PBL38621-2 Ericsson, PBL38621-2 Datasheet - Page 12

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

PBL 386 21/2
switching occurs when the line voltage
passes the value
For correct functionality it is important to
connect the terminal VBAT2 to the second
power supply via the diode D
An optional diode D
terminal VB and the VB2 power supply, see
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 C
CODEC Receive Interface
The PBL 386 21/2 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 receive output
via the resistor R
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
the RSN terminal and ground. With current
directions defined as in figure 13, current
summation gives:
where V
CODEC at the receive output.
From this equation the resistor R
calculated as
For the value on I
The resistor R
transmission.
Table 3. The SLIC internal bias current with
the direction of the current defined as
positive when floating into the terminal RSN.
12
R
R
1 25
SLIC
PBL 386 21/2
R
,
|VB2| - 40 · I
I
RSN
T
VB2
I
CODEC
RSN
, D
125
,
I
BB
RT
is the reference voltage of the
and D
R
1 25
R
,
R
RX
has no influence on the ac
T
V
RX
I
L
RRX
, is dc biased with +1.25V.
RSN
CODEC
- V
125
BB
,
VB2
, see table 3.
125
TRO
,
connected between
are removed.
I
I
-55
RR
RSN
= 3.6
R
125
V
RX
VB2
R
,
[ A]
CODEC
R
in figure 11.
R
between
R
can be
Programmable overhead voltage(POV)
With the POV function the overhead
voltage can be increased.
If the POV pin is left open the overhead
voltage is internally set to 1.1 V
overhead voltage is equal in on-hook and
off-hook. If a resistor R
between the POV pin and AGND, the
overhead voltage can be set to higher
values, typical values can be seen in
figure 10. The R
V
for THD <1% and the signal frequency
1000Hz.
Observe that the 4-wire output terminal V
can not handle more than 3.2 V
gain 2-wire to 4-wire is 0dB, 3.2 V
maximum also for the 2-wire side. Signal
levels between 3.2 and 6.4 V
2-wire side can be handled with the PTG
shorted so that the gain G
-6.02dB. Please note that the 2-wire
impedance, R
gain has to be recalculated if the PTG is
shorted.
Please note that the maximum signal
current at the 2-wire side can not be
greater than 9 mA.
How to use POV:
1.
2.
3.
Analog Temperature Guard
The widely varying environmental
conditions in which SLICs operate may
lead to the chip temperature limitations
being exceeded. The PBL 386 21/2 SLIC
reduce the dc line current when the chip
temperature reaches approximately 145 C
and increases it again automatically when
the temperature drops. Accordingly trans-
mission is not lost under high ambient
temperature conditions.
The detector output, DET, is forced to a
logic low level when the temperature guard
is active.
TRO
(signal headroom) are typical values
Decide what overhead
voltage(V
function is only needed if the
overhead voltage exceeds 1.1 V
In figure 10 the corresponding R
for the decided V
If the overhead voltage exceeds
3.2 V
changed to -6.02dB by connecting
the PTG pin to AGND. Please note
that the 2-wire impedance, R
the 4-wire to 4-wire gain has to be
recalculated.
Peak
, the G
R
TRO
OV
and the 4-wire to 4-wire
) is needed. The POV
and corresponding
2-4S
TRO
OV
gain has to be
is connected
2-4S
can be found.
Peak
become
Peak.
Peak.
on the
So if the
R
The
Peak
and
Peak
OV
TX
is
Loop Monitoring Functions
The loop current, ground key and ring trip
detectors report their status through a com-
mon output, DET. The detector to be
connected to DET is selected via the three
bit wide control interface C1, C2 and C3.
Please refer to section Control Inputs for a
description of the control interface.
Loop Current Detector
The loop current detector is indicating that
the telephone is off hook and that current is
flowing in the loop by putting the output
DET to a logical low level when selected.
The loop current threshold value, I
which the loop current detector changes
state is programmable by selecting the
value of resistor R
pin PLD and ground and is calculated
according to
R
The current detector is internally filtered
and is not influenced by the ac signal at the
two wire side.
Ground Key Detector
The ground key detector is indicating when
the ground key is pressed (active) by putting
the output pin DET to a logical high level
when selected. The ground key detector
circuit senses the difference in TIPX and
RINGX currents. When the current at the
RINGX side exceeds the current at the
TIPX side with the threshold value the
detector is triggered. For threshold current
values, please refer to the datasheet.
Ring Trip Detector
Ring trip detection is accomplished by
connecting an external network to a
comparator in the SLIC with inputs DT and
DR. The ringing source can be balanced or
unbalanced superimposed on V
The unbalanced ringing source may be
applied to either the ring lead or the tip lead
with return via the other wire. A ring relay
driven by the SLIC ring relay driver connects
the ringing source to tip and ring.
The ring trip function is based on a polarity
change at the comparator input when the
line goes off-hook. In the on-hook state no
dc current flows through the loop and the
voltage at comparator input DT is more
positive than the voltage at input DR. When
the line goes off-hook, while the ring relay
LD
I
500
LTh
LD
. R
LD
connects between
B
or GND.
LTh
, at