NCY9100 Compandor The NCY9100 is a versatile low cost dual gain control circuit in which either channel may be used as a dynamic range compressor or expandor. Each channel has a full−wave rectifier to detect the average value of the signal, a linerarized temperature−compensated variable gain cell, and an operational amplifier. The NCY9100 is well suited for use in cellular radio and radio communications systems, modems, telephone, and satellite broadcast/receive audio systems. http://onsemi.com MARKING DIAGRAMS Features • • • • • • • • • 16 Complete Compressor and Expandor in one IChip Temperature Compensated Greater than 110 dB Dynamic Range Operates Down to 6.0 VDC System Levels Adjustable with External Components Distortion may be Trimmed Out Dynamic Noise Reduction Systems Voltage Controlled Amplifier This is a Pb−Free Device 16 1 NCY9100 AWLYYWWG SOIC−16 WB D SUFFIX CASE 751G 1 A WL YY WW G = Assembly Location = Wafer Lot = Year = Work Week = Pb−Free Package Applications • • • • • Cellular Radio High Level Limiter Low Level Expandor − Noise Gate Dynamic Filters CD Player PIN CONNECTIONS RECT CAP 1 1 16 RECT CAP 2 RECT IN 1 2 15 DG CELL IN 1 3 14 RECT IN 2 DG CELL IN 2 VCC GND 4 13 INV. IN 1 RES. R3 1 5 12 INV. IN 2 6 11 RES. R3 2 OUTPUT 1 7 10 OUTPUT 2 THD TRIM 1 8 9 THD TRIM 2 TOP VIEW ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 9 of this data sheet. *For additional information on our Pb−Free strategy and soldering details, please download the ON Semiconductor Soldering and Mounting Techniques Reference Manual, SOLDERRM/D. © Semiconductor Components Industries, LLC, 2009 April, 2009 − Rev. 0 1 Publication Order Number: NCY9100/D NCY9100 THD TRIM DG IN R2 20kW RECT IN R1 10kW INVERTER IN R3 VARIABLE GAIN R3 20kW − R4 30kW VREF 1.8V OUTPUT + RECTIFIER RECT CAP Figure 1. Block Diagram MAXIMUM RATINGS Rating Symbol Value Unit VCC 18 VDC Operating Ambient Temperature Range TA −40 to +85 °C Operating Junction Temperature TJ 150 °C Power Dissipation PD 400 mW RqJA 105 °C/W Maximum Operating Voltage Thermal Resistance, Junction−to−Ambient Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability. http://onsemi.com 2 NCY9100 ELECTRICAL CHARACTERISTICS (VCC = +15 V, TA = 25°C, unless otherwise noted) Characteristic Symbol Test Conditions Min Typ Max Unit Supply Voltage VCC − 6.0 − 18 V Supply Current ICC No Signal − 4.2 4.8 mA Output Current Capability IOUT − ± 20 − − mA SR − − ± .5 − V/ms Untrimmed Trimmed − 0.5 0.1 2.0 % Resistor Tolerance − − ±5 ± 15 % Internal Reference Voltage − 1.65 1.8 1.95 V Output DC Shift (Note 3) Untrimmed − ± 90 ± 150 mV Expandor Output Noise No Signal, 15 Hz−20 kHz (Note 1) − 20 60 mV 1.0 kHz −1.5 0 +1.5 dBm Gain Change (Notes 2 and 4) − − ± 0.1 − dB Reference Drift (Note 4) − − +2.0, −25 +20, −50 mV −40°C to +85°C − +10, −12 − % Rectifier Input, VCC = +6.0 V V2 = +6.0 dBm, V1 = 0 dB V2 = −30 dBm, V1 = 0 dB − − − Output Slew Rate Gain Cell Distortion (Note 2) Unity Gain Level (Note 5) Resistor Drift (Note 4) Tracking Error (Measured Relative to Value at Unity Gain) Equals [VO − VO (unity gain)] dB − V2dBm Channel Separation 1. 2. 3. 4. 5. Input to V1 and V2 grounded. Measured at 0 dBm, 1.0 kHz. Expandor AC input change from no signal to 0 dBm. Relative to value at TA = 25°C. 0 dBm = 775 mVRMS. http://onsemi.com 3 dB +0.2 +0.2 −1.0, +1.5 60 − dB NCY9100 Circuit Description as brought out externally. A resistor, R3, is brought out from the summing node and allows compressor or expander gain to be determined only by internal components. The output stage is capable of ± 20 mA output current. This allows a +13 dBm (3.5 VRMS) output into a 300 W load which, with a series resistor and proper transformer, can result in +13 dBm with a 600 W output impedance. A bandgap reference provides the reference voltage for all summing nodes, a regulated supply voltage for the rectifier and DG cell, and a bias current for the DG cell. The low tempco of this type of reference provides very stable biasing over a wide temperature range. The typical performance characteristics illustration shows the basic input−output transfer curve for basic compressor or expander circuits. The NCY9100 compandor building blocks, as shown in the block diagram, are a full−wave rectifier, a variable gain cell, an operational amplifier and a bias system. The