CH1837/8
Data Access Arrangement Modules
V.34bis Family of High Speed DAA Modules
INTRODUCTION
Ring Detection. To announce an incoming call, the
The Cermetek CH1837/8 Family of Data Access
telephone company’s central office (CO) applies an
Arrangement (DAAs) products are designed to meet
AC ringing signal to the PSTN line.
The DAA is
the performance requirements of 33.6Kbps modems,
designed to detect this signal. The CH1837/8 sets the
such
as
V.34bis,
for
embedded
applications.
RI pin Low during the second ring period and restores
CH1837/8 meets or exceeds the requirements for V.34
it to High for the period between subsequent rings.
and can be used in lower speed applications as well.
While the AC ring signal is present on tip and ring, the
The isolation voltage and surge protection meets, as a
RI output is pulsed at the same frequency as the
minimum, the UL 1459 requirements. Further, the
incoming AC ringing signal, thereby creating a square
CH1837/8 has been tested to meet FCC Part 68 and is
wave output, typically at 20 Hz.
Figure 2 shows
Canadian DOT CSA CS-03 Part I approvable.
additional filtering which may be employed to provide
an envelope indication of the ring signal’s presence.
The CH1837/8 is compatible with all popular V.34bis
The ring detection circuit in the CH1837/8 family is
modem/fax chip sets.
Application examples are
designed to deter false indications caused by pulse
included in this datasheet. The CH1837/8 family offers
dialing or noise on the PSTN line.
a Quick-to-Market DAA solution for high performance
modem designs.
The RI output of the all CH1837/8 products is diode
protected thereby allowing an external pull-up resistor
(R>100k ohms) to +5V to be utilized to activate the
FEATURES
ring detection circuit when the DAA is not connected to
power. This can be handy for designs in which power
consumption is of concern.
When circuited in this
manner, there is virtually no current draw until a ring
modem
signal is present. Refer to Figure 5.
chip sets
RI Output:
Opto coupler, 30KW pull-up
Active low
Square wave 15-68 Hz (Tip. 20Hz)
Sensitivity: 38 Vrms across Tip & Ring
Hook Switch Control. The OFFHK input is used to
toggle the CH1837/8 DAA from Off-Hook to On-Hook
and back to Off-Hook.
and V.22
(Canada) Approvable
DESCRIPTION OF FUNCTIONAL BLOCKS
AND DISCUSSION OF BASIC OPERATIONS
Figure 1 contains a functional block drawing of the
CH1837/8 family of DAA products. Each CH1837/8
product consists of:
1. Isolation barrier
2. Off-Hook Switch/Ring Detect
3. PSTN Line Surge and High Voltage Protection
circuit
Figure 1. Function Block Diagram of CH1837/8
DAA Family.
Additionally, the 2-to-4 Wire Conversion circuit is
present in all CH1837 products.
2004 Cermetek Microelectronics, Inc.
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CH1837/8 Data Access Arrangement Modules
When the OFFHK input is low, the DAA is On-Hook.
The CH1837/8 family of DAAs does not attenuate the
On-Hook indicates to the CO that the DAA is ready to
transmit signal. Therefore, a transmit signal of –9 dBm
receive calls. When OFFHK input is high, the DAA is
applied to XMIT will comply with the FCC Part 68
Off-Hook. The Off-Hook state allows the CO supplied
requirement for data signals across Tip and Ring.
PSTN loop current to flow thereby indicating to the CO
that the DAA is either answering a call or preparing to
place a call.
Attenuation
0.0 dB
Input impedance
150K Ω
OFFHK Input: Active High
Typical input signal
0dBm or 0.775 V rms with
OFFHK Active Current: 5 mA
the Signal referenced to
GND and AC coupled
2-Wire to 4-Wire Hybrid Converter. This circuit block
performs two functions:
1. It applies the XMIT signal to the PSTN line and
2. It subtracts the XMIT signal from the total signal
RECEIVE SIGNALS
The incoming analog signal appears across TIP and
present on the PSTN line thereby deriving the
RING. The CH1837/8 derives the incoming signal and
RCV signal.
presents it at RCV with respect to GND. The user
must AC couple RCV through a 0.1uF capacitor as
The accuracy of the RCV signal derivation depends on
indicated in Figure 2.
how closely the impedance of the PSTN line matches
an ideal 600 Ohms. Generally, a small amount of the
The CH1837/8 does not gain the receive signal.
