CH1840
Low Profile Data Access Arrangement (DAA) Modules
INTRODUCTION
FEATURES
The CH1840 is an ultra small, low profile Data Access
Arrangement (DAA).
Its modular construction and
single +5 Volt D.C. power requirement simplify your
losses.
development process. Specifically designed for both
voice and data, this allows direct connection of these
circuits to the telephone lines. The CH1840 has FCC
to +85C.
Part 68 registration that can be transferred to your
product. Simply attach the included registration sticker
to the outside of your product. This eliminates the
costs and delays associated with Part 68 testing and
registration.
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.
FUNCTIONAL DESCRIPTION
The CH1840 requires only 1.5 square inches of circuit
The operation of the CH1840 can be broken down into
board space and presents a profile of only 0.35 inches
the functional blocks shown in Figure 1.
in height. This DAA can either be mounted directly on
a printed circuit board or socketed.
Connection is
1) Phone line control
made through 0.025-inch square pins on 0.10-inch
2) Billing delay
centers.
The telephone line connection is made
3) Ring detection
through a user supplied RJ-11 jack.
4) Signal Path
5) 2- to 4-wire converter
The CH1840 DAA is designed for use with a variety of
Control inputs and status outputs for the CH1840 are
voice circuitry and LSI modem/fax chip sets.
This
compatible with 5 Volt CMOS.
See the Electrical
device is ideal for fax and modem applications up
Specifications.
through V.32bis. The CH1840 is pin compatible with
the CH1817.
Figure 1.
CH1840 DAA Functional Block Diagram.
2004 Cermetek Microelectronics, Inc.
Page 1
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
Phone Line Control.
In the Public Switched
RING DETECTION
Telephone Network (PSTN), the wires from a
The central office signals an incoming call by placing a
telephone to the phone company’s central office (CO)
ring signal on the local loop. The CH1840 monitors
are referred to as the local loop.
the loop for this signal. The Ring Indication output, RI,
is normally HIGH. When ringing appears, RI is set
2-Wire To 4-Wire Hybrid Converter. This block has
LOW during the typically 2 second ring period and is
two functions:
restored to HIGH for the typically 4 seconds between
rings. The ring detection circuit is designed to prevent
Drawing current from the local loop signals the central
false indications due to noise or pulse dialing on the
office that the telephone is Off Hook, that is, either
line.
answering a call or preparing to place a call. In the
CH1840, this function is controlled by the OFFHK
The RI output of the CH1840 is diode protected so that
signal. When this input is LOW, the CH1840 is On-
an external pull-up resister(R> 100Kohm) to +5V may
Hook, indicating to the central office that it is not using
be utilized to activate the ring detection circuit when
the line.
CH1840 can pulse dial by togging the
the DAA is not connected to power.
This can be
OFFHK input
handy with designs in which power consumption is of
concern.
When circuited in this manner, there is
For data calls, FCC Part 68 rules require silence on
virtually no current draw until a ring signal is present.
the phone line for at least 2 seconds after the call has
See Figure 3.
been completed to allow central office to exchange
billing information. The CH1840 assures conformance
TRANSMIT SIGNAL
to this requirement by stating a two-second timer on
The outgoing analog signal to be transmitted through
the LOW to HIGHT transition to OFFHK and
the phone line should be applied to the XMIT pin (with
squelching transmitted signals until the time expires.
respect to GND
The CH1840 defeats this function when Voice Mode is
selected on the Data/Voice pin.
The CH1840 attenuates the transmit signal by 9.5, dB
(0dB for the D option applied to XMIT will comply with
the FCC Part 68 requirement 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 -9dBm at Tip and Ring.
Figure 2.
Typical CH1840 Application.
2004 Cermetek Microelectronics, Inc.
Page 2
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
excessive Power is detected and returns LOW when
the transmitted signal is unsquelched.
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.
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
Figure 3. Low Power Ring Detection
the total signal on the phone to produce the received
signal.
