L9214A/G
Low-Cost Ringing SLIC
Preliminary Data Sheet
October 2001
use of the state input pins. It is possible to select either
fast or slow slew rates to alter the crest factor of the
ringing signal. This allows designers to set the external
capacitors to a specific factor and change the ringing
frequency under software control while maintaining the
crest factor between 1.2 and 1.6 for the trapezoidal sig-
nal.
Supervision
The L9214 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. Additionally, a common-mode current
detector for tip or ring ground detection is included for
ground key applications.
During the ring mode, it is also possible to supply a
pulse-width modulated, PWM, signal into the device’s
B1 input. This signal is used to produce the power ring
signal. This signal must be removed during nonring
mode states. The user may input any crest factor ring
signal using this method; thus, the device will support a
sine wave (crest factor 1.414) or a lower or higher crest
factor input for increased power efficiency ring signal.
Various crest factors are shown below.
Loop Closure
The loop closure has a fixed typical 10 mA on- to off-
hook threshold in the active mode and a fixed 10 mA
on- to off-hook threshold from the scan mode. In either
case, there is a 2 mA hysteresis with VCC = 5.0 V and
with VCC = 3.3 V.
80
60
Ring Trip
40
The ring trip detector requires an external filter at the
input, minimizing external components. An R + R//C
combination of 75 kΩ and 133 kΩ // 1 µF, for a filter
pole at 3.3 Hz, is recommended for a 3 REN config-
uration. For a 5 REN configuration, a 150 kΩ and
100 kΩ // 1 µF (for a filter pole at 2.65 Hz) combination
is recommended.
20
0
–20
–40
–60
–80
0.00 0.04 0.08 0.12 0.16 0.20
0.02 0.06 0.10 0.14 0.18
The ring trip threshold is internally fixed and is indepen-
dent of battery voltage. The threshold, IRT = 20.1 mA.
TIME (s)
12-3346a (F)
Note: Slew rate = 5.65 V/ms; trise = tfall = 23 ms; pwidth = 2 ms;
period = 50 ms.
Tip or Ring Ground Detector
Figure 10. Ringing Waveform Crest Factor = 1.6
In the ground key or ground start applications a com-
mon-mode current detector is used to indicate either a
tip- or ring-ground has occurred (ground key) or an off-
hook has occurred (ground start). The detection thresh-
old is set by connecting a resistor from ICM to VCC.
80
60
40
1000 * VCC/RICM (kΩ) = ITH (mA)
20
0
where:
–20
–40
–60
RICM > 80 kΩ @ VCC = 3.3 V
RICM > 150 kΩ @ VCC = 5.0 V
Additionally, a filter capacitor across RICM will set the
time constant of the detector. No hysteresis is associ-
ated with this detector.
–80
0.00 0.04 0.08 0.12 0.16 0.20
0.02 0.06 0.10 0.14 0.18
TIME (s)
12-3347a (F)
Note: Slew rate = 10.83 V/ms; trise = tfall = 12 ms; pwidth = 13 ms;
period = 50 ms.
Power Ring
The device offers a ring mode, in which a power ring
signal is provided to the tip/ring pair. The standard
method of ringing is to perform trapezoidal ringing by
Figure 11. Ringing Waveform Crest Factor = 1.2
Agere Systems Inc.
27
AGERE [ AGERE SYSTEMS ]
