CH1840DM_技术文档

CH1840

ermetek

C

microelectronics

Low Profile Data Access Arrangement (DAA) Modules

FEATURES

INTRODUCTION

•

Works with all modem chip sets

Available in 0 dB, -6 dB, and -9 dB insertion losses

Available in extended temperature operation,

-40^oC to +85^oC

The CH1840 is an ultra small, low profile Data Access Arrange-

ment (DAA). Its modular construction and single +5 Volt D.C. power

requirement simplify your development process. Specifically de-

signed for both voice and data, this device allows direct connec-

tion of these circuits to the telephone lines. The CH1840 has FCC

Part 68 registration that can be transferred to your product. Simply

attach the included registration sticker to the outside of your prod-

uct. This eliminates the costs and delays associated with Part 68

testing and registration.

•

Complete DAA function

Voice and data

FCC Part 68 registered

Registration conveyed to user

Hook switch control

Ring detection

The CH1840 has also been designed to meet the requirements of

Canada’s Department of Communication (DOC). However, it is

necessary to register your product with the DOC before use in

Canada.

Single +5V operation

Pulse dial capability

FUNCTIONAL DESCRIPTION

The operation of the CH1840 can be broken down into the

functional blocks shown in Figure 1.

1) Phone line control

The CH1840 requires only 1.5 square inches of circuit board space

and presents a profile of only 0.35 inches in height. This DAA can

either be mounted directly on a printed circuit board or socketed.

Connection is made through 0.025 inch square pins on 0.10 inch

centers. The telephone line connection is made through a user

supplied RJ-11 jack.

2) Billing delay

3) Ring detection

4) Signal Path

5) 2- to 4-wire converter

Control inputs and status outputs for the CH1840 are compat-

ible with 5 Volt CMOS. See the Electrical Specifications.

The CH1840 DAA is designed for use with a variety of voice circuitry

and LSI modem/fax chip sets. This device is ideal for fax and

modem applications up through V.32bis. The CH1840 is pin com-

patible with the CH1817.

Phone Line Control

In the Public Switched Telephone Network (PSTN), the wires

from a telephone to the phone company’s central office (CO) are

referred to as the local loop.

Figure 1. CH1840 Functional Block Diagram

Page 1

Document No. 607-0011 Rev. A (5/00)

Drawing current from the local loop signals the central office that

the telephone is Off Hook, that is, either answering a call or prepar-

ing to place a call. In the CH1840, this function is controlled by the

OFFHK signal. When this input is LOW, the CH1840 is On-Hook,

indicating to the central office it is not using the line. The CH1840

can pulse dial by toggling the OFFHK input.

For data calls, FCC Part 68 rules require silence on the phone line

for at least 2 seconds after the call has been completed to allow

central office to exchange billing information. The CH1840 as-

sures conformance to this requirement by starting a two-second

timer on the LOW to HIGH transition to OFFHK and squelching

transmitted signals until the time expires. The CH1840 defeats

this function when Voice Mode is selected on the Data/Voice pin.

Ring Detection

The central office signals an incoming call by placing a ring signal

on the local loop. The CH1840 monitors the loop for this signal.

The Ring Indication output, RI, is normally HIGH. When ringing

appears, RI is set LOW during the typically 2 second ring period

and is restored to HIGH for the typically 4 seconds between rings.

The ring detection circuit is designed to prevent false indications

due to noise or pulse dialing on the line.

Figure 3. Low Power Ring Detection

The CH1840 attenuates the transmit signal by 9.5 dB, 0 dB for the

D option). Thus, a transmit signal of 0 dBm for the CH1840 ( -9.5

dBm for D) applied to XMIT will comply with the FCC Part 68 re-

quirement for data signals of -9dBm across Tip and Ring. In all

cases in the data mode, the CH1840 prevents the signal level

from being greater than -9 dBm at Tip and Ring.

The RI output of the CH1840 is diode protected so that an external

pull-up resistor (R> 100Kohm) to +5V may be utilized to activate

the ring detection circuit when the DAA is not connected to power.

This can be handy with designs in which power consumption is of

concern. When circuited in this manner, there is virtually no current

draw until a ring signal is present. See Figure 3.

For live voice or DTMF, when the CH1840 family products are in

voice mode, the output can be 0 dBm. In voice mode, the squelch

will not let the output signal exceed 0 dBm. Hence, by applying a

0 dBm signal to the CH1840D and a +9.5 dBm signal to the

CH1840, it will achieve the maximum signal output.

Transmit Signal

CH1840 Family

CH1840

Nominal Insertion Loss

The outgoing analog signal to be transmitted through the phone

line should be applied to the XMIT pin (with respect to GND) and

must be AC coupled, as shown in Figure 2. For the CH1840D, a

XMIT(+) and XMIT(-) pin designation provides a differential input.

-9.5 dB

0 dB

CH1840D

Figure 2. TypicalApplication

Page 2

Document No. 607-0011 Rev. A (5/00)

The D designation refers to differential input between the XMIT (+)

and XMIT (-) pins. This is required and is a convenient input for

certain types of modem chip sets.

