Data Sheet
March 1997
L7554 Low-Power SLIC
Applications (continued)
Table 10. Parts List for Loop Start and Ground Start Applications
Name
Value
Function
Integrated Circuits
SLIC
L7554
Subscriber loop interface circuit (SLIC).
Protector
250 V Thyristor type
L7581
Secondary protection.
Switches ringing signals.
First-generation codec.
Ringing Relay
Codec
T7513
Overvoltage Protection
RPT
20 Ω, Fusible
20 Ω, Fusible
Protection resistor.
Protection resistor.
RPR
Power Supply
CBAT1
0.1 µF, 20%, 100 V
0.1 µF, 20%, 10 V
0.47 µF, 20%, 100 V
0.1 µF, 20%, 100 V
VBAT filter capacitor.
CCC
VCC filter.
CF1
With CF2, improves idle channel noise.
With CF1, improves idle channel noise.
CF2
dc Profile
RPROG
66.8 kΩ, 1%, 1/4 W
Sets dc loop current limit.
ac Characteristics
CB2
0.1 µF, 20%, 100 V
330 µF, 20%, 10 V
86.6 kΩ, 1%, 1/4 W
48.7 kΩ, 1%, 1/4 W
20.0 kΩ, 1%, 1/4 W
ac/dc separation capacitor.
CGB
RT1
Loop stability.
With RGP and RRCV, sets ac termination impedance.
With RGP and RT1, sets receive gain.
RRCV
RGP
With RT1 and RRCV, sets ac termination impedance
and receive gain.
CGP
330 pF, 10 V, 20%
18.7 kΩ, 1%, 1/4 W
28.0 kΩ, 1%, 1/4 W
28.0 kΩ, 1%, 1/4 W
Loop stability.
RT2
With RX, sets transmit gain in codec.
With RT2, sets transmit gain in codec.
Sets hybrid balance.
RX
RHB1
Supervision
RLCTH
RTS1
24.9 kΩ, 1%, 1/4 W
402 Ω, 5%, 2 W
Sets loop closure (off-hook) threshold.
Ringing source series resistor.
RTS2
274 kΩ, 5%, 1/4 W
With CRTS2, forms first pole of a double pole,
2 Hz ring trip sense filter.
CRTS1
0.022 µF, 20%, 5 V
0.27 µF, 20%, 100 V
2 MΩ, 5%, 1/4 W
2 MΩ, 5%, 1/4 W
With RTSN, RTSP, forms second 2 Hz filter pole.
With RTS2, forms first 2 Hz filter pole.
CRTS2
RTSN
With CRTS1, RTSP, forms second 2 Hz filter pole.
With CRTS1, RTSN, forms second 2 Hz filter pole.
RTSP
Ground Start
CICM
0.47 µF, 20%, 10 V
100 kΩ, 20%, 1/4 W
82.5 kΩ, 1%, 1/4 W
Provides 60 Hz filtering for ring ground detection.
Digital output pull-up resistor.
RGDET
RICM2
Sets ring ground detection threshold.
Lucent Technologies Inc.
15
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