LM1036 Dual DC Operated Tone/Volume/Balance Circuit General Description Features The LM1036 is a DC controlled tone (bass/treble), volume and balance circuit for stereo applications in car radio, TV and audio systems. An additional control input allows loudness compensation to be simply effected. Four control inputs provide control of the bass, treble, balance and volume functions through application of DC voltages from a remote control system or, alternatively, from four potentiometers which may be biased from a zener regulated supply provided on the circuit. Each tone response is defined by a single capacitor chosen to give the desired characteristic. n n n n n Wide supply voltage range, 9V to 16V Large volume control range, 75 dB typical Tone control, ± 15 dB typical Channel separation, 75 dB typical Low distortion, 0.06% typical for an input level of 0.3 Vrms n High signal to noise, 80 dB typical for an input level of 0.3 Vrms n Few external components required Block and Connection Diagram Dual-In-Line Package DS005142-1 Order Number LM1036N See NS Package Number N20A © 1999 National Semiconductor Corporation DS005142 www.national.com LM1036 Dual DC Operated Tone/Volume/Balance Circuit January 1995 Absolute Maximum Ratings (Note 1) Storage Temperature Range Power Dissipation Lead Temp. (Soldering, 10 seconds) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Control Pin Voltage (Pins 4, 7, 9, 12, 14) Operating Temperature Range −65˚C to +150˚C 1W 260˚C Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. 16V VCC 0˚C to +70˚C Electrical Characteristics VCC = 12V, TA = 25˚C (unless otherwise stated) Parameter Supply Voltage Range Conditions Min Pin 11 Supply Current Zener Regulated Output Typ 9 35 Units 16 V 45 mA 5 mA Pin 17 Voltage 5.4 Current Maximum Output Voltage Max Pins 8, 13; f = 1 kHz VCC = 9V, Maximum Gain V 0.8 Vrms VCC = 12V 0.8 1.0 Vrms Maximum Input Voltage Pins 2, 19; f = 1 kHz, VCC 2V Gain = −10 dB 1.3 1.6 Vrms Input Resistance 20 30 kΩ Volume Control Range Pins 2, 19; f = 1 kHz Pins 8, 13; f = 1 kHz V(Pin 12) = V(Pin 17); f = 1 kHz f = 1 kHz Gain Tracking f = 1 kHz Channel 1–Channel 2 0 dB through −40 dB 1 2 dB Balance Control Range −40 dB through −60 dB Pins 8, 13; f = 1 kHz 1 dB Output Resistance Maximum Gain −2 0 70 75 −26 Bass Control Range (Note 3) Treble Control Range (Note 3) Total Harmonic Distortion Channel Separation Signal/Noise Ratio f = 40 Hz, Cb = 0.39 µF V(Pin 14) = V(Pin 17) 2 dB dB 3 dB −20 dB 12 15 18 dB V(Pin 14) = 0V f = 16 kHz, Ct, = 0.01 µF V(Pin 4) = V(Pin 17) −12 −15 −18 dB 12 15 18 dB V(Pin 4) = 0V f = 1 kHz, VIN = 0.3 Vrms Gain = 0 dB −12 −15 −18 dB 0.06 0.3 % Gain = −30 dB f = 1 kHz, Maximum Gain 60 Unweighted 100 Hz–20 kHz Maximum Gain, 0 dB = 0.3 Vrms CCIR/ARM (Note 4) Gain = 0 dB, VIN = 0.3 Vrms Gain = −20 dB, VIN = 1.0 Vrms Output Noise Voltage at Ω 20 75 CCIR/ARM (Note 4) 0.03 % 75 dB 80 dB 79 dB 72 dB 10 16 µV Minimum Gain Supply Ripple Rejection Control Input Currents 200 mVrms, 1 kHz Ripple Pins 4, 7, 9, 12, 14 (V = 0V) Frequency Response −1 dB (Flat Response 35 250 20 Hz–16 kHz) Note 2: The maximum permissible input level is dependent on tone and volume settings. See Application Notes. www.national.com 50 −0.6 2 dB −2.5 µA kHz Electrical Characteristics (Continued) Note 3: The tone control range is defined by capacitors Cb and Ct. See Application Notes. Note 4: Gaussian noise, measured over a period of 50 ms per channel, with a CCIR filter referenced to 2 kHz and an average-responding meter. Typical Performance Characteristics Volume Control Characteristics Balance Control Characteristic Tone Control Characteristic DS005142-22 DS005142-21 DS005142-20 Tone Characteristic (Gain vs Frequency) Tone Characteristic (Gain vs Frequency) DS005142-23 Input Signal Handling vs Supply Voltage Loudness Compensated Volume Characteristic DS005142-25 DS005142-24 Channel Separation vs Frequency THD vs Gain DS005142-27 DS005142-28 DS005142-26 3 www.national.com Typical Performance Characteristics Loudness Control Characteristic (Continued) Output Noise Voltage vs Gain THD vs Input Voltage DS005142-31 DS005142-29 DS005142-30 Application Notes maximum boost defined by Cb and Ct. There is no loudness compensation when pin 7 is connected to pin 17. Pin 7 can be connected to pin 12 to give the loudness compensated volume characteristic as illustrated without the addition of further external components. (Tone settings are for flat response, Cb and Ct as given in Application Circuit.) Modification to the loudness characteristic is possible by changing the capacitors Cb and Ct for a different basic response or, by a resistor