUTB1
ROUT1
ROUT2
ROUT3
TIN1
TIN2
TIN3
TIN4
TIN5
C2-
C2+
C1-
C1+
U6
VIN
LM1117T-3.3
VOUT
GND
28
25
1
3
24
23
22
19
17
16
21
20
18
13
14
C7
0.047UF
G1
0.1UF
C1
Reference Design For CO561AD-S/20PC-3
VCC
SPKR
AGND
DGND
DTRTTL
DCDTTL
CTSTTL
DSRTTL
RITTL
TXDTTL
RXDTTL
RTSTTL
VCC
1
1
5
26
GND
3
1
GND
2
J2
CD232
DTR232
TX232
CTS232
RX232
RTS232
DSR232
RI232
DC-JACK-MALE
Connect-ONE Ltd.
Title
Monday, November 25, 2002
Document Number
204
GND
GND
11
1
6
2
7
3
8
4
9
5
10
GND
Sheet
J3
1
DB-9/FEMALE
1
1
of
1
Reference Desighn for Embedded iModem Using C0561AD-S/20PC-3
Size
B
2
Date:
Rev
1.1
D
C
B
A
Page 4
© 2003 Connect One Ltd.
8
7
6
4
1
VCC
C
B
A
PB SW
GND
8
GND
2
2
1
1
VCC
GND
GND
55
67
GND
3
Figure 2: Internet Modem Schematic
RD105
Alternative Reset Circuit
The Reset signal, based on U5 in Figure 2, may be replaced with a low-cost RC network.
τ should be greater than 10 mSec (see Figure 3):
Vcc
D
10K
iChip
CO561AD-S
-RES
Pin 12
10U
Figure 3: Low-cost RC Reset Circuit
© 2003 Connect One Ltd.
Page 5
RD105
Bill of Materials for 3.3V Internet Modem Reference Design
Qty
Reference Designator
P/N, Description
1.
11
2.
2
C1, C2, C5, C10, C13,
C15, C17, C19, C20,
C21, C22
C3, C4
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
4
1
1
1
2
1
3
1
1
1
1
C6, C8, C11, C18
C7
C9
C12
C14, C16
D1
D2, D3, D4
F1
J2
J3
J1
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
1
1
1
3
1
2
1
1
1
1
LS1
L1
R1
R2, R5, R7
R3
R4, R8
R6
S1
U1
U2
220PF/2KV
GHM3045X7R221K-GC
10UF/16V
0.047UF Ceramic
1NF
1000UF/16V
22PF, Ceramic
1N4001
LED 3MM
TR600-150
DC-JACK-MALE
DB-9/FEMALE
RJ11
- SS-6446-NF-A431
HPE-1206, Speaker 50 Ω
ZJYS51R5–2PT
10
330Ω
470Ω
4.7KΩ
100KΩ
PB Switch
MT5600SMI
LM386M-1
24. 1
U3
LM1117T-3.3
25. 1
26. 1
27. 1
U4
U5
U6
CO561AD-S/20PC-3
MC34164P-3
MAX3238CAI
28. 1
Y1
18.432MHz, parallel
resonance, 100ppm
Manufacturer
#
0.1UF, Ceramic
Murata Erie
RayChem
Stewart
Promover
TDK
Multi-Tech
National
Semiconductor
National
Semiconductor
Connect One Ltd.
On Semiconductor
Maxim Integrated
Products
Table 2: 3.3V Internet Modem Bill of Materials
© 2003 Connect One Ltd.
Page 6
RD105
5-Volt Internet Modem
In order to implement a 5-Volt version of this reference design, several components need
to be exchanged. Table 3 defines the required component changes.
#
Qty
Reference Designator
Changed P/N, Description
17 3
22 1
24 1
R2, R5, R7
U1
U3
470Ω
MT5634SMI-ENI
LM1117T-5
25 1
26 1
U4
U5
CO561AD-S/20PC-5
MC34164P-5
Manufacturer
Multi-Tech
National
Semiconductor
Connect One Ltd.
On Semiconductor
Table 3: Component Changes for 5-Volt Design
© 2003 Connect One Ltd.
Page 7
RD105
PCB Design and Layout Considerations
Design Consideration
Good engineering practices must be adhered to when designing a printed circuit board
(PCB) containing the SocketModem module. Suppression of noise is essential to the
proper operation and performance of the modem itself and for surrounding equipment.
Two aspects of noise in an OEM board design containing the SocketModem module must
be considered: on-board/off-board generated noise that can affect analog signal levels and
analog-to-digital conversion (ADC)/digital-to-analog conversion (DAC), and on-board
generated noise that can radiate off-board.
