Publication# 16854

Rev: D Amendment: /0

Issue Date: October 1999

Am79534/Am79535

Subscriber Line Interface Circuit

DISTINCTIVE CHARACTERISTICS

s Programmable constant-current 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

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

Two-Wire

Interface

HPA

HPB

DA

DB

BGND

VBAT

A(TIP)

B(RING)

Ground-Key

Detector

Signal Transmission

Power-Feed

Controller

Ring-Trip Detector

VCC

VEE

AGND

RINGOUT

C1

C2

E1

E0

DET

RSN

VTX

RD

RDC

Ring Relay Driver

Input Decoder

and Control

Off-Hook Detector

Test Relay Driver

TESTOUT

C3

C4

GKFIL

Switching Regulator

VREG

L

CHS

QBAT

CHCLK

Notes:

1. Am79534—E0 and E1 inputs; ring and test relay drivers sourced internally to BGND.

2. Am79535—E0 and E1 inputs; ring relay driver sourced internally to BGND; ground-key filter pin.

16854C-01