4-30

-

16

-

C4

Activates Test Relay TRLY1.

15

17

16

C3

TTL Compatible Logic Input. The logic states of C1, C2 and C3 determine the operating states of the

SLIC. Reference Table 1 for details.

16

18

17

C2

TTL Compatible Logic Input. The logic states of C1, C2 and C3 determine the operating states of the

SLIC. Reference Table 1 for details.

17

19

18

C1

TTL Compatible Logic Input. The logic states of C1, C2 and C3 determine the operating states of the

SLIC. Reference Table 1 for details.

18

20

19

SHD

Switch Hook Detect - Active during off hook, ground key and loopback. Reference Table 1 for details.

19

21

15

GKD_LVM

Ground Key Detector and Line Voltage Measurement - Reference Table 1 for details.

20

22

20

5V Supply.

21

23

21

RD

Loop Current Threshold Programming Pin - A resistor between this pin and ground will determine the

trigger level for the loop current detect circuit. See Equation 7.

22

24

22

ROH

Off Hook Overload Setting Resistor - Used to set combined overhead for voice and pulse metering

signals. See Equation 10.

23

25

23

ILIM

Current Limit Programming Pin - A resistor between this pin and ground will determine the constant

current limit of the feed curve. See Equation 11.

24

26

24

RSYNC_REV

Ring Synchronization Input and Reversal Time Setting. A resistor between this pin and GND

determines the polarity reversal time. Synchronization of the closing of the relay at zero voltage is

achieved via a ring sync pulse (5V to 0V) synchronized to the ring signal zero voltage crossing

(Reference Figure 18).

25

27

28

AGND

Analog ground

26

28

25

VRX

Receive Input - Ground referenced 4-wire side.

27

29

26

SPM

Pulse Metering Signal Input. If pulse metering is not used, then this pin should be grounded as close

to the device pin as possible.

28

30

27

VTX

Transmit Output - Ground referenced 4-wire side.

-

31

-

TRLY2

Test Relay Driver 2.

-

32

-

TRLY1

Test Relay Driver 1.

28

PIN

PLCC

32

PIN

PLCC

28

PIN

SOIC

SYMBOL

DESCRIPTION

HC55120, HC55121, HC55130, HC55131, HC55140, HC55141, HC55142, HC55143, HC55150, HC55151