Data Sheet
April 2000
L8560 Low-Power SLIC with Ringing
28
Lucent Technologies Inc.
Applications
(continued)
Power Ringing
(continued)
12-3286
Figure 28. POTS Controlled from an ISDN Terminal Adapter
PROT.
SLIC
RINGER
CODEC
TDM
μ
P
ISDN
TA
TO
TELEPHONE SET
RJ-11
XMT
RCV
TO ISDN
SERVICE
RJ-45
DX, DR
CLK, FS
DTMF
DECODER
Power Ringing Load
Bellcore TA-909 specifies that a minimum 40 Vrms
must be delivered to a 5 REN ringing load of 1380
+
40
μ
F. During the ringing state, V
BAT1
is automatically
applied to the tip/ring power amplifiers. For 5 REN
load, it is recommended that V
BAT1
be set to –65 Vdc.
Also during the power ring state, the dc current limit is
automatically boosted by a factor of 2.8 over the cur-
rent limit set by resistor R
PROG
. Both of these factors
are necessary to ensure delivery of 40 Vrms to the
North American 5 REN ringing load of 1380
+ 40
μ
F.
Crest Factor
The balanced trapezoidal ring signal is generated by
simply toggling the SLIC between the powerup state
forward and powerup reverse battery states. The state
change is done by applying a square wave (whose fre-
quency is the desired ring frequency) to logic input B1.
Capacitors FB1 and FB2 are used to control or ramp
the speed of the transition of the battery reverse, thus
shaping the balanced ring signal. Waveforms of crest
factors 1.6 and 1.2 are shown in Figure 29 and Figure
30.
In a real application, the ringing trapezoidal waveform
crest factor can be estimated by:
Crest factor =
Where: f = ringing frequency; C
FB
= (C
FB1
+ C
FB2
)/2;
I
CS
= 29
μ
A @
±
8% accuracy over temperature;
V
OH
= SLIC overhead during ring.
12-3346a (F)
Note: Slew rate = 5.65 V/ms; trise = tfall = 23 ms; pwidth = 2 ms;
period = 50 ms.
Figure 29. Ringing Waveform Crest Factor = 1.6
12-3347a (F)
Note: Slew rate = 10.83 V/ms; trise = tfall = 12 ms; pwidth = 13 ms;
period = 50 ms.
Figure 30. Ringing Waveform Crest Factor = 1.2
3
1
----------------------------------------------------------------------------
I
CS
)
×
–
------------------------------------------------------------------------------------------
TIME (s)
–80
–60
–40
–20
0
20
40
60
80
0.00
0.02 0.06
0.04 0.08
0.10
0.12
0.14
0.16
0.18
0.20
V
TIME (s)
–80
–60
–40
–20
0
20
40
60
80
0.00
0.02 0.06
0.04 0.08
0.10
0.12
0.14
0.16
0.18
0.20
V