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參數(shù)資料
| 型號(hào)： | L7597 |
| 廠商： | Lineage Power |
| 英文描述： | Resistive Subscriber Line Interface Circuit (SLIC), Ring Relay, and Protector (SRP) for Short Loop and TA-909 Applications(用于短環(huán)路和TA-909的電阻性用戶線接口、振鈴繼電器和保護(hù)器) |
| 中文描述： | 電阻用戶線接口電路（SLIC），環(huán)繼電器和保護(hù)（SRP）的短環(huán)路和TA - 909應(yīng)用（用于短環(huán)路和電訊- 909的電阻性用戶線接口，振鈴繼電器和保護(hù)器） |
| 文件頁數(shù)： | 23/34頁 |
| 文件大?。?/td> | 564K |
| 代理商： | L7597 |
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Lucent Technologies Inc.
23
Advance Data Sheet
March 1997
Relay, and Protector (SRP) for Short Loop and TA-909 Applications
L7597 Resistive Subscriber Line Interface Circuit (SLIC), Ring
Applications
(continued)
Resistor Module
(continued)
Resistors R
3
—R
6
set the gain of the SLIC in the
transmit (2-wire to 4-wire) direction. This is shown in
Figure 7.
5-5277 (F)
Figure 7. L7597 SLIC Matching Requirements
The matching of resistors R
3
—R
6
will determine the
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
3
—R
6
will be relatively
low. Given design margin and thick-film technology
capabilities, a power rating of 250 mW for these resis-
tors is not unreasonable.
Resistors R
7
and R
8
are used to couple the PT and PR
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
7
and R
8
is given by:
(48 V – 6 V) E2/2.0 k
= 0.882 W
per R
7
and R
8
resistor pair
882 mW/2 = 441 mW
per resistor (R
7
and R
8
)
Hence, the operating power rating of 500 mW for R
7
and R
8
. This is the normal rating for R
7
and R
8
under
normal operating conditions. The ability of these resis-
tors to withstand fault conditions depends on the power
rating. Resistor R
9
is also included on the thick-film
resistor module. This resistor is used to set the gain of
the battery noise cancellation circuit. See the Battery
Noise Cancellation section of this data sheet for design
equations to set the value of R
9
.
Power ringing is applied to the line circuit through resis-
tor R
10
. One side of R
10
is connected to L7597 node
RSW. RSW is the output of the integrated solid-state
ringing access switch, SW3. The other side of R
10
is
connected to the 200
Ring feed resistor, R
1
. Resistor
R
10
also serves as a current-limiting resistor. Fault cur-
rent through the solid-state ringing access switch,
SW3, is limited by R
10
. SW3 is rated for 2 A maximum
for a 10
μ
s x 1000
μ
s (lightning) pulse. Continuous cur-
rent through this switch should be less than 150 mA.
R
10
in MMCresistor modules A31A8574AA and MMC
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, UL497A, FCC
Part 68.302 (d) & (e), and REA Form 397G specifica-
tion. The MMCA11A8574AA 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
1
and R
2
, in the external resistor module. Under
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
resistors, and pin V
BF
is isolated from the loop
by the Ring-side, 200
dc feed resistor. These pins
must have adequate fault protection which operates
outside of their normal operating voltages. All three
pins are protected by SCRs which clamp the surge cur-
rents (both positive and negative) to FGND. The sense
inputs, TS and RS, are protected with diodes to battery
TIP
RING
R
5
200 k
R
6
200 k
R
4
100 k
–
+
XMT
R
3
100 k
* ULis a registered trademark of Underwriters Laboratories, Inc.
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