LUCL8576BP-D AGERE [Agere Systems], LUCL8576BP-D Datasheet - Page 19

• Manufacturer Part Number: LUCL8576BP-D
• Description: Dual Ringing SLIC
• Manufacturer: AGERE [Agere Systems]

May 2001
Applications
Power Ringing
Power Ringing Load
Telcordia GR-909 specifies that a minimum 40 Vrms
must be delivered to a 5 REN ringing load of 1386
40 F. For 5 REN load, it is recommended that V
set to –68.5 Vdc. During the power ring state, the dc
current limit is automatically boosted by a factor of 3.5
over the current limit set by resistor R
these factors are necessary to ensure delivery of
40 Vrms to the North American 5 REN ringing load of
1386
Ring Trip
Ring trip is accomplished by filtering the voltage seen
at node DC
comparator. DC
ring current, and under short dc loop conditions, on-
hook ringing current and off-hook current provide suffi-
cient voltage differential at DC
ring trip condition has occurred. The ring trip compara-
tor threshold is set via a resistor between the ring trip
comparator and DC
The output of NSTAT is automatically set to detect ring
trip during the balanced ring mode. During quiet inter-
vals of ringing, the output of NSTAT is automatically
determined by the loop closure detector.
Refer to Figure 2 for the following discussion.
Capacitor C
single-pole, low-pass filter that smooths the voltage
seen at DC
the ripple seen at DC
tion of the voltage at DC
tripped level.
Agere Systems Inc.
+ 40 F.
OUT
OUT
RT
. The pole of the filter will influence both
in conjunction with resistor R
and applying it to the integrated ring trip
OUT
(continued)
(continued)
OUT
is a voltage proportional to the tip/
OUT
.
OUT
and the speed of the transi-
from the pretrip to the
OUT
to distinguish that a
PROG
. Both of
TFLT
form a
BAT
be
+
the 0.1 µF C
7.5 k R
To determine the low-pass pole:
Using the recommended 383 k R
4.15 Hz.
The loop current at ring trip is given by:
Using the recommended 52.3 k R
ring trip threshold current is set for 54 mA.
Reference Design for ISDN TA Applications
For a complete reference design, please refer to the
POTS for ISDN, WLL, and FITL/FITH Applications,
Featuring Ringing SLIC Solutions Application Note,
which provides a detailed discussion of the reference
design functionality. The design presented utilizes a dc
to dc converter and requires only a +5 V and a +12 V
supply to operate. The schematic in Figure 2 of this
document portrays the SLIC and codec portions of that
design.
ac Design
There are four key ac design parameters. Termination
impedance is the impedance looking into the 2-wire
port of the line card. It is set to match the impedance of
the telephone loop in order to minimize signal reflec-
tions back to the telephone set. Transmit gain is mea-
sured from the 2-wire port to the PCM highway, while
receive gain is measured from the PCM highway to
the 2-wire port or telephone loop. Finally, the hybrid
balance circuit cancels the unwanted amount of the
received signal that appears at the transmit port.
GX2
I
LOOP(TRIP)
RT
resistor in a 20 Hz ringing application, the
capacitor, the low-pass pole is set at
f(Hz) =
L8576B Dual Ringing SLIC
= 7.76 mA
---------------------------------------------- -
2 R
TFLT
1
R
-------------- -
R
C
TFLT
TTH
TTH
GX2
RT
resistor and the
resistor and
19