PBL38620-2 Ericsson, PBL38620-2 Datasheet - Page 14

• Manufacturer Part Number: PBL38620-2
• Description: Subscriber Line Interface Circuit
• Manufacturer: Ericsson

Overvoltage Protection
The PBL 386 20/2 SLIC must be protected
against overvoltages on the telephone line
caused by lightning, ac power contact and
induction. Refer to Maximum Ratings, TIPX
and RINGX terminals, for maximum
allowable continuous and transient currents
that may be applied to the SLIC.
Secondary Protection
The circuit shown in figure 12 utilizes series
resistors together with a programmable
overvoltage protector (e.g Power
Innovations TISPPBL2), serving as a
secondary protection.
The TISPPBL2 is a dual forward-conduc-
ting buffered p-gate overvoltage protector.
The protector gate references the protection
(clamping) voltage to negative supply
voltage (i.e the battery voltage,V
PBL 386 20/2
14
Figure 12. single-channel subscriber line interface with PBL 386 20/2 and combination CODEC/filter.
RESISTORS (Values according to IEC E96 series):
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
SG
LD
OV
LC
REF
R
T
TX
B
RX
FB
1
2
3
4
RT
P1
F1
, R
, R
P2
F2
= 0
= 49.9 k
= User programmable
= 38.3 k
= 49.9 k
= 64.9 k
= 105 k
= 24.9 k
= 22.1 k
= 52.3 k
Depending on CODEC/filter
= 604 k
= 604 k
= 249 k
= 280 k
= 330
= Line resistor, 40
10
VB2
VB
+12 V /+5V
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
1% 1/10 W
5% 2 W
1% 1/10 W
D
RING
VB
D
TIP
BB
1%
K
R
D
VB2
C
C
VB
VB2
(Note 1)
B
).
R
R
R
E
RT
F2
F1
RG
R
R
C
OVP
1
2
GG
As the protection voltage will track the
negative supply voltage the overvoltage
stress on the SLIC is minimized.
Positive overvoltages are clamped to gro-
und by a diode. Negative overvoltages are
initially clamped close to the SLIC negative
supply rail voltage and the protector will
crowbar into a low voltage on-state
condition, by firing an internal thyristor.
A gate decoupling capacitor, C
to carry enough charge to supply a high
enough current to quickly turn on the
thyristor in the protector. C
close to the overvoltage protection device.
Without the capacitor even the low
inductance in the track to the V
limit the current and delay the activation of
the thyristor clamp.
CAPACITORS (Values according to IEC E96 series):
C
C
C
C
C
C
C
C
C
C
C
DIODES:
D
D
D
VB
VB2
VCC
TC
RC
HP
LP
TX
GG
1
2
VB
VB2
BB
C
1
VB
R
R
P2
P1
R
= 100 nF
= 150 nF
= 100 nF
= 2.2 nF
= 2.2 nF
= 47 nF
= 150 nF
= 100 nF
= 220 nF
= 330 nF
= 330 nF
= 1N4448
= 1N4448
= 1N4448
3
R
4
SLIC No. 2 etc.
C
C
C
2
R
RC
TC
SG
C
C
HP
LP
100 V 10%
100 V 10%
100 V 10%
100 V 10%
100 V 10%
100 V 10%
100 V 10%
10 V 10%
10 V 10%
63 V 10%
63 V 10%
PTG
RRLY
RINGX
BGND
TIPX
VBAT
VBAT2
PSG
GG
PBL 386 20/2
HP
NC
NC
LP
DT
DR
PLCC 28-PIN
shall be placed
PACKAGE
GG
Bat
, is needed
supply will
AGND
RSN
POV
VCC
VTX
REF
PLC
PLD
DET
NC
NC
C1
C2
C3
SYSTEM CONTROL
VCC
R
R
R
R
REF
LC
OV
LD
INTERFACE
Note:
1) R
OVP:
Secondary protection (e. g. Power Innovations
TISPPBL2). The ground terminals of the secondary
protection should be connected to the common
ground on the Printed Board Assembly with a track
as short and wide as possible, preferable a
groundplane.
The fuse resistors R
purposes of being non- destructive energy
dissipators, when transients are clamped
and of being fuses, when the line is exposed
to a power cross.
If a PTC is choosen for R
important to always use PTC´s in series
with resistors not sensitive to temperature,
as the PTC will act as a capacitance for fast
transients and therefore will not protect the
SLIC.
R
R
P1
T
R
C
and R
TX
P2
R
R
RX
may be omitted if D
TX
C
VCC
PBL 386 20/2
R
B
F
R
CODEC/
-
+
VCC
-
+
0
FB
Filter
serve the dual
F
0
VB
, note that it is
is in place.