arrangement of these blocks in the IC result in a circuit which can perform well with few external components, yet can be adapted to many diverse applications. The full−wave rectifier rectifies the input current which flows from the rectifier input, to an internal summing node which is biased at VREF. The rectified current is averaged on an external filter capacitor tied to the CRECT terminal, and the average value of the input current controls the gain of the variable gain cell. The gain will thus be proportional to the average value of the input signal for capacitively−coupled voltage inputs as shown in the following equation. Note that for capacitively−coupled inputs there is no offset voltage capable of producing a gain error. The only error will come from the bias current of the rectifier (supplied internally) which is less than 0.1 mA. COMPRESSOR INPUT LEVEL OR EXPANDOR OUTPUT LEVEL (dBm) +20 |V * V REF | avg G T IN R1 or GT | V IN | avg R1 The speed with which gain changes to follow changes in input signal levels is determined by the rectifier filter capacitor. A small capacitor will yield rapid response but will not fully filter low frequency signals. Any ripple on the gain control signal will modulate the signal passing through the variable gain cell. In an expander or compressor application, this would lead to third harmonic distortion, so there is a trade−off to be made between fast attack and decay times and distortion. For step changes in amplitude, the change in gain with time is shown by this equation. G(t) + (G initial * G final) t + 10kW *t et 0 −10 −20 −30 −40 −50 −60 −70 −80 −40 −30 −20 −10 0 +10 COMPRESSOR OUTPUT LEVEL OR EXPANDOR INPUT LEVEL (dBm) Figure 2. Basic Input−Output Transfer Curve ) G final VCC = 15V C RECT 0.1mF The variable gain cell is a current−in, current−out device with the ratio IOUT/IIN controlled by the rectifier. IIN is the current which flows from the DG input to an internal summing node biased at VREF. The following equation applies for capacitively−coupled inputs. The output current, IOUT, is fed to the summing node of the op amp. I IN + +10 10mF 13 6, 11 2.2mF 20kW V1 3, 14 V IN * V REF V + IN R2 R2 20kW DG 4 7, 10 VREF 2.2mF 10kW V2 2, 15 A compensation scheme built into the DG cell compensates for temperature and cancels out odd harmonic distortion. The only distortion which remains is even harmonics, and they exist only because of internal offset voltages. The THD trim terminal provides a means for nulling the internal offsets for low distortion operation. The operational amplifier (which is internally compensated) has the non−inverting input tied to VREF, and the inverting input connected to the DG cell output as well − + 30kW 1, 16 5, 12 2.2mF 8.2kW 8, 9 200pF Figure 3. Typical Test Circuit http://onsemi.com 4 VO NCY9100 INTRODUCTION Much interest has been expressed in high performance electronic gain control circuits. For non−critical applications, an integrated circuit operational transconductance amplifier can be used, but when high−performance is required, one has to resort to complex discrete circuitry with many expensive, well−matched components. This paper describes an inexpensive integrated circuit, the NCY9100 Compandor, which offers a pair of high performance gain control circuits featuring low distortion (<0.1%), high signal−to−noise ratio (90 dB), and wide dynamic range (110 dB). requires a simple full−wave averaging rectifier with good accuracy, since the rectifier accuracy determines the (input) output level tracking accuracy. The gain cell determines the distortion and noise characteristics, and the phone system specifications here are very loose. These specs could have been met with a simple Operational Transconductance Multiplier, or OTA, but the gain of an OTA is proportional to temperature and this is very undesirable. Therefore, a linearized transconductance multiplier was designed which is insensitive to temperature and offers low noise and low distortion performance. These features make the circuit useful in audio and data systems as well as in telecommunications systems. Circuit Background EXPANSION INPUT LEVEL +20 COMPRESSION The NCY9100 Compandor was originally designed to satisfy the requirements of the telephone system. When several telephone channels are multiplexed onto