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T H AT Corporation
FEATURES
* * * * * High CMRR: typically 90dB at 60Hz Wide bandwidth and high slew rate Low distortion and low noise Available in 0 dB, -3 dB, and -6 dB versions Pin compatible with SSM2143 and INA137 * * * * *
Balanced Line Receiver ICs THAT 1240, 1243, 1246 APPLICATIONS
Balanced Audio Line Receivers Summing Amplifiers Differential Amplifiers Current Shunt Monitors Ground Loop Eliminator
Description
The THAT 124x series of precision differential amplifiers are designed primarily for use as audio balanced line receivers. Gains of 0 db, -3 dB, and -6 dB are available to suit various applications requirements. The THAT 1246 is drop-in compatible with the Burr-Brown INA137 and Analog Devices SSM2143, while the THAT 1240 is drop-in compatible with the SSM2140. All devices exhibit 90 dB of typical common-mode rejection, slew rates of 12 V/ms, a 20MHz bandwidth, and 0.0006% THD. Both surface-mount and DIP packages are available. The THAT 124x family are laser-trimmed to obtain the precision resistor matching needed for high CMR performance. Fashioned in THAT Corporation's proprietary dielectric isolation (DI) process, the THAT 124x series provides the sonic benefit of discrete designs, with the compact size, reliability, matching, and thermal tracking of a fully integrated solution.
Vcc
Pin Name Ref InIn+
DIP Pin 1 2 3 4 5 6 7 8
SO Pin 1 2 3 4 5 6 7 8
In-
Sense
Vee Sense Vout
Vout
Vcc NC
Table 1. 1240 Series pin assignments
In+
Ref
Gain 0 dB -3 dB
Plastic DIP 1240P 1243P 1246P
Plastic SO 1240S 1243S 1246S
Vee
NC
-6 dB
Figure 1. THAT1240-series equivalent circuit diagram
Table 2. Ordering information
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 2
Balanced Line Receiver ICs Preliminary Information
SPECIFICATIONS1 Absolute Maximum Ratings (TA = 25C)
Positive Supply Voltage (VCC) Negative Supply Voltage (VEE) Storage Temperature Range (TST) Output Short-Circuit Duration (tSH) Positive Input Voltage (Ref, Sense) Positive Input Voltage (In+,In-) Negative Input Voltage (In+, In-) +18 V -18 V -40 to +125C Continuous +18 V THAT1240 Vcc x 2 Vee x 2 Power Dissipation (PD) (TA = 75C) Operating Temperature Range (TOP) Junction Temperature (TJ) Lead Temperature (Soldering 60 seconds) Negative Input Voltage (Ref, Sense) THAT1243 Vcc x 2.4 Vee x 2.4 THAT1246 Vcc x 3 Vee x 3 TBD mW 0 to +70C 150C TBD C -18 V
Recommended Operating Conditions
Parameter Positive Supply Voltage Negative Supply Voltage Symbol VCC VEE Conditions Min +2.2 -2.2 Typ Max +18 -18 Units V V
Electrical Characteristics2
Parameter Supply Current Input Voltage Range Symbol ICC VIN-DIFF Conditions No signal Differential (equal and opposite swing) THAT1240 (0 dB gain) THAT1243 (-3 dB gain) THAT1246 (-6 dB gain) Common mode THAT1240 (0 dB gain) THAT1243 (-3 dB gain) THAT1246 (-6 dB gain) Common mode (all versions) Differential THAT1240 THAT1243 THAT1246 Min -- Typ 2.1 Max 3.4 Units mA
-- -- -- -- -- -- -- -- -- --
21.5 24.5 27.5 27.5 29.1 31.0 9 18 21 24
-- -- -- -- -- -- -- -- -- --
dBu3 dBu dBu dBu dBu dBu kW kW kW kW
VIN-CM
Input Impedance4
ZIN-CM ZIN-DIFF
Common Mode Rejection
CMR
Matched source impedances; VCM = 10V DC 70 60 Hz 70 20 kHz -- 44 kHz -- At 60 Hz, with VCC = -VEE THAT1240 THAT1243
90 90 85 60
-- -- -- --
dB dB dB dB
Power Supply Rejection5
PSR
-- --
82 80
-- --
dB dB
1. 2. 3. 4. 5.
All specifications are subject to change without notice. Unless otherwise noted, TA=25C, VCC = +15V, VEE = -15V, Gain=-6dB 0 dBu = 0.775Vrms. See test circuit in Figure 2. Defined with respect to differential gain.
