Preliminary Data Sheet
September 2001
High-Voltage Ringing SLIC for VoIP Applications
L9500A
Agere Systems Inc.
23
Applications
(continued)
Battery Reversal Rate
The rate of battery reverse is controlled or ramped by
capacitors FB1 and FB2. A chart showing FB1 and FB2
values vs. typical ramp time is given below. Leave FB1
and FB2 open if it is not desired to ramp the rate of bat-
tery reversal.
Table 20. FB1 and FB2 Values vs. Typical Ramp
Time
Supervision
The L9500 offers the loop closure and ring trip supervi-
sion functions. Internal to the device, the outputs of
these detectors are multiplexed into a single package
output (NSTAT). The ring trip detector is valid on
NSTAT during the ring mode and loop closure detector
is valid on NSTAT during active and on-hook transmis-
sion modes. Additionally, common-mode current is
detected for ground start applications. This status is
output onto NSTAT and is valid during ground start
mode.
Loop Closure
The loop closure has a fixed typical 10.5 mA on- to off-
hook threshold in the active mode and a fixed 11.5 mA
on- to off-hook threshold from the scan mode. In either
case, there is a 2 mA hysteresis with V
CC
= 5 V and a
2 mA hysteresis with V
CC
= 3.3 V.
Ring Trip
The ring trip detector requires only a single-pole filter at
the input, minimizing external components. An R/C
combination of 383 k
and 0.1
μ
F, for a filter pole at
5.15 Hz, is recommended.
The ring trip threshold is internally fixed as a function of
battery voltage and is given by:
RT (mA) = 67 * {(0.0045 * V
BAT1
) + 0.317}
where:
RT is ring trip current in mA.
V
BAT1
is the magnitude of the ring battery in V.
There is a 6 mA to 8 mA hysteresis.
Ground Start
In the ground start applications, the loop closure detec-
tor detector is also used to indicate that ring-ground
has occurred. During ground start mode, loop current
will be common mode, rather than differential as in loop
start mode. Thus, in ground start the threshold of the
loop closure detector is reduced by one half the thresh-
old seen in the loop start mode.This ouput is seen at
the NSTAT output pin.
C
FB1
and C
FB2
0.01
μ
F
0.1
μ
F
0.22
μ
F
0.47
μ
F
1.0
μ
F
1.22
μ
F
1.3
μ
F
1.4
μ
F
1.6
μ
F
Transition Time
20 ms
220 ms
440 ms
900 ms
1.8 s
2.25 s
2.5 s
2.7 s
3.2 s