a common line, the resulting signal−to−noise ratio is poor and companding is used to allow a wider dynamic range to be passed through the channel. Figure 4 graphically shows what a compandor can do for the signal−to−noise ratio of a restricted dynamic range channel. The input level range of +20 to −80 dB is shown undergoing a 2−to−1 compression where a 2.0 dB input level change is compressed into a 1.0 dB output level change by the compressor. The original 100 dB of dynamic range is thus compressed to a 50 dB range for transmission through a restricted dynamic range channel. A complementary expansion on the receiving end restores the original signal levels and reduces the channel noise by as much as 45 dB. The significant circuits in a compressor or expander are the rectifier and the gain control element. The phone system Basic Hook−up and Operation Figure 5 shows the block diagram of one half of the chip, (there are two identical channels on the IC). The full−wave averaging rectifier provides a gain control current, IG, for the variable gain (DG) cell. The output of the DG cell is a current which is fed to the summing node of the operational amplifier. Resistors are provided to establish circuit gain and set the output DC bias. The circuit is intended for use in single power supply systems, so the internal summing nodes must be biased at some voltage above ground. An internal band gap voltage reference provides a very stable, low noise 1.8 V reference denoted VREF. The non−inverting input of the op amp is tied to VREF, and the summing nodes of the rectifier and DG cell (located at the right of R1 and R2) have the same potential. The THD trim pin is also at the VREF potential. THD TRIM 8,9 R3 OUTPUT LEVEL −20 GIN 0dB 0dB −40 −40 R2 3,14 20kW RECTIN R1 2,15 10kW NOISE −80 R3 −80 INVIN 6,11 5,12 20kW DG − IG R4 VREF 30kW 1.8V 1,16 + OUTPUT 7,10 VCC PIN 13 GND PIN 4 CRECT Figure 4. Restricted Dynamic Range Channel Figure 5. Chip Block Diagram (1 of 2 Channels) http://onsemi.com 5 NCY9100 Figure 6 shows how the circuit is hooked up to realize an expandor. The input signal, VIN, is applied to the inputs of both the rectifier and the DG cell. When the input signal drops by 6.0 dB, the gain control current will drop by a factor of 2, and so the gain will drop 6.0 dB. The output level at VOUT will thus drop 12 dB, giving us the desired 2−to−1 expansion. R1 R2 DG VOUT + R4 R4 VREF NOTE: GAIN + + ǒ R1 R2 IB 2R 3 V INavg Ǔ 1 2 IB = 140mA VREF R1 VOUT − − VIN *CIN2 CDC * CIN * R 3 VIN CF* CRECT * RDC * RDC * R3 *CIN1 R2 DG *EXTERNAL COMPONENTS Figure 7. Basic Compressor *CRECT Circuit Details − Rectifier NOTE: ǒ GAIN + IB = 140mA Figure 8 shows the concept behind the full−wave averaging rectifier. The input current to the summing node of the op amp, VIN/R1, is supplied by the output of the op amp. If we can mirror the op amp output current into a unipolar current, we will have an ideal rectifier. The output current is averaged by R5, CR, which set the averaging time constant, and then mirrored with a gain of 2 to become IG, the gain control current. Ǔ 2 R 3 V IN (avg) 2 R1 R2 IB *EXTERNAL COMPONENTS Figure 6. Basic Expander Figure 7 shows the hook−up for a compressor. This is essentially an expandor placed in the feedback loop of the op amp. The DG cell is setup to provide AC feedback only, so a separate DC feedback loop is provided by the two RDC and CDC. The values of RDC will determine the DC bias at the output of the op amp. The output will bias to: V OUT DC + ǒ I = VIN / R1 R1 Ǔ VIN ) R DC2 R 1 ) DC1 V REF R4 ǒ V OUT DC + 1 ) R DCTOT 30kW − + CR Ǔ 1.8V V+ R5 10kW The output of the expander will bias up to: V OUT DC + ǒ ǒ 1 ) RR Ǔ V 3 4 REF Figure 8. Rectifier Concept Ǔ V OUT DC + 1 ) 20kW 1.8V + 3.0V 30kW The output will bias to 3.0 V when the internal resistors are used. External resistors may be placed in series with R3, (which will affect the gain), or in parallel with R4 to raise the DC bias to any desired value. http://onsemi.com 6 IG NCY9100 Figure 9 shows the rectifier circuit in more detail. The op amp is a one−stage op amp, biased so that only one output device is on at a time. The non−inverting input, (the base of Q1), which is shown grounded, is actually tied to the internal 1.8 V, VREF. The inverting input is tied to the op amp output, (the