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Rev. 04/29/02 Preliminary Information
Page 3
Electrical Characteristics (Cont'd)
Parameter Total Harmonic Distortion Symbol THD Conditions Min Typ Max Units
VIN-DIFF = 10 dBV; BW = 20 kHz; f = 1 kHz RL = 2 kW -- BW = 20 kHz THAT1240 THAT1243 THAT1246 RL = 2 kW; CL = 300 pF RL = 2 kW; CL = 10 pF THAT1240 THAT1243 THAT1246 RL = 2 kW; CL = 300 pF THAT1240 THAT1243 THAT1246 f = 1 kHz RL = 2 kW No signal RL = 0 W
0.0006
--
%
Output Noise
en(OUT)
-- -- -- 7
-106 -107 -109 12
-- -- -- --
dBu dBu dBu V/s
Slew Rate Small Signal Bandwidth
SR BW-3dB
12 17 23 11 13 14 -- 12.5 -7 -- -- 300
24 33 44 17 18 20 0.03 13 0 25 -- --
-- -- -- -- -- -- 0.5 -- +7 -- 2 --
MHz MHz MHz MHz MHz MHz % V mV mA kW pF
Output Gain Error Output Voltage Swing Output Offset Voltage Output Short Circuit Current Resistive Load Capacitive Load
GER(OUT) VO VOFF ISC RLmin CLmax
Vcc InR1
b
R2
Sense
~
1/2Udiff Vout
1/2Udiff
~
In+
R3 a
R4
RL Ref CL
VCM ~
Vee
Part no. THAT1240 THAT1243 THAT1246
Gain 0 dB -3 dB -6 dB
R1 = R3 9 kU 10.5 kU 12 kU
R2 = R4 9 kU 7.5 kU 6 kU
Figure 2. THAT1240 series test circuit THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 4
Balanced Line Receiver ICs Preliminary Information
Application Notes
The THAT 1240, 1243, and 1246 are precision differential amplifiers with gains of zero, -3 and -6 dB respectively, and are primarily intended as balanced line receivers for pro audio. However, their topology lends itself to other applications as well. Figures 3 and 4 show the THAT 1240 and THAT 1246 configured as zero and -6 dB line receivers respectively. These devices can be used to retrofit circuits currently using the SSM 2141, INA134, SSM2143, or INA137. While the THAT 1240 and THAT 1246 are form, fit and functionally compatible with their competitors' equivalent versions, their slew rate and bandwidth are superior. Like other amplifiers of this type, all of THAT Corporation's line receivers can accept common mode voltages that exceed the power supply rails. Consider Figure 2. Assume that the circuit is configured as shown, but with no differential excitation. In+ and In- are shorted together, as are Vout and Sense. Ref is tied to ground. a and b will be held at the same voltage by feedback. The maximum voltage allowed at the internal node a is VCC minus 2V, while the minimum voltage is VEE plus 2V. The voltage at a can be calculated a = VPK - CM [
R4 R3+ R4
Figure 5 shows a THAT 1240 configured as a precision summing amplifier. This circuit uses both the In+ and Ref pins as inputs. Refering to Figure 2, it can be shown by superposition that the voltage at a will be
R R a = (In+ ) [ R 4+4 3] + Ref [ R 4+3 3] R R
Lo
2
In-
5 Sense Vout 6 Hi - Lo
Hi
3
Ref In+ 1 U1 1240
Figure 3. Zero dB line receiver
Lo
2
]
Hi
Isolating VPK-CM, we see that
R VPK - CM = a [ R 4+4 3 ] R
5 InSense 6 ( Hi - Lo ) * 0.5 Vout Ref 3 In+ 1 U1 1246
Thus, the maximum input in dBu would be e (Vcc - 2V ) [R 4+ R 3] u R4 2 u VIN max - dbu = 20 log e . 0775 e u e u With 18V supplies, the THAT 1240 can tolerate a maximum common mode input of 29.3 dBu. Under the same conditions, the THAT1243 can tolerate 30.0 dBu and the THAT 1246 can tolerate 32.9 dBu. These numbers are slightly higher than the datasheet specifications, since they're calculated with a slightly higher supply voltage. Also note that high levels of common mode input compromise the maximum differential mode signal that can be handled by these ICs.
