Publication# 16855

Rev: E Amendment: /0

Issue Date: October 1999

Am79574

Subscriber Line Interface Circuit

DISTINCTIVE CHARACTERISTICS

s Programmable constant resistance feed

s Line-feed characteristics independent of

battery variations

s Programmable loop-detect threshold

s On-chip switching regulator for low-power

dissipation

s Pin for external ground-key noise filter

capacitor available

s Ground-key detect option available

s Two-wire impedance set by single external

impedance

s Polarity reversal feature

s Tip Open state for ground-start lines

s Test relay driver optional

s On-hook transmission

BLOCK DIAGRAM

VTX

RD

RDC

C1

C2

C3

C4

E1

E0

Input Decoder

and Control

Two-Wire

Interface

Switching

Regulator

Test Relay Driver

Ring Relay Driver

RINGOUT

TESTOUT

GKFIL

A(TIP)

HPA

HPB

DA

DB

L

BGND

CHS

CHCLK

AGND

16855C-001

Signal

Transmission

Power-Feed

Controller

Off-Hook

Detector

Ground-Key

Detector

Ring-Trip Detector

DET

Notes:

1. Am79574—E0 and E1 inputs; ring and test relay drivers sourced internally to BGND.

RSN

B(RING)

VREG

VBAT

QBAT

VCC

VEE