T H AT Corporation Balanced Line Receiver ICs THAT 1240, 1243, 1246 FEATURES APPLICATIONS · High CMRR: typically 90dB at 60Hz · Balanced Audio Line Receivers · Wide bandwidth and high slew rate · Summing Amplifiers · Low distortion and low noise · Differential Amplifiers · Available in 0 dB, -3 dB, and -6 dB versions · Current Shunt Monitors · · Ground Loop Eliminator Pin compatible with SSM2143 and INA137 Description 20MHz bandwidth, and 0.0006% THD. Both surface-mount and DIP packages are available. 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 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. 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 Vcc In- Sense Vout Pin Name DIP Pin SO Pin Ref 1 1 In- 2 2 In+ 3 3 Vee 4 4 Sense 5 5 Vout 6 6 Vcc 7 7 NC 8 8 Table 1. 1240 Series pin assignments In+ Ref Vee NC Figure 1. THAT1240-series equivalent circuit diagram Gain Plastic DIP Plastic SO 0 dB 1240P 1240S -3 dB 1243P 1243S -6 dB 1246P 1246S 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 = 25°C) Positive Supply Voltage (VCC) Negative Supply Voltage (VEE) +18 V Power Dissipation (PD) (TA = 75°C) -18 V Operating Temperature Range (TOP) Storage Temperature Range (TST) -40 to +125°C Output Short-Circuit Duration (tSH) Continuous Positive Input Voltage (Ref, Sense) +18 V TBD mW 0 to +70°C Junction Temperature (TJ) 150°C Lead Temperature (Soldering 60 seconds) Negative Input Voltage (Ref, Sense) THAT1240 THAT1243 Positive Input Voltage (In+,In-) Vcc x 2 Vcc x 2.4 Vcc x 3 Negative Input Voltage (In+, In-) Vee x 2 Vee x 2.4 Vee x 3 TBD °C -18 V THAT1246 Recommended Operating Conditions Parameter Symbol Conditions Min Typ Max Units Positive Supply Voltage VCC +2.2 +18 V Negative Supply Voltage VEE -2.2 -18 V Electrical Characteristics2 Parameter Supply Current Input Voltage Range Symbol Conditions Min Typ Max Units ICC No signal — 2.1 3.4 mA VIN-DIFF 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) — — — 21.5 24.5 27.5 — — — dBu3 dBu dBu — — — 27.5 29.1 31.0 — — — dBu dBu dBu — 9 — kW — — — 18 21 24 — — — kW kW kW Matched source impedances; VCM = ±10V DC 70 60 Hz 70 20 kHz — 44 kHz — 90 90 85 60 — — — — dB dB dB dB 82 80 — — dB dB VIN-CM Input Impedance4 ZIN-CM ZIN-DIFF Common Mode Rejection Power Supply Rejection5 1. 2. 3. 4. 5. CMR PSR Common mode (all versions) Differential THAT1240 THAT1243 THAT1246 At 60 Hz, with VCC = -VEE THAT1240 THAT1243 — — All specifications are subject to change without notice. Unless otherwise noted, TA=25°C, 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 Symbol Total Harmonic Distortion THD Output Noise Conditions Min VIN-DIFF = 10 dBV; BW = 20 kHz; f = 1 kHz RL = 2 kW — en(OUT) Typ Max Units 0.0006 — % BW = 20 kHz THAT1240 THAT1243 THAT1246 — — — -106 -107 -109 — — — dBu dBu dBu SR RL = 2 kW; CL = 300 pF 7 12 — V/µs BW-3dB RL = 2 kW; CL = 10 pF THAT1240 THAT1243 THAT1246 RL = 2 kW; CL = 300 pF THAT1240 THAT1243 THAT1246 12 17 23 24 33 44 — — — MHz MHz MHz 11 