CH1837A/8A Data Access Arrangement Module
V.34bis High Speed DAA Module
INTRODUCTION
DESCRIPTION OF FUNCTIONAL BLOCKS
The Cermetek CH1837A Data Access Arrangement
AND DISCUSSION OF BASIC OPERATIONS
(DAA)
is
designed
to
meet
the
performance
Figure 1 contains a functional block drawing of the
requirements of 33.6Kbps modems, such as V.34bis,
CH1837A. Each CH1837A product consists of:
for embedded applications. The CH1837A meets or
1) Isolation barrier.
exceeds the requirements for V.34 and can be used in
2) Off-Hook Switch/Ring Detect circuit.
lower speed applications as well. The isolation voltage
3) PSTN Line Surge and High Voltage Protection
and surge protection meets, as a minimum, North
circuitry.
American UL60950/3 edition (USA) and CSA C22.2
rd
4) 2-to-4 Wire Conversion circuit.
950 (Canada) requirements. Further, the CH1837A will
meet FCC Part 68 (TIA/EIA/IS-968) and is Canadian
V cc
VND
DOT CSA CS-03 Part I approvable when properly
designed in.
SURGE AND
TIP
The CH1837A is compatible with all popular V.34bis
ISOLATION
PROTECTION
modem/fax chip sets.
Application examples are
CIRCUITRY
RING
included in this datasheet.
The CH1837A offers a
Quick-to-Market DAA solution for high performance
T1
T2
XMIT+
modem designs.
HYBRID
OFF HOOK
XMIT-
2W/4W
SWITCH
The CH1837A is exceptionally well suited for voice-
RCV
CONVERTER
RING DET.
over-data (VoIP) and other internet-based telephony
and data communication applications.
RI
OFFHK
For those applications not requiring a two to four wire
hybrid converter circuit, the CH1838A provides all the
features of the CH1837A (except the hybrid converter)
Figure 1. Function Block Diagram of CH1837A.
while offering some cost savings.
Note that the
CH1838A is a special order product only.
Consult
Figure 2 contains a functional block drawing of the
Cermetek for availability and delivery.
CH1838A. Each CH1838A product consists of:
1) Isolation Barrier.
2) Off-hook Switch/Ring Detect circuit.
FEATURES
3) PSTN Line surge and High Voltage Protection
Circuitry.
Figure 2. Function Block Diagram of CH1838A.
sets.
V cc
VND
SURGE AND
TIP
(CH1837A only).
ISOLATION
PROTECTION
edition Listed and CSA C22.2 950
CIRCUITRY
RING
Compliant. See UL File E104957.
T2
OFF HOOK
N/C
N/C
SWITCH
RING DET.
T1
RI
and V.22.
OFFHK
(Canada) Approvable.
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
Ring Detection. To announce an incoming call, the
OFFHK Input:
Active HIGH
telephone company’s central office (CO) applies an
OFFHK active Current: 5mA
AC ringing signal to the PSTN line. The CH1837A/8A
is designed to detect this signal. The CH1837A/8A
uses the AC ring signal to produce a square wave
pulse train output at the CH1837A/8A RI pin. This
pulse train is the same frequency as the incoming AC
ring signal and is typically 20 Hz. Figure 3 shows
external filtering which may be employed to provide an
envelope indication of the ring signal using the
CH1837A/8A RI output. The ring detection circuit in
the CH1837A/8A family is designed to deter false
indications caused by pulse dialing or noise on the
PSTN line.
Additionally, the RI output of the CH1837A/8A is diode
protected thereby allowing an external pull-up resistor
(R>100k ohms) to +5V to be utilized to activate the
ring detection circuit when the CH1837A/8A is not
connected to power. This can be handy for designs in
which power consumption is of concern.
When
Figure 4. Low Power Ring Detection Circuit.
circuited in this manner, there is virtually no current
draw until a ring signal is present. Refer to Figure 4.
2-Wire to 4-Wire Hybrid Converter (CH1837A only).
This circuit block performs two functions:
1. It applies the XMIT signal to the PSTN line, and
RI Output:
Opt coupler, 30K Ω pull-up, Active
2. It subtracts the XMIT signal from the total signal
LOW
present on the PSTN line thereby deriving the
Square wave 15-68HZ (TIP. 20Hz)
RCV signal.
Sensitivity: 38Vrms across TIP and RING
The accuracy of the RCV signal derivation depends on
how closely the impedance of the PSTN line matches
an ideal 600 Ohms. Generally, a small amount of the
XMIT signal will appear at RCV due to the non-ideal
nature of the PSTN line impedance. The ratio of the
applied XMIT signal to the received XMIT signal is
called Trans-Hybrid Rejection, or Trans-Hybrid Loss.
