53
Pin Descriptions
22 PIN
PDIP
24 PIN
SOIC
SYMBOL
DESCRIPTION
1
1
TIP
An analog input connected to the TIP (more positive) side of the subscriber loop through a 150
feed resistor.
Functions with the Ring terminal to receive voice signals from the telephone and for loop
monitoring purposes.
2
2
RING
An analog input connected to the RING (more negative) side of the subscriber loop through a 150
feed re-
sistor. Functions with the Tip terminal to receive voice signals from the telephone and for loop monitoring
purposes.
3
3
V
CC
Positive Voltage Source - Most positive supply. V
CC
is typically 5V.
4
N/C
No Connect. For proper operation this pin should be left floating.
4
5
C
1
Capacitor - An external capacitor to be connected between this terminal and analog ground. Required for
proper operation of the voice band hybrid. Typical value is 0.3
μ
F, 30V.
5
6
DGND
Digital Ground - To be connected to zero potential and serves as a reference for all digital inputs and outputs
on the SLIC microcircuit.
6
7
RS
This pin should be tied to 5V.
7
8
N/C
No Connect. For proper operation this pin should be left floating.
8
9
TF
Tip Feed - A low impedance analog output connected to the TIP terminal through a 150
feed resistor. Pro-
vides voice signals to the telephone set and sink longitudinal current.
9
10
RF
Ring Feed - A low impedance analog output connected to the RING terminal through a 150
feed resistor.
Functions with the TF terminal to provide loop current, feed voice signals to the telephone set, and sink lon-
gitudinal current.
10
11
V
BAT
Negative Voltage Source - Most negative supply. V
BAT
has an operational range of -24V to -58V.
Frequently referred to as “battery”.
11
12
BGND
Battery Ground - To be connected to zero potential. All loop current and some quiescent current flows into
this ground terminal.
12
13
SHD
Switch Hook Detection - A low active LS TTL - compatible logic output. This output is enabled for loop cur-
rents exceeding 10mA and disabled for loop currents less than 5mA.
13
14
N/C
No Connect. For proper operation this pin should be left floating.
15
N/C
No Connect. For proper operation this pin should be left floating.
14
16
N/C
No Connect. For proper operation this pin should be left floating.
15
17
N/C
No Connect. For proper operation this pin should be left floating.
16
18
T1
Used during production testing. For proper operation this pin should be connected to pin T2.
17
19
T2
Used during production testing. For proper operation this pin should be connected to pin T1.
18
20
T3
Used during production testing. For proper operation this pin should be connected to Analog Ground pin
AGND.
19
21
RX
Receive Input - A high impedance analog input which is internally biased. Capacitive coupling to this input is
required. AC signals appearing at this input differentially drive the Tip feed and Ring feed terminals, which in
turn drive tip and ring through 300
of feed resistance on each side of the line.
20
22
N/C
No Connect. For proper operation this pin should be left floating.
21
23
AGND
Analog Ground - To be connected to zero potential and serves as a reference for the transmit output (TX)
and receive input (RX) terminals.
22
24
TX
Transmit Output - A low impedance analog output which represents the differential voltage across Tip and
Ring. This output is unbalanced and referenced to analog ground. Since the DC level of this output varies
with loop current, capacitive coupling to the next stage is essential.
NOTE: All grounds (AGND, BGND, and DGND) must be applied before V
CC
or V
BAT
. Failure to do so may result in premature failure of the part. If
a user wishes to run separate grounds off a line card, the AG must be applied first.
HC5503T