L9214A/G
Low-Cost Ringing SLIC
Preliminary Data Sheet
October 2001
The point of change over between VBAT2 and VBAT1
occurs at:
Applications (continued)
Overhead Voltage (continued)
Ring Mode
|VBAT2| – (0.9 + 2.5) V > [(2RP + RDC + RL) * ILOOP] V
VBAT2 is typically applied under off-hook conditions for
power conservation and SLIC thermal considerations.
The L9214 is intended for short- and medium-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. Where
VBAT2 is insufficient to support the loop length, the
power will be taken from VBAT1.
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.
The AX amplifier at VTX is active during the ring mode,
differential ring current may be sensed at VTX during
the ring mode.
Battery Reversal Rate
Loop Range
The rate of battery reverse is controlled or ramped by
capacitors FB1 and FB2. A chart showing FB1/FB2 val-
ues versus typical ramp time is given below. Leave
FB1 and FB2 open if it is not desired to ramp the rate of
battery reversal.
The dc loop range for medium-loop applications is cal-
culated using:
( VBAT1 – VOHH)
----------------------------------------------
ILOOP
RL =
– 2RP – Rdc
The dc loop range for short-loop applications is calcu-
lated using:
Table 19. FB1/FB2 Values vs. Typical Ramp Time at
VBAT1 = –65 V
( VBAT2 – VOHL)
----------------------------------------------
ILOOP
RL =
– 2RP – Rdc
Transition Time Transition Time
Fast, B3 = 0
CFB1/CFB2
Slow, B3 = 1
20 ms
220 ms
440 ms
900 ms
1.8 s
where:
VOHH = 19.5 (2.5 V + 17 V) and
VOHL = 3.4 V (2.5 V + 0.9 V)
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
7 ms
75 ms
145 ms
300 ms
600 ms
750 ms
830 ms
900 ms
1070 ms
and where:
RL = loop resistance, not including protection resistors.
RP = protection resistor value.
Rdc = SLIC internal dc feed resistance.
|VBAT1| and |VBAT2| = battery voltage magnitude.
ILOOP = loop current.
2.25 s
2.5 s
2.7 s
3.2 s
VOHH = overhead voltage when power is drawn from
VBAT1.
VOHL = overhead voltage when power is drawn from
VBAT2.
26
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