13 14 17 18 20 — — — MHz MHz MHz GER(OUT) f = 1 kHz — ±0.03 ±0.5 % Output Voltage Swing VO RL = 2 kW ±12.5 ±13 — V Output Offset Voltage VOFF No signal -7 0 +7 mV ISC RL = 0 W — ±25 — mA Slew Rate Small Signal Bandwidth Output Gain Error Output Short Circuit Current Resistive Load RLmin — — 2 kW Capacitive Load CLmax 300 — — pF Vcc In- ~ R1 R2 b Sense ½Udiff Vout ½Udiff ~ In+ R4 R3 RL Ref CL a VCM ~ Vee Part no. Gain R1 = R3 R2 = R4 THAT1240 0 dB 9 kÙ 9 kÙ THAT1243 -3 dB 10.5 kÙ 7.5 kÙ THAT1246 -6 dB 12 kÙ 6 kÙ 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 a = (In+ ) [ R 4R+4R 3] + Ref [ R 4R+3R 3] Lo 5 In- Sense Vout Hi 3 Hi - Lo 6 Ref In+ 1 U1 1240 Figure 3. Zero dB line receiver Lo ] Isolating VPK-CM, we see that 2 Hi VPK - CM = a [ R 4R+4R 3 ] 2 5 InSense 6 ( Hi - Lo ) * 0.5 Vout Ref 3 In+ 1 U1 1246 Thus, the maximum input in dBu would be Figure 4. -6 dB line receiver é (Vcc - 2V ) ´ [R 4+ R 3] ù R4 2 ú VIN max - dbu = 20 log ê . 0775 êë úû 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. 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 5 InSense R8 6 Vout 2k10 Ref 3 In+ U1 1 THAT 1246 C4 +24 dBu 6n8 In Hi +24 dBu In R9 249R Zero dBu Out 2 5 InSense 6 Vout 3 Ref In+ U2 1 THAT 1246 In Lo AIN- to ADC R19 2k10 U3A 1 3 AIN+ to ADC 1/2 Vref of ADC 2 4570 Figure 6. Circuit for audio ADCs with balanced inputs Since R3=R4 in the THAT 1240, this equation can be simplified to a= 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. ( In +) + Ref 2 The output voltage would then be 2) Vout = a ´ (1 + R R1 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 +6dB -3dB C3 C1 U3 2180B 22p VCC R3 In Lo 2 5 InSense Vout In Hi 3 6 Ref In+ 1 VCC 2 C2 R2 22u U1 1243 1 EC+ 4 SYM IN 20k0 GND EC- 3 6 7 V+ OUT V- 5 R4 5k1 Control Voltage VEE 14k0 8 2 1 3 U4A 4570 100n 6 7 4 Vcc 8 Cap2 In Out+ 3 Gnd Out- 1 Cap1 Vee 2 5 U2 VEE THAT1430 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 R1 1M0 Out Hi Out Lo Page 6 e n line receiver = Balanced Line Receiver ICs Preliminary Information dBu 10 ( -130 ) ´ 0775 , 20 20kHz nV = 173 . Hz The noise of the 249W resistor is 2.05 nV/ÖHz. 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 Hz The noise floor can then be calculated to be é 2.68 nV ´ 20kHz ù Hz ú = -126 . 2 dBu Noise dBu = 20 log ê 0775 . úû êë 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 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. 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 di- mensions are shown in Figures 8 and 9, while the pinouts are given in Table 1. E J C B F 1 B G A C H K F D H G A D ITEM A B C D E F G H J K E MILLIMETERS 9.52±0.10 6.35±0.10 7.49/8.13 0.46 2.54 3.68/4.32 0.25 3.18±0.10 8.13/9.40 3.30±0.10 INCHES 0.375±0.004 0.250±0.004 0.295/0.320 0.018 0.100 0.145/0.170 0.010 0.125±0.004 0.320/0.370 0.130±0.004 Figure 8. -P (DIP) version package outline drawing 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 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