emitters of Q5 and Q6), and the input summing resistor R1. The single diode between the bases of Q5 and Q6 assures that only one device is on at a time. To detect the output current of the op amp, we simply use the collector currents of the output devices Q5 and Q6. Q6 will conduct when the input swings positive and Q5 conducts when the input swings negative. The collector currents will be in error by the a of Q5 or Q6 on negative or positive signal swings, respectively. ICs such as this have typical NPN b’s of 200 and PNP b’s of 40. The a’s of 0.995 and 0.975 will produce errors of 0.5% on negative swings and 2.5% on positive swings. The 1.5% average of these errors yields a mere 0.13 dB gain error. the error of the input bias current. For highest accuracy, the rectifier should be coupled capacitively. At high input levels the b of the PNP Q6 will begin to suffer, and there will be an increasing error until the circuit saturates. Saturation can be avoided by limiting the current into the rectifier input to 250 mA. If necessary, an external resistor may be placed in series with R1 to limit the current to this value. Figure 10 shows the rectifier accuracy vs. input level at a frequency of 1.0 kHz. ERROR GAIN dB +1 0 −1 V+ Figure 10. Rectifier Accuracy Q3 Q7 At very high frequencies, the response of the rectifier will fall off. The roll−off will be more pronounced at lower input levels due to the increasing amount of gain required to switch between Q5 or Q6 conducting. The rectifier frequency response for input levels of 0 dBm, −20 dBm, and −40 dBm is shown in Figure 11. The response at all three levels is flat to well above the audio range. Q4 Q5 Q1 Q2 D1 R1 10kW VIN RS 10kW Q6 I1 −40 −20 0 RECTIFIER INPUT dBm Q8 I2 Q9 GAIN ERROR (dB) CR V− NOTE: I G + 2 V IN avg R1 Figure 9. Simplified Rectifier Schematic At very low input signal levels the bias current of Q2, (typically 50 nA), will become significant as it must be supplied by Q5. Another low level error can be caused by DC coupling into the rectifier. If an offset voltage exists between the VIN input pin and the base of Q2, an error current of VOS/R1 will be generated. A mere 1.0 mV of offset will cause an input current of 100 nA which will produce twice INPUT = 0dBm 0 3 −20dBm −40dBm 10k 1MEG FREQUENCY (Hz) Figure 11. Rectifier Frequency Response vs. Input Level http://onsemi.com 7 NCY9100 Variable Gain Cell This equation is linear and temperature−insensitive, but it assumes ideal transistors. If the transistors are not perfectly matched, a parabolic, non−linearity is generated, which results in second harmonic distortion. Figure 13 gives an indication of the magnitude of the distortion caused by a given input level and offset voltage. The distortion is linearly proportional to the magnitude of the offset and the input level. Saturation of the gain cell occurs at a +8 dBm level. At a nominal operating level of 0 dBm, a 1.0 mV offset will yield 0.34% of second harmonic distortion. Most circuits are somewhat better than this, which means our overall offsets are typically about mV. The distortion is not affected by the magnitude of the gain control current, and it does not increase as the gain is changed. This second harmonic distortion could be eliminated by making perfect transistors, but since that would be difficult, we have had to resort to other methods. A trim pin has been provided to allow trimming of the internal offsets to zero, which effectively eliminated second harmonic distortion. Figure 14 shows the simple trim network required. Figure 12 is a diagram of the variable gain cell. This is a linearized two−quadrant transconductance multiplier. Q1, Q2 and the op amp provide a predistorted drive signal for the gain control pair, Q3 and Q4. The gain is controlled by IG and a current mirror provides the output current. V+ I1 140mA − + R2 20k VIN Q1 Q2 Q4 Q3 IIN I2 (= 2I1) 280mA IG V− 3 % THD NOTE: I OUT 4 I I V + G I IN + G IN I1 I2 R2 Figure 12. Simplified DG Cell Schematic The op amp maintains the base and collector of Q1 at ground potential (VREF) by controlling the base of Q2. The input current IIN (= VIN/R2) is thus forced to flow through Q1 along with the current I1, so IC1 = I1 + IIN. Since I2 has been set at twice the value of I1, the current through Q2 is: 3mV 2 2mV 1 1mV .34 −6 0 +6 