The accuracy of this subtraction process
For live voice or DTMF, when the CH1840 family
depends on how closely the impedance of the phone
products are in voice mode, the output can be 0 dBm.
line matches 600 ohms. Generally, a small amount of
In voice mode, the squelch will not let the output signal
the XMIT signal will appear at RCV. The ratio of the
exceed 0 dBm. Hence, by applying a 0dBm signal to
XMIT signal applied to the signal returned is called
the CH1840D and a +9.5 dBm signal to the CH1840, it
trans-hybrid rejection. The CH1840 has a high trans-
will achieve the maximum signal output.
hybrid loss, which is at least 18dB rejection from 300
Hz to 4 KHz bandwidth.
CH1840 Family
Normal Insertion Loss
CH1840
-9.5 dB
CH1840D
0 dB
VOICE SIGNALS
Voice signals are much more complex in nature than
data signals. A voice signal is comprised of numerous
The D designation refers to differential input between
frequencies combined at varying intensities. Whereas
the XMIT (+) and (-) pins. This is required and is a
a data signal is comprised of no more than a few
convenient input for certain types of modem ship sets.
discreet frequencies.
This difference dictates that
voice signals receive more attention before connecting
to the telephone lines.
RECEIVE SIGNAL
Receive Signal is presented at RCV with respect to
The FCC restricts voice and data signals to between
GND and must be AC coupled to your receive input.
300 Hz and 3300Hz. This is because the Telephone
The CH1840 does not add any gain to the receive
Company uses frequencies below 300 Hz for low-
signal. Receive signals can vary from a maximum
speed tele type and frequencies above 3300 Hz for
strength of 9dBm to below –50 dBm for data mode and
internal signaling and multiplexing.
up to 0 dBm strength when DTMF and live voice are
being received.
Data signals easily meet the FCC requirements
without additional filtering. However, bandpass filters
are essential for voice communication.
EXCESSIVE SIGNAL DETECT
FCC Part 68 rules limit the average power of data
A bandpass filter is utilized on the transmit line. This
signals transmitted to the phone line. To meet this
filter ensures that the signal meets FCC requirements.
requirement, the CH1840 monitors the transmit audio
It also shapes the signal to minimize the phone line
signal at XMIT. If the signal level exceeds 0 dBm.
distortion.
The output PSQ is normally LOW. It is set HIGH when
2004 Cermetek Microelectronics, Inc.
Page 3
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
Table 1.Pin descriptions
Pin
Name
I/O
Function
1
TIP
I/O
TIP . Direct connection to the telephone line through a standard jack.
2
RING
I/O
RING . Direct connection to the telephone line through a standard jack.
3
N/C
-
Not Used . Please leave unconnected
4
OFFHK
I
OFF HOOK , Input. When set LOW, the CH1840 is placed On-Hook. When set
HIGH, the CH1840 is placed Off-Hook to answer or place a call. This input can also
be used for pulse dialing.
5
RI
O
RING INDICATION , Output. RI is driven LOW during the typically 2 second ring
period and HIGH during the typically 4 seconds between rings. RI is otherwise HIGH.
NOTE: RI pulses square wave along with ring signal frequency. The square wave
can be suppressed to produce an envelope of the AC ring with the application circuit
shown in Figure 2.
6
D/V
I
DATA/VOICE SELECT , Input. When driven LOW or left unconnected, Data Mode is
selected and the Billing Delay and Power Squelch are enabled. When driven HIGH,
Voice Mode is selected and the Billing Delay and Power Squelch are disabled.
7
PSQ
O
POWER SQUELCH , Output. PSQ indicates the status of the signal limiting squelch
circuit. When PSQ is HIGH, the transmit path is squelched. PSQ is also active when
On-Hook and in Data Mode.
8
RCV
O
RECEIVE , Output. RCV is the audio signal received from the phone line. This output
is symmetrical with respect to +2.5V. AC coupling is recommended for most designs.
9
XMIT(-)
I
Input must be used with pin 11 in differential mode only. When not used, please
leave unconnected.
10
VCC
I
+5V Power Supply, Input.
