Lucent Technologies Inc.

5

Data Sheet

March 1997

L7554 Low-Power SLIC

Table 1. Pin Descriptions (continued)

Pin

Symbol Type

Description

20

VITR

O

Transmit ac Output Voltage. This output is a voltage that is directly proportional to the

differential ac Tip/Ring current.

21

I

Common-Mode Current Sense. To program ring ground sense threshold, connect a

be left unconnected.

22

O

Ring Ground Detect. When high, this open-collector output indicates the presence of a

ring ground. To use, connect a 100 k

23

B0

I

State Control Input. B0, B1, and B2 determine the state of the SLIC. See Table 2.

24

AGND

—

Analog Signal Ground.

25

AGND

—

Analog Signal Ground.

26

DCR

I

dc Resistance for Low Loop Currents. Leave open for dc feed resistance of 118

Ω, or

short to DCOUT for 618

Ω. Intermediate values can be set by a simple resistor divider

from DCOUT to ground with the tap at DCR.

27

BGND

—

Battery Ground. Ground return for the battery supply.

29

VTX

O

This output is a voltage that is directly proportional to the differential Tip/Ring current.

30

PT

I/O

Protected Tip. The output of the tip driver amplifier and input to loop sensing. Connect to

loop through overvoltage protection.

31

RTSN

I

Ring Trip Sense Negative. Connect this pin to the ringing generator signal through a

high-value resistor.

32

RTSP

I

Ring Trip Sense Positive. Connect this pin to the ring relay and the ringer series resistor

through a high-value resistor.

33

NRDET

O

Ring Trip Detector Output. When low, this logic output indicates that ringing is tripped.

34

NLC

O

Loop Detector Output. When low, this logic output indicates an off-hook condition.

35

B2

I

State Control Input. B0, B1, and B2 determine the state of the SLIC. See Table 2.

36

B1

I/O

State Control Input. B0, B1, and B2 determine the state of the SLIC. See Table 2.

37

XMT

O

Transmit ac Output Voltage. The output of the uncommitted operational amplifier.

38

SN

I

Summing Node. The inverting input of the uncommitted operational amplifier. A resistor

or network to XMT sets the gain.

39

FB1

I

Forward Battery Slowdown. A 0.1

µF capacitor from FB1 to AGND and from FB2 to

AGND will ramp the polarity reversal transition for added flexibility in applications requiring

quiet polarity reversal. If not needed, the pin can be left open.

40

FB2

I

Forward Battery Slowdown. A 0.1

µF capacitor from FB2 to AGND and from FB1 to

AGND will ramp the polarity reversal transition for added flexibility in applications requiring

quiet polarity reversal. If not needed, the pin can be left open.