network between pins 7 and 12 for a different threshold and slope. TONE RESPONSE The maximum boost and cut can be optimized for individual applications by selection of the appropriate values of Ct (treble) and Cb (bass). The tone responses are defined by the relationships: SIGNAL HANDLING The volume control function of the LM1036 is carried out in two stages, controlled by the DC voltage on pin 12, to improve signal handling capability and provide a reduction of output noise level at reduced gain. The first stage is before the tone control processing and provides an initial 15 dB of gain reduction, so ensuring that the tone sections are not overdriven by large input levels when operating with a low volume setting. Any combination of tone and volume settings may be used provided the output level does not exceed 1 Vrms, VCC = 12V (0.8 Vrms, VCC = 9V). At reduced gain ( < −6 dB)the input stage will overload if the input level exceeds 1.6 Vrms, VCC = 12V (1.1 Vrms, VCC = 9V). As there is volume control on the input stages, the inputs may be operated with a lower overload margin than would otherwise be acceptable, allowing a possible improvement in signal to noise ratio. Where ab = at = 0 for maximum bass and treble boost respectively and ab = at = 1 for maximum cut. For the values of Cb and Ct of 0.39 µF and 0.01 µF as shown in the Application Circuit, 15 dB of boost or cut is obtained at 40 Hz and 16 kHz. ZENER VOLTAGE A zener voltage (pin 17 = 5.4V) is provided which may be used to bias the control potentiometers. Setting a DC level of one half of the zener voltage on the control inputs, pins 4, 9, and 14, results in the balanced gain and flat response condition. Typical spread on the zener voltage is ± 100 mV and this must be taken into account if control signals are used which are not referenced to the zener voltage. If this is the case, then they will need to be derived with similar accuracy. LOUDNESS COMPENSATION A simple loudness compensation may be effected by applying a DC control voltage to pin 7. This operates on the tone control stages to produce an additional boost limited by the www.national.com 4 Application Circuit DS005142-3 Applications Information Figure 2 and Figure 3 show the effect of changing the response defining capacitors Ct and Cb to 2Ct, Cb/2 and 4Ct, Cb/4 respectively, giving increased tone control ranges. The values of the bypass capacitors may become significant and affect the lower frequencies in the bass response curves. OBTAINING MODIFIED RESPONSE CURVES The LM1036 is a dual DC controlled bass, treble, balance and volume integrated circuit ideal for stereo audio systems. In the various applications where the LM1036 can be used, there may be requirements for responses different to those of the standard application circuit given in the data sheet. This application section details some of the simple variations possible on the standard responses, to assist the choice of optimum characteristics for particular applications. TONE CONTROLS Summarizing the relationship given in the data sheet, basically for an increase in the treble control range Ct must be increased, and for increased bass range Cb must be reduced. Figure 1 shows the typical tone response obtained in the standard application circuit. (Ct = 0.01 µF, Cb = 0.39 µF). Response curves are given for various amounts of boost and cut. DS005142-5 FIGURE 2. Tone Characteristic (Gain vs Frequency) DS005142-6 DS005142-4 FIGURE 3. Tone Characteristic (Gain vs Frequency) FIGURE 1. Tone Characteristic (Gain vs Frequency) 5 www.national.com Applications Information (Continued) Figure 4 shows the effect of changing Ct and Cb in the opposite direction to Ct/2, 2Cb respectively giving reduced control ranges. The various results corresponding to the different Ct and Cb values may be mixed if it is required to give a particular emphasis to, for example, the bass control. The particular case with Cb/2, Ct is illustrated in Figure 5. Restriction of Tone Control Action at High or Low Frequencies It may be desired in some applications to level off the tone responses above or below certain frequencies for example to reduce high frequence noise. This may be achieved for the treble response by including a resistor in series with Ct. The treble boost and cut will be 3 dB less than the standard circuit when R = XC. A similar effect may be obtained for the bass response by reducing the value of the AC bypass capacitors on pins 5 (channel 1) and 16 (channel 2). The internal resistance at these pins is 1.3 kΩ and the bass boost/cut will be approximately 3 dB less with XC at this value. An example