11
XMIT(+)
I
TRANSMIT , Input. Analog signal input. Audio data and voice signals presented here
will be monitored for excessive power, filtered through a bandpass, and applied to the
phone line unless squelched. One input pin of two when used in differential mode
with pin 9.
12
GND
I
SIGNAL AND POWER COMMON GROUND , Input.
2004 Cermetek Microelectronics, Inc.
Page 4
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
SAMPLE APPLICATION
induced coupling with other signals on the host
Figure 2 illustrates a typical application of the CH1840.
circuit card.
When transmitting data the controller must assert the
D/V pin low to provide the two second billing delay
5. The DAA Module is a sensitive subsystem that
required by the FCC. When transmitting voice signals,
should be treated as any other integrated
the controller shoud drive the D/V pin high.
This
component.
Pay special attention to the power
disavles the billing delay, and power squelch
supply to the DAA. The device handles signals in
the millivolt range. Even though it is designed to
One of the requirements of an FCC approved DAA is
handle noise in the power supply, steps should be
that the signal transmitted to Tip and Ring does not
taken to assure the noise level does not exceed
exceed –9.0 dBm.
The Ch1840 incorporates an
50mV peak-peak.
automatic squelch
6. For data calls, Part 68 rules require silence on the
phone line for at least 2 seconds after a data call
CH1840-D: 0 dB XMIT ATTENUATION
has been completed to allow central offices to
The D option has 0.0 dB insertion loss (typical) with
exchange billing information and specifies the
respect to a differential input between XMIT (-) and
transmit level must not exceed -9dBm. The FCC
XMIT (+). This allows the maximum signal strength of
rules also require that for voice calls the final
–9dBm to be input while maintaining FCC compliance.
system meet the requirements of Part 68 for Out-of
To use the CH1840-D as single end input device,
Band
Energy,
and
DTMF
Transmit
Levels.
ground the XMIT (-) pin through a 0.1uF capacitor.
Because
the
CH1840
already
meets
FCC
requirements for Part 68 registration for High
Voltage isolation and Surge Protection, the
MOUNTING THE DAA
certification of the product is normally a simple
The DAA can be soldered directly to the host circuit
process that often can be completed directly with
card or installed in sockets. To avoid the problems of
the FCC. If desired, independent testing labs are
contamination, hand soldering is preferred to wave
available that can test the system and submit the
soldering. When hand cleaning use only deionized
required paperwork to the FCC for approval.
water; when wave soldering use washless flux.
Cermetek can assist with the registration.
7. The CH1840 DAA as is meets or exceeds the
DESIGN CONSIDERATIONS
hazardous
voltage,
surge
and
leakage
The CH1840 DAA includes circuits that couple the
requirements of the FCC.
For applications that
modem signals to the phone line and provides FCC
connect to Canadian phone lines, governed by the
required
isolation
and
protection.
The
FCC
DOC (Department of Communications) and to
registration process by the host product can be
further protect the CH1840 from field failure on
minimized provided that the following guidelines are
excessively poor quality lines and to maintain UL
followed.
recognition, a higher level of transient protection is
required, thereby making mandatory the circuit
1. The mounting of the DAA in the final assembly
consisting of two fuses and one varistor as shown
must be made so that it is isolated from exposure to
in Figure 3. Adding these three devices will not
any hazardous voltages within the assembly.
affect FCC registration. Components L1, L2, C1,
Adequate separation and restraint of cables and
C2 are optional and serve two purposes. First, they
cords must be provided.
restrict high frequency signals from reaching the
phone line and thereby add EMI protection.
2. Connection to the phone line should be made
Second, they protect against externally generated
through a standard FCC approved RJ-11C jack or
RFI from degrading the modem’s ability to operate
equivalent.
on proper carrier signals. Adding these devices will
not affect FCC, DOC, or UL registration.
