SI3068-B-FS View Datasheet(PDF) - Silicon Laboratories
Part Name
Description
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SI3068-B-FS Datasheet PDF : 40 Pages
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Si3068
4. Telephone Line Interface
Functional Description
Together, the integrated system-side and Si3068
comprise an integrated direct access arrangement
(DAA) that provides a programmable line interface to
meet the telephone line interface requirements of
countries worldwide. The device implements Silicon
Laboratories’ patented isolation technology, which offers
the highest level of integration by replacing an analog
front end (AFE), an isolation transformer, relays, opto-
isolators, a 2- to 4-wire hybrid, and other circuitry.
The Si3068 can be fully programmed to meet
international requirements and is compliant with FCC,
JATE, and numerous other country-specific PTT
specifications as shown in Table 5. Also, the Si3068
meets the most stringent requirements for out-of-band
energy, emissions, immunity, lightning surges, and
safety.
4.1. Initialization
The following is an example initialization procedure:
1. Select the desired sample rate using the SRC bits
(Register 7, bits 3:0).
2. Power up the line side by clearing the PDL bit
(Register 6, bit 4).
3. Enable AOUT (if applicable) by setting ARM[7:0]
(Register 20, bits 7:0) and ATM[7:0] (Register 21,
bits 7:0) to the desired level.
4. Prior to receiving or transmitting data, ensure FDT
(Register 12) is set indicating the Si3068 is ready for
normal operation.
After the procedure is complete, the DAA is ready for
off-hook, on-hook line monitoring, and ring detection.
4.2. Isolation Barrier
The Si3068 achieves an isolation barrier through low-
cost, high-voltage capacitors in conjunction with Silicon
Laboratories’ proprietary signal processing techniques.
These techniques eliminate signal degradation from
capacitor mismatches, common mode interference, or
noise coupling. The C1, C2, C8, and C9 capacitors
isolate the system-side device from the Si3068 line-side
device. All transmit, receive, control, ring detect, and
caller ID data are communicated through this barrier. Y2
class capacitors can be used to achieve surge
performance of 6 kV or greater.
The isolated communications link is disabled by default.
To enable it, the PDL bit (Register 6, bit 4) must be
cleared. No communication between the system-side
and Si3068 can occur until this bit is cleared and the
FDT bit (Register 12, bit 6) is high.
4.3. Parallel Handset Detection
The Si3068 can detect a parallel handset going off-
hook. When the DAA is off-hook, the loop current can
be monitored via the LCS bits (Register 12, bits 4:0). A
significant drop in loop current can signal a parallel
handset going off-hook. If a parallel handset causes the
LCS bits to read 0s, the DropOut Detect Interrupt bit
(Register 4, bit 3) can be checked to verify that a valid
line still exists.
For the Si3068 to operate in parallel with another
handset, the parallel handset must have a sufficiently
high dc termination impedance to support two DAAs off
hook on the same line.
Table 5. Country-Specific PTT Specifications
Country
Argentina
Kyrgyzstan
Armenia
Macao
Bahamas
Mexico
Bangladesh
Belarus
Moldova
New Zealand2
Bermuda
Paraguay
Brazil
Peru
Brunei
Puerto Rico
Canada
Russia
Caribbean
Saudi Arabia
Chile
China
Singapore
South Korea3
Colombia
Sri Lanka
Costa Rica
Taiwan
Dominican Republic
Thailand
Ecuador
Tunisia
El Salvador
UAE
Georgia
Ukraine
Guam
Uruguay
Hong Kong
Uzbekistan
India
USA
Indonesia
Japan1
Venezuela
Vietnam
Kazakhstan
Yemen
Kuwait
Notes:
1. DCR exceeds 300 Ω; disclaimer required in
product documentation.
2. 600 Ω ac termination used; disclaimer required in
product documentation.
3. Additional components required to pass ringer
impedance specifications.
10
Rev. 1.0
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