HC-5502B_03 Datasheet, PDF (6/11 Pages) Intersil Corporation – EIA/ITU PABX SLIC with 30mA Loop Feed

HC-5502B
Pin Descriptions (Continued)
28 PIN PLCC 24 PIN DIP SYMBOL
DESCRIPTION
25
21
RX
Receive Input, 4-Wire Side - 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 amplifiers, which in turn drive tip and ring through 300Ω of feed resistance on each
side of the line.
26
22
C₄
Capacitor #4 - An external capacitor to be connected between this terminal and analog ground. This
capacitor prevents false ground key indication and false ring trip detection from occurring when
longitudinal currents are induced onto the subscriber loop from nearby power lines and other noise
sources. This capacitor is also required for the proper operation of ring trip detection. Typical value
is 0.5µF to 1.0µF, 20V. This capacitor should be nonpolarized.
27
23
AG
Analog Ground - To be connected to zero potential and serves as a reference for the transmit output
(Note 5) (TX) and receive input (RX) terminals.
28
24
TX
Transmit Output, 4-Wire Side - A low impedance analog output which represents the differential
voltage across Tip and Ring. Transhybrid balancing must be performed (using the SLIC
microcircuit’s spare op amp) beyond this output to completely implement two to four wire conversion.
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.
1, 8, 5, 22
NC
No internal connection.
NOTE:
5. All grounds (AG, BG, and DG) must be applied before V_B+ or V_B-. 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.
Functional Diagram
RING
RS
VOLTAGE ^{RING SYNC}
RC
RING COMMAND
RD
TIP
RING
RELAY
TIP
150Ω
150Ω
2 WIRE
LOOP
V_B-
RING
SECONDARY
PROTECTION
TF
V_B-
BG
RF
150Ω
RING
150Ω
PD
POWER DENIAL
RING
CONTROL
RING
TRIP
LOOP
MONITORING
DIFF
AMP
-
+
SHD SWITCH HOOK
DETECTION
GKD _{GROUND KEY}
DETECTION
TX _TRANSMIT
OUTPUT
BATTERY
FEED
+1
LOOP
CURRENT
LIMITER
LINE
DRIVERS
-1
+
-
OP
AMP
SLIC MICROCIRCUIT
OUT
+IN
-IN
RX RECEIVE
INPUT
6