CH1782A 데이터 시트보기 (PDF) - Cermetek Microelectronics
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CH1782A Datasheet PDF : 19 Pages
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Cermetek Microelectronics, Inc.
CH1782A Family of Ultra Small Modem Modules V.22bis-2400bps
Figure 6. PSTN Line Interface for all CH1782A Products.
1. Currently Limiting PSTN Protection Line
Device.
Currently limiting devices are mandatory to meet
UL 1459 safety standards. To maintain conveyed
FCC Part 68 approval, the current limiting
components identified as F1 and F2 in dashed
Box #1 must also survive FCC Part 68 surge
testing. Refer to Cermetek Application Note #126,
Supplemental PSTN Line Protection, for more
details. Refer to Application Note # 130, Summary
of Recommend Suppliers, for a list of suppliers
and associated part numbers.
A. A Polyfuse (rated at 0.15 amps) is preferred
because it resets automatically upon removal
of the current flow. Non-resettable devices
are also acceptable. Refer to Application Note
#130 for a complete list of recommended
vendors and associated part numbers.
B. Resistors (10Ω carbon film or 1/8 watt
minimum) may be used in Canada, as Canada
has no requirements that PSTN equipment be
operational after a Type B surge test.
C. Although CSA CS-03 Part 1 (Canada) follows
the requirements of FCC Part 68 (USA),
Cermetek recommends contacting DOT
(Canada) and/or a certified independent lab to
verify compliance. For Canada, use either
10Ω resistors (carbon film or SMD parts 1/8
watt minimum) as described in paragraph B
above.
2. Over Voltage and Lightning Protection.
A. Surge Protection is provided by internal
circuitry contained within all CH1782A No
additional external components are required to
maintain conveyed FCC Part 68 approval for
all CH1782A.
B. In most environments, 2 terminal surge
suppressors are adequate. For severe
environments, use an external 3 terminal
device with an earth ground.
3. EMI/RFI Suppression.
No external EMI/RFI noise suppression circuitry is
required to maintain conveyed FCC Part 68
approval. However, additional suppression, if
required for other reasons, may be added as
described below in Sections 3A-3B without
adversely affecting FCC Part 68 approval.
A. To provide adequate EMI/RFI suppression,
the capacitor/inductor network contained in
dashed Box #3 should be located as close to
the RJ11 Jack as possible. Further, this
network should be provided with an excellent
ground path to the chassis.
B. Capacitors C1 and C2 should not exceed
0.005µf. They must have a rating of 1.5KV
and typically are 0.001µf ± 20%. Inductors L1
and L2 may be either individual inductors or a
dual inductor. Refer to Application Note #130
for a complete list of recommended vendors
and associated part numbers. For UL
applications, choose capacitors and inductors
that are UL 1459 listed. The actual values of
the components used may vary depending on
the end product design.
2002 Cermetek Microelectronics, Inc.
Page 14
Document No. 607-0009 Revision C (01/03)
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