IDT821621 Просмотр технического описания (PDF) - Integrated Device Technology
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IDT821621 Datasheet PDF : 21 Pages
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IDT821621
Ring Relay
KR
SLIC
RINGOUT
LONG HAUL SLIC
DC FEEDING
The IDT821621 provides constant-current feeding as shown in
Figure 4.
RB1
+
Ringing
Source
RB2
-
R2
R1
R3
R4
Tip Line
Ring Line
KR
RF
KR
RF
DA
CRT2
CRT1
DB
A(TIP)
B(RING)
Figure 2 Ring-trip Detection
RELAY DRIVERS CONTROL
The IDT821621 provides an on-chip ring relay driver (RINGOUT) to
control the external ring relay. This ring relay driver is active only in
Ringing state. It is an internal transistor with the emitter internally
connected to BGND and the collector as the driver output (see Figure 3).
During ringing, the ring relay driver is activated and the ringing source is
connected by an external ring relay to the Tip and Ring lines through
ring feed resistors.
The IDT821621 also provides three additional relay drivers
(RYOUT1, RYOUT2 and RYOUT3) on the chip. All of them are open-
collector drivers with emitters internally connected to BGND. They allow
for direct operation of external test relays. The digital pins D1 to D3 are
used to control the relay drivers RYOUT1, RYOUT2 and RYOUT3
respectively. Logic low on D1 to D3 activates their respective relay
drivers.
RINGOUT
RYOUT1
RYOUT2
RYOUT3
BGND
BGND
Figure 3 Relay Drivers Schematic
60
VAB
(volts)
Note 3
Note 2
Note 1
0
IL (mA)
30
Figure 4 DC Feeding Characteristics
Notes:
1.
VAB
=
ILRL′=
------------1----2---5---0--------------
RDC1 + RDC2
RL′,w
here
RL′
=
RL + 2RF
2.
VAB
=
0.857( VBAT
+
3.3
)
–
IL
-R----D----C----1----+------R----D----C----2-
300
3.
VAB
=
0.857( VBAT
+
1.2
)
–
IL
-R----D----C----1----+-----R-----D----C----2-
300
The feed current is programmable. Two resistors RDC1 and RDC2,
and a capacitor CDC form the network for programming the feed current.
See Figure 5.
a
RL
IL
b
A(TIP)
RSN
SLIC
B(RING) RDC
RDC1
RDC2
CDC
Feed current is programmed by RDC1 and RDC2.
Figure 5 DC Feed Programming Circuit
The feed current IFEED is calculated by the following equation:
IFEED
=
------------1----2---5---0--------------
RDC1 + RDC2
An external capacitor CCAS connected to the CAS pin is used to filter
noise that may originate from the battery source and prevent the output
amplifiers from saturating. The value of this anti-saturation capacitor is
Functional Description
8
October 8, 2003
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