HC-5504B Datasheet, PDF (6/9 Pages) Intersil Corporation – EIA/ITU PABX SLIC with 40mA Loop Feed

HC-5504B
Pin Descriptions (Continued)
28 PIN
PLCC
24 PIN
DIP/SOIC SYMBOL
DESCRIPTION
24
20
+IN The non-inverting analog input of the spare operational amplifier.
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
terminals, 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 ca-
pacitor prevents false ground key indication and false ring trip detection from occurring when longitudinal
currents are induced onto the subscriber loop from near by power lines and other noise sources. This ca-
pacitor 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 (TX)
(Note 5) 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 cou-
pling to the next stage is essential.
1, 8, 15, 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
RS
RING SYNC
RC
RING COMMAND
RD
TIP
1/2 RING
TIP
RELAY _150Ω
150Ω
2 WIRE
TF
LOOP
V_B-
SECONDARY
PROTECTION
BG
V_B-
RF
1/2 RING
RELAY
RFS
150Ω
RING
RING
VOLTAGE
V_B-
150Ω
RING
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
SLIC MICROCIRCUIT
+
-
OP
AMP
OUT
+IN
-IN
RX _RECEIVE
INPUT
56