Cermetek Microelectronics, Inc.
CH1817 Family of Low Profile DAA Modules
Figure 3.
Telephone Line Interface.
1. RJ-11 Jacks must be provided by one of the
vendors on the list.
Refer to Application Note
#130, Summary of Recommended Suppliers.
2. Current Line Device: F1 and F2 – 1.25amp.
A. UL 1459 must use a current limit device. A
Poly Fuse is recommended as this device
resets automatically after each power surge.
B. Resistors (10ohm carbon film or SMD 1/8W
minimum)
may
be
used
for
non
UL
applications.
3. Over Voltage and Lightning Protection.
A. DOC (Canada) may require external current
limiting devices. Use 1ohm resistors (carbon
film or SMD parts 1/8W minimum) in each lead
(TIP and RING). You may substitute fuses or
the Poly Fuse described in Section 2.
Figure 4. Low Power Ring Detection.
B. For lightning prone areas where there are
more than 2 storms per year, provide an earth
ground connection and use a three terminal
sidactor or similar device that provides metallic
and longitudinal protection.
This must also
include the current protection in Section 2.
4. EMI/RFI Suppression.
The capacitor/ inductor network should be located
as close to the RJ-11 Jack as possible with an
excellent ground path to the chassis. Capacitors
C1 and C2 should not exceed 0.005
µF. They
must have a rating of 1.5KV and typically have a
value of 0.001
µF ± 20%. Inductors L1 and L2 are
ferrite cylinders and provide attenuation to high
frequencies
from
system
level
components
external to the CH1817. The required values must
be empirically determined for each product design
2002 Cermetek Microelectronics, Inc.
Page 5
Document No. 607-0007 Revision B (01/02)
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