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Publication# 21776 Rev: B Amendment: /0
Issue Date: July 1998
PRELIMINARY
Am79R70
Ringing Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
a73 Ideal for ISDN-TA and set top applications
a73 On-chip ringing with on-chip ring-trip detector
a73 Low standby state power
a73 Battery operation:
—V
BAT1
: –40 V to –67 V
—V
BAT2
: –19 V to V
BAT1
a73 On-chip battery switching and feed selection
a73 On-hook transmission
a73 Polarity reversal option
a73 Programmable constant-current feed
a73 Programmable Open Circuit voltage
a73 Programmable loop-detect threshold
a73 Current gain = 1000
a73 Two-wire impedance set by single component
a73 Ground-key detector
a73 Tip Open state for ground-start lines
a73 Internal V
EE
regulator
(no external –5 V power supply required)
a73 Two on-chip relay drivers and snubber circuits
BLOCK DIAGRAM
E1
D2
D1
Two-Wire
Interface
HPA
HPB
Input Decoder
and Control
Relay
Driver
Ring-Trip
Detector
Power-Feed
Controller
RTRIP1
RTRIP2
BGNDVCC VNEG
RD
RDC
AGND/DGND
VBAT2
A(TIP)
B(RING)
RYOUT1
RDCR
C1
Switch
Driver
VBAT1
RSGL
Ground-Key
Detector
Off-Hook
Detector
Relay
Driver RYOUT2
C2
C3
RSGH
B2EN
RSN
VTX
Signal
Transmission
RINGIN
RYE
DET