XMIT signal will appear at RCV due to the non-ideal
Receive signals can vary from a maximum strength of
nature of the PSTN line impedance. The ratio of the
-9dBm to below -50dBm.
applied XMIT signal to the received XMIT signal is
called Trans-Hybrid Rejection, or Trans-Hybrid Loss.
Attenuation
0.0 dB
PSTN Line Isolation and Surge/Peak Voltage
Input impedance
150K Ω
Protection. The Public Switched Telephone Network
Typical input signal
0dBm or 0.775 Vrms with
(PSTN) line isolation barrier circuitry provides isolation
the Signal referenced to
and the required surge and high voltage protection.
GND and AC coupled
This circuitry effectively isolates the user’s equipment
from both the PSTN line and the CO. All CH1837/8
CH1838. The CH1838 products do not contain the 2-
products are designed to meet both FCC Part 68
to-4 wire converter circuit. The CH1838 is intended for
(USA) and DOT CSA CS-03 Part I (Canada) isolation
those applications where the 2-to-4 wire conversion is
and surge requirements.
Among the more critical
performed by the modem chip set.
parameters, the PSTN isolation barrier will provide at
least 1000VAC RMS isolation and 1500V peak surge
Pins RCV and XMIT(+) are replaced by pins T1 (Pin 8)
protection.
and T2 (Pin 5). T1 and T2 are connected directly to
the internal isolation barrier circuitry. Figure 3 shows a
typical application using a V.34 modem chip set with
TRANSMIT SIGNALS
built-in 2-to-4 wire conversion.
Use PSTN line
All outgoing signals are presented to the XMIT(-) pin
interface as shown in Figure 5.
Other application
with respect to GND for single ended operation or
notes for specific chip sets are available from
between
XMIT(-)
and
XMIT(+)
for
differential
Cermetek.
operation.
CH1837C/CH1838C.
The
CH1837C
and
the
For single-ended operation, the outgoing analog signal
CH1838C contain two additional pins. These pins are
is applied to the XMIT(-) pin with respect to GND. This
CR and CT.
By connecting CR and CT through
signal must be AC coupled using a 0.1uF capacitor as
separate capacitors and switches/relays to TIP and
shown in Figure 2.
In single ended operation, the
RING (respectively), the Caller ID signal can be
XMIT(+) pin must be connected to GND through a
presented at RCV (See Figure 2).
0.1uF capacitor.
For differential operation, the outgoing analog signal is
UL RECOGNITION
applied across pins XMIT(+) and XMIT(-). This signal
To further protect the end product containing the
must be AC coupled through a 0.1uF capacitor present
CH1837/8 from field failure due to large transients
on both the XMIT(-) and XMIT(+) pins as shown in
present on poor quality lines and to maintain U.L.
Figure 2.
recognition, an additional level of transient protection
is required. Refer to Figure 5 for mandatory additional
protection circuitry.
2004 Cermetek Microelectronics, Inc.
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Cermetek Microelectronics, Inc.
CH1837/8 Data Access Arrangement Modules
DESIGN CONSIDERATIONS
MOUNTING THE DAA
The CH1837/8 DAA includes circuitry that couple the
There
are
two
mounting
techniques
that
are
modem signals to the PSTN line and provide the FCC
recommended for physically connecting the CH1837/8
required voltage isolation and surge protection.
DAA to a PCB:
Cermetek offers the following end product design
1. Direct soldering.
guidelines as suggestions only. These guidelines are
2. Sockets.
intended to facilitate the usage of Cermetek DAA
modules and to assist the user with FCC certification
Direct Soldering. The CH1837/8 DAA products may
of their end product.
be wave soldered onto a circuit card. All CH1837/8
products are hermetically sealed and will not be
1. Mount the DAA in the final assembly so that it is
harmed
by
industry
standard
wave
soldering
isolated from exposure to any hazardous voltages
processes.
within the assembly.
Adequate separation and
restraint of cables and cords must be provided.
To avoid the problems of flux contamination, hand
soldering is preferred to wave soldering.
