that1250 THAT Corporation, that1250 Datasheet - Page 5

• Manufacturer Part Number: that1250
• Description: Low Cost, Balanced Line Receiver Ics
• Manufacturer: THAT Corporation

THAT 1250 Series
Low-cost Balanced Line Receiver ICs
superposition of both differential and common-
mode limitations.
Output Considerations
supplying 25 mA into a short circuit. While they will
survive a short, power dissipation will rise dramati-
cally if the output is shorted. Junction temperature
must be kept under 125 ºC to maintain the devices’
specifications.
load capacitance.
Power Supply Considerations
tive to the power supply, but they do contain wide
bandwidth opamps. Accordingly, small local bypass
In+
In-
The 1250-series devices are typically capable of
These devices are stable with up to 300 pF of
The 1250-series parts are not particularly sensi-
Figure 3. Representative input protection circuit
47p
C3
In+
Figure 4. RFI and supply bypassing
V
EE
470p
C4
470p
C5
V
CC
R
3
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
100n
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
2
3
C2
100n
C1
In-
In+
V
V
V
R
CC
CC
V
EE
+
-
7
4
EE
4
Sens
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1
5
Out
EE
THAT1256/1253/1250
V
U1
CC
6
Copyright © 2008, THAT Corporation
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Out
Page 5 of 8
capacitors should be located within a few inches of
the supply pins on these parts, as shown in Figure 4.
Selecting a Gain Variation
structures to suit different applications. The 1256 is
customarily configured for -6 dB gain, but by revers-
ing the resistor connections, can also be configured
for +6 dB. The 1253 is most often configured for -3
dB gain, but can also be configured for +3 dB. The
choice of input gain is determined by the input
voltage range to be accommodated, and the power
supply voltages used within the circuit.
ratio, the input stage should be selected and config-
ured for the highest possible gain that will ensure
that maximum-level input signals will not clip the
input stage or succeeding stages. For example, with
±18 V supply rails, the 1250-series parts have a
maximum output signal swing of +23 dBu. In order
to
maximum gain for the stage is -1 dB. With ±15 V
supply rails, the maximum output signal swing is
~+21.1 dBu; here, -3 dB is the maximum gain. In
each case, a 1253 configured for -3 dB gain is the
ideal choice.
provide enough headroom at its output to support a
+24 dBu input signal. The 1256 (configured for -6
dB gain) will increase noise, thus reducing dynamic
range, by attenuating the input signal more than
necessary to support a +24 dBu input.
THAT recommends the -3 dB input configuration
possible only with the 1253 in order to preserve
dynamic range within a reasonable range of power
supply voltages and external headroom limits.
accommodate +24
The three different parts offer different gain
To minimize noise and maximize signal-to-noise
In fact, for most professional audio applications,
+In
-In
2
3
In+
In-
Figure 5. Zero dB line receiver
The 1250 (0dB gain only) will not
9k
9k
4
7
V
V
CC
EE
dBu
Document 600068 Rev 02
U1
THAT1250
9k
9k
Sense
input signals,
Vout
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1
Output
the