of such modified response curves is shown in Figure 6. The input coupling capacitors may also modify the low frequency response. It will be seen from Figure 2 and Figure 3 that modifying Ct and Cb for greater control range also has the effect of flattening the tone control extremes and this may be utilized, with or without additional modification as outlined above, for the most suitable tone control range and response shape. DS005142-7 FIGURE 4. Tone Characteristic (Gain vs Frequency) DS005142-8 FIGURE 5. Tone Characteristic (Gain vs Frequency) Other Advantages of DC Controls The DC controls make the addition of other features easy to arrange. For example, the negative-going peaks of the output amplifiers may be detected below a certain level, and used to bias back the bass control from a high boost condition, to prevent overloading the speaker with low frequency components. LOUDNESS CONTROL The loudness control is achieved through control of the tone sections by the voltage applied to pin 7; therefore, the tone and loudness functions are not independent. There is normally 1 dB more bass than treble boost (40 Hz–16 kHz) with loudness control in the standard circuit. If a greater difference is desired, it is necessary to introduce an offset by means of Ct or Cb or by changing the nominal control voltage ranges. DS005142-9 FIGURE 6. Tone Characteristic (Gain vs Frequency) Figure 7 shows the typical loudness curves obtained in the standard application circuit at various volume levels (Cb = 0.39 µF). DS005142-10 FIGURE 7. Loudness Compensated Volume Characteristic Figure 8 and Figure 9 illustrate the loudness characteristics obtained with Cb changed to Cb/2 and Cb/4 respectively, Ct www.national.com 6 Applications Information (Continued) being kept at the nominal 0.01 µF. These values naturally modify the bass tone response as in Figure 2 and Figure 3. With pins 7 (loudness) and 12 (volume) directly connected, loudness control starts at typically −8 dB volume, with most of the control action complete by −30 dB. Figure 10 and Figure 11 show the effect of resistively offsetting the voltage applied to pin 7 towards the control reference voltage (pin 17). Because the control inputs are high impedance, this is easily done and high value resistors may be used for minimal additional loading. It is possible to reduce the rate of onset of control to extend the active range to −50 dB volume control and below. The control on pin 7 may also be divided down towards ground bringing the control action on earlier. This is illustrated in Figure 12, With a suitable level shifting network between pins 12 and 7, the onset of loudness control and its rate of change may be readily modified. DS005142-12 FIGURE 9. Loudness Compensated Volume Characteristic DS005142-13 FIGURE 10. Loudness Compensated Volume Characteristic DS005142-11 FIGURE 8. Loudness Compensated Volume Characteristic DS005142-14 FIGURE 11. Loudness Compensated Volume Characteristic DS005142-15 FIGURE 12. Loudness Compensated Volume Characteristic 7 www.national.com Applications Information USE OF THE LM1036 ABOVE AUDIO FREQUENCIES The LM1036 has a basic response typically 1 dB down at 250 kHz (tone controls flat) and therefore by scaling Cb and Ct, it is possible to arrange for operation over a wide frequency range for possible use in wide band equalization applications. As an example Figure 15 shows the responses obtained centered on 10 kHz with Cb = 0.039 µF and Ct = 0.001 µF. (Continued) When adjusted for maximum boost in the usual application circuit, the LM1036 cannot give additional boost from the loudness control with reducing gain. If it is required, some additional boost can be obtained by restricting the tone control range and modifying Ct, Cb, to compensate. A circuit illustrating this for the case of bass boost is shown in Figure 13. The resulting responses are given in Figure 14 showing the continuing loudness control action possible with bass boost previously applied. DS005142-16 FIGURE 13. Modified Application Circuit for Additional Bass Boost with Loudness Control DS005142-18 DS005142-17 FIGURE 15. Tone Characteristic (Gain vs Frequency) FIGURE 14. Loudness Compensated Volume Characteristic www.national.com 8 Simplified Schematic Diagram (One Channel) DS005142-19 *Connections reversed 9 www.national.com LM1036 Dual DC Operated Tone/Volume/Balance Circuit Physical Dimensions inches (millimeters) unless otherwise noted Molded Dual-In-Line Package (N) Order Number LM1036N NS Package Number N20A LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 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