When
2. Connect to the PSTN line through a standard FCC
cleaning, use only deionized water.
approved RJ-11C jack or equivalent. For RJ-11,
use the two center pins.
Socketing.
The socketing approach to mounting
eliminates cleaning and desoldering concerns. When
3. All PCB traces from the CH1837/8 TIP, RING, CR,
the socket is used, it must make a solid connection to
and CT pins must be at least 0.1 inch spacing
all pins.
Failure to do so will cause unreliable or
from all other traces or other conducting material.
intermittent operation.
The purpose for this spacing is to maintain 1500
VAC isolation between the incoming PSTN line
When using sockets, steps should be taken to assure
and the other traces. PSTN related PCB Traces
that the DAA module remains tightly seated in the
should have a width of 0.020 inches or greater.
socket after the end product is shipped.
It is
recommended that some type of mechanical restraint
4. TIP and RING PCB traces should be as short as
be provided to keep the CH1837/8 seated to avoid any
possible and should be oriented to prevent direct
possibility that the CH1837/8 works loose due to
or induced coupling with other signals present on
exposure to vibration and/or shock during shipment.
the PCB.
Recommended sockets are AMP series 535541 or
5. The CH1837/8 processes signals in the millivolt
87334; Berg series 76308; 65780, 66954; or Robinson
range. Even though the CH1837/8 is designed to
Nugent series SB5, or any 0.025” square strip socket.
handle noise in the power supply, steps should be
taken to assure that the noise level does not
exceed 50 mV peak-to-peak. Particular attention
FCC
(USA)
AND
DOT
(CANADA)
should be paid to both the power supply and the
REGISTRATION
ground line PCB traces.
FCC Part 68 or DOT CS-03 registration of the end
product containing the CH1837A/8A DAA is normally
6. For data calls, FCC Part 68 rules require silence
quite simple. The process involves testing the end
on the PSTN line for at least 2 seconds after a
system for compliance and submitting the test data to
data call has been completed to allow central
the FCC or DOT for review.
offices to exchange billing information. Further,
Part 68 specifies that the transmit level must not
Typically, independent approved testing labs are
exceed -9dBm.
contracted to perform the required tests on the end
product and to submit the required paperwork to the
7. For voice calls, the FCC rules require that the end
FCC or DOT. If desired, Cermetek can assist with the
product must meet the requirements of Part 68 for
Registration activity.
See Application Note # 130,
Out-of-Band Energy, and DTMF Transmit Levels.
Summary of Recommended Suppliers. The user is
assigned the registration and assumes all risk for
registration compliance.
HANDLING AND ASSEMBLY
RECOMMENDATIONS
The CH1837/8 DAA Module contains static-sensitive
components and should only be handled by personnel
and in areas that are properly protected against static
discharge.
Industry standard ESD and EOS
procedures and precautions should be observed when
handling CH1837/8 products.
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Cermetek Microelectronics, Inc.
CH1837/8 Data Access Arrangement Modules
Table 1. CH1837/8 Pin Descriptions.
Pin #
I/O
CH1837 7/C
CH1838/8C
Function
1
I/O
TIP
TIP
Direct PSTN line connection.
2
I/O
RING
RING
Direct PSTN line connection.
3
I
OFFHK
OFFHK
Used to toggle CH1837/8 product between On-Hook and Off-Hook.
When set LOW, CH1837/8 is placed On-Hook. When set HIGH,
CH1837/8 is placed Off-Hook to answer or place a call. See Note
1.
4
O
RI
RI
Indicates the presence of a ring signal between TIP and RING pins.
RI output is a square wave coincident with the incoming AC ring
signal. The RI square wave output can be conditioned to produce
an envelope of the incoming AC ring signal by using the circuit in
Figure 2.
5
O
RCV
----
Audio output signal with respect to GND. AC couple RCV through
0.1uF capacitor to eliminate any DC offset. CH1837 products only.
5
I/O
-----
T1
Direct connection to isolation barrier. CH1838 products only.
6
I
XMIT(-)
N/C
Audio input signal for CH1837 products when used in differential
mode only.
Connect to GND through 0.1uF capacitor when
CH1837Xused in single ended input via Pin 8. No Connect for
CH1838X products.
