CH2124 データシートの表示（PDF） - Cermetek Microelectronics

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CH2124

HIGH SPEED INTERNET MODEM FAMILY

Cermetek Microelectronics 

Cermetek Microelectronics, Inc.

High Speed Internet Modem Family

Figure 3. PSTN Line Interface for all iNet Appliance Products.

1. Currently Limiting PSTN Protection Line

Device.

Currently limiting devices are mandatory to meet

UL 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 PTC (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 (see Figure 3). No additional external

components are required to maintain

conveyed FCC Part 68 approval.

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 RJ-11C 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 1950 listed. The actual values of

the components used may vary depending on

the end product design.

2003 Cermetek Microelectronics, Inc.

Page 10

Document No. 607-0017 Revision G1 (06/03)

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