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| EL4450C EL4450C Wideband Four-Quadrant Multiplier Features * Complete four-quadrant multiplier with output amp--requires no extra components * Good linearity of 0.3% * 90 MHz bandwidth for both X and Y inputs * Operates on 5V to 15V supplies * All inputs are differential * 400V/s slew rate General Description The EL4450C is a complete four-quadrant multiplier circuit. It offers wide bandwidth and good linearity while including a powerful output voltage amplifier, drawing modest supply current. The EL4450C operates on 5V supplies and has an analog input range of 2V, making it ideal for video signal processing. AC characteristics do not vary over the 5V to 15V supply range. The multiplier has an operational temperature range of -40C to +85C and are packaged in plastic 14-pin P-DIP and SO. Applications * * * * Modulation/Demodulation RMS computation Real-time power computation Nonlinearity correction/generation Ordering Information Part No. EL4450CN EL4450CS Temp. Range -40C to +85C -40C to +85C Package 14-Pin P-DIP 14-Lead SO Outline # MDP0031 MDP0027 Connection Diagrams January 1996 Rev B (c) 1995 Elantec, Inc. EL4450C EL4450C Wideband Four-Quadrant Multiplier Absolute Maximum Ratings (T V+ VS VIN VIN IIN Positive Supply Voltage V+ to V- Supply Voltage Voltage at any Input or Feedback Difference between Pairs of Inputs or Feedback Current into any Input or Feedback Pin A = 25 C) 16.5V 33V V+ to V6V 4 mA IOUT PD TA TS Output Current Maximum Power Dissipation Operating Temperature Range Storage Temperature Range 30 mA See Curves -40C to +85C -60C to +150C Important Note: All parameters having Min/Max specifications are guaranteed. The Test Level column indicates the specific device testing actually performed during production and Quality inspection. Elantec performs most electrical tests using modern high-speed automatic test equipment, specifically the LTX77 Series system. Unless otherwise noted, all tests are pulsed tests, therefor TJ = TC = TA. Test Level I II III IV V Test Procedure 100% production tested and QA sample tested per QA test plan QCX0002. 100% production tested at TA = 25C and QA sample tested at TA = 25C, TMAX and TMIN per QA test plan QCX0002. QA sample tested per QA test plan QCX0002. Parameter is guaranteed (but not tested) by Design and Characterization Data. Parameter is typical value at TA = 25C for information purposes only. Open-Loop DC Electrical Characteristics Power Supplies at 5V, TA = 25C, VFB = VOUT. Parameter VDIFF VCM VOS IB IOS Gain NLx NLy RIN CMRR PSRR VO ISC IS Description Differential Input Voltage--Clipping 0.2% nonlinearity Common-Mode Range of VDIFF = 0, VS = 5V VS = 15V Input Offset Voltage Input Bias Current Input Offset Current between XIN+ and XIN-, YIN+ and YIN-, REF and FB Gain Factor of VOUT = Gain x XIN+ x YIN Nonlinearity of X Input; XIN between -1V and +1V Nonlinearity of Y Input; YIN between -1V and +1V Input resistance Common-Mode Rejection Ratio, XIN and YIN Power-Supply Rejection Ratio, FB Output Voltage Swing (VIN = 0, VREF Varied) Output Short-Circuit Current Supply Current, VS = 15V VS = 5V VS = 15V XIN+ to XIN-, YIN+ to YIN-, REF to FB 70 60 2.5 12.5 40 0.45 2.5 12.5 Min 1.8 Typ 2.0 1.0 2.8 12.8 8 9 0.5 0.5 0.3 0.2 230 90 90 72 2.8 12.8 85 15.4 18 I I mA mA I I I dB dB V 35 20 4 0.55 0.7 0.35 Max Test Level I V I I I I I I I I V Units V V V V mV A A V/V2 % % k 2 EL4450C EL4450C Wideband Four-Quadrant Multiplier Closed-Loop AC Electrical Characteristics Power Supplies at 12V, TA = 25C, RL = 5003/4, CL = 15pF Parameter BW, -3 dB BW, 0.1 dB Peaking SR VN 0.1 dB Flatness Bandwidth Frequency Response Peaking Slew Rate, VOUT between -2