PBL38650-2 Datasheet, PDF (14/16 Pages) Ericsson – Subscriber Line Interface Circuit

PBL 386 50/2
DC characteristics
A
A
B
C
B
C
D
D
E
G
F
F
H
A:
I_L
(@
V_TR
=
0V)
=
I_LProg
+
|V_Bat|
-
V_OHVirt - R_Feed
60 · 10³
·
(I_LProg
+
4·10^-3)
B: R_feedB = 2 · 30 kΩ
10³
C:
I_LConst(typ) = I_LProg = _RLC - 4·10^-3
V_TR = |V_Bat| - V_OHVirt - R_Feed · (I_LProg + 4·10^-3)
D:
R_Feed
=
R_SG
+ 2 · 10⁴
200
J
V_TR [V]
E:
I
L
≈
6
mA
F: Apparent battery V_Bat(@ I_L = 0) =|V_Bat| - V_OHVirt - (R_Feed · 4·10^-3)
G:
R
feedG
=
2
·
25
Ω
H: V_TROpen = |V_Bat| - V_OH
J: Virtual battery V_BatVirt (@ I_L = 4 mA) = |V_Bat| - V_OHVirt
Figure 13. Battery feed characteristics (without the protection resistors on the line).
Loop Monitoring Functions
The loop current, ground key and ring
trip detectors report their status through a
common 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 thresh-
old value, I_LTh, at which the loop current
detector changes state is programmable
by selecting the value of resistor R_LD. R_LD
connects between pin PLD and ground
and is calculated according to
R_LD
=
500
I_LTh
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 thresh-
old 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_B or GND. 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 is ener-
14