2-Wire to 4-Wire Converter

This block has two functions: (1) it applies the XMIT signal to the

phone line, (2) it subtracts this signal from the total signal on the

phone to produce the received signal. The accuracy of this sub-

traction process depends on how closely the impedance of the

phone line matches 600 ohms. Generally, a small amount of the

XMIT signal will appear at RCV. The ratio of the XMIT signal ap-

plied to the signal returned is called trans-hybrid rejection. The

CH1840 has a high trans-hybrid loss, which is at least 18 dB re-

jection from 300 Hz to 4 KHz bandwidth.

Receive Signal

Receive Signal is presented at RCV with respect to GND and must

be AC coupled to your receive input. The CH1840 does not add

any gain to the receive signal. Receive signals can vary from a

maximum strength of -9 dBm to below -50 dBm for data mode and

up to 0 dBm strength when DTMF and live voice are being re-

ceived.

VOICE SIGNALS

Excessive Signal Detect

Voice signals are much more complex in nature than data signals.

A voice signal is comprised of numerous frequencies combined at

varying intensities. Whereas a data signal is comprised of no more

than a few discreet frequencies. This difference dictates that voice

signals receive more attention before connecting to the telephone

lines.

FCC Part 68 rules limit the average power of data signals trans-

mitted to the phone line. To meet this requirement, the CH1840

monitors the transmit audio signal at XMIT. If the signal level ex-

ceeds 0 dBm, prior to the DAA attenuation, the transmit audio is

prevented from reaching the phone line until the average input

level is again below 0 dBm. The output PSQ is normally LOW. It is

set HIGH when excessive power is detected and returns LOW

when the transmitted signal is unsquelched.

The FCC restricts voice and data signals to between 300 Hz and

3300 Hz. This is because the telephone company uses frequen-

cies below 300 Hz for low-speed teletype and frequencies above

3300 Hz for internal signaling and multiplexing.

Since FCC Part 68 rules have no limitation to the signal strength of

live voice transmission, the squelch feature is defeated when Voice

Mode is selected on the Data/Voice pin. The PSQ output always

becomes inactive when the CH1840 is in Voice Mode. Note: When

transmitting recorded or synthesized voice, the signal must be

treated as Data per FCC; thus Data Mode must be selected on the

Data/Voice pin.

Data signals easily meet the FCC requirements without additional

filtering. However, bandpass filters are essential for voice com-

munication.

A bandpass filter is utilized on the transmit line. This filter ensures

that the signal meets FCC requirements. It also shapes the sig-

nal to minimize the phone line distortion.

Table 1. Pin Descriptions

Page 3

Document No. 607-0011 Rev. A (5/00)

6)

TIP and RING traces should be as short as possible and

SAMPLE APPLICATION

should be oriented to prevent direct or induced coupling with other

signals on the host circuit card.

Figure 2 illustrates a typical application of the CH1840. When

transmitting data the controller must assert the D/V pin low to

provide the two second billing delay required by the FCC. When

transmitting voice signals, the controller should drive the D/V pin

high. This disables the billing delay, and power squelch.

7)

No additional application circuitry should be connected be-

tween the CH1840 and the phone line RJ-11C jack, except as

described in note 10 below.

8) The registration label included with the product must be affixed

to the outside of your product where it is easily visible to your end

user.

One of the requirements of an FCC approved DAA is that the

signal transmitted to Tip and Ring does not exceed -9.0 dBm.

The CH1840 incorporates an automatic squelch. If the signal

exceeds -9.5 dBm, the DAA will discontinue transmission until the

signal returns to acceptable levels. The PSQ output indicates

when the squelch circuit has been activated. By utilizing PSQ to

drive the illustrated LED circuit, a visual indication of the squelch

activation can be attained.

9) The CH1840 Module is a sensitive subsystem that should be

treated as any other integrated component. Pay special attention

to the power supply to the DAA. The device handles signals in the

millivolt range. Although it is designed to handle noise in the

power supply, steps should be taken to assure the noise level

does not exceed 50 mV peak-to-peak. Failure to provide such

operating conditions could cause the CH1840 to malfunction.

10) The CH1840 DAA meets or exceeds the hazardous voltage,

surge and leakage requirements of the FCC. For applications that

connect to Canadian phone lines, governed by the DOC (Depart-

ment of Communications) and to further protect the CH1840 from

field failure due to poor lines, a higher level of transient protection

is required, thereby making mandatory the circuit consisting of two

fuses and one varistor as shown in Figure 4. Adding these three

devices will not affect FCC or U.L. registration.

DESIGN CONSIDERATIONS

The following guidelines for your product desgin must be fol-

lowed to meet the requirements of FCC Part 68 rules.

1) The mounting of the DAA in the final assembly must be

made so that it is isolated from exposure to any hazard-

ous voltages within the assembly. Adequate separation

and restraint of cables and cords must be provided.

2) The circuitry from the registered unit to the telephone line

must be provided in wiring that carries no other circuitry

than that specifically allowed in the rules ( such as A and

A1 leads).

