le79r70 Zarlink Semiconductor, le79r70 Datasheet - Page 14

• Manufacturer Part Number: le79r70
• 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
320 CF
SLEW
= 150 kΩ, C
LRT
•
= Loop-detection threshold resistance for ring trip and CF = Crest factor of ringing signal (≈ 1.25)
Battery
•
----------------------------------------------------------------------------------------------------------------------------------------- -
V
0
BAT1
SLEW
R
L
–
5
= 0.33 µF.)
–
b
a
(
24 µA 320 CF
I
SLEW
L
Feed current programmed by R
•
V
• C
BAT1
•
A
Figure 2. Ringing Waveforms
SLEW
B
Figure 3. Feed Programming
•
) ≈ tr.
(
Zarlink Semiconductor Inc.
This is the best time for
switching between RINGING
and other states for minimizing
detect switching transients.
R
SLIC
LRT
+
150
14
+
2R
RSN
RDC
F
)
DC1
)
•
(
and R
R
LRT
+
DC2
150
R
R
+
DC2
DC1
2R
F
Ringing Reference
(Input to R
)
B(RING)
A(TIP)
C
DC
SLEW
)