PCT1789W DATA SHEET
PRELIMINARY
PCT303DW FUNCTIONAL DESCRIPTION
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PCT303DW FUNCTIONAL DESCRIPTION
The PCT303DW is an integrated direct access
arrangement (DAA) that provides a programmable line
interface to meet international telephone-line
requirements. The device implements Silicon
Laboratories’ proprietary ISOLink™ technology which
offers the highest level of integration by replacing an
analog front end (AFE), an isolation transformer, relays,
opto-isolators, and a 2–4-wire hybrid with two 16-pin
small outline packages (SOIC). The chipset can be fully
programmed to meet international requirements, and
the device is compliant with FCC, NET4, CTR21, JATE,
and country-specific PTT specifications. In addition, the
PCT303DW has been designed to meet the most
stringent world-wide requirements for out-of-band
energy, billing-tone immunity, lightning surges, and
safety requirements.
DC Termination
The PCT303DW has four programmable modes related
to DC termination. Two bits in register 16 (DCT1, DCT0)
set the DC characteristics. While the modes are
designed to support the extreme conditions in various
countries, the user can determine if a line in a given
country can support a mode with a higher transmit
power level and switch to the appropriate mode. This
decision will depend on the amount of loop current
available on the line.
Mode 1 (0,1) is a low-voltage mode with no current
limiting; it supports transmit signals up to –2.71 dBm.
The low voltage requirement is dictated by countries
such as Japan and Australia. See Figure 7.
Mode 1
10.5
10
9.5
9
The PCT303DW solution needs only a few low-cost
discrete components to achieve global compliance. See
Figure 2 on page 6 for a typical application circuit.
8.5
8
Isolation Barrier
The PCT303DW achieves an isolation barrier through a
low-cost, high-voltage capacitor in conjunction with
ISOLink signal processing techniques. These
techniques eliminate any signal degradation due to
capacitor mismatches, common mode interference, or
noise coupling. As shown in Figure 2, the C1, C2, and
C4 capacitors isolate the PCT303D (DSP side) from the
PCT303W (line side). All transmit, receive, control, and
caller ID data are communicated through this barrier.
7.5
7
6.5
6
5.5
.05 .06
.01
.09 .1
.11
.02 .03 .04
.07 .08
Loop Current (A)
Figure 7 Mode 1 I/V Characteristics (0,1)
The Isolation Pass is disabled by default. To enable it,
the PDL bit in register 6 must be cleared. No
communication between the PCT303D and PCT303W
can occur until this bit is cleared. The clock generator
must be programmed to an acceptable sample rate prior
to clearing the PDL bit.
Mode 2 (1,0) is the default DC termination mode, with no
current limiting, providing a maximum transmit level of
–1 dBm at Tip and Ring. This mode meets FCC
requirements in addition to the requirements of many
European countries. Figure
characteristics of mode 2.
8
shows the I/V
AC Termination
The PCT303DW supports international AC Termination
requirements with two selectable impedances, one real
and one complex. Mode 0 is a nominal 600-ohm
termination that supports the FCC 68 requirement in
addition to the requirement of many European countries.
Mode 1 is a complex impedance as dictated by
countries such as the UK and Germany, and also
specified by CTR21. This complex impedance is set by
circuitry internal to the PCT303DW as well as the
external components connected to REXT2.
PRELIMINARY
PC-TEL, Inc.
17
1789W0DOCDAT06A-0299
ETC [ ETC ]
