IDT821621J IDT, Integrated Device Technology Inc, IDT821621J Datasheet - Page 11

• 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

calculated by the equation below:
IMPEDANCE MATCHING
of an external impedance (R
pins (see
R
between the RSN and VTX pins must be taken into account.
RECEIVE GAIN SETTING
calculated by the following equation:
VRX and RSN; R
11
IDT821621
T,
Functional Description
for details.
Where, f
The two-wire AC input impedance R
Where, R
The 4-wire to 2-wire gain (G
Where, R
the internal current amplifier pole and any external stray capacitance
G
R
C
T
42L
CAS
Figure
=
C
F
=
L
250 R
=
is the desired filter cut-off frequency.
is the value of the fuse resistor. Note that when computing
is the terminating impedance; R
---------- -
R
R
----------------------------
1.7 10
13). R
(
RX
L
T
2WIN
is defined above; R
•
•
------------------------------------------------------- -
R
1
T
T
5
–
is calculated by the following equation:
+
πf
2R
250 R
C
500R
F
T
(
)
) connected between the RSN and VTX
42L
L
T
+
) is defined as the receive gain. It is
2R
F
F
)
2WIN
is the fuse resistor. See
is programmed by means
RX
is connected between
Figure
9
THERMAL MANAGEMENT
the thermal energy from the SLIC to an external resistor R
connected between the TMG and VBAT pins as shown in
This resistor shares some of the loop current and limits the on-chip
power dissipation in Active state.
condition: with the programmed loop current being fed into a short circuit
loop from the nominal battery, all of the loop current is supplied by R
So, R
The IDT821621 uses a power management technique of offloading
The selection of R
The power dissipated in the resistor R
The power dissipated in the SLIC during Active state is:
TMG
P
P
R
RTMG
SLIC
TMG
can be calculated by the equation below:
≥
=
=


-------------------------- - 70Ω
V
V
(
----------------------------------------------------------- - R
BAT
BAT
I
V
LOOP
BAT
(
–
•
R
TMG
8V
I
TMG
–
L
8V
–
–
P
normally needs to satisfy the following
+
RTMG
–
70Ω
(
I
L


•
)
–
2
R
R
L
L
)
( )
)
TMG
I
2
L
•
2
during Active state is:
+
TMG
0.12W
LONG HAUL SLIC
October 8, 2003
TMG.
Figure
R
TMG
TMG.
13.
is