SI2493-C-FT Silicon Laboratories Inc, SI2493-C-FT Datasheet - Page 156

• Manufacturer Part Number: SI2493-C-FT
• Description: 56 KBPS, V.92 ISOMODEM SYSTEM-SIDE - LEAD-FREE TSSOP 0 TO 7
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2493-C-FT

• Mfg Application Notes: SI2493/57/34/15/04, Appl Note AN93
• Data Format: V.21, V.22, V.23, V.29, V.32, V.34, V.90, V.92, Bell 103, Bell 212A
• Baud Rates: 56k
• Interface: Parallel
• Voltage - Supply: 3 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AN93
Module Design and Application
Considerations
Modem modules are more susceptible to radiated fields
and ESD discharges than modems routed directly on
the motherboard because the module ground plane is
discontinuous and elevated above the motherboard
ground plane. This separation also creates the
possibility of loops that couple these interfering signals
to the modem. Additionally, system designers can
adversely impact the ESD and EMI immunity and
performance of a properly-designed module with a poor
motherboard layout.
Module Design
Particular attention should be paid to power supply
bypassing and reset line filtering when designing a
modem module. Trace routing is normally very short on
modules since they are generally designed to be as
small as possible. Care should be taken to use ground
and power planes in the low-voltage circuitry whenever
possible and to minimize the number of vias in the
ground and power traces. Ground and power should
each be connected to the motherboard through one pin
only to avoid the creation of loops. Bypassing and
filtering components should be placed as close to the
modem chip as possible with the shortest possible
traces to a solid ground. It is recommended that a pi
filter be placed in series with the module V
156
Motherboard
Connector
RESET
GND
VCC
1.0 μF
Figure 29. Modem Module V
.01 μF
Murata BLM 18A
CC
G601 SN1
pin with a
Rev. 0.9
filter, such as the one shown in Figure 29, on the reset
line. This filter also provides a proper power-on reset to
the modem. Careful module design is critical since the
module designer frequently has little control over the
motherboard design and the environment in which the
module will be used.
Motherboard Design
Motherboard design is critical to proper modem module
performance and immunity to EMI and ESD events.
First and foremost, good design and layout practices
must be followed. Use ground and power planes
whenever possible. Keep all traces short and direct.
Use ground fill on the top and bottom layers. Use
adequate power supply bypassing, and use special
precautions with the power and reset lines to the
modem module. Bypass V
module connector. Be sure the modem module is
connected to V
sure ground is connected to the modem module through
one pin connected to the motherboard ground plane.
The modem reset line is sensitive and must be kept
very short and routed well away from any circuitry or
components that could be subjected to an ESD event.
Finally, mount the modem module as close to the
motherboard as possible. Avoid high-profile sockets that
increase the separation between the modem module
and the motherboard.
.01 μF
CC
and RESET Filter
1.0 μF
CC
through a single pin. Likewise, be
To Modem Chip V
(Si2493/57/34/15/04
10 kΩ
2.2 μF
(Si2493/57/34/15/04 pin 12)
To RESET
pins 5, 21)
CC
GND
right at the modem
CC