73K324L-28IHRF 查看數據表（PDF） - Teridian Semiconductor Corporation
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73K324L-28IHRF
Teridian Semiconductor Corporation
73K324L-28IHRF Datasheet PDF : 30 Pages
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73K324L
CCITT V.22bis,V.23,V.22,V.21, Bell 212A
Single-Chip Modem
DATA SHEET
APPLICATIONS INFORMATION (continued)
DIRECT ACCESS ARRANGEMENT (DAA)
The telephone line interfaces show two examples of
how the “hybrid” may be implemented. The split
supply design (Figure 1) is a typical two op-amp
hybrid. The receive op-amp serves two purposes. It
supplies gain to amplify the receive signal to the
proper level for the modem’s detectors and
demodulator, and it removes the transmitted signal
from the receive signal present at the transformer.
This is done by supplying a portion of the
transmitted signal to the non-inverting input of the
receive op-amp at the same amplitude as the signal
appearing at the transformer, making the transmit
signal Common mode.
The single-supply hybrid is more complex than the
dual-supply version described above, but its use
eliminates the need for a second power supply. This
circuit (Figure 2) uses a bridged drive to allow
undistorted signals to be sent with a single 5 volt
supply.
C1
390 pF
Because DTMF tones utilize a higher amplitude than
data, these signals will clip if a single-ended drive
approach is used. The bridged driver uses an extra
op-amp (U1A) to invert the signal coming from the
gain setting op-amp (U1B) before sending it to the
other leg of the transformer. Each op-amp then
supplies half the drive signal to the transformer. The
receive amplifier (U1C) picks off its signal at the
junction of the impedance matching resistor and the
transformer. Because the bottom leg of the
transformer is being driven in one direction by U1A
and the resistor is driven in the opposite direction at
the same time by U1B, the junction of the
transformer and resistor remains relatively constant
and the receive signal is unaffected.
DESIGN CONSIDERATIONS
TERIDIAN Semiconductor's 1-chip modem products
include all basic modem functions. This makes these
devices adaptable for use in a variety of
applications, and as easy to control as conventional
digital bus peripherals.
RXA
C3
0.1 µF
C6
0.1 µF
TXA
VOLTAGE
REFERENCE
R11*
R4
37.4K 1%
* U1C
8
-
9
C4
0.0047 µF
+ 10
R5 3.3K
5
+
6
-
+5V
4
7
11* U1B
R6
22.1K
R7
20K 1%
C5
750 pF
R9
20K 1%
R8
20K 1%
+5V
R10*
2 - * U1A 1
3
+
C7
0.1 µF
+
C8
10 µF
R1
20K 1%
R2
20K 1%
R3
475 1%
T1
MIDCOM
671-8005
C2
0.033 µF
Note: Op-amp U1
must be rated for
single 5V operation.
R10 & R11 values
depend on Op-amp
T
C10
+5V
0.47 µF
250V
R13
U2 22K
4N35
D2
3.3V
ZENERS
D3
D1
IN4004
R12
22K
VR1
MOV
V250L20
+5V
K1
D4
IN914
R
R14
10K
Q1
2N2222A
HOOK
RING
FIGURE 2: Single 5V Hybrid Version
Page: 25 of 30
© 2005, 2008 TERIDIAN Semiconductor Corporation
Rev 7.1
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