PBL38621-2 Ericsson, PBL38621-2 Datasheet - Page 11

• Manufacturer Part Number: PBL38621-2
• Description: Subscriber Line Interface Circuit
• Manufacturer: Ericsson

hybrid balance to accommodate different
line impedances without change of
hardware. In addition, the transmit and
receive gain may be adjusted. Please, refer
to the programmable CODEC/filter data
sheets for design information.
Longitudinal Impedance
A feed back loop counteracts longitudinal
voltages at the two-wire port by injecting
longitudinal currents in opposing phase.
appear as longitudinal currents and the
TIPX and RINGX terminals will experience
very small longitudinal voltage excursions,
leaving metallic voltages well within the
SLIC common mode range.
wire, Z
20 to longitudinal disturbances. It should
be noted that longitudinal currents may
exceed the dc loop current without distur-
bing the vf transmission.
Capacitors C
The capacitors designated C
in figure 11, connected between TIPX
and ground as well as between RINGX
and ground, can be used for RFI filtering.
The recommended value for C
is 2200 pF. Higher capacitance values
may be used, but care must be taken to
prevent degradation of either longitudinal
balance or return loss. C
contribute to a metallic impedance of
1/( ·f·C
impedance of 1/(2· ·f·C
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
frequency response break point of the ac
loop in the SLIC. Refer to table 1 for a
recommended value of C
Example: A C
position the low end frequency response
3dB break point of the ac loop at 5.6 Hz
(f
where R
High-Pass Transmit Filter
The capacitor C
between the VTX output and the
CODEC/filter forms, together with R
or the input impedance of a programmable
CODEC/filter, a high-pass RC filter. It is
3dB
Thus longitudinal disturbances will
The SLIC longitudinal impedance per
) according to f
LoT
TC
HP
) = 1/( ·f·C
HP
and Z
= 600 k .
positions the low end
HP
TC
value of 47 nF will
TX
and C
LoR
3dB
in figure 11 connected
, appears as typically
RC
= 1/(2
), a TIPX to ground
RC
TC
TC
) and a RINGX
HP
and C
.
TC
R
TC
and C
HP
and C
RC
RC
C
HP
TX
).
HP
and/
RC
)
RC
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 the
high end frequency break point of the low
pass filter in the dc loop in the SLIC. C
together with C
Wire Impedance) forms the total two wire
output 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 a suitable value
on C
to longitudinal balance (T-L bal.) at 200Hz
is given in table 1 for the chosen value on
C
Table 1. R
tant current feeding characteristics.
For values outside table 1, please contact
Ericsson Microelectronics for assistance.
Figure 9. Hybrid function.
R
[ ]
2·25
LP
Feed
.
LP
. The typical value of the transversal
[k ]
R
38621/2
0
SG
SG
, C
LP
PBL
HP
LP
LP
[nF]
150
C
, which connects between
and Z
and C
LP
VTX
RSN
T
@ 200Hz
HP
T-L bal.
(see section Two-
LP
[dB]
values for cons-
-46
also influences
Z
T
Z
R
[nF]
C
RX
TX
47
HP
Z
LP
B
Battery Feed
The PBL 386 21/2 SLIC emulate a battery
characteristic with current limitation
adjustable.The open loop voltage measured
between the TIPX and RINGX terminals is
tracking the battery voltage V
signalling headroom, or overhead voltage
V
connected between terminal POV on the
SLIC and ground. Please refer to section
“Programmable overhead voltage(POV)”.
The battery voltage overhead, V
on the programmed signal overhead voltage
V
at open loop conditions according to
V
Refer to table 2 for the typical value on
V
Table 2. Battery overhead.
The current limit (reference A - C in figure
12) is adjusted by connecting a resistor,
R
according to the equation:
R
where R
A second, lower battery voltage may be
connected to the device at terminal VBAT2
to reduce short loop power dissipation.
the two battery supply voltages without
need for external control. The silent battery
The SLIC automatically switches between
TRO
TRO
TR
OH
LC
LC
SLIC
PBL 386 21/2
(at I
, between terminal PLC and ground
.
=
, is programmable with a resistor R
. V
OH
L
I
LProg
1000
LC
= 0 mA) = V
defines the TIP to RING voltage
is in k for I
Combination
CODEC/Filter
+ 4
R
FB
PBL 386 21/2
Bat
V
2.5 +V
LProg
OH
- V
(typ) [V]
in mA.
V
V
OH
RX
T
TROprog
.
OH
, depends
Bat
. The
11
OV