THAT1246 ETC, THAT1246 Datasheet - Page 5

• Manufacturer Part Number: THAT1246
• Description: (THAT1240 / THAT1243 / THAT1246) Balanced Line Receiver ICs
• Manufacturer: ETC

Rev. 04/29/02
Preliminary Information
can be simplified to
Since R3=R4 in the THAT 1240, this equation
a
The output voltage would then be
Vout
Since R2=R1, combining equations results in
Vout
In Lo
In Hi
=
(
In
=
=
2
3
+ +
(
a
)
2
In
In-
In+
´ +
R
+ +
(
ef
Sense
1
)
Ref
-3dB
R
R
R
1
5
1
ef
2
+24 dBu In
Vout
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
)
In Lo
In Hi
U1
1243
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
6
22u
C2
Control Voltage
3
2
Figure 7. Automated gain control of a balanced signal
Figure 6. Circuit for audio ADCs with balanced inputs
In-
In+
20k0
Sense
R2
1
Ref
5
1
Vout
U3
2180B
THAT
1246
U2
EC+
IN
EC-
3
2
SYM
GND
2
3
6
4
6
In-
In+
-3dB
VCC
VEE
V+
V-
Sense
OUT
Ref
5
1
7
5k1
R4
5
8
Vout
THAT
1246
U1
1
U3A
4570
2
3
+24 dBu
6
typical audio ADC with balanced inputs. This circuit
accepts
THAT 1246s, the signal level between their respective
outputs is +24 dBu. An attenuator network brings
the signal down another 24 dB while attenuating the
noise of the line receivers as well.
and since there are two of them, the total noise level
going into the resistive pad will be -106 dBu. The
pad reduces the noise level to -130 dBu at the input
to the ADC. The noise density resulting from the line
receivers will therefore be
14k0
3
2
22p
C3
R3
U4A
4570
Figure 6 shows a convenient method of driving a
The output noise of a THAT 1246 is -109 dBu,
2k10
2k10
R19
1/2 Vref of ADC
R8
1
+24
C4
6n8
dBu
R9
249R
4
3
Gnd
In
VCC
VEE
Vee
Vcc
in,
AIN+ to ADC
AIN- to ADC
Zero dBu Out
6
5
Cap2
Cap1
+6dB
2
and
7
Out+
Out-
U2
THAT1430
100n
C1
8
using
1
1M0
a
R1
Out Lo
Out Hi
pair
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