
Advance Data Sheet
October 2000
Short-Loop Sine Wave Ringing SLIC
L9215A/G
Lucent Technologies Inc.
25
Applications
(continued)
Overhead Voltage
(continued)
Active Mode
(continued)
Adding 0.5 V for tolerance, the overhead needs to be
increased to (7.021 V + 0.5 V) = 7.521 V to allow for an
undistorted on-hook transmission of a 1 Vrms meter
pulse into 200
. This is done by applying voltage to
pin V
OH
.
V
OH
(V) = 6.0 V + 5 * V
OVH
(V)
7.521 V = 6 V + 5 * V
OVH
V
OVH
= 0.304
Thus, a nominal 0.304 V is applied to pin V
OVH
to
increase the overhead.
On-Hook Transmission Mode
If the magnitude of the primary battery is greater than a
nominal 51 V, the magnitude of the open loop tip to ring
open loop voltage is clamped between 41 V and 49 V.
If the magnitude of the primary battery is less than a
nominal 51 V, the overhead voltage will track the mag-
nitude of the battery voltage, i.e., the magnitude of the
open circuit tip to ring voltage will be 6 V to 8 V less
than battery. In the on-hook transmission mode, over-
head is unaffected by V
OVH
.
Again, the overhead is not symmetrical with respect to
tip and ring. With the magnitude of the primary battery
greater than a nominal 51 V, the tip to ground voltage is
clamped between 2.1 V and 2.6 V and the ring to
ground voltage is clamped between 44 V and 51 V. If
the magnitude of the primary battery is less than a
nominal 51 V, the tip to ground voltage is 2.1 V to 2.6 V
and the ring to battery voltage is typically 4 V.
Scan Mode
If the magnitude of the primary battery is greater than a
nominal 51 V, the magnitude of the open loop tip to ring
open loop voltage is clamped between 44 V and 51 V.
If the magnitude of the primary battery is less than a
nominal 51 V, the overhead voltage will track the mag-
nitude of the battery voltage, i.e., the magnitude of the
open circuit tip to ring voltage will be 4 V to 6 V less
than battery. In the scan mode, overhead is unaffected
by V
OVH
.
Again, the overhead is not symmetrical with respect to
tip and ring. With the magnitude of the primary battery
greater than a nominal 51 V, the tip to ground voltage is
clamped between 0.4 V and 0.6 V and the ring to
ground voltage is clamped between 44 V and 51 V. If
the magnitude of the primary battery is less than a
nominal 51 V, the tip to ground voltage is 0.4 V to 0.6 V
and the ring to battery voltage is typically 4 V.
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. In the
ring mode, overhead is unaffected by V
OVH
.
During the ring mode, to conserve power the receive
input at RCVN/RCVP is deactivated. During the ring
mode, to conserve power the ACC amplifier in the
transmit direction at VITR is deactivated. However the
AX amplifier at VTX is active during the ring mode, dif-
ferential 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 L9215 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 deter-
mine operating loop length.
Battery Reversal Rate
The rate of battery reverse is controlled or ramped by
capacitors FB1 and FB2. A chart showing FB1 and FB2
values versus typical ramp time is given below. Leave
FB1 and FB2 open if it is not desired to ramp the rate of
battery reversal.
Table 15. FB1 and FB2 Values vs. Typical Ramp
Time
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
BAT2
V
V
OH
–
I
LIMIT