LM7705 Low Noise Negative Bias Generator General Description Features The LM7705 is a switched capacitor voltage inverter with a low noise, −0.23V fixed negative voltage regulator. This device is designed to be used with low voltage amplifiers to enable the amplifiers output to swing to zero volts. The −0.23 volts is used to supply the negative supply pin of an amplifier while maintaining less then 5.5 volts across the amplifier. Railto-Rail output amplifiers cannot output zero volts when operating from a single supply voltage and can result in error accumulation due to amplifier output saturation voltage being amplified by following gain stages. A small negative supply voltage will prevent the amplifiers output from saturating at zero volts and will help maintain an accurate zero through a signal processing chain. Additionally, when an amplifier is used to drive an ADC’s input, it can output a zero voltage signal and the full input range of an ADC can be used. The LM7705 has a shutdown pin to minimize standby power consumption ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Regulated output voltage Output voltage tolerance Output voltage ripple Max output current Supply voltage Conversion efficiency Quiescent current Shutdown current Turn on time Operating temperature range 8-Pin MSOP Package −0.232V 5% 4 mVPP 26 mA 3V to 5.25V up to 98% 78 µA 20 nA 500 µs −40°C to 125°C Applications ■ True zero amplifier output ■ Portable instrumentation ■ Low voltage split power supplies Typical Application 20173001 © 2009 National Semiconductor Corporation 201730 www.national.com LM7705 Low Noise Negative Bias Generator June 10, 2009 LM7705 Charge Device Model Storage Temp. Range Junction Temperature (Note 7) Mounting Temperature Infrared or Convection (20 sec) Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage VDD - VSS SD ESD Tolerance (Note 2) Human Body Model For input pins only For all other pins Machine Model +5.75V VDD+0.3V, VSS-0.3V 750V −65°C to 150°C 150°C max 260°C Operating Ratings Supply Voltage ( VDD to GND) Supply Voltage ( VDD wrt VOUT) Temperature Range 2000V 2000V 200V 3V to 5.25V 3.23V to 5.48V −40°C to 125°C Thermal Resistance (θJA ) 8-Pin MSOP 253°C/W 3.3V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TA = 25°C, VDD = 3.3V, VSS = 0V, SD = 0V, CFLY= 5 µF, CRES = 22 µF, COUT = 22 µF. Boldface limits apply at temperature extremes (Note 5). Symbol VOUT Parameter Output Voltage Conditions Min (Note 6) Typical (Note 7) Max (Note 6) IOUT = 0 mA −0.242 −0.251 −0.232 −0.219 −0.209 IOUT = −20 mA −0.242 −0.251 −0.226 −0.219 −0.209 V VR Output Voltage Ripple IOUT = −20 mA IS Supply Current No Load ISD Shutdown Supply Current SD = VDD 20 nA ηPOWER Current Conversion Efficiency −5 mA ≤ IOUT ≤ −20 mA 98 % ηPOWER Current Conversion Efficiency IOUT = −5 mA 98 % tON Turn On Time IOUT = −5 mA 500 μs t OFF Turn Off Time IOUT = −5 mA 700 μs tOFF CP Turn Off Time Charge Pump IOUT = −5 mA 11 ZOUT Output Impedance −1 mA ≤ IOUT ≤ −20 mA IO_MAX Maximum Output Current VOUT < −200 mV fOSC Oscillator Frequency VIL Shutdown Input Low VIH Shutdown Input High IC Shutdown Pin Input Current SD = VDD Load Regulation 0 mA ≤ IOUT ≤ −20 mA Line Regulation 3V ≤ VDD ≤ 5.25V (No Load) www.national.com 4 Units 50 78 0.23 mVPP 100 150 μs 0.8 1.3 -26 kHz 1.6 1.25 1.85 2.15 V V 50 2 Ω mA 92 -0.2 μA pA 0.12 0.6 0.85 %/mA 0.29 0.7 1.1 %/V Unless otherwise specified, all limits are guaranteed for TA = 25°C, VDD = 5.0V, VSS = 0V, SD = 0V, CFLY = 5 µF, CRES = 22 µF, COUT = 22 µF. Boldfacelimits apply at temperature extremes (Note 5). Symbol VOUT Parameter Output Voltage Conditions Min (Note 6) Typical (Note 7) Max (Note 6) IOUT = 0 mA −0.242 −0.251 −0.233 −0.219 −0.209 IOUT = −20 mA −0.242 −0.251 −0.226 −0.219 −0.209 4 Units V VR Output Voltage Ripple IOUT = −20 mA IS Supply Current No Load ISD Shutdown Supply Current SD = VDD 20 nA ηPOWER Current Conversion Efficiency −5 mA ≤ IOUT ≤ −20 mA 98 % ηPOWER Current Conversion Efficiency IOUT = −5 mA 98 % tON Turn On Time IOUT = −5 mA 200 μs t OFF Turn Off Time IOUT = −5 mA 700 μs tOFF CP Turn Off Time Charge Pump IOUT = −5 mA 11 μs ZOUT Output Impedance −1 mA ≤ IOUT ≤ −20 mA IO_MAX Maximum Output Current VOUT < − 200 mV fOSC Oscillator Frequency VIL Shutdown Input Low VIH Shutdown Input High IC Shutdown Pin Input Current SD = VDD Load Regulation 0 mA ≤ IOUT ≤ −20 mA Line Regulation 3V ≤ VDD ≤ 5.25V (No Load) 60 103 0.26 mVPP 135 240 μA 0.8 1.3 −35 Ω mA 91 kHz 2.55 1.95 V 2.8 3.25 V 50 −0.2 pA 0.14 0.6 0.85 %/mA 0.29 0.7 1.1 %/V Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine model, applicable std JESD22–A115–A (ESSD MM srd of JEDEC). Field induced Charge-Device Model, applicable std. JESD22–C101–C. (ESD FICDM std of JEDEC). Note 3: The maximum power dissipation is a function of TJ(MAX), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) - TA)/ θJA. All numbers apply for packages soldered directly onto a PC board. Note 4: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA. Note 5: Boldface limits apply to temperature range of −40°C to 125°C Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material. 