CH1786LC Cermetek Microelectronics, CH1786LC Datasheet - Page 14

• Manufacturer Part Number: CH1786LC
• Manufacturer: Cermetek Microelectronics

Specifications of CH1786LC

• Main Category: Single Chip
• Data Rate: 2.34375Kbps
• Power Supply Type: Analog
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.25V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Lead Free Status / RoHS Status: Supplier Unconfirmed

Cermetek Microelectronics, Inc.
1. Currently Limiting PSTN Protection Line
2. PSTN Current Limiting Resistors.
3. Over Voltage and Lightning Protection.
2004 Cermetek Microelectronics, Inc.
Figure 7.
Device.
Currently limiting devices are mandatory to meet
UL safety standards. To maintain conveyed FCC
Part 68 approval, the current limiting components
identified as F1 and F2 in dashed Box #1 must
also survive FCC Part 68 surge testing. Refer to
Cermetek Application Note #126, Supplemental
PSTN Line Protection, for more details. Refer to
Application Note # 130, Summary of Recommend
Suppliers, for a list of suppliers and associated
part numbers.
A resettable/repairable fuse (rated at 0.15 amps)
is preferred because it resets automatically upon
removal of the current flow.
devices are also acceptable. Although CSA CS-
03 Part 1 (Canada) follows the requirements of
FCC Part 68 (USA), Cermetek recommends
contacting DOT (Canada) and/or a certified
independent lab to verify compliance.
Low value (10Ω) carbon film 1/4 watt resistors may
be required (identified as R1 and R2 in dashed
Box 2), depending on end product application
environment, to enhance performance by reducing
susceptibility to PSTN current surges that may
occur before the OVERVOLTAGE PROTECTION
device (identified as D1 in dashed Box 3)
becomes fully activated.
Refer to Cermetek Application Note # 130,
Summary of Recommended Supplies, for a list of
suppliers.
Surge Protection is provided by internal circuitry
contained within all CH1786s (except CH1786NH).
No additional external components are required to
maintain conveyed FCC Part 68 approval for all
CH1786s Products (except CH1786NH). External
PSTN Line Interface for all CH1786 Products.
Non-resettable
Page 14
4. Optional External Over Voltage and Lightning
5. EMI/RFI Suppression.
protection as indicated in dashed Box 4 MUST BE
included when using CH1786NH products.
Protection.
In most environments, the internal two terminal
surge suppressor (see dashed Box 3) is adequate.
For severe environments, use an external three
terminal device with an earth ground as is shown
in dashed Box 4.
EMI/RFI suppression is recommended. This is for
obtaining FCC part 15 A and/or B. It is also used
to suppress external EMI / RFI signals that can
affect modem operation, such as strong radio
signals, should the modem be near a source of
such signals.
suppression circuitry is required to maintain
conveyed FCC Part 68 approval.
suppression may be added as described below
without adversely affecting FCC Part 68 approval.
A. To provide adequate EMI/RFI suppression,
B. Capacitors C1 and C2 should not exceed
the capacitor/inductor network contained in
dashed Box 5 should be located as close to
the RJ-11C Jack as possible.
network should be provided with an excellent
ground path to the chassis.
0.005µf. They must have a rating of 1.5KV
and typically are 0.001µf ± 20%. Inductors L1
and L2 may be either individual inductors or a
dual inductor. Refer to Application Note #130
for a complete list of recommended vendors
and associated part numbers.
applications, choose capacitors and inductors
that are UL 1950 listed. The actual values of
the components used may vary depending on
the end product design and the nature of the
EMI/ RFI. Consult an FCC part 15 consultant
if required.
CH1786 Family of Ultra Small 2400bps Modems
Document No. 607-0004 Revision L4 (08/04)
No external EMI/RFI noise
Further, this
Additional
For UL