3. Circuit board traces from the DAA’s TIP and RING
pins must exceed 0.1 inch spacing from all other
traces or other conducting material. The purpose
MOUNTING THE CH1840
for this pacing is to maintain 1000 VAC isolation
The CH1840 can be soldered directly to the host
between the phone line and the other traces.
circuit card or installed in sockets. Direct soldering
Traces should have a nominal width of 0.020
provides the most sound connection. To avoid the
inches or greater.
problems of flux contamination, hand soldering is
preferred
to
wave
soldering.
Many
socket
4. TIP and RING traces should be as short as
manufacturers offer socket strips that accept the 0.025
possible and should be oriented to prevent direct or
inch square pins on 0.10 inch centers. When using
sockets mechanical restraint of the CH1840 should be
2004 Cermetek Microelectronics, Inc.
Page 5
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
provided to keep it seated during shipment. Plastic
(officially) serviced or returned for repairs. If upon
cable wraps are secure yet easily removed.
the above disconnection your regular service still
has problems, notify your telco that they may have
The DAA module contains static sensitive devices and
a problem. Request prompt service at no cost to
should be handled by personnel and in areas that are
you the user. If a problem is found in premises
properly protected against static discharge.
wiring not telco installed, you are subject to a
service charge. If a fault is in telco installed wiring,
There
are
two
mounting
techniques
that
are
you may be subject to a service call charge.
recommended for physically connecting the module to
your circuit card; 1) sockets, and 2) direct soldering.
5) Unless otherwise noted in the User’s Manual (eg:
Each approach has its own set of benefits and
fuses,
etc.),
user
may
not
under
any
challenges.
circumstances (in or out of warranty) attempt any
service, adjustments or repairs on this unit.
It
If the DAA module is wave soldered on a circuit card,
must be returned to the factory or authorized U.S.
please use washless flux or hand solder. This part is
service agency for all such work. Locations (or
not hermetically sealed. Water or chemical intrusion
phone numbers) of factory or authorized U.S.
into the case can cause malfunction and void the
service points are listed in this user’s manual.
warranty.
6) Special FCC rules apply to equipment connected
behind PBX or KTS.
FOR YOUR USER’S MANUAL
The Part 68 rules require the following or the
7) Changes in Attestation Procedure for Plugs and
equivalent information be provided to the end user of
Jacks; (Name of Applicant) attests that the
equipment containing a DAA:
network interface plugs or jacks used on this
equipment comply with and will continue to comply
with the mechanical requirements specified in Part
FCC NOTICE TO THE USERS
68. Subpart F. Specifically the dimensions,
1) UPON REQUEST ONLY, you must provide the
tolerances and metallic plating requirements. The
following data to your telephone utility company
compliance of these connectors will be assured by
(telco):
purchase specifications and incoming inspections.
a) Notice of intention to install or permanently
Documentation of
such specifications and/or
remove an FCC Part 68 registered device or
inspections will be provided the FCC within 30
system, and the FCC Registration Number.
days of their request for same.
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 telco.
Typically this will be RJ-11C/W for single lines.
*The *-flagged items above are noted on the
equipments 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 their
network which may affect the operation of your
equipment, provided you are given adequate
advance written notice to permit correct operation.
4) In cases 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
2004 Cermetek Microelectronics, Inc.
Page 6
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
Figure 4
Telephone Line Interface.
1. RJ-11 Jacks must be provided by one of the
B. For lightning prone areas where there are
vendors on the list.
Refer to Application Note
more than 2 storms per year, provide an earth
#130, Summary of Recommended Suppliers.
ground connection and use a three terminal
sidactor or similar device that provides metallic
2. Current Line Device: F1 and F2 – 1.25amp.
and longitudinal protection.
This must also
A. UL 1459 must use a current limit device. A
include the current protection in Section 2.
Poly Fuse is recommended as this device
resets automatically after each power surge.
4. EMI/RFI Suppression.
The capacitor/ inductor network should be located
B. Resistors (10ohm carbon film or SMD 1/8W
as close to the RJ-11 Jack as possible with an
minimum)
may
be
used
for
non
UL
excellent ground path to the chassis. Capacitors
applications.
C1 and C2 should not exceed 0.005 µ F.
