le79r79 Zarlink Semiconductor, le79r79 Datasheet - Page 16

• Manufacturer Part Number: le79r79
• Description: Ringing Subscriber Line Interface Circuit
• Manufacturer: Zarlink Semiconductor

RING-TRIP COMPONENTS
R
Ring waveform rise time ≈ 0.214 • (R
For a 1.25 crest factor @ 20 Hz, tr ≈ 10 mS.
∴ (R
C
R
C
R
SLEW
SLEW
RT2
RT
RT1
where R
SLEW
=
, C
=
=
should be changed if a different crest factor is desired.
1.5 µF
12 kΩ
300 CF
SLEW
= 150 kΩ, C
LRT
•
= Loop-detection threshold resistance for ring trip and CF = Crest factor of ringing signal (≈ 1.25)
•
----------------------------------------------------------------------------------------------------------------------------------------------- -
Vbat 3.5
SLEW
R
–
L
= 0.33 µF.)
Battery
–
a
b
(
15 µA 300 CF
0
I
SLEW
L
Feed current programmed by R
•
• C
V
BAT1
SLEW
•
B (RING)
A (TIP)
Figure 4. Ringing Waveforms
Figure 5. Feed Programming
) ≈ tr.
Zarlink Semiconductor Inc.
•
(
R
SLIC
This is the best time for switching
between Ringing and other states
for minimizing detect switching
transients.
LRT
+
16
150
RSN
RDC
+
DC1
2R
and R
F
)
)
•
DC2
(
R
LRT
A(TIP)
B(RING)
Ringing Reference
(Input to R
+
R
R
150
DC1
DC2
+
2R
SLEW
F
)
)
C
DC