PBL 386 40/2
The current limit (reference C in figure
13) is adjusted by connecting a resistor,
RLC, between terminal PLC and ground
according to the equation:
receive output via the resistor RRX, is dc
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 RR be-
tween the RSN terminal and ground.
With current directions defined as in
figure 14, current summation gives:
Battery Feed
The PBL 386 40/2 SLIC emulate resistive
loop Feed, programmable between
2·50Ω and 2·900 Ω, with adjustable
current limitation. In the current limited
region the loop current has a slight slope
corresponding to 2·30 kΩ, see figure 13
reference B.
The open loop voltage measured
between the TIPX and RINGX terminals
is tracking the battery voltage VBat. The
1000
ILProg + 4
RLC
=
where RLC is in kΩ for ILProg in mA.
A second, lower battery voltage may
be connected to the device at terminal
VBAT2 to reduce short loop power
−IRSN = IRT + IRRX + IRR
=
signalling headroom, or overhead voltage dissipation. The SLIC automatically
VTRO, is programmable with a resistor ROV switches between the two battery supply
1,25 1,25 − VCODEC
1,25
RR
+
+
connected between terminal POV on the
SLIC and ground. Please refer to section
voltages without need for external
control. The silent battery switching
RT
RRX
“Programmable overhead voltage(POV)”. occurs when the line voltage passes the
where VCODEC is the reference voltage of
the CODEC at the receive output.
From this equation the resistor RR can be
calculated as
The battery voltage overhead, VOH
depends on the programmed signal
,
value |VB2| - 40·IL - (VOHVirt -1.3),
if IL > 6 mA.
overhead voltage VTRO. VOH defines the
TIPX to RINGX voltage at open loop
conditions according to VTR(at IL = 0 mA)
For correct functionality it is important
to connect the terminal VBAT2 to the
second power supply via the diode DVB2
in figure 12.
1,25
RR
=
1,25 − VCODEC
1,25
RT
= |VBat| - VOH
.
−IRSN
−
−
Refer to table 2 for typical values on
OH and VOHVirt. The overhead voltage is
An optional diode DBB connected
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.
If a second battery voltage is not used,
VBAT2 is connected to VBAT on the
SLIC and CVB2, DBB and DVB2 are re-
moved.
RRX
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 2·25 Ω(reference G in figure 13).
The virtual battery overhead, VOHVirt, is
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.
For values on IRSN, see table 3.
The resistor RR has no influence on the
ac transmission.
SLIC
IRSN [µA]
PBL 386 40/2
-55
Table 3. The SLIC internal bias current
with the direction of the current defined
as positive when floating into the terminal
RSN.
Metering applications
For designs with metering applications
please contact Ericsson Microelectronics
for assistance.
CODEC Receive Interface
Programmable overhead voltage(POV)
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
With the POV function the overhead
voltage can be increased.
If the POV pin is left open the overhead
voltage is internally set to 3,2 VPeak in off-
hook and 1,3 VPeak on-hook. If a resistor
ROV is connected between the POV pin
SLIC
VOH(typ)
[V]
VOHVirt(typ)
[V]
PBL 386 40/2 3.0 +VTRO 4.9 +VTRO
7
6
5
4
3
2
1
0
Table 2. Battery overhead.
The resistive loop Feed (reference D in
figure 13) is programmed by connecting
a resistor, RSG, between terminals PSG
and VBAT according to the equation:
off-hook
on-hook
RSG + 2·104
RFeed
=
+ 2RF
200
0
10
20
30
(KΩ)
40
50
60
where RFeed is in Ω for RSG, and RF in Ω.
R
ov
Figure 11. Programmable overhead voltage (POV). RL = 600 Ω or ∞.
12
ERICSSON [ ERICSSON ]