INPUT LEVEL (dBm) Figure 13. DG Cell Distortion vs. Offset Voltage I2 − (I1 + IIN) = I1 − IIN = IC2. The op amp has thus forced a linear current swing between Q1 and Q2 by providing the proper drive to the base of Q2. This drive signal will be linear for small signals, but very non−linear for large signals, since it is compensating for the non−linearity of the differential pair, Q1 and Q2, under large signal conditions. The key to the circuit is that this same predistorted drive signal is applied to the gain control pair, Q3 and Q4. When two differential pairs of transistors have the same signal applied, their collector current ratios will be identical regardless of the magnitude of the currents. This gives us: VCC R 3.6V 6.2kW To THD Trim 20kW ≈200pF I C1 I I ) I IN + C4 + 1 I C2 I C3 I 1 * I IN Figure 14. THD Trim Network plus the relationships IG = IC3 + IC4 and IOUT = IC4 − IC3 will yield the multiplier transfer function, I OUT + 4mV IG V I I + IN G I 1 IN R2 I1 http://onsemi.com 8 NCY9100 Figure 15 shows the noise performance of the DG cell. The maximum output level before clipping occurs in the gain cell is plotted along with the output noise in a 20 kHz bandwidth. Note that the noise drops as the gain is reduced for the first 20 dB of gain reduction. At high gains, the signal to noise ratio is 90 dB, and the total dynamic range from maximum signal to minimum noise is 110 dB. VCC R−SELECT FOR 3.6V TO PIN 3 OR 14 100kW 470kW +20 OUTPUT (dBm) 0 Figure 16. Control Signal Feedthrough MAXIMUM SIGNAL LEVEL −20 90dB 110dB −40 Operation Amplifier The main op amp shown in the chip block diagram is equivalent to a 741 with a 1.0 MHz bandwidth. Figure 17 shows the basic circuit. Split collectors are used in the input pair to reduce gM, so that a small compensation capacitor of just 10 pF may be used. The output stage, although capable of output currents in excess of 20 mA, is biased for a low quiescent current to conserve power. When driving heavy loads, this leads to a small amount of crossover distortion. −60 −80 −100 −40 NOISE IN 20kHz BW −20 0 VCA GAIN (0dB) Figure 15. Dynamic Range I2 I1 Control signal feedthrough is generated in the gain cell by imperfect device matching and mismatches in the current sources, I1 and I2. When no input signal is present, changing IG will cause a small output signal. The distortion trim is effective in nulling out any control signal feedthrough, but in general, the null for minimum feedthrough will be different than the null in distortion. The control signal feedthrough can be trimmed independently of distortion by tying a current source to the DG input pin. This effectively trims I1. Figure 16 shows such a trim network. −IN Q1 Q2 +IN CC D1 D2 Q6 OUT Q2 Q3 Q4 Figure 17. Operational Amplifier ORDERING INFORMATION Device NCY9100DWR2G Description Temperature Range Shipping† SO−16 WB Package (Pb−Free) −40 to +85°C 1000 / Tape & Reel †For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D. http://onsemi.com 9 NCY9100 PACKAGE DIMENSIONS5 SOIC−16 WB D SUFFIX CASE 751G−03 ISSUE C A D 9 h X 45 _ E M 0.25 8X H B M 16 q 1 NOTES: 1. DIMENSIONS ARE IN MILLIMETERS. 2. INTERPRET DIMENSIONS AND TOLERANCES PER ASME Y14.5M, 1994. 3. DIMENSIONS D AND E DO NOT INLCUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 PER SIDE. 5. DIMENSION B DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.13 TOTAL IN EXCESS OF THE B DIMENSION AT MAXIMUM MATERIAL CONDITION. MILLIMETERS DIM MIN MAX A 2.35 2.65 A1 0.10 0.25 B 0.35 0.49 C 0.23 0.32 D 10.15 10.45 E 7.40 7.60 e 1.27 BSC H 10.05 10.55 h 0.25 0.75 L 0.50 0.90 q 0_ 7_ 8 16X M T A S B S 14X e A1 L A 0.25 B B SEATING PLANE T C ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. 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This literature is subject to all applicable copyright laws and is not for resale in any manner. PUBLICATION ORDERING INFORMATION LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303−675−2175 or 800−344−3860 Toll Free USA/Canada Fax: 303−675−2176 or 800−344−3867 Toll Free USA/Canada Email: [email protected] N. American Technical Support: 800−282−9855 Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: 421 33 790 2910 Japan Customer Focus Center Phone: 81−3−5773−3850 http://onsemi.com 10 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative NCY9100/D