7
I
V CC
V CC
+5V+5%.
8
I
XMIT(+)
----
Audio input signal.
AC couple through 0.1uF capacitor.
For
CH1837X products, can be used in differential mode with XMIT(-)
or in single ended mode with respect to GND.
For CH1838,
operation in single ended mode only with respect to GND.
8
I
----
T2
Direct connection to isolation barrier. CH1838 product only.
9
I
GND
GND
Ground.
10
I
CR
CR
Caller ID connection to RING input pin. CR should be connected
through a switch/relay and a 0.47uF 100V capacitor to the RING
pin. Refer to the circuit in Figure 2. When both the CR switch/relay
and the CT switch/relay are closed, the CH1837C/8C will AC
terminate the incoming PSTN line and present the caller ID signal
on RCV. CR pin is only present on CH1837C/8C product.
11
I
CT
CT
Caller ID connection to TIP input pin. CT should be connected
through a switch/relay and a 0.47uF 100V capacitor to the TIP pin.
Refer to the circuit in Figure 2. When both the CT switch/relay and
the CR switch/relay are closed, the CH1837C/8C will AC terminate
the incoming PSTN line and present the caller ID signal on RCV.
CR pin is only present on CH1837C/8C product.
Notes:
1. When answering incoming calls in response to a ring indication on RI, internal degradation may occur if OFFHK
is set HIGH before RI returns to its HIGH state.
2004 Cermetek Microelectronics, Inc.
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Cermetek Microelectronics, Inc.
CH1837/8 Data Access Arrangement Modules
Figure 2. Typical Application.
Figure 3. CH1838 Typical Connection to Modem.
Figure 4. Low Power Ring Detection Circuit.
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Cermetek Microelectronics, Inc.
CH1837/8 Data Access Arrangement Modules
Table 2. CH1837A/8A Electrical Specifications.
Parameter
Conditions
Min.
Typ.
Max.
Units
Logic
Input HIGH
2.4
V
Input LOW
0.4
V
Input Leakage HIGH
500
µ A
Input Leakage LOW
-500
µ A
Output HIGH
IOH=0.05mA
3.0
V
Output LOW
IOL=2.0mA
0.4
V
Isolation Protection
Between TIP and RING
All CH1837/8 Products
100
VAC RMS
Surge Protection
Between TIP and RING
All CH1837/8 Products
1500
V Peak
Transmission Insertion Loss
Attenuation between the transmitter input
PSTN
line
at
1.8kHz
with
600ohms -0.8
0
+0.8
dB
termination (flat from 300-4kHz)
Frequency Response
(Ref=1800Hz Transit)
200-4kHz
-0.3
+0.3
dBm
Distortion Noise-Transmit
-10dBm transmit power (600Hz)
-82
dBm
Receive Gain
Gain between PSTN line and receive output -0.5
0
+0.5
dB
at 1800Hz with 600 ohm resistive termination
(flat from 300-4kHz)
Receive Frequency Response
(Ref = 1800Hz Receive)
200-4kHz
-0.3
+0.3
dBm
nd
rd
th
Receive 2 /3 /4
-10dB at TIP and RING
-82
dBm
Harmonic Distortion
Noise-Receive
400Hz-4kHz
-82
dBm
PSTN Line Input Impedance
At 1800Hz
550
600
650
Ohm
On-Hook Impedance
10
20
mOhms
Loop Current
48VDC from TIP to RING. Not applicable to 20
100
mA
CH1837LL.
Longitudinal Balance
OH=0 (On-Hook)
66
dBm
FCC Part 68.310 and DOT
OH=1 (Off-Hook)
66
dbm
Return Loss
1kHz
25
dBm
(Zref=600ohm, 2.16 µ F)
Trans-Hybrid Loss
Attenuation between the transmitter input 22
25
dB
and receiver output at 1kHz with 600ohm
complex termination
Transmit Input Impedance
At 1800Hz
120
150
200
kOhm
Receive Output Impedance
At 1800Hz
10
100
Ohms
Ring Select Sensitivity
AC voltage between TIP and RING
38
V rms
Hook Switch Control Current
Drive capable of sourcing current
4
mA
Weight
20
gm
Supply Current
V CC =+5VDC ± 5%, Off-Hook
8
mA
V CC =+5VDC ± 5%, On-Hook
5
mA
Ringer Equivalence
Type A
0.2A
REN
2004 Cermetek Microelectronics, Inc.
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CH1837/8 Data Access Arrangement Modules
Figure 5. PSTN Line Interface.