Components L1, L2, C1, C2 are optional and serve two

purposes. First, they restrict high frequency signals from

reaching the phone line and thereby add EMI protection.

Second, they protect against externally generated RFI

from degrading the modem’s ability to operate on proper

carrier signals. Adding these devices will not affect

FCC, DOC, or U.L. registration.

3) See Section “For Your User’s Manual” for information that

must appear in your User’s Manual.

4) Connection to the phone line should be made through a

standard RJ-11C jack or equivalent.

5) Circuit board traces from the CH1840’s TIP and RING

pins must exceed 0.1 inch spacing to one another and

0.2 inches spacing from all other traces or other conduct-

ing material. Traces should have a nominal width of 0.020

inches or greater.

Figure 4. Telephone Line Interfaces

Page 4

Document No. 607-0011 Rev. A (5/00)

Mounting the CH1840

The CH1840 can be soldered directly to the host circuit card or

installed in sockets. Direct soldering provides the most sound

connection. To avoid the problems of flux contamination, hand

soldering is preferred to wave soldering. Many socket manufac-

turers offer socket strips that accept the 0.025 inch square pins

on 0.10 inch centers. When using mechanical sockets, restraint

of the CH1840 should be provided to keep it seated during ship-

ment. Plastic cablewraps are secure yet easily removed.

6. Special FCC rules apply to equipment connected behind a

PBX or KTS.

Changes in Attestation Procedure for Plugs and Jacks: (Name

of applicant) attests that the network interface plugs or jacks

used on this equipment comply with and will continue to com-

ply with the mechanical requirements specified in Part 68, Sub-

part F, specifically the dimensions, tolerances and metallic plat-

ing requirements. The compliance of these connectors will be

assured by purchase specifications and incoming inspection.

Documentation of such specifications and/or inspections will

be provided by the FCC within 30 days of their request for the

same.

7.

FOR YOUR USER’S MANUAL

The Part 68 rules require the following or the equivalent informa-

tion be provided to the end user of equipment containing a DAA:

FCC NOTICE TO THE USERS

1. UPON REQUEST ONLY, you must provide the following data to

your telephone utility company (telco):

a) Notice of intention to install or permanently remove an FCC

Part 68 registered device or system, and the *FCC Registra-

tion Number.

b) *The Ringer Equivalence Number (REN) (see device label).

Note that if several devices are connected to the same line,

the RENs must not add up to more than 5.0 (A or B). This

REN figure is important to your telco.

c) *The (USOC) jack type to be provided by the telco. Typically

this will be RJ-11C/W for single lines.

*The *-flagged items above are noted on the equipment’s

FCC Compliance label.

2. This device may not be used on telco-operated coin phone

lines. Party lines and privately owned coin-phones are

subject to local State regulatory policies, and possible

additional State special requirements.

3. The telco has the right to make changes to its network which

may affect the operation of your equipment, provided you are

given adequate advance written notice to permit correct oper-

ation.

4. In case of operational problems, disconnect your unit by

removing the modular plug from the telco jack. If your regular

phone (or other device or system) still works properly, your

[product name] has a problem and must remain disconnected

and (officially) serviced or returned for repairs. If upon the

above connection, your regular service still has problems,

notify your telco that they may have a problem. Request

prompt service at no cost to you the user. If a problem is

found in premises wiring not telco-installed, you are subject

to a service charge. If a fault is in telco-installed wiring, you

may be subject to a service call charge.

5. Unless otherwise noted in the User’s Manual (e.g.: fuses,

etc.), user may not under any circumstances (in or out of war-

ranty) attempt any service, adjustments or repairs on this

unit. It must be returned to the factory or authorized U.S.

service agency for all such work. Locations (or phone

numbers) of factory or authorized U.S. service points are listed

in this user’s manual.

Page 5

Document No. 607-0011 Rev. A (5/00)

Table 2

CH1840 DAA Electrical Specifications

T_A= 0^oC to 55^oC unless otherwise specified

Extended Temperature (ET) versions available for T_A= -40^oC to +85^oC

Page 6

Document No. 607-0011 Rev. A (5/00)

Figure 5. Pin Connections

Figure 6. Mechanical Specifications

ermetek

C

microelectronics

406 TASMAN DRIVE · SUNNYVALE, CALIFORNIA 94089 · TEL: (408) 752-5000 FAX: (408) 752-5004

E-mail: cermstaf@cermetek.com

website: www.cermetek.com

Cermetek reserves the right to make changes in specifications at any time and without notice. The information furnished by

Cermetek in this publication is believed to be accurate and reliable. However, no responsibility is assumed by Cermetek for its use,

or for any infringements of patents or other rights of third parties resulting from its use. No license is granted under any patents or

patent rights of Cermetek.

Printed in U.S.A.

Document No. 607-0011 Rev. A (5/00)

Page 7


型号：	CH1840DM
厂家：	ETC
描述：	Telecomm/Datacomm 电信/数据通信\n 电信数据通信
文件：	总7页 (文件大小：357K)
中文：	中文翻译
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CH1840DM [ETC]

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