L8576B Dual Ringing SLIC
Data Sheet
May 2001
Pin Information
(continued)
Table 1. Pin Descriptions
(continued)
Pin,
Pin,
Circuit Circuit Symbol Type
a
b
40
39
6
7
RNGNG
NSTAT
I
u
O
u
Name/Function
Ringing Input.
Refer to Operating States section. A pull-up device is
included.
Loop Detector Output/Ring Trip Detector Output.
When low, this lead indi-
cates an off-hook condition. When in ringing mode, a low output on this lead
indicates a ring trip. A pull-up device is included.
Disconnect Input.
Refer to Operating States section. A pull-up device is
included.
Power Resistor.
Connect a resistor between this pin and V
BAT
. A 2.2 kΩ, 2 W
resistor should be used for a V
BAT
of –68.5 V. See the Applications section to
calculate resistor values for other V
BAT
potentials.
Protected Tip.
The input to the tip fault protection and output of tip current
drive amplifier. Connect this pin to the tip of the loop through a 30
Ω
overvolt-
age protection resistor.
Protected Ring.
The input to the ring fault protection and output of ring cur-
rent drive amplifier. Connect this pin to the ring of the loop through a 30
Ω
overvoltage protection resistor.
Transmit ac Output Voltage.
This output is a voltage that is directly propor-
tional to the differential tip/ring current.
Transmit Gain 2.
Transmit gain and current limiting for ringing is set by the
value of R
GX2
. R
GX2
is connected between TG2 and VITR.
Transmit Gain 1.
Transmit gain is set by the series resistor combination of
R
GX1
and R
GX2
from this lead to TG2.
Ring Trip Filter.
Connect this lead to RTTH via a resistor and to AGND with a
capacitor to filter the ring trip circuit to prevent spurious responses.
Ring Trip Threshold.
Connect this lead to DC
OUT
via a resistor to set the ring
trip threshold.
dc Voltage Out.
This output is a voltage that is directly proportional to the
absolute value of the differential tip/ring current.
Current-Limit Program Input.
A resistor to DC
OUT
sets the dc current limit of
the circuit.
Receive Signal Input (+).
This high-impedance input controls the ac differen-
tial voltage on tip/ring.
Receive Signal Input (–).
This high-impedance input controls the ac differen-
tial voltage on tip/ring.
Analog Signal Ground.
Analog 5 V Power Supply.
Ringing Slope Resistor.
Connect this lead to AGND with a resistor to set the
slope of the ringing waveform. Note that this pin is shared with both sections.
38
37
8
9
NDISC
RPWR
I
u
—
36
10
PT
I/O
35
11
PR
I/O
34
33
32
31
30
29
28
27
26
25
24
23
12
13
14
15
16
17
18
19
20
21
22
23
VITR
TG2
TG1
RTFLT
RTTH
DC
OUT
I
PROG
RCVP
RCVN
AGND
V
CC
RRNG
O
—
—
—
—
O
I
I
I
—
—
—
* On the printed-wiring board (PWB), make the leads to BGND and V
BAT
as wide as possible for thermal and electrical reasons. Also, maxi-
mize the amount of PWB copper on all leads connected to this device for the lowest operating temperature.
Note: I
u
and O
u
indicate a pull-up device is included on this lead.
6
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