PSTN Line Isolation and Surge/Peak Voltage
Protection. The Public Switched Telephone Network
(PSTN) line isolation barrier circuitry provides isolation
and the required surge and high voltage protection.
This circuitry effectively isolates the user’s equipment
from both the PSTN line and the CO.
The
CH1837A/8A has been designed to meet both FCC
Part 68 (USA) and DOT CSA CS-03 Part I (Canada)
isolation and surge requirements when circuited as
Figure 3. Typical Application.
indicated in Figure 5.
Among the more critical
parameters, the PSTN isolation barrier will provide at
Hook Switch Control.
least 1500VAC RMS isolation and 2122V peak surge
protection.
The CH1837A/8A is also UL60950/3
rd
The OFFHK input is used to toggle the CH1837A/8A
from On-Hook to Off-Hook and back to On-Hook.
edition listed and meets CSA C222-950 test conditions
when connected as indicated in Figure 5.
When the OFFHK input is TTL Low, the CH1837A/8A
is On-Hook. The On-Hook state indicates to the CO
that the CH1837A/8A is ready to receive calls.
TRANSMIT SIGNALS
The CH1837A/8A does not attenuate the transmit
When the OFFHK input is TTL High, the CH1837A/8A
signal before it applies the signal across tip and ring.
is Off-Hook. The Off-Hook state indicates to the CO
Therefore, a transmit signal of –9dBm applied to XMIT
that the CH1837A/8A is either answering a call or
will comply with the FCC Part 68 requirement for data
preparing to place a call.
signals across Tip and Ring.
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
CH1837A. The user presents all outgoing transmit
when circuited per Figure 5 herein. Cermetek offers
signals to the XMIT(-) pin with respect to GND for
the following end product design guidelines as
single ended operation or between XMIT(-) and
suggestions only. These guidelines are intended to
XMIT(+) for differential operation. This signal must be
facilitate the usage of Cermetek DAA modules and to
AC coupled through a 0.1 µ F capacitor present on both
assist the user with FCC certification of their end
the XMIT(-) and XMIT(+) pins as shown in Figure 3.
product.
For single-ended operation, the outgoing analog signal
1. Mount the DAA in the final assembly so that it is
is applied to the XMIT(-) pin with respect to GND. This
isolated from exposure to any hazardous voltages
signal must be AC coupled using a 0.1 µ F capacitor as
within the assembly.
Adequate separation and
shown in Figure 3. In single ended signal operation,
restraint of cables and cords must be provided.
the XMIT(+) pin must be connected to GND through a
0.1 µ F capacitor.
2. Connect to the PSTN line through a standard FCC
approved RJ-11C jack or equivalent. For RJ-11,
CH1838A.
All incoming and outgoing signals are
use the two center pins .
presented between T1 and T2. The user must provide
an external hybrid conversion circuit and/or control the
3. All PCB traces from the CH1837A/8A TIP and
flow of the transmit and receive signals into/from the
RING pins must be at least 0.1 inch spacing from
CH1838A.
all other traces or other conducting material. The
purpose for this spacing is to maintain 1500 VC
isolation between the incoming PSTN line and the
RECEIVE SIGNALS
other traces. PSTN related PCB Traces should
The incoming analog signal appears across TIP and
have a width of 0.020 inches or greater.
RING. The CH1837A/8A does not amplify the receive
signal. Receive signals can vary from a maximum
4. TIP and RING PCB traces should be as short as
strength of -9dBm to below -50dBm.
possible and should be oriented to prevent direct
or induced coupling with other signals present on
CH1837A. The CH1837A derives the incoming signal
the PCB.
and presents it at RCV with respect to GND. The user
must AC couple RCV through a 0.1 µ F capacitor as
5. The CH1837A/8A processes signals in the millivolt
indicated in Figure 3.
range. Even though the CH1837A/8A is designed
to handle noise in the power supply, steps should
CH1838A.
The CH1838A presents the incoming
be taken to assure that the noise level does not
signal between T1 and T2. The user must provide an
exceed 50 mV peak-to-peak. Particular attention
external hybrid conversion circuit and/or control the
should be paid to both the power supply and the
flow of the transmit and receive signals into/from the
ground line PCB traces.
CH1838A.
