IDT821621J IDT, Integrated Device Technology Inc, IDT821621J Datasheet - Page 9

• Manufacturer Part Number: IDT821621J
• Manufacturer: IDT, Integrated Device Technology Inc

Specifications of IDT821621J

• Number Of Channels: 1
• On-hook Transmission: Yes
• Polarity Reversal: No
• On-chip Ring Relay Driver: Yes
• Operating Supply Voltage (typ): 3.3/5V
• Operating Temp Range: -40C to 85C
• Package Type: PLCC
• Operating Temperature Classification: Industrial
• Pin Count: 32
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Not Compliant

Table 2 — SLIC Operating States
FUNCTIONAL DESCRIPTION
functions. It provides many user programmable features including 2-wire
impedance matching, loop-detect threshold and ring-trip threshold
setting, constant current feeding, 4-wire to 2-wire gain setting, etc. The
following sections describe these functions in detail.
SLIC STATES CONTROL
Standby state. A combination of the control pins C2 and C1 select one of
the possible four operating states. See
IDT821621 provides an off-hook detector and a ring-trip detector on chip
to support the necessary signaling functions. The selection of the
detectors is based on the SLIC operating state. The output of the
detectors is reported through the DET pin. Once a hook switch event or
ring-trip event occurs, the DET pin goes low.
outputs are in high impedance condition. In this state, the off-hook
detector is inoperative and the power dissipation reduces to the lowest.
The Disconnect state is useful for out-of-service lines.
activated and the TIP and RING outputs are in high impedance
condition. The ringing source is connected by an external ring relay to
the line. In Ringing state, the status of the ring-trip detector is reported
by the DET pin.
convention applies. All signal transmission and loop supervision
functions are active. The status of the off-hook detector is gated to the
DET pin.
resulting in low power dissipation. The off-hook detection function
operates normally, but signal transmission is not enabled. This state
allows for monitoring off-hook transitions while maintaining lowest
possible power consumption.
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IDT821621
Functional Description
State
The IDT821621 implements the basic telephone line interface
The IDT821621 can be operated in Disconnect, Ringing, Active or
When the SLIC is in Disconnect state, both the TIP and RING
When the SLIC is in Ringing state, the ring relay driver (RINGOUT) is
In Active state, the SLIC is fully functional. The standard battery
In Standby state, most of the internal circuitry is powered down,
Disconnect
Ringing
Active
Standby
0
1
2
3
C2
0
0
1
1
Control Pins
C1
0
1
0
1
Two-Wire Status
Disconnect
Standby
Ringing
Active
Table 2
Off-hook Detector
Off-hook Detector
Ring-trip Detector
Ring-trip Detector
for details. The
DET Output
7
OFF-HOOK DETECTOR
Active or Standby state. The output of the DET pin goes low when an
off-hook event is detected.
which is connected between the RD and AGND pins. See
details.
following equations:
determines the on-hook to off-hook time constant. The value of C
typical on-hook to off-hook time constant of 0.5 ms is calculated by:
RING-TRIP DETECTOR
Ringing state, the on-chip ring relay driver (RINGOUT) is activated and
the ringing source is connected by the ring relay to the Tip and Ring
lines through the resistors R
DET pin. When the loop goes off-hook, the bridging resistors R
R
DB to go positive with respect to DA and the DET pin goes low.
hook, the bridging resistors should be chosen as that:
event occurs, otherwise, the loop is in on-hook state.
3
B(RING)
The off-hook detector monitors the hook switch of the loop during
The loop-detect threshold is programmed by an external resistor R
The loop current threshold I
The R-C network, formed by the capacitor C
Figure 2
The ring-trip detector monitors the loop status and reports it via the
and R
If R
Where: R
If the line resistance is less than R
A(TIP)
LMAX
C
R
----------
R
I
D
B1
ON
4
3
, and the filter capacitors C
=
=
shows a general ringing circuit for the IDT821621. During
FEED
is the maximum line resistance to be detected as an off-
=
Two-wire
Interface
0.5ms
---------------- -
Figure 1 Loop-Detect Threshold Setting
R
----------
R
510
--------- -
R
R
B2
SLIC
D
4
D
= R
=
1
(
------------------------------------------------- -
R
+ R
LMAX
Off-hook
Detector
2
R
1
LMAX
and R
+
R
Interface
FEED
ON
Digital
2
.
RT1
and I
)
LMAX
I
and C
OFF
OFF
, it means that an off-hook
=
RT2
C1
C2
DET
AGND
RD
are calculated by the
415
--------- -
R
LONG HAUL SLIC
D
D
cause the voltage on
and the resistor R
October 8, 2003
R
D
Figure 1
B1
C
D
D
, R
for a
B2
for
D,
D,
,