PBL 386 30/1
The current limit (reference C in figure
12) is adjusted by connecting a resistor,
RLC, between terminal PLC and ground
according to the equation:
applications and to fit both single and dual
battery feed CODECs. The RSN terminal,
connecting to the CODEC receive output
viatheresistorRRX,isdcbiasedwith+1,25V.
This makes it possible to compensate for
currents floating due to dc voltage
differences between RSN and the CODEC
outputwithoutusinganycapacitors. Thisis
done by connecting a resistor RR between
the RSN terminal and ground. With current
directions defined as in figure 13, current
summation gives:
Battery Feed
The PBL 386 30/1 SLIC emulate resistive
loop feed, programmable between 2·50 Ω
and 2·900 Ω, with adjustable current limita-
tion. In the current limited region the loop
current has a slight slope corresponding to
2·30 kΩ, see figure 12 reference B.
The open loop voltage measured
between the TIPX and RINGX terminals is
tracking the battery voltage VBat. The
signalling headroom, or overhead voltage
VTRO, is programmable with a resistor ROV
connected between terminal POV on the
SLIC and ground. Please refer to section
“Programmable overhead voltage(POV)”.
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
toreduceshortlooppowerdissipation. 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·IL - (VOHVirt -1,3), if IL > 6mA.
For correct functionality it is important to
connect the terminal VBAT2 to the second
powersupplyviathediodeDVB2 infigure11.
−IRSN = IRT + IRRX + IRR
=
1,25 1,25 − VCODEC
1,25
RR
+
+
The battery voltage overhead, VOH
,
RT
RRX
depends on the programmed signal
overhead voltage. VOH defines the TIP to
RING voltage at open loop conditions
whereVCODEC isthereferencevoltageofthe
CODEC at the receive output.
From this equation the resistor RR can be
according to VTR(at IL = 0 mA) = |VBat| - VOH
.
Refer to table 2 for typical values on VOH
andVOHVirt.Theoverheadvoltageischanged
when the line current is approaching open
loop conditions. To ensure maximum open
loopvoltage, evenwithaleakingtelephone
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
corresponding to 2·25 Ω(reference G in
figure 12).
The virtual battery overhead, VOHvirt, is
defined as the difference between the
battery voltage and the crossing point of all
possibleresistivefeedingslopes,seefigure
12referenceJ.Thevirtualbatteryoverhead
is a theoretical constant needed to be able
to calculate the feeding characteristics.
AnoptionaldiodeDBB connectedbetween calculated as
terminalVBandtheVB2powersupply,see
1,25
1,25 − VCODEC
figure 11, 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 removed.
RR
=
1,25
RT
−IRSN
−
−
RRX
For values on IRSN, see table 3.
The resistor RR has no influence on the ac
transmission.
Metering applications
SLIC
IRSN [µA]
For designs with metering applications
please contact Ericsson Components for
assistance.
PBL 386 30/1
-55
CODEC Receive Interface
The PBL 386 30/1 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
Table3. TheSLICinternalbiascurrentwith
the direction of the current defined as
positivewhenfloatingintotheterminalRSN.
SLIC
VOH(typ)
(V)
VOHvirt(typ)
(V)
PBL 386 30/1
3.0 +VTRO 4.9 +VTRO
7
6
5
4
3
2
1
0
Table 2. Battery overhead.
off-hook
on-hook
The resistive loop feed (reference D in
figure 12) is programmed by connecting a
resistor, RSG, between terminals PSG and
VBAT according to the equation:
RSG + 2 · 104
RFeed
=
+ 2RF + 2RP
200
0
10
20
30
40
50
60
where RFeed is in Ω for RSG, RP and RF in Ω.
R
ov
(KΩ)
Figure 10. Programmable overhead voltage (POV). RL = 600 Ω or ∞.
4-204
ERICSSON [ ERICSSON ]
