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CH1817
Family of Low Profile DAA Modules
INTRODUCTION
The CH1817 is a Family of Low Profile Data Access
Arrangement (DAA) Modules. They are compatible
with all modem chip sets. These devices have been
tested to meet or exceed FCC Part 68 requirements
and are Canadian DOC approvable. They are also
recognized by Underwriters Laboratories to UL 1459
Specifications.
The CH1817 modules are ultra small (1.0” x 1.0”
x0.35”) affording an easy integration into space-
sensitive designs, including laptop and hand-held
computer based products. The CH1817 family of
products may be socketed or mounted directly onto a
Printed Circuit Board (PCB). The telephone line
connection is made through TIP and RING to an RJ-11
jack or equivalent.
The CH1817 is intended for use with FAX/modem chip
sets that have a data throughput of up through
V.32bis. For High Speed Applications, Cermetek
recommends the CH1837A.
FEATURES
• Low Profile, Ultra small size: 1.0” x 1.0” x 0.35”
• Complete DAA function
• Ring detection
• Built-in 2-wire to 4-wire conversion
• Lightweight
• Multimedia compatible
• +5V operation
• 1000 VAC isolation
• 800 Volt surge protection
• V.32bis/14,400bps, applications
• UL1459 recognized
• CH1817-L: Low power consumption and Common
mode noise rejection filter
• CH1817-LM (special order): Reduced transmit
attenuation
• CH1817-D: Differential transmission input and 0dB
transmission insertion loss.
DataShee
FUNCTIONAL DESCRIPTION
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Ring Detection. Referring to the block diagram in
Figure 1, incoming ring detection is performed by the
CH1817 and the RI pin is set Low during the 2 second
(typical) ring period and is restored to High for the 4
seconds (typical) between rings. During incoming ring
signal activity, the RI output is pulsed at the same
frequency as the ringing signal, typically 20Hz. Figure
2 contains additional external circuitry which may be
used to provide an envelope indication of the ring
signal. The internal ring detection circuit is designed
to deter false indications due to pulse dialing or noise
on the line.
VCC
ISOLATION
GND
SURGE
AND
PROTECTION
CIRCUITRY
TIP
RING
The RI output of the CH1817 is diode protected.
Therefore, an external pull-up resistor (R>100Kohm)
to +5V may be utilized to activate the ring detection
circuit when the CH1817 is not connected to power.
This can be handy in designs where power
consumption is of concern. When circuited in this
manner, there is virtually no current draw until a ring
signal is present.
XMIT
RCV
RI
HYBRID
2W/4W
CONVERTER
OFFHK
OFF-HOOK
SWITCH
RING DET.
RI
Output: Active low
Opto coupler, 30KΩ pull-up
Square wave: 15-68Hz (Typ. 20Hz)
Sensitivity: 38Vrms across Tip & Ring
DataSheet4U.com
Figure 1. CH1817 DAA Functional Block Diagram.
2002 Cermetek Microelectronics, Inc.
DataSheet4 U .com
Page 1
Document No. 607-0007 Revision B (01/02)
www.DataSheet4U.com
Cermetek Microelectronics, Inc.
Hook Switch. The OFFHK input is used to control the
on-hook and off-hook status of the CH1817. When
OFFHK is low, the CH1817 is in the On-Hook State.
This indicates to the CO that the CH1817 is ready to
receive calls. When OFFHK is high, the CH1817
allows the CO supplied loop current to flow, indicating
either it is answering a call or preparing to place a call.
OFFHK
Input: Active High
Active Current: 4mA
CH1817 Family of Low Profile DAA Modules
TRANSMIT SIGNAL
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 CH1817-D a XMIT (+) and XMIT (-)
pins provide a differential input. The CH1817-L
attenuates the transmit signal by 9.5dB, 0dB for the –D
option. Therefore, a transmit signal of 0dBm for the –L
option (-9.5 dB for –D) applied to XMIT will comply
with the FCC Part 68 requirement for data signals of –
9dBm across TIP and RING.
et4U.com
2-Wire To 4-Wire Hybrid Converter. This block has
two functions:
RECEIVE SIGNAL
1. It applies the XMIT signal to the phone line.
The incoming analog signal appearing between TIP
2. It subtracts the desired signal from the total
and RING is presented at RCV with respect to GND
outgoing signal on the phone line to derive the
and must be AC coupled to the user equipment
RCV signal.
receive input. The CH1817 does not gain the receive
signal. Receive signals can vary from a maximum
The accuracy of this derivation depends on how
strength of –9dBm to below –50dBm.
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 applied XMIT
RCV
signal to the received XMIT signal is called Trans-
Gain: 0dB
Hybrid Rejection, or Trans-Hybrid Loss. On a 600Ω
Out impedance: 100Ω
phone line, the CH1817 DAAs have very high trans-
Typical Output Signal:
hybrid rejection, typically 23 dB.
-9dBm to –50dBm
2.5Vrms to 0.27mVrms
DataShee
The
FCC
requires
NOTE
that the DTMF
tone
not
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Signal referenced to GND
AC coupling required
0dBm.
Attenuation
Input Impedance
CH1817-D
0dBm
150KΩ
XMIT
CH1817-L
9.5dBm
150KΩ
CH1817-DM
6.5dBm
150KΩ
CH1817-LM
6.5dBm
150KΩ
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Figure 2. Typical CH1817 Application.
2002 Cermetek Microelectronics, Inc.
DataSheet4 U .com
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Document No. 607-0007 Revision B (01/02)
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