8-23

Specifications HC-5504DLC

Functional Diagram

19

16

RC

Ring Command - A low active TTL - Compatible logic input. When enabled, the relay driver (RD)

output goes low on the next high level of the ring sync (RS) input, as long as the SLIC is not in the

power denial state (PD = 0) or the subscriber is not already off- hook (SHD = 0).

20

17

C2

Capacitor #2 - An external capacitor to be connected between this terminal and digital ground.

Prevents false ground key indications from occurring during ring trip detection. Typical value is

0.15

µF, 10V. This capacitor is not used if ground key function is not required and (Pin 17) may be left

open or connected to digital ground.

21

18

OUT

The analog output of the spare operational amplifier. The output voltage swing is typically

±5V.

23

19

-IN

The inverting analog input of the spare operational amplifier.

24

20

+IN

The non-inverting analog input of the spare operational amplifier.

25

21

RX

Receive Input, Four 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 300

Ω 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 near by power lines and other noise

sources. This capacitor is also required for the proper operation of ring trip detection. Typical value is

0.5

µF, 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) and receive input (RX) terminals.

28

24

TX

Transmit Output, Four 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.

1,8,15,22

NC

No Internal Connection.

wishes to run separate grounds off a line card, the AG must be applied first.

Pin Descriptions (Continued)

28 PIN

PLCC

24 PIN

DIP/SOIC

SYMBOL

DESCRIPTION

+

DIFF

AMP

+

OP

AMP

LOOP

MONITORING

RING

CONTROL

2 WIRE

LOOP

SECONDARY

PROTECTION

LINE

DRIVERS

TIP

RING

PD

POWER DENIAL

150

Ω

RING

150

Ω

RF

BG

150

Ω

TF

TIP

RD

RC

RS

RING SYNC

RING COMMAND

RING

TRIP

SHD

GKD

TX

TRANSMIT

OUTPUT

OUT

+IN

-IN

RX

RECEIVE

INPUT

SLIC MICROCIRCUIT

1/2 RING

RELAY

RING

VOLTAGE

RFS

1/2 RING

RELAY

150

Ω

SWITCH HOOK

DETECTION

GROUND KEY

DETECTION

-1

+1

BATTERY

FEED

LOOP

CURRENT

LIMITER