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Publication# 080135 Rev: E Amendment: /0
Issue Date: October 1999
Am79M574
Metering Subscriber Line Interface Circuit
DISTINCTIVE CHARACTERISTICS
Programmable constant-resistance feed
Programmable loop-detect threshold
Ground-key detect
Performs polarity reversal
Line-feed characteristics independent of
battery variations
Test relay driver optional
Supports 2.2 Vrms metering (12 and 16 kHz)
On-chip switching regulator for low-power
dissipation
Two-wire impedance set by single external
impedance
Tip Open state for ground-start lines
On-hook transmission
BLOCK DIAGRAM
VCC
Input Decoder
and Control
VREG
VBAT
16857C-001
C1
C2
C3
C4
E1
E0
Ring Relay Driver
RINGOUT
TESTOUT
Test Relay Driver
Off-Hook Detector
Signal Transmission
Ground-Key
Detector
Power-Feed
Controller
Ring-Trip Detector
Switching Regulator
Two-Wire
Interface
RSN
VTX
RD
RDC
A(TIP)
HPA
HPB
B(RING)
DA
DB
L
BGND
QBAT
DET
VEE
Notes:
1. Am79M574—E0 and E1 inputs; ring and test relay drivers sourced internally to BGND.
2. Current gain (K1) = 1000.
CHCLK
AGND
CHS
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