BGNDVCC VNEG AGND/DGND
Switch
Driver
VBAT1
B2EN
E1 Two-Wire
Interface
HPA
HPB
Input Decoder
and Control
Ring-Trip
Detector
Power-Feed
Controller
RD
RDC
VBAT2
B(RING)
RDCR
C1
RSGL
Ground-Key
Detector
Off-Hook
Detector
C2
C3
RSGH
RSN
VTX
Signal
Transmission
RINGIN
DET
Am79R79
Ringing Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
a73 Ideal for short-loop applications
a73 Ideal for ISDN terminal adaptor and fixed radio
access applications
a73 On-chip ringing with on-chip ring-trip detector
a73 Low standby state power
a73 Battery operation:
—V
BAT1
: –40.5 V to –75 V
—V
BAT2
: –19 V to V
BAT1
a73 On-chip battery switching and feed selection
a73 On-hook transmission
a73 Two-wire impedance set by single external
impedance
a73 Programmable constant-current feed
a73 Programmable Open Circuit voltage
a73 Programmable loop-detect threshold
a73 Current gain = 1000
a73 Ground-key detector
a73 Tip Open state for ground-start lines
a73 Polarity reversal option available
a73 Internal V
EE
regulator (no external –5 V power
supply required)
a73 Two on-chip relay drivers and snubber circuits
(32 PLCC)
BLOCK DIAGRAM
D2
D1
Relay
Driver
RTRIP1
RTRIP2
A(TIP)
RYOUT1
Relay
Driver RYOUT2
RYE
Publication# 19752 Rev: G Amendment: /0
Issue Date: October 1999