6. For data calls, FCC Part 68 rules require silence
on the PSTN line for at least 2 seconds after a
data call has been completed to allow central
Attenuation:
0.0dN
offices to exchange billing information. Further,
Input Impedance:
150K Ω
Part 68 specifies that the transmit level must not
Typical Input Signal:
0dBm or 0.775Vrms with the
exceed -9dBm.
Signal referenced to GND and
AC coupled
7. For voice calls, the FCC rules require that the end
product must meet the requirements of Part 68 for
Out-of-Band Energy, and DTMF Transmit Levels.
UL RECOGNITION
To further protect the end product containing the
CH1837A/8A from field failures caused by large
HANDLING
AND
ASSEMBLY
transients present on poor quality PSTN lines and to
RECOMMENDATIONS
maintain UL recognition, an additional level of external
The CH1837A/8A DAA Module contains static-
transient protection is required. Refer to Figure 5 for
sensitive components and should only be handled by
mandatory additional protection circuitry.
personnel and in areas that are properly protected
against static discharge. Industry standard ESD and
EOS procedures and precautions should be observed
DESIGN CONSIDERATIONS
when handling CH1837A/8A products.
The CH1837A/8A DAA includes circuitry that couples
the modem signals to the PSTN line and provides the
FCC required voltage isolation and surge protection
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
MOUNTING THE DAA
There are two mounting techniques recommended for
physically connecting the CH1837A/8A DAA to a PCB:
1. Direct soldering.
2. Sockets.
Direct Soldering. The CH1837A/8A may be wave
soldered onto a circuit card. All CH1837A/8A products
are hermetically sealed and will not be harmed by
industry standard wave soldering processes.
To avoid the problems of flux contamination, hand
soldering is preferred to wave soldering.
When
cleaning, use only demonized water.
Socketing.
The socketing approach to mounting
eliminates cleaning and desoldering concerns. When
the socket is used, it must make a solid connection to
all pins.
Failure to do so will cause unreliable or
intermittent operation.
When using sockets, steps should be taken to assure
that the DAA module remains tightly seated in the
socket after the end product is shipped.
It is
recommended that some type of mechanical restraint
be provided to keep the CH1837A/8A seated to avoid
any possibility that the CH1837A/8A works loose
during shipment.
See Application Note # 130,
Summary of Recommended Suppliers for a list of
recommended socket manufacturers.
FCC (USA) AND DOT (CANADA)
REGISTRATION
FCC Part 68 or DOT CS-03 registration of the end
product containing the CH1837A/8A DAA is normally
quite simple. The process involves testing the end
system for compliance and submitting the test data to
the FCC or DOT for review.
Typically, independent approved testing labs are
contracted to perform the required tests on the end
product and to submit the required paperwork to the
FCC or DOT. If desired, Cermetek can assist with the
Registration activity.
See Application Note # 130,
Summary of Recommended Suppliers. The user is
assigned the registration and assumes all risk for
registration compliance.
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
Table 1. CH1837A Pin Description.
PIN
I/O
CH1837A
FUNCTION
1
I/O
TIP
TIP. Direct PSTN line connection.
2
I/O
RING
RING. Direct PSTN line connection.
3
I
OFFHK
OFF-HOOK. Used to toggle CH1837A product between On-Hook and Off-Hook.
When set LOW, CH1837A is On-Hook. When set HIGH, CH1837A is set Off-Hook
to answer or place a call. See Note 1.
4
O
RI
RING INDICATION. 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 4. See Notes 2 and 3.
5
O
RCV
RECEIVE. Audio output signal with respect to GND. AC couple RCV through
0.1 µ F capacitor to eliminate any DC offset.
6
I
XMIT(-)
TRANSMIT(+). Audio input signal. AC couple through 0.1 µ F capacitor. The
CH1837A can be used in differential mode with XMIT(+) or in single ended mode
with respect to GND.
7
I
V CC
POWER SUPPLY. +5V ± 5%. Supply line noise should be less than 50mV peak to
peak.
8
I
XMIT(+)
TRANSMIT(-). Audio input signal for CH1837A/Fwhen used in differential mode
only. Connect to GND through 0.1 µ F capacity when CH1837A used in single
ended input via PIN 8.
9
I
GND
GROUND. Supply line noise should be less than 50mV peak to peak.
Note:
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.
2. For CH1837A, the RI output is 2X the frequency of the incoming ring signal.
Table 2. CH1838A Pin Description.
PIN
I/O
CH1838A
FUNCTION
1
I/O
TIP
TIP. Direct PSTN line connection.
2
I/O
RING
RING. Direct PSTN line connection.
