L
VBAT
Switching
Regulator
BGND
CHS CHCLK VEE AGND/DGNDQBAT VCC
RSN
VREG
Signal
Transmission
Off-Hook Detector
Power-Feed
Controller
Ring-Trip
Detector
RD
RDC
DA
DB
B(RING)
Am79M576A
Metering Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
a73 Programmable constant-resistance feed
a73 Programmable loop-detect threshold
a73 Ground-key detect
a73 Performs polarity reversal
a73 Ring relay driver
a73 Supports 2.2 Vrms metering (12 and 16 kHz)
a73 Line feed characteristics independent of battery
variations
a73 On-chip switching regulator for low-power
dissipation
a73 Two-wire impedance set by single external
impedance
a73 Tip Open state for ground-start lines
a73 On-hook transmission
BLOCK DIAGRAM
VTX
DET
Input Decoder
and Control
Ground-Key
Detector
Ring Relay
RINGOUT/DGND
Two-Wire
HPA
HPB
Interface
VCCRING
Driver
C1
C2
C3
E0
E1
A(TIP)
Publication# 18412 Rev: D Amendment: /0
Issue Date: October 1999