PBL38640-2 Ericsson, PBL38640-2 Datasheet - Page 12

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

12
Battery Feed
The PBL 386 40/2 SLIC emulate resistive
loop Feed, programmable between
2
current limitation. In the current limited
region the loop current has a slight slope
corresponding to 2
reference B.
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)”.
depends on the programmed signal
overhead voltage V
TIPX to RINGX voltage at open loop
conditions according to V
= |V
V
changed when the line current is ap-
proaching open loop conditions. To
ensure maximum open loop voltage,
even with a leaking telephone line, this
occurs at a line current of approximately
6 mA. When the overhead voltage has
changed, the line voltage is kept nearly
constant with a steep slope correspon-
ding to 2
defined as the difference between the
battery voltage and the crossing point of
all possible resistive Feeding slopes, see
figure 13 reference J. The virtual battery
overhead is a theoretical constant
needed to be able to calculate the
Feeding characteristics.
Table 2. Battery overhead.
figure 13) is programmed by connecting
a resistor, R
and VBAT according to the equation:
where R
PBL 386 40/2
SLIC
PBL 386 40/2
·
TRO
OH
50 and 2
The open loop voltage measured
The battery voltage overhead, V
Refer to table 2 for typical values on
The virtual battery overhead, V
The resistive loop Feed (reference D in
R
Feed
Bat
and V
, is programmable with a resistor R
| - V
=
Feed
·
25 (reference G in figure 13).
R
OHVirt
OH
SG
·
.
SG
is in
900
200
+ 2·10
. The overhead voltage is
, between terminals PSG
V
[V]
3.0 +V
, with adjustable
·
OH(typ)
for R
30 k , see figure 13
TRO
4
+ 2R
. V
TRO
SG
OH
TR
, and R
F
(at I
defines the
V
[V]
4.9 +V
L
OHVirt(typ)
Bat
= 0 mA)
F
OHVirt
. The
OH
in .
,
TRO
, is
OV
Figure 11. Programmable overhead voltage (POV). R
13) is adjusted by connecting a resistor,
R
according to the equation:
where R
be connected to the device at terminal
VBAT2 to reduce short loop power
dissipation. The SLIC automatically
switches between the two battery supply
voltages without need for external
control. The silent battery switching
occurs when the line voltage passes the
value |VB2| - 40
if I
to connect the terminal VBAT2 to the
second power supply via the diode D
in figure 12.
between terminal VB and the VB2 power
supply, see figure 12, will make sure that
the SLIC continues to work on the
second battery even if the first battery
voltage disappears.
VBAT2 is connected to VBAT on the
SLIC and C
moved.
Metering applications
For designs with metering applications
please contact Ericsson Microelectronics
for assistance.
CODEC Receive Interface
The PBL 386 40/2 SLIC have got a
completely new receive interface at the
four wire side which makes it possible to
reduce the number of capacitors in the
applications and to fit both single and
dual battery Feed CODECs. The RSN
terminal, connecting to the CODEC
LC
The current limit (reference C in figure
R
A second, lower battery voltage may
L
For correct functionality it is important
An optional diode D
If a second battery voltage is not used,
, between terminal PLC and ground
> 6 mA.
LC
7
6
5
4
3
2
1
0
0
=
LC
I
LProg
1000
is in k for I
VB2
+ 4
, D
10
·
I
L
BB
- (V
and D
OHVirt
BB
LProg
connected
VB2
20
-1.3),
in mA.
are re-
R ov (K )
30
VB2
receive output via the resistor R
biased with +1.25V. This makes it
possible to compensate for currents
floating due to dc voltage differences
between RSN and the CODEC output
without using any capacitors. This is
done by connecting a resistor R
tween the RSN terminal and ground.
With current directions defined as in
figure 14, current summation gives:
where V
the CODEC at the receive output.
From this equation the resistor R
calculated as
For values on I
The resistor R
ac transmission.
Table 3. The SLIC internal bias current
with the direction of the current defined
as positive when floating into the terminal
RSN.
Programmable overhead voltage(POV)
voltage can be increased.
voltage is internally set to 3,2 V
hook and 1,3 V
R
R
OV
With the POV function the overhead
If the POV pin is left open the overhead
40
1 25
R
R
,
I
SLIC
PBL 386 40/2
RSN
T
is connected between the POV pin
I
RSN
125
CODEC
L
,
I
RT
= 600
50
R
is the reference voltage of
V
RX
I
1 25
R
RRX
R
,
RSN
CODEC
Peak
has no influence on the
T
, see table 3.
125
or .
on-hook. If a resistor
,
I
RR
125
,
60
125
R
,
R
R
I
-55
RSN
V
RX
CODEC
[ A]
Peak
RX
R
R
be-
off-hook
on-hook
, is dc
can be
in off-