They
must have a rating of 1.5KV and typically have a
3. Over Voltage and Lightning Protection.
value of 0.001 µ F ± 20%. Inductors L1 and L2 are
A. DOC (Canada) may require external current
ferrite cylinders and provide attenuation to high
limiting devices. Use 1ohm resistors (carbon
frequencies
from
system
level
components
film or SMD parts 1/8W minimum) in each lead
external to the CH1840. The required values must
(TIP and RING). You may substitute fuses or
be empirically determined for each product design
the Poly Fuse described in Section 2.
2004 Cermetek Microelectronics, Inc.
Page 7
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
Table 2.
CH1840 DAA Electrical Specifications.
T A =0°C to 55°C unless otherwise specified
Extended Temperature (ET) versions available for T A =-40°C to +85°C
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Logic
Input HIGH
V IH
2.4
V
Input LOW
V IL
0.4
V
Input Leakage HIGH
I IH
500
µ A
Input Leakage LOW
I IL
-500
µ A
Output HIGH
V OH
IOH=0.2mA
3.0
V
Output LOW
V OL
IOL=2.0mA
0.4
V
Telephone Line Interface
Z LINE
600
Ohms
AC Impedance
Isolation Protection
Conforms to FCC Part 68 hazardous
1K
V RMS
voltage and leakage
Surge Protection
Conforms to FCC Part 68 for surge
800
V Peak
Transmit Level
V TRX
Measured at XMIT, 1800Hz
CH1840
0.774
V RMS
(Voice Mode) CH1840D
0.251
V RMS
Transmission
Insertion
G TRX
1800Hz, 600 Ohms, 35mA loop current
Loss
CH1840
9.5
10
10.5
dB
(Voice Mode) CH1840D
-9.5
0.0
0.5
dB
Receive Insertion Gain
G RCV
1800Hz, 600 Ohms, 35mA loop current
-0.5
0
+0.5
dB
Trans-Hybrid Loss
G TH
600 Ohms+3& between TIP & RING
18
23
dB
600HZ to 4000Hz
On-Hook Impedance
Z ONHK
OFFHK = 0 volts
10
20
Mohm
Loop Current
ILOOP
OFFHK = 5 volts
20
80
mA
Receive
Output
ZRNC
Measured at RCV
50
Ohms
Impedance
Transmit
Input
Z TRX
Measured at XMIT @ 1800Hz
50
100
kOhm
Impedance
FCC Registration Number
Supplied on unit label
Ringer Equivalence
REN
Supplied on unit label
0.2A
REN
TIMERS
Ring Detection Delay
T RGD
Ringing at 40Hz, 45 V RMS
200
360
ms
Billing Delay Timer
T BD
20
2.5
30
sec
Hook Switch
Drive capable of sourcing current
4
mA
Power Supply Current
V CC =+5VDC ± 5%, Off-Hook
6
10
mA
V CC =+5VDC ± 5%, On-Hook
3
6
mA
2004 Cermetek Microelectronics, Inc.
Page 8
Document No. 607-0011 Revision B1 (09/04)
Cermetek Microelectronics, Inc.
CH1840 Family of Low Profile DAA Modules
Figure 6. Pin Connections.
Figure 7. Mechanical Specifications.
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, Cermetek assumes no responsibility 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.
Cermetek provides the user with a FCC (USA) and IC (Canada) Approved or device. However, Cermetek does not have influence
over nor knowledge of the specific user application environment. Therefore, for FCC and IC Approved or Approvable devices, the
user assumes all risk for maintaining compliance to registration.
Printed in U.S.A
406 TASMAN DRIVE | SUNNYVALE CA 94089 | LOCAL: 408-752-5000 | TOLL FREE: 1-800-882-6271 | FAX: 408-752-5004
CERMETEK WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
iModem Network WEB SITE: http://www.imodem.net/ or https://sunnyvale.imodem.net/
2004 Cermetek Microelectronics, Inc.
Page 9
Document No. 607-0011 Revision B1 (09/04)