Figure 4. -6 dB line receiver
2
In+ Ref
5 InSense 6 Vout Ref 3 U1 In+ 1 1240
(In+)+ Ref
Figure 5. Precision summing circuit
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Rev. 04/29/02 Preliminary Information
Page 5
2
In Hi
5 InSense R8 6 Vout 2k10 Ref 3 In+ U1 1 THAT 1246 C4 +24 dBu 6n8
AIN- to ADC
R9 249R
Zero dBu Out
+24 dBu In
In Lo
5 InSense 6 Vout 3 Ref In+ U2 1 THAT 1246
2
R19 2k10 AIN+ to ADC
U3A 1 4570
3 2
1/2 Vref of ADC
Figure 6. Circuit for audio ADCs with balanced inputs
Since R3=R4 in the THAT 1240, this equation can be simplified to a=
( In +) + Ref 2
The output voltage would then be
2 Vout = a (1 + R1 ) R
Figure 6 shows a convenient method of driving a typical audio ADC with balanced inputs. This circuit accepts +24 dBu in, and using a pair of 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. The output noise of a THAT 1246 is -109 dBu, 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
Since R2=R1, combining equations results in Vout = (In+ ) + Ref
-3dB
-3dB C3
+6dB
C1 U3 2180B 22p R3 VCC 7
V+ OUT V-
R1 1M0
In Lo 2
5 InSense Vout Ref In+ 1
6
C2 22u
R2 20k0
1
EC+ 4 SYM IN GND EC-
2
14k0 8 2 3 U4A 4570 1
In Hi 3
U1 1243
6
5 R4 5k1 VEE
3
Control Voltage
100n 6 7 4 Vcc 8 Cap2 In Out+ 3 Gnd Out- 1 Cap1 Vee 2 5 U2 VEE THAT1430
VCC
Out Hi Out Lo
Figure 7. Automated gain control of a balanced signal
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 6
Balanced Line Receiver ICs Preliminary Information
e n line receiver =
10 ( -130dBu) 0775 , 20 20kHz
= 173 nV .
Hz
The noise of the 249W resistor is 2.05 nV/OHz. We can assume that the noise contribution of R8 and R19 will be negligible, and therefore, the total noise density going into the input of the ADC will be e n total = (1. 73 nV )2 + (2. 06 nV )2 = 2. 68 nV
Hz Hz
gain on each half of the balanced signal. Unfortunately, this can results in common mode to differential mode conversion (degradation of CMRR) when there are even slight differences in gain between the VCAs. A better approach is to convert the signal to single-ended, alter the gain, and then convert back to balanced. In Figure 7 we use a THAT 1243 -3 dB line receiver to do the balanced to single-ended conversion. The VCA section also has a static gain of -3 dB due to the ratio of R2 and R3. This circuit can accept 24 dBu, since the THAT 1243 output stage is capable of 21 dBu without distortion. Reducing R3 to 14 kW results in a 3 dB reduction in VCA output noise. This arrangement results in 3 dB greater dynamic range compared to the case where a -6 dB line receiver and a VCA with zero dB static gain are used. After the VCA, the signal is restored to 24 dBu by the THAT 1430.
Hz
The noise floor can then be calculated to be e 2.68 nV 20kHz u Hz u = -126 . 2 dBu Noise dBu = 20 log e 0775 . u e u e Figure 7 shows an excellent method for controlling gain in a balanced system. There is often a temptation in these systems to keep the signal balanced and use two VCAs to independently control the
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Rev. 04/29/02 Preliminary Information
Page 7
Package Information
The THAT 1240 series is available in both 8-pin mini-DIP and 8-pin SOIC packages. The package dimensions are shown in Figures 8 and 9, while the pinouts are given in Table 1.
E
F
B 1 A K F H D
ITEM A B C D E F G H J K
C G
J
B C H D A
G
E
MILLIMETERS 9.520.10 6.350.10 7.49/8.13 0.46 2.54 3.68/4.32 0.25 3.180.10 8.13/9.40 3.300.10 INCHES 0.3750.004 0.2500.004 0.295/0.320 0.018 0.100 0.145/0.170 0.010 0.1250.004 0.320/0.370 0.1300.004
ITEM A B C D E F G H
MILLIMETERS 4.80/4.98 3.81/3.99 5.80/6.20 0.36/0.46 1.27 1.35/1.73 0.19/0.25 0.41/1.27
INCHES 0.189/0.196 0.150/0.157 0.228/0.244 0.014/0.018 0.050 0.053/0.068 0.0075/0.0098 0.016/0.05
Figure 8. -P (DIP) version package outline drawing
Figure 9. -S (SO) version package outline drawing
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com
Page 8
Balanced Line Receiver ICs Preliminary Information
Notes:
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA Tel: +1 (508) 478-9200; Fax: +1 (508) 478-0990; Web: www.thatcorp.com

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