STLC3080 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STLC3080' PDF : 23 Pages View PDF
Figure D2. relation between Icrt and Iline.
ICRT
+30uA
STLC3080
ILINEth=IthRS1/RR
ILINEth=7.5mA(typ)
ILINE
(if RR=600Ω and RS1=RS2=600KΩ)
-30uA
RS1 must be connected to the positive RR; RR
should be connected directly to the ringing gener-
ator as it is in the figure. The ratio between RS1
and RR must be chosen considering that there is
an offset current in the input stage equal to
7.5µA. This offset has been introduced to take in
account the leackage current of the line.
In fig.D2 is shown the relation between the CRT
charging current ICRT and the line current ILINE. In
the range -30µA<ICRT<+30µA ICRT is propor-
tional to ILINE while it remains limited to ±30µA
for higher value of ILINE. Consequently, in case of
short loops, the ring-trip detection time is inde-
pendent on the loop resistance, as the CRT
charging is performed at a fixed current. In case
of long loops the detection time will increase as
the ICRT decreases proportionally to the loop re-
sistance.
Figure D3. Ring Trip detection signals.
Vring=60Vrms @ f=25Hz VB=-48Volt
DET
RING
wire
CRT
OFF_HOOK RING-TRIP DETECTION
21/23
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