Both on-board and off-board generated noise that is coupled on-board can affect
interfacing signal levels and quality, especially in low level analog signals. Of particular
concern is noise in frequency ranges affecting modem performance.
On-board generated electromagnetic interference (EMI) noise that can be radiated or
conducted off-board is a separate, but equally important, concern. This noise can affect
the operation of surrounding equipment. Most local governing agencies have stringent
certification requirements that must be met for use in specific environments.
Proper PC board layout (component placement, signal routing, trace thickness and
geometry, etc.), component selection (composition, value, and tolerance), interface
connections, and shielding are required for the board design to achieve desired modem
performance and to attain EMI certification.
PC Board Layout Guidelines
1. In a 2-layer design, all unused space around and under components should be
filled with copper connected to the board ground on both sides of the board, and
connected in such a manner as to avoid small islands. Isolated islands should be
avoided by connecting all grounds on the same side at several points and to the
ground plane on the opposite side through the board at several points. In a modem
design, connect the SocketModem DGND and AGND pins to the ground plane.
2. In a 4-layer design, provide an adequate ground plane covering the entire board.
In a modem design, SocketModem DGND and AGND pins are tied together on
the SocketModem. Do not split analog and digital ground planes.
3. As a general rule, route digital signals on the component side of the PCB and the
analog signals on the solder side. The sides may be reversed to match particular
OEM requirements. Route the digital traces perpendicular to the analog traces to
minimize signals cross coupling.
4. Route the modem signals to provide maximum isolation between noise sources
and noise sensitive inputs. When layout requirements necessitate routing these
signals together, they should be separated by neutral signals.
© 2003 Connect One Ltd.
Page 8
RD105
5. All power and ground traces should be at least 0.05 in. wide.
6. 0.1 UF ceramic capacitors should be placed as close as possible to the power pins.
When internal power plane is used, the traces connecting between the power pins
of the components and the vias should be kept short and to have bypass capacitor
between the via and the pin.
7. In a modem design, TIP and RING signal traces are to be no closer than 0.062"
from any other traces for U.S. applications. TIP and RING signal traces are to be
no closer than 2.5mm (0.1”) from any other traces for European applications.
2.5mm spacing must be used if the host board is to support both U.S. and
European SocketModems. In multi layer design, power and ground planes should
be cleared underneath the traces, which belong to the primary (TIP and RING)
circuit. Try to avoid vias.
8. In a modem design, if the SocketModem is mounted flush with the host PCB, the
host PCB should be clear of all traces directly underneath the SocketModem
oscillator section. It is strongly suggested that the SocketModem be mounted at
least 0.130 inch above the host board.
Electromagnetic Interference (EMI) Considerations
In a modem design, the following guidelines are offered to specifically help minimize
EMI generation. Some of these guidelines are the same as, or similar to, the general
guidelines but are mentioned again to reinforce their importance. In order to minimize the
contribution of the SocketModem-based design to EMI, the designer must understand the
major sources of EMI and how to reduce them to acceptable levels.
1. Keep traces carrying high frequency signals as short as possible.
2. Decouple power from ground with decoupling capacitors as close to the active
components’ power pins as possible.
3. Eliminate ground loops, which are unexpected current return paths to the power
source and ground.
4. Decouple the telephone line cables at the telephone line jacks. Typically, use
common mode chokes and shunt capacitors. Methods to decouple telephone lines
are similar to decoupling power lines, however, telephone line decoupling may be
more difficult and deserves additional attention. A commonly used design aid is
to place footprints for these components and populate as necessary during
performance/EMI testing and certification.
5. Decouple the power cord at the power cord interface with decoupling capacitors.
Methods to decouple power lines are similar to decoupling telephone lines.
© 2003 Connect One Ltd.
Page 9
RD105
6. Locate cables and connectors so as to avoid coupling from high frequency
circuits.
7. Avoid right angle turns on high frequency traces. Forty-five degree corners are
good, however, radius turns are better.
Other Considerations in a Modem Design
The pins of all SocketModem are grouped according to function. The DAA interface,
host interface, and LED interface pins are all conveniently arranged, easing the host
board layout design. Multi-Tech has tested each of the W.Class SocketModems for
compliance with their respective country’s PTT requirements and has received PTT
certificates that cover, without additional expense to the user, all applications that use
these SocketModems in their respective countries. The certificates apply only to designs
that route TIP and RING (pins 1 and 2) directly to the Telco jack. Only specified EMI
filtering components are allowed on these two signals.
© 2003 Connect One Ltd.
Page 10
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