Data Sheet
May 2001
L8576B Dual Ringing SLIC
Pin Information (continued)
Table 1. Pin Descriptions (continued)
Pin,
Pin,
Circuit Circuit Symbol Type
Name/Function
a
b
40
6
RNGNG
NSTAT
Iu
Ringing Input. Refer to Operating States section. A pull-up device is
included.
39
7
Ou 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.
38
37
8
9
NDISC
RPWR
Iu
Disconnect Input. Refer to Operating States section. A pull-up device is
included.
—
Power Resistor. Connect a resistor between this pin and VBAT. A 2.2 kΩ, 2 W
resistor should be used for a VBAT of –68.5 V. See the Applications section to
calculate resistor values for other VBAT potentials.
36
35
10
11
PT
I/O 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.
PR
I/O 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.
34
33
32
31
30
29
28
27
26
12
13
14
15
16
17
18
19
20
VITR
TG2
O
—
—
—
—
O
I
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 RGX2. RGX2 is connected between TG2 and VITR.
TG1
Transmit Gain 1. Transmit gain is set by the series resistor combination of
RGX1 and RGX2 from this lead to TG2.
RTFLT
RTTH
DCOUT
IPROG
RCVP
RCVN
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 DCOUT 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 DCOUT sets the dc current limit of
the circuit.
I
Receive Signal Input (+). This high-impedance input controls the ac differen-
tial voltage on tip/ring.
I
Receive Signal Input (–). This high-impedance input controls the ac differen-
tial voltage on tip/ring.
25
24
23
21
22
23
AGND
VCC
—
—
—
Analog Signal Ground.
Analog 5 V Power Supply.
RRNG
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.
* On the printed-wiring board (PWB), make the leads to BGND and VBAT 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.
u
u
Note: I and O indicate a pull-up device is included on this lead.
6
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
