PBL38640-2 Ericsson, PBL38640-2 Datasheet - Page 11

• Manufacturer Part Number: PBL38640-2
• Description: Subscriber Line Interface Circuit
• Manufacturer: Ericsson

When choosing R
load of the VTX terminal is >20 k .
yields a balance network containing an
inductor, an alternate method is recom-
mended. Contact Ericsson Microelectron-
ics for assistance.
used together with programmable
CODEC/filters. The programmable
CODEC/filter allows for system controller
adjustment of hybrid balance to accom-
modate different line impedances without
change of hardware. In addition, the
transmit and receive gain may be ad-
justed. Please, refer to the programm-
able CODEC/filter data sheets for design
information.
Longitudinal Impedance
A Feed back loop counteracts longitudi-
nal voltages at the two-wire port by
injecting longitudinal currents in opposing
phase.
appear as longitudinal currents and the
TIPX and RINGX terminals will experi-
ence very small longitudinal voltage
excursions, leaving metallic voltages well
within the SLIC common mode range.
wire, Z
20
should be noted that longitudinal currents
may exceed the dc loop current without
disturbing the vf transmission.
Capacitors C
The capacitors designated C
in figure 12, connected between TIPX
and ground as well as between RINGX
and ground, can be used for RFI filter-
ing.. The recommended value for C
and C
values may be used, but care must be
taken to prevent degradation of either
longitudinal balance or return loss. C
and C
ance of 1/( ·f·C
ground impedance of 1/(2· ·f·C
RINGX to ground impedance of 1/
(2· ·f·C
AC - DC Separation Capacitor, C
The high pass filter capacitor connected
between terminals HP and TIPX provides
the separation of the ac signal from the
dc part. C
If calculation of the Z
The PBL 386 40/2 SLIC may also be
Thus longitudinal disturbances will
The SLIC longitudinal impedance per
to longitudinal disturbances. It
RC
RC
LoT
RC
is 2200 pF. Higher capacitance
contribute to a metallic imped-
).
and Z
HP
positions the low end
TC
TC
LoR
and C
) = 1/( ·f·C
TX
, appears as typically
, make sure the output
RC
B
formula above
RC
TC
), a TIPX to
and C
TC
) and a
HP
TC
TC
RC
frequency response break point of the ac
loop in the SLIC. Refer to table 1 for
recommended values of C
Example: A C
position the low end frequency response
3dB break point of the ac loop at 1.8 Hz
(f
where R
High-Pass Transmit Filter
The capacitor C
between the VTX output and the
CODEC/filter forms, together with R
and/or the input impedance of a pro-
grammable CODEC/filter, a high-pass
RC filter. It is recommended to position
the 3 dB break point of this filter between
30 and 80 Hz to get a faster response for
the dc steps that may occur at DTMF
signalling.
Capacitor C
The capacitor C
the terminals CLP and VBAT, positions
together with the resistive loop feed resis-
tor R
end frequency break point of the low pass
filter in the dc loop in the SLIC. C
with R
Impedance) forms the total two wire output
Figure 10. Hybrid function.
3dB
386 40/2
) according to f
SG
SG
(see section Battery Feed), the high
, C
HP
PBL
HP
= 600 k .
LP
and Z
HP
LP
TX
value of 150 nF will
, which connects between
VTX
RSN
in figure 12 connected
T
3dB
(see section Two-Wire
= 1/(2· ·R
Z
T
HP
.
LP
R
Z
HP
TX
RX
together
·C
TX
HP
)
Z
B
impedance of the SLIC. The choise of
these programmable components have an
influence on the power supply rejection
ratio (PSRR) from VBAT to the two wire
side at sub-audio frequencies. At these
frequencies capacitor C
the transversal to longitudinal balance in
the SLIC. Table 1 suggests suitable values
on C
Typical values of the transversal to longitu-
dinal balance (T-L bal.) at 200Hz is given in
table 1 for the chosen values on C
Table 1. R
different Feeding characteristics.
R
[ ]
2 50
2 200
2 400
2 800
Feed
LP
for different Feeding characteristics.
R
[k ]
0
60.4
147
301
SG
SG
, C
Combination
CODEC/Filter
R
FB
LP
and C
C
[nF]
150
100
47
22
PBL 386 40/2
LP
HP
LP
T-L bal. C
@200Hz
[dB]
-46
-46
-43
-36
also influences
values for
V
V
RX
T
LP
.
[nF]
47
150
150
150
HP
11