Preliminary Data Sheet
September 2001
Short-Loop Ringing SLIC with Ground Start
L9216A/G
24
Agere Systems Inc.
Applications
(continued)
Overhead Voltage
(continued)
Ring Mode
In the ring mode, to maximize ringing loop length, the
overhead is decreased to the saturation of the tip ring
drive amplifiers, a nominal 4 V. The tip to ground volt-
age is 1 V, and the ring to V
BAT1
voltage is 3 V.
During the ring mode, to conserve power, the receive
input at RCVN/RCVP is deactivated. During the ring
mode, to conserve power, the AAC amplifier in the
transmit direction at VITR is deactivated. However, if
the AX amplifier at VTX is active during the ring mode,
differential ring current may be sensed at VTX during
the ring mode.
Loop Range
The dc loop range is calculated using:
R
L
=
– 2R
P
– R
DC
V
BAT2
is typically applied under off-hook conditions for
power conservation and SLIC thermal considerations.
The L9216 is intended for short-loop applications and,
therefore, will always be in current limit during off-hook
conditions. However, note that the ringing loop length
rather than the dc loop length, will be the factor to
determine operating loop length.
Battery Reversal Rate
The rate of battery reverse is controlled or ramped by
capacitors FB1 and FB2. Table 20 below shows FB1
and FB2 values vs. typical ramp time. Leave FB1 and
FB2 open if it is not desired to ramp the rate of battery
reversal.
Table 20. FB1 and FB2 Values vs. Typical Ramp
Time
Supervision
The L9216 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.
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
1 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.
Tip or Ring Ground Detector
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).
For ground start applications detection may be seen at
the output of the common mode current detector
(RGDET) or the loop closure detector (NSTAT).
If ICM is used, the detection threshold is set by con-
necting a resistor from ICM to V
CC
.
205 x V
CC
/R
ICM
(k
) = I
TH
(mA)
Additionally, a filter capacitor across R
ICM
will set the
time constant of the detector. No hysteresis is associ-
ated with this detector. The RC filter at ICM gives
immunity to longitudinal currents.
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
--------------------------------------
I
LIMIT