Cermetek Microelectronics, Inc.
CH1817 Family of Low Profile DAA Modules
5. The DAA Module is a sensitive subsystem that
should be treated as any other integrated
component.
Pay special attention to the power
supply to the DAA. The device handles signals in
the millivolt range. Even though it is designed to
handle noise in the power supply, steps should be
taken to assure the noise level does not exceed
50mV peak-peak.
CH1817-L: LOW POWER
The L Family is a Low Power version of the CH1817
DAA.
When Off-Hook, this DAA draws only 4mA
through Vcc. When On-Hook, the L Family can be
configured so that the Ring Detection circuit can be
activated by a pull-up resistor on RI while Vcc has
been disconnected from the power supply, thus
making the On-Hook power consumption virtually zero
(See Figure 4).
6. For data calls, Part 68 rules require silence on the
phone line for at least 2 seconds after a data call
has been completed to allow central offices to
exchange billing information and specifies the
transmit level must not exceed -9dBm. The FCC
rules also require that for voice calls the final
system meet the requirements of Part 68 for Out-of
Band
Energy,
and
DTMF
Transmit
Levels.
Because
the
CH1817
already
meets
FCC
requirements for Part 68 registration for High
Voltage isolation and Surge Protection, the
certification of the product is normally a simple
process that often can be completed directly with
the FCC. If desired, independent testing labs are
available that can test the system and submit the
required paperwork to the FCC for approval.
Cermetek can assist with the registration.
CH1817-D: 0 dB XMIT ATTENUATION
The D option has 0.0 dB insertion loss (typical) with
respect to a differential input between XMIT (-) and
XMIT (+). This allows the maximum signal strength of
–9dBm to be input while maintaining FCC compliance.
To use the CH1817-D as single end input device,
ground the XMIT (-) pin through a 0.1uF capacitor.
MOUNTING THE DAA
The DAA can be soldered directly to the host circuit
card or installed in sockets. To avoid the problems of
contamination, hand soldering is preferred to wave
soldering. When hand cleaning use only deionized
water; when wave soldering use washless flux.
7. The CH1817 DAA as is meets or exceeds the
hazardous
voltage,
surge
and
leakage
requirements of the FCC.
For applications that
connect to Canadian phone lines, governed by the
DOC (Department of Communications) and to
further protect the CH1817 from field failure on
excessively poor quality lines and to maintain UL
recognition, a higher level of transient protection is
required, thereby making mandatory the circuit
consisting of two fuses and one varistor as shown
in Figure 3. Adding these three devices will not
affect FCC registration. Components L1, L2, C1,
C2 are optional and serve two purposes. First, they
restrict high frequency signals from reaching the
phone line and thereby add EMI protection.
Second, they protect against externally generated
RFI from degrading the modem’s ability to operate
on proper carrier signals. Adding these devices will
not affect FCC, DOC, or UL registration.
DESIGN CONSIDERATIONS
The CH1817 DAA includes circuits that couple the
modem signals to the phone line and provides FCC
required
isolation
and
protection.
The
FCC
registration process by the host product can be
minimized provided that the following guidelines are
followed.
1. The mounting of the DAA in the final assembly
must be made so that it is isolated from exposure to
any hazardous voltages within the assembly.
Adequate separation and restraint of cables and
cords must be provided.
2. Connection to the phone line should be made
through a standard FCC approved RJ-11C jack or
equivalent.
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
for this pacing is to maintain 1000 VAC isolation
between the phone line and the other traces.
Traces should have a nominal width of 0.020
inches or greater.
4. TIP and RING traces should be as short as
possible and should be oriented to prevent direct or
induced coupling with other signals on the host
circuit card.
2002 Cermetek Microelectronics, Inc.
Page 4
Document No. 607-0007 Revision B (01/02)
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