SI2414 SILABS [Silicon Laboratories], SI2414 Datasheet - Page 67

• Manufacturer Part Number: SI2414
• Manufacturer: SILABS [Silicon Laboratories]

A
Introduction
This appendix describes the detailed functionality of the
integrated DAA included in the Si2456/33/14//Si3015
chipset.
DAA Isolation Barrier
The Si2456/33/14 chipset consists of the Si3015 line
side device and the Si2456/33/14 modem device. The
Si2456/33/14 achieves an isolation barrier through a
low-cost high-voltage capacitor in conjunction with
Silicon
processing techniques. These techniques eliminate any
signal degradation due to capacitor mismatches,
common mode interference, or noise coupling. As
shown in the "Typical Application Circuit" on page 11,
the C1, C4, C24, and C25 capacitors isolate the Si2456/
33/14 (DSP-side) from the Si3015 (line-side). All
transmit, receive, and control data are communicated
through this barrier.
Emissions/Immunity
The Si2456/33/14 chipset and recommended DAA
schematic are fully-compliant with and pass all
international electromagnetic emissions and conducted
immunity tests (includes FCC part 15,68; EN50082-1).
Careful attention to the "Bill of Materials: Si2456/33/14
Chipset" on page 12, “Typical Application Circuit”
schematic on page 11, and layout guidelines ensure
compliance with these international standards. In
designs with difficult layout constraints, the addition of
the C22 and C30 capacitors to the C24 and C25
recommended
performance on emissions and conducted immunity. For
such designs, a population option for C22 and C30 may
allow additional flexibility for optimization after the
printed circuit board has been completed.
EN55022 and CISPR-22 Compliance
Pending ratification in July 2001 of the CISPR-22
standard, effective August 1, 2001, compliance to the
EN55022:1998 standard is necessary to conform to the
European Union’s EMC Directive and display the CE
mark on designs intended for sale in the European
Union. However, EN55022 and CISPR-22 compliance
is currently under review. Consequently, as of June
2001, compliance requirements may change, and the
compliance date may be extended beyond August
2001.
compliance to the CISPR-22 specification. The “Typical
P P E N D I X
Additionally,
Laboratories’
capacitors
A—DAA O
some
proprietary
may
countries
improve
ISOcap
may
P E R A T I O N
modem
require
signal
Rev. 0.9
Application Circuit” schematic on page 11 and global
"Bill of Materials: Si2456/33/14 Chipset" on page 12
contained in this data sheet are designed to be
compliant to these standards. It should be noted that L1,
L2, R31, R32, C38, and C39 are only necessary for
those products intended for sale in the European Union
or any countries that require CISPR-22 compliance. If
this is not the target market, L1 and L2 can be replaced
with 0 Ω resistors, and R31, R32, C38, and C39 need
not be populated.
While this population option achieves EN55022 and
CISPR-22 compliance, there are several system-
dependent
considering. The first relates to the direct current
resistance (DCR) of the inductors. If the selected
inductors have a DCR of less than 3 Ω each, countries
that require 300 Ω or less of dc resistance at TIP and
RING with 20 mA of loop current can be satisfied with
the Japan DC termination mode (DCT = 01). If the
selected inductors have a DCR of greater than 3 Ω but
less than 8 Ω each, low voltage dc termination mode
(DCT = 00) must be used to satisfy the above
requirement. In either case, Silicon Laboratories
strongly recommends that users of the ISOmodem
adhere to the section, "DC Termination" on page 68, for
their dc termination requirements.
The second consideration relates to the power supply of
the target system. The recommended values for L1, L2,
R31, R32, C38, and C39 assume that the target system
provides a direct current connection between the target
system’s reference ground (Si2456/33/14 GND) and an
external ground (often the third prong of a power plug).
If there is no direct connection between the reference
ground and external ground, smaller inductor values are
possible. It should be understood that this consideration
is system-dependent, and the impedance between the
system ground and the external ground in the range of
500 kHz and 10 MHz should be well known. Please
contact a Silicon Laboratories technical representative if
you need assistance in analyzing or testing your system
for this consideration.
Si2456/Si2433/Si2414
and
country-dependent
issues
worth
67