PBL 3766
R
FB
U
C
HP
U
1
2
-5V
HPR
VTX
VEE
HPT
RD
20/15
22/19
23/20
21/16
19/14
18/13
16/12
R
R
D
RT
R
R
TX
C
RT
R
1
-
+
DT
R
R
B
T
R
2
RSN
U
3
R
F
-48V
TIPX
RINGX
GND
Tip
RX
K1 K1
R
27/21
28/22
2/1
DC
V
BAT
A
G
CODEC/Filter
+
Ring
RDC
C1
K2 K2
14/11
13/10
12/9
C
TISP
C
C
R
F
DC
R
C
Note 6
C
U1
U2
SLIC (Subscriber Line Interface
Circuit). PBL 3766
Combination CODEC/filter, e.g.
TP3054 (or programmable
CODEC/filter, e.g. SLAC)
Secordary protection (e g Texas
Instruments TISP PBL1)
Ring relay, 2C contacts. Note 1
TC
VCC
C2
+5V
4/2
DET
E0
RINGRLY
5/3
11/8
To other line
interfaces
D
K
R
2
VBAT
Notes 2 & 3
7/4
9/7
D
RSG
N/C
U3
KR
3
D
1
PTC
Note 5
Ringing
R
C
Note 4
Bat
-48V
Bat
Note 1
R
SG
-5V
Digital
Interface
D1, D2 Diode, e.g. 1N4454
(-48V +90V
)
RMS
D3
RF
Diode, e.g. 1N4004
Line resistor, 40 Ω
1% match, e.g. Ericsson
Components
PBR 51XX
Notes
R1
R2
RB
RBat
RD
Resistor, 150 kΩ, 5%, 1/4 W
Resistor, 2 MΩ, 5%, 1/4 W
Resistor, 17.8 kΩ, %, 1/4 W
Resistor, 5.1 Ω, 5%, 1/4 W
Optional. Refer to paragraph
“Loop Current Detector”.
Resistor, 41.2 kΩ, 5%, 1/4 W
Resistor, 24.3 kΩ, 1%, 1/4 W
Resistor, 261 kΩ, 1%, 1/4 W
Resistor, 150 Ω, 5%, 2 W
Resistor, 0 Ω (for VBat = -48V)
Resistor, 523 kΩ, 1%, 1/4 W
Resistor, 20.0 kΩ, 1%, 1/4 W
Capacitor, 0.47 µF, 20%, 100 V
Capacitor, 1.5 µF, 20%, 10 V
Capacitor, 0.033 µF, 20%, 100V
Capacitor, 0.39 µF, 20%, 100 V
1. The relay coil may be connected to a negative voltage, down to the VBat limit. For VBat = -48 V
relay coils with voltage ratings from 5 V to 48 V may be used.
2. The plastic leaded chip carrier terminals 3, 6, 10, 17 and 24 shall all be connected to the VBat
supply trace to provide heat sinking.
3. The dual-in line package terminals 5, 6, 17 and 18 shall all be connected to the VBat supply trace
to provide heat sinking.
RDC
RFB
RRX
RRT
RSG
RT
RTX
CBat
CDC
CHP
CRT
4. The plastic leaded chip carrier terminals 8, 15 and 25 are not internally connected to the chip.
These terminals may be connected to ground to provide shielding.
5. It may be desirable to include a PTC or other type of short circuit protection for the ringing
generator.
6. The ground terminals of the secondary protection should be connected to the ground terminal of
the SLIC, and to the common ground on the Printed Board Assembly with a track as short and
wide as possible, preferable a groundplane.
CTC, CRC Capacitor, 2200 pF, 20%, 100 V
CTISP
Capacitor, 220 nF, 20%, 100 V
Figure 11. Single channel subscriber line interface with PBL 3766 and a combination CODEC/filter.
Capacitors CTC and CRC
1/(π·f·CRC), a TIPX to ground impedance
of 1/(2·π·f·CTC) and a RINGX to ground
impedance of 1/(2·π·f·CRC).
gram in figure 12 shows the PBL 3766
active state battery feed system. The
magnitude of the constant current is set
by a programming resistor, RDC.
The capacitors designated CTC and CRC in
figure 11, connected between TIPX and
ground as well as between RINGX and
ground, are recommended as an addition
to the overvoltage protection network.
Very fast transients, appearing on tip and
ring, may pass by the diode and SCR
clamps in the overvoltage protection
network, before these devices have had
time to activate and could damage the
SLIC. CTC and CRC short such very fast
transients to ground. The recommended
value for CTC and CRC is 2200 pF. Higher
capacitance values may be used, but
care must be taken to prevent
Ac - Dc Separation Capacitor, CHP
To permit the line drive amplifiers to
operate without vf signal distortion even
on high resistance or open circuit loops,
a saturation guard circuit limits the loop
voltage, when the tip to ring dc voltage
approaches the available battery supply
voltage. The saturation guard function
allows the PBL 3766 to transmit and
receive vf signals with the telephone on-
hook.
The high pass filter capacitor connected
between terminals HPT and HPR pro-
vides the separation between circuits
sensing tip-ring dc conditions and circuits
processing ac signals. A CHP value of
33 nF will position the low end frequency
response 3dB break point at 12 Hz (f3dB
according to f3dB = 1/(2π·RHP·CHP) where
HP ≈ 400 kΩ.
)
R
Figure 13 shows an example of
Battery Feed
PBL 3766 active state battery feed.
With the SLIC set to the stand-by state,
most of the circuit is disabled, including
thelinedriveamplifiers, toconservepower.
Overview
degradation of either longitudinal balance
or return loss. CTC and CRC contribute a
metallic impedance of 1/(π·f·CTC) ≈
The PBL 3766 SLIC synthesizes a cons-
tant current feed system. The block dia-
4-12
ERICSSON [ ERICSSON ]