1.
Currently Limiting PSTN Protection Line
B. In most environments, 2 terminal surge
Device.
suppressors are adequate.
For severe
Currently limiting devices are mandatory to meet
environments, use an external 3 terminal
UL safety standards. For FCC Part 68 approval,
device (as indicated in Figure 5) with an earth
the current limiting components identified as F1
ground.
and F2 in dashed Box #1 must also survive FCC
Part 68 surge testing.
Refer to Cermetek
Application Note #126, Supplemental PSTN Line
3. EMI/RFI Suppression.
Protection, for more details. Refer to Application
Additional suppression, if required, may be added
Note # 130, Summary of Recommend Suppliers,
as described below in Sections 3A-3B without
for a list of suppliers and associated part numbers.
adversely affecting FCC Part 68 approval or
UL60950 listing.
A. A Polyfuse (rated at 0.15 amps) is preferred
because it resets automatically upon removal
A. To provide adequate EMI/RFI suppression,
of the current flow.
Non-resettable devices
the capacitor/inductor network contained in
are also acceptable. Refer to Application Note
dashed Box #3 should be located as close to
#130 for a complete list of recommended
the RJ11 Jack as possible.
Further, this
vendors and associated part numbers.
network should be provided with an excellent
ground path to the chassis.
B. Resistors (10 Ω carbon film or 1/8 watt
minimum) may be used in Canada, as Canada
B. Capacitors C1 and C2 should not exceed
has no requirements that PSTN equipment be
0.005 µ f. They must have a rating of 1.5KV
operational after a Type B surge test.
and typically are 0.001 µ f ± 20%. Inductors L1
and L2 may be either individual inductors or a
C. Although CSA CS-03 Part 1 (Canada) follows
dual inductor. Refer to Application Note #130
the requirements of FCC Part 68 (USA),
for a complete list of recommended vendors
Cermetek
recommends
contacting
DOT
and associated part numbers.
For UL
(Canada) and/or a certified independent lab to
applications, choose capacitors and inductors
verify compliance.
For Canada, use either
that are UL60950 listed. The actual values of
10 Ω resistors (carbon film or SMD parts 1/8
the components used may vary depending on
watt minimum) as described in paragraph B
the end product design.
above.
2. Over Voltage and Lightning Protection.
A. The required UL60950 and FCC Part 68 surge
protection (identified as D1 in dashed Box 2)
must be supplied externally. The purchaser
must include some form of surge protection as
described herein to obtain FCC Part 68
approval and to maintain UL60950/3 edition
rd
listing.
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0010 Revision Q (08/04)
Cermetek Microelectronics, Inc.
CH1837/8 Data Access Arrangement Modules
Table 3. Summary CH1837/8 Family of Products.
Model
Summary of Features
Operating Temperature
CH1837
33.6kbps DAA, 2-to-4 Wire Conversion, FCC Part 68 and UL 1459
0 ° C to +70 ° C
compliant
CH1837C
33.6kbps DAA, 2-to-4 Wire Conversion, Caller ID, FCC Part 68 and
0 ° C to +70 ° C
UL 1459 Compliant
CH1837C ET
33.6kbps DAA, 2-to-4 Wire Conversion, Caller ID, FCC Part 68 and
-40 ° C to +85 ° C
UL 1459 Compliant
CH1838
33.6kbps DAA, FCC Part 68 and UL 1459 Compliant
0 ° C to +70 ° C
CH1838C
33.6kbps DAA, Caller ID, FCC Part 68 and UL 1459 Compliant
0 ° C to +70 ° C
CH1838C ET
33.6kbps DAA, Caller ID, FCC Part 68 and UL 1459 Compliant
-40 ° C to +85 ° C
Figure 6. Physical Dimensions
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/DOT Approved or Approvable device. However, Cermetek does not have influence nor
over knowledge of the specific user application environment. Therefore, for FCC 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.
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