3
I
OFFHK
OFF-HOOK. Used to toggle CH1838 product between On-Hook and Off-Hook.
When set LOW, CH1838 is On-Hook. When set HIGH, CH1838 is set Off-Hook to
answer or place a call. See Note 1.
4
O
RI
RING INDICATION. 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 4. The RI output is 2X
the frequency of the incoming ring signal.
5
I/O
T1
RECEIVE. Audio input and output signal with respect to T2.
6
N/C
N/C
AUDIO INPUT/OUTPUT. Internally not connected. Either let float or connect to
GND.
7
I
V CC
POWER SUPPLY. +5V ± 5%. Supply line noise should be less than 50mV peak to
peak.
8
I/O
T2
AUDIO INPUT/OUTPUT. Audio input and output signal with respect to T1.
9
I
GND
GROUND. Supply line noise should be less than 50mV peak to peak.
Note:
1. When answering incoming calls in response to a ring indicator 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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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
Table 3. 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
CH1837A/8A
1500
VAC RMS
Surge Protection
Between TIP and RING
CH1837A/8A
2212
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.
20
100
mA
Longitudinal Balance
OH=0 (On-Hook)
66
dBm
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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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
Figure 5. PSTN Line Interface.
approval and to maintain UL60950/3 edition
rd
1. Currently Limiting PSTN Protection Line
Device.
listing.
Currently limiting devices are mandatory to meet
B. In most environments, 2 terminal surge
UL safety standards. For FCC Part 68 approval,
suppressors are adequate.
For severe
the current limiting components identified as F1
environments, use an external 3 terminal
and F2 in dashed Box #1 must also survive FCC
device (as indicated in Figure 5) with an earth
Part 68 surge testing.
Refer to Cermetek
ground.
Application Note #126, Supplemental PSTN Line
Protection, for more details. Refer to Application
Note # 130, Summary of Recommend Suppliers,
3. EMI/RFI Suppression.
for a list of suppliers and associated part numbers.
Additional suppression, if required, may be added
as described below in Sections 3A-3B without
adversely affecting FCC Part 68 approval or
A. A Polyfuse (rated at 0.15 amps) is preferred
UL60950 listing.
because it resets automatically upon removal
of the current flow.
Non-resettable devices
are also acceptable. Refer to Application Note
A. To provide adequate EMI/RFI suppression,
#130 for a complete list of recommended
the capacitor/inductor network contained in
vendors and associated part numbers.
dashed Box #3 should be located as close to
the RJ11 Jack as possible.
Further, this
network should be provided with an excellent
B. Resistors (10 Ω carbon film or 1/8 watt
ground path to the chassis.
minimum) may be used in Canada, as Canada
has no requirements that PSTN equipment be
operational after a Type B surge test.
B. Capacitors C1 and C2 should not exceed
0.005 µ f. They must have a rating of 1.5KV
C. Although CSA CS-03 Part 1 (Canada) follows
and typically are 0.001 µ f ± 20%. Inductors L1
the requirements of FCC Part 68 (USA),
and L2 may be either individual inductors or a
Cermetek
recommends
contacting
DOT
dual inductor. Refer to Application Note #130
(Canada) and/or a certified independent lab to
for a complete list of recommended vendors
verify compliance.
For Canada, use either
and associated part numbers.
For UL
applications, choose capacitors and inductors
10 Ω resistors (carbon film or SMD parts 1/8
that are UL60950 listed. The actual values of
watt minimum) as described in paragraph B
the components used may vary depending on
above.
the end product design.
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
2004 Cermetek Microelectronics, Inc.
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Document No. 607-0014 Revision C3 (02/04)
Cermetek Microelectronics, Inc.
CH1837A/8A Data Access Arrangement Module
Table 4. Summary CH1837A/8A Product Features.
Model
Summary of Features
Operating Temperature
CH1837A
33.6kbps DAA, 2-to-4 Wire Conversion, FCC Part 68 Compliant,
0 ° C to +70 ° C
UL60950/3 edition Listed. RI is 2X the incoming ring frequency.
rd
rd
CH1838A
33.6kbps DAA, FCC Part 68 Compliant, UL60950/3
edition Listed
0 ° C to +70 ° C
Special Order Option to Standard CH1837A product.
Notes:
1. Pins are 0.010 inches X 0.020 inches.
*2. Nominal pin length is 0.200 inches for CH1837A/8A.
3. Nominal case tolerance ± 0.02 inches.
4. Nominal pin tolerance ± 0.03 inches.
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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Document No. 607-0014 Revision C3 (02/04)