NE570DR2

NE570 Compandor The NE570 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 NE570 is well suited for use in cellular radio and radio communications systems, modems, telephone, and satellite broadcast/receive audio systems. http://onsemi.com MARKING DIAGRAM Features • • • • • • • Complete Compressor and Expandor in One IC 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 Pb−Free Packages are Available* 16 NE570D AWLYYWWG 1 SOIC−16 WB D SUFFIX CASE 751G Applications • • • • • • • Cellular Radio Telephone Trunk Comandor High Level Limiter Low Level Expandor − Noise Gate Dynamic Noise Reduction Systems Voltage−Controlled Amplifier Dynamic Filters A WL YY WW G RECT_CAP_1 1 16 RECT_CAP_2 RECT_IN_1 2 15 RECT_IN_2 DG_CELL_IN_1 3 14 DG_CELL_IN_2 °C GND 4 13 VCC 150 °C INV_IN_1 5 12 INV_IN_2 400 mW RES_R3_1 6 11 RES_R3_2 °C/W OUTPUT_1 7 10 OUTPUT_2 THD_TRIM_1 8 9 THD_TRIM_2 Symbol Value Unit VCC 24 VDC Operating Ambient Temperature Range TA 0 to +70 Operating Junction Temperature TJ Power Dissipation PD Maximum Operating Voltage Thermal Resistance, Junction−to−Ambient 105 RqJA 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. THD TRIM DG CELL IN RECT IN R2 20 kW R1 10 kW = Assembly Location = Wafer Lot = Year = Work Week = Pb−Free Package PIN CONNECTIONS MAXIMUM RATINGS Rating 1 Plastic Small Outline Package; 16 Leads; Body Width 7.5 mm VARIABLE GAIN R3 INVERTER IN R3 20 kW (Top View) ORDERING INFORMATION See detailed ordering and shipping information in the package dimensions section on page 9 of this data sheet. − OUTPUT VREF R4 1.8 V 30 kW + RECTIFIER RECT CAP Figure 1. Block Diagram *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, 2006 May, 2006 − Rev. 4 1 Publication Order Number: NE570/D NE570 PIN FUNCTION DESCRIPTION Pin Symbol 1 RECT CAP 1 2 RECT IN 1 3 DG CELL IN 1 Description External Capacitor Pinout for Rectifier 1 Rectifier 1 Input Variable Gain Cell 1 Input 4 GND 5 INV. IN 1 Ground 6 RES. R3 1 R3 Pinout 1 7 OUTPUT 1 Output 1 8 THD TRIM 1 Total Harmonic Distortion Trim 1 9 THD TRIM 2 Total Harmonic Distortion Trim 2 10 OUTPUT 2 Output 2 11 RES. R3 2 R3 Pinout 2 12 INV. IN 2 13 VCC 14 DG CELL IN 2 15 RECT IN 2 16 RECT CAP 2 Inverted Input 1 Inverted Input 2 Positive Power Supply Variable Gain Cell 2 Input Rectifier 2 Input External Capacitor Pinout for Rectifier 2 ELECTRICAL CHARACTERISTICS VCC = +15 V, TA = 25 °C; unless otherwise stated. Characteristic Test Conditions Supply Voltage Supply Current No Signal Output Current Capability Min Typ Max Unit VCC 6.0 − 24 V ICC − 4.3 4.8 mA IOUT ±20 − − mA SR − ±0.5 − V/ms Untrimmed − 0.3 1.0 % Trimmed − 0.05 − % − ±5 ±15 % 1.7 1.8 1.9 V Output Slew Rate Gain Cell Distortion (Note 1) Symbol Resistor Tolerance Internal Reference Voltage Output DC Shift (Note 2) Untrimmed − ±90 ±150 mV Expandor Output Noise No signal, 15 Hz to 20 kHz (Note 3) − 20 45 mV −1.0 0 +1.0 dBm ±0.1 ±0.2 dB Unity Gain Level (Note 4) Gain Change (Notes 1 and 5) TA = 0°C to +70°C − Reference Drift (Note 5) TA = 0°C to +70°C − ±5.0 ±10 mV Resistor Drift (Note 5) TA = 0°C to +70°C − +8.0, −5.0 − % Rectifier Input VCC = +6.0 V V2 = +6.0 dBm, V1 = 0 dB V2 = −30 dBm, V1 = 0 dB − − ±0.2 +0.2 − −0.5, +1.0 dB dB − 60 − dB Tracking Error (measured relative to value at unity gain) equals [VO − VO (unity gain)] dB − V2 dBm Channel Separation 1. 2. 3. 4. 5. Measured at 0 dBm, 1.0 kHz. Expandor AC input change from no signal to 0 dBm. Input to V1 and V2 grounded. 0 dB = 775 mVRMS. Relative to value at TA = 25°C. http://onsemi.com 2 NE570 CIRCUIT DESCRIPTION The NE570 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. GT 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 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. |V IN * V REF | avg R1 GT COMPRESSOR INPUT LEVEL OR EXPANDOR OUTPUT LEVEL (dBm) or | 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) e t + 10kW *t t ) G final C RECT 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 + V IN * V REF V + IN R2 R2 +20 +10 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 A compensation scheme built into the DG cell compensates for temperature and cancels out odd harmonic http://onsemi.com 3 NE570 VCC = 15 V 0.1 mF 10 mF 13 6, 11 20 kW V1 3, 14 20 kW DG 7, 10 − + 2.2 mF VO VREF 2, 15 10 kW 30 kW V2 2.2 mF 4 5, 12 1, 16 2.2 mF 8.2 kW 8, 9 200 pF Figure 3. Typical Test Circuit 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 NE570 Compandor, which offers a pair of high performance gain control circuits featuring low distortion (