Publication# 18408 Rev: D Amendment: /0
Issue Date: October 1999
Am7945
Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
a73 Programmable constant-current feed
a73 Current gain = 200
a73 Programmable loop-detect threshold
a73 Low power Standby state
a73 Ground-key detector
a73 Tip Open state for ground-start lines
a73 –19 V to –56.5 V battery operation
a73 On-chip Thermal Management (TMG) feature
a73 Two-wire impedance set by single external
impedance
a73 On-hook transmission
a73 On-chip ring relay driver and relay snubber
circuit
a73 Ideal for low cost PABX and key telephone
systems
BLOCK DIAGRAM
VCC VEE AGND/DGND
RSN
VTX
RD
RDC
CAS
C1
C2
C3
E0
E1
DET
Two-Wire
Interface
HPA
HPB
DA
DB
BGND
VBAT
A(TIP)
B(RING)
TMG
Ground-Key
Detector
Signal
Transmission
Off-Hook
Detector
Power-Feed
Controller
Ring-Trip
Detector
RINGOUT
Ring Relay
Driver
Input Decoder
and Control