LUCL8574DP-D AGERE [Agere Systems], LUCL8574DP-D Datasheet - Page 24

• Manufacturer Part Number: LUCL8574DP-D
• Description: L8574D Resistive Subscriber Line Interface Circuit(SLIC), Ring Relay,and Protector(SRP)for Long Loop and TR-57 Applications
• Manufacturer: AGERE [Agere Systems]

L8574D Resistive Subscriber Line Interface Circuit (SLIC), Ring
Relay, and Protector (SRP) for Long Loop and TR-57 Applications
Applications
Resistor Module
Resistors R
transmit (2-wire to 4-wire) direction. This is shown in
Figure 7.
The matching of resistors R
gain accuracy of the SLIC; therefore, these resistors
must be matched accordingly. Their matching require-
ments are given in Table 16.
Because of the high resistance values, the normal
operating power of resistors R
low. Given design margin and thick-film technology
capabilities, a power rating of 250 mW for these resis-
tors is not unreasonable.
Resistors R
current drive amplifiers to Tip and Ring. Since PT and
PR drive amplifiers are current sources, the value of
the series resistance does not affect the loop length or
other performance of the SLIC, and may be arbitrarily
high for protection purposes. A value of 1 k is ade-
quate for protection purposes.
Under normal operating conditions, these resistors will
see the battery voltage less the Tip/Ring voltage.
Assuming a Tip/Ring voltage of 6 V (representative of a
short into a handset), the normal continuous operating
power of R
(48 V – 6 V) E2/2.0 k = 0.882 W per R
tor pair
882 mW/2 = 441 mW per resistor (R
Hence, the operating power rating of 500 mW for R
and R
24
24
Figure 7. L8574 SLIC Matching Requirements
8
. This is the normal rating for R
RING
TIP
7
3
7
and R
—R
and R
6
200 k
200 k
set the gain of the SLIC in the
(continued)
8
8
R
R
is given by:
are used to couple the PT and PR
5
6
(continued)
R
100 k
3
—R
4
+
100 k
–
3
—R
R
6
3
will determine the
6
7
will be relatively
7
and R
and R
7
and R
XMT
8
)
8
under
8
5-5277 (F)
resis-
7
* UL is a registered trademark of Underwriters Laboratories, Inc.
normal operating conditions. The ability of these resis-
tors to withstand fault conditions depends on the power
rating.
Resistor R
module. This resistor is used to set the gain of the bat-
tery noise cancellation circuit. See the Battery Noise
Cancellation section of this data sheet for design equa-
tions to set the value of R
Power ringing is applied to the line circuit through resis-
tor R
RSW. RSW is the output of the integrated solid-state
ringing access switch, SW3. The other side of R
connected to the 200
R
rent through the solid-state ringing access switch,
SW3, is limited by R
for a 10 s x 1000 s (lightning) pulse. Continuous cur-
rent through this switch should be less than 150 mA.
R
A11A8574AA is chosen to be 600 .
Protection
Because of the resistive feed architecture, a simple
inexpensive protection scheme that does not require
an external protection device may be used. The MMC
A31A8574 resistor module has specifications which
are qualified to ITU-T K20, UL * 1459, UL 497A, FCC
Part 68.302 (d) & (e), and REA Form 397G specifica-
tion. The MMC A11A8574AA resistor module, in addi-
tion to meeting all the specifications of the MMC
A31A8574, also meets Bellcore 1089 requirements.
Lightning and power-cross protection are provided
by the two external dc feed (and current-limiting) resis-
tors, R
fault conditions, these resistors serve as fault current-
limiting resistors. These resistors are designed to sur-
vive lightning surges. They are also designed to contin-
uously dissipate 4 W each and to survive 1 Arms @
60 Hz power crosses of 1 second in duration. Sus-
tained power dissipation above these levels will cause
degradation and eventual failure; however, the resistors
are designed to fail gracefully under these conditions.
Pins PT and PR are isolated from the loop by external
1000
by the Ring-side, 200
must have adequate fault protection which operates
outside of their normal operating voltages. All three
pins are protected by SCRs which clamp the surge
currents (both positive and negative) to FGND. The
10
10
also serves as a current-limiting resistor. Fault cur-
in resistor modules MMC A31A8574AA and MMC
10
. One side of R
1
resistors, and pin V
and R
9
is also included on the thick-film resistor
2
, in the external resistor module. Under
10
10
. SW3 is rated for 2 A maximum
Ring feed resistor, R
is connected to L8574 node
dc feed resistor. These pins
9
.
BF
is isolated from the loop
Lucent Technologies Inc.
October 1998
Data Sheet
1
. Resistor
10
is