3 www.national.com LM7705 5.0V Electrical Characteristics LM7705 Connection Diagram 8-Pin MSOP 20173002 Top View Pin Descriptions Pin Number Symbol 1 CF+ CFLY Positive Capacitor Connection Description 2 VSS Power Ground 3 SD Shutdown Pin If SD pin is LOW, device is ON If SD pin is HIGH, device is OFF 4 VDD Positive Supply Voltage 5 VSS Power Ground 6 VOUT Output Voltage 7 CRES Reserve Capacitor Connection 8 CF- CFLY Negative Capacitor Connection Ordering Information Package Part Number Package Marking LM7705MM 8-Pin MSOP LM7705MME Transport Media NSC Drawing 1k Units Tape and Reel F26A 250 Units Tape and Reel LM7705MMX MUA08A 3.5k Units Tape and Reel Block Diagram 20173003 LM7705 www.national.com 4 LM7705 Typical Performance Characteristics VDD = 3.3V and TA = 25°C unless otherwise noted. Output Voltage vs. Supply Voltage Supply Current vs. Supply Voltage 20173010 20173011 Output Voltage vs. Output Current Output Voltage vs. Output Current 20173012 20173013 Output Voltage Ripple vs. Temperature Output Voltage Ripple vs. Temperature 20173014 20173015 5 www.national.com LM7705 Supply Current vs. Output Current Supply Current vs. Output Current 20173016 20173017 Current Conversion Efficiency vs. Output Current Current Conversion Efficiency vs. Output Current 20173018 20173019 Turn On Time Turn On Time 20173020 www.national.com 20173021 6 LM7705 Load Regulation vs. Temperature Load Regulation vs. Temperature 20173023 20173022 Transient Response Transient Response 20173024 20173025 Transient Response Transient Response 20173029 20173030 7 www.national.com LM7705 Output voltage vs. shutdown Voltage Supply Current vs. Shutdown Voltage 20173026 20173027 Oscillator Frequency vs. Temperature 20173028 www.national.com 8 LM7705 Application Information This applications section will give a description of the functionality of the LM7705. The LM7705 is a switched capacitor voltage inverter with a low noise, −0.23V fixed negative bias output. The part will operate over a supply voltage range of 3 to 5.25 Volt. Applying a logical low level to the SD input will activate the part, and generate a fixed −0.23V output voltage. The part can be disabled; the output is switched to ground level, by applying a logical high level to the SD input of the part. 20173031 FIGURE 2. LM7705 Architecture The architecture given in Figure 2 shows that the LM7705 contains 3 functional blocks: • Pre-regulator • Charge pump inverter • Post-regulator The output voltage is stabilized by: • Controlling the power supplied from the power supply to the charge pump input by the pre-regulator • The power supplied from the charge pump output to the load by the post-regulator. A more detailed block diagram of the negative bias generator is given in Figure 3. The control of the pre-regulator is based on measuring the output voltage of the charge pump. The goal of the post-regulator is to provide an accurate controlled negative voltage at the output, and acts as a low pass filter to attenuate the output voltage ripple. The voltage ripple is a result of the switching behavior of the charge pump and is dependent of the output current and the values of the used capacitors. FUNCTIONAL DESCRIPTION The LM7705, low noise negative bias generator, can be used for many applications requiring a fixed negative voltage. A key application for the LM7705 is an amplifier with a true zero output voltage using the original parts, while not exceeding the maximum supply voltage ratings of the amplifier. The voltage inversion in the LM7705 is achieved using a switched capacitor technique with two external capacitors (CFLY and CRES). An internal oscillator and a switching network transfers charge between the two storage capacitors. This switched capacitor technique is given in Figure 1. 20173034 FIGURE 1. Voltage Inverter The internal oscillator generates two anti-phase clock signals. Clock 1 controls switches S1 and S2. Clock 2 controls switches S3 and S4. When Switches S1 and S2 are closed, capacitor CFLY is charged to V+. When switches S3 and S4 are closed (S1 and S2 are open) charge from CFLY is transferred to CRES and the output voltage OUT is equal to -V+. Due to the switched capacitor technique a small ripple will be present at the output voltage, with a frequency of the oscillator. The magnitude of this ripple will increase for increasing output currents. The magnitude of the ripple can be influenced by changing the values of the used capacitors. In the next section a more detailed technical description of the LM7705 will be given. 20173003 FIGURE 3. Charge Pump Inverter with Input/Output Control In the next section a simple equation will be derived, that shows the relation between the ripple of the output current, the frequency of the internal clock generator and the value of the capacitor placed at the output of the LM7705. Charge Pump Theory This section uses a simplified but realistic equivalent circuit that represents the basic function of the charge pump. The schematic is given in Figure 4. TECHNICAL DESCRIPTION As indicated in the functional description section, the main function of the LM7705 is to supply a stabilized negative bias voltage to a load, using only a positive supply voltage. A general block diagram for this charge pump inverter is given in Figure 2. The external power supply and load are added in this diagram as well. 20173033 FIGURE 4. Charge Pump 9 www.national.com LM7705 When the switch is in position A, capacitor CFLY will charge to voltage V1. The total charge on capacitor CFLY is Q1 = CFLY x V 1. The switch then moves to position B, discharging CFLY to voltage V2. After this discharge, the charge on CFLY will be Q2 = CFLY x V2. Note that the charge has been transferred from the source V1 to the output V2. The amount of charge transferred is: Key Specification The key specifications for the LM7705 are given in the following overview: Supply Voltage The LM7705 will operate over a supply voltage range of 3V to 5.25V, and meet the specifications given in the Electrical Table. Supply voltage lower than 3.3 Volt will decrease performance (The output voltage will shift towards zero, and the current sink capabilities will decrease) A voltage higher than 5.25V will exceed the Abs Max ratings and therefore damage the part. Output Voltage/ Line Regulation The fixed and regulated output voltage of −0.23 V has tight limits, as indicated in the Electrical Characteristics table, to guarantee a stable voltage level. The usage of the pre- and post regulator in combination with the charge pump inverter ensures good line regulation of 0.29%/V Output current/ Load regulation The LM7705 can sink currents > 26 mA, causing an output voltage shift to −200 mV. A specified load-regulation of 0.14% mA/V ensures a minor voltage deviation for load current up to 20 mA. Quiescent current The LM7705 consumes a quiescent current less than 100 µA. Sinking a load current, will result in a current conversion efficiency better than 90%, even for load currents of 1 mA, increasing to 98% for a current of 5mA. (1) When the switch changes between A and B at a frequency f, the charge transfer per unit time, or current is: (2) The switched capacitor network can be replaced by an equivalent resistor, as indicated in Figure 5. 20173032 FIGURE 5. Switched Capacitor Equivalent Circuit The value of this resistor is dependent on both the capacitor value and the switching frequency as given in Equation 3 In the next section a general amplifier application requiring a true-zero output, will be discussed, showing an increased performance using the LM7705. (3) The value for REQ can be calculated from Equation 3 and is given in Equation 4 GENERAL AMPLIFIER APPLICATION This section will discuss a general DC coupled amplifier application. First, one of the limitations of a DC coupled amplifier is discussed. This is illustrated with two application examples. A solution is a given for solving this limitation by using the LM7705. (4) Equation 4 show that the value for the resistance at an increased internal switching frequency, allows a lower value for the used capacitor. www.national.com Due to the architecture of the output stage of general amplifiers, the output transistors will saturate. As a result, the output of a general purpose op amp can only swing to a few 100 mV of the supply rails. Amplifiers using CMOS technology do have a lower output saturation voltage. This is illustrated in Figure 6. E.g. National Semiconductors LM7332 can swing to 200 mV to the negative rail, for a 10 kΩ load, over all temperatures. 10 LM7705 20173035 FIGURE 8. Sensor with DC Output and a Single Supply Op Amp The sensor has a DC output signal that is amplified by the op amp. For an optimal signal-to-noise ratio, the output voltage swing of the op amp should be matched to the input voltage range of the Analog to Digital Converter (ADC). For the high side of the range this can be done by adjusting the gain of the op amp. However, the low side of the range can’t be adjusted and is affected by the output swing of the op amp. Example: Assume the output voltage range of the sensor is 0 to 90 mV. The available op amp is a LMP7701, using a 0/+5V supply voltage, having an output drive of 50 mV from both rails. This results in an output range of 50 mV to 4.95V. Let choose two resistors values for RG1 and RF1 that result in a gain of 50x. The output of the LMP7701 should swing from 0 mV to 4.5V. The higher value is no problem, however the lower swing is limited by the output of the LM7701 and won’t go below 50 mV instead of the desired 0V, causing a nonlinearity in the sensor reading. When using a 12 bit ADC, and a reference voltage of 5 Volt (having an ADC step size of approximate 1.2 mV), the output saturation results in a loss of the lower 40 quantization levels of the ADCs dynamic range. 20173040 FIGURE 6. Limitation of the Output of an Amplifier The introduction of operational amplifiers with output Rail-torail drive capabilities is a strong improvement and the (output) performance of op amps is for many applications no longer a limiting factor. For example, National Semiconductors LMP7701 (a typical rail-to-rail op amp), has an output drive capability of only 50 mV over all temperatures for a 10 kΩ load resistance. This is close to the lower supply voltage rail. However, for true zero output applications with a single supply, the saturation voltage of the output stage is still a limiting factor. This limitation has a negative impact on the functionality of true zero output applications. This is illustrated in Figure 7. Two-Stage, Single Supply True Zero Amplifier This sensor application produces a DC signal, amplified by a two cascaded op amps, having a single supply. The output voltage of the second op amp is converted to the digital domain. Figure 9 shows the basic setup of this application. 20173041 FIGURE 7. Output Limitation for Single Supply True Zero Output Aapplication In the following section, two applications will be discussed, showing the limitations of the output stage of an op amp in a single supply configuration. • A single stage true zero amplifier, with a 12 bit ADC back end. • A dual stage true zero amplifier, with a 12 bit ADC back end. 20173036 One-stage, Single Supply True Zero Amplifier This application shows a sensor with a DC output signal, amplified by a single supply op amp. The output voltage of the op amp is converted to the digital domain using an Analog to Digital Converter (ADC). Figure 8 shows the basic setup of this application. FIGURE 9. Sensor with DC Output and a 2-Stage, Single Supply Op Amp. 11 www.national.com LM7705 • The sensor generates a DC output signal. In this case, a DC coupled, 2-stage amplifier is used. The output voltage swing of the second op amp should me matched to the input voltage range of the Analog to Digital Converter (ADC). For the high side of the range this can be done by adjusting the gain of the op amp. However, the low side of the range can’t be adjusted and is affected by the output drive of the op amp. Example: Assume; the output voltage range of the sensor is 0 to 90 mV. The available op amp is a LMP7702 (Dual LMP7701 op amp) that can be used for A1 and A2. The op amp is using a 0/+5V supply voltage, having an output drive of 50mV from both rails. This results in an output range of 50 mV to 4.95V for each individual amplifier. Let choose two resistors values for RG1 and RF1 that result in a gain of 10x for the first stage (A1) and a gain of 5x for the second stage (A2) The output of the A2 in the LMP7702 should swing from 0V to 4.5 Volt. This swing is limited by the 2 different factors: 1. The high voltage swing is no problem; however the low voltage swing is limited by the output saturation voltage of A2 from the LM7702 and won’t go below 50mV instead of the desired 0V. 2. Another effect has more impact. The output saturation voltage of the first stage will cause an offset for the input of the second stage. This offset of A1 is amplified by the gain of the second stage (10x in this example), resulting in an output offset voltage of 500mV. This is significantly more that the 50 mV (VDSAT) of A2. When using a 12 bit ADC, and a reference voltage of 5 Volt (having an ADC step size of approximate 1.2 mV), the output saturation results in a loss of the lower 400 quantization levels of the ADCs dynamic range. This will cause a major non-linearity in the sensor reading. Operates with only a single positive supply, and is therefore a much cheaper solution. • The LM7705 generates a negative supply voltage of only −0.23V. This is more than enough to create a True-zero output for most op amps. • In many applications, this “small” extension of the supply voltage range can be within the abs max rating for many op amps, so an expensive redesign is not necessary. In the next section a typical amplifier application will be evaluated. The performance of an amplifier will be measured in a single supply configuration. The results will be compared with an amplifier using a LM7705 supplying a negative voltage to the bias pin. TYPICAL AMPLIFIER APPLICATION This section shows the measurement results of a true zero output amplifier application with an analog to digital converter (ADC) used as back-end. The biasing of the op amp can be done in two ways: • A single supply configuration • A single supply in combination with the LM7705, extending the negative supply from ground level to a fixed -0.23 Voltage. Basic Setup The basic setup of this true zero output amplifier is given in Figure 11. The LMP7701 op amp is configured as a voltage follower to demonstrate the output limitation, due to the saturation of the output stage. The negative power supply pin of the op amp can be connected to ground level or to the output of the negative bias generator, to demonstrate the VDSAT effect at the output voltage range. Dual Supply, True Zero Amplifiers The limitations of the output stage of the op amp, as indicated in both examples, can be omitted by using a dual supply op amp. The output stage of the used op amp can then still swing from 50 mV of the supply rails. However, the functional output range of the op amp is now from ground level to a value near the positive supply rail. Figure 10 shows the output drive of an amplifier in a true zero output voltage application. 20173043 FIGURE 11. Typical True Zero Output Voltage Application with/without LM7705 20173042 The output voltage of the LMP7701 is converted to the digital domain using an ADC122S021. This is an 12 bit analog to digital converter with a serial data output. Data processing and graphical displaying is done with a computer. The negative power supply pin of the op amp can be connected to ground level or to the output of the negative bias generator, to demonstrate the effect at the output voltage range of the op amp. FIGURE 10. Amplifier output drive with a dual supply Disadvantages of this solution are: • The usage of a dual supply instead of a simple single supply is more expensive. • A dual supply voltage for the op amps requires parts that can handle a larger operating range for the supply voltage. If the op amps used in the current solution can’t handle this, a redesign can be required. A better solution is to use the LM7705. This low noise negative bias generator has some major advantages with respect to a dual supply solution: www.national.com 12 Measurement Results The output voltage range of the LMP7701 has been measured, especially the range to ground level. A small DC signal, with a voltage swing of 50 mVPP is applied to the input. The digitized output voltage of the op amp is measured over a given time period, when its negative supply pin is connected to ground level or connected to the output of the LM7705. Figure 12A and Figure 12B show the digitized output voltage of the LMP7701 op amp. Supply Voltage/Reference Voltage Supply voltage +5V ADC Voltage Reference +5V LMP7701 VDSAT (typical) 18 mV VDSAT (over temperature) 50 mV LM7705 Output voltage ripple 4 mVPP Output voltage noise 10 mVPP ADC Type ADC122S021 Resolution 12 bit Quantization level 5V/4096 = 1.2mV 20173045 20173044 (A) (B) FIGURE 12. Digitized Output Voltage without (A) and with (B) LM7705 • Figure 12A shows the digitized output voltage of the op amp when its negative supply pin is connected to ground level. The output of the amplifier saturates at a level of 14 mv (this is in line with the typical value of 18 mV given in the datasheet) The graph shows some fluctuations (1 bit quantization error). Figure 12B show the digitized output voltage of the op amp when its negative supply pin is connected to the output of the LM7705. Again, the graph shows some 1 bit quantization errors caused by the voltage ripple and output noise. In this case the op amps output level can reach the true zero output level. The graphs in Figure 12 show that: • With a single supply, the output of the amplifier is limited by the VDSAT of the output stage. • The amplifier can be used as a true zero output using a LM7705. • The quantization error of the digitized output voltage is caused by the noise and the voltage ripple. Using the LM7705 does not increase the quantization error in this set up. DESIGN RECOMMENDATIONS The LM7705 is a switched capacitor voltage inverter. This means that charge is transferred from different external capacitors, to generate a negative voltage. For this reason the part is very sensitive for contact resistance between the package and external capacitors. It’s also recommended to use low ESR capacitors for CFLY, CRES and COUT in combination with short traces. To prevent large variations at the VDD pin of the package it is recommended to add a decouple capacitor as close to the pin as possible. The output voltage noise can be suppressed using a small RF capacitor, will a value of e.g. 100 nF. 13 www.national.com LM7705 The key specifications of the used components are given in the next part of the section. LM7705 Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin MSOP NS Package Number MUA08A www.national.com 14 LM7705 Notes 15 www.national.com LM7705 Low Noise Negative Bias Generator Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Solutions www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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