L9215A/G
Short-Loop Sine Wave Ringing SLIC
Data Sheet
September 2001
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.
Applications (continued)
Overhead Voltage (continued)
Active Mode (continued)
Loop Range
Adding 0.5 V for tolerance, the overhead needs to be
increased to (8.121 V + 0.5 V) = 8.621 V to allow for an
undistorted on-hook transmission of a 1 Vrms meter
pulse into 200 Ω. This is done by applying voltage to
pin VOH.
The dc loop range is calculated using:
VBAT2 – VOH
-------------------------------------
RL =
– 2RP – RDC
ILIMIT
VOH (V) = 6.0 V + 5 * VOVH (V)
8.621 V = 6 V + 5 * VOVH
VOVH = 0.5242 V
VBAT2 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
determine operating loop length.
Thus, a nominal 0.5242 V is applied to pin VOVH to
increase the overhead.
Scan Mode
If the magnitude of the primary battery is greater than
51 V, the magnitude of the open loop tip-to-ring open
loop voltage is clamped typically 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
magnitude 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 VOVH.
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 20. FB1 and FB2 Values vs. Typical Ramp
Time
On-Hook Transmission Mode
CFB1 and CFB2
Transition Time
If the magnitude of the primary battery is greater than
51 V, the magnitude of the open loop tip-to-ring open
loop voltage is clamped typically 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
magnitude 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 scan mode, overhead is unaffected
by VOVH.
0.01 µF
0.1 µF
0.22 µF
0.47 µF
1.0 µF
1.22 µF
1.3 µF
1.4 µF
1.6 µF
20 ms
220 ms
440 ms
900 ms
1.8 s
2.25 s
2.5 s
2.7 s
3.2 s
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 VBAT1 voltage is 3 V. In the
ring mode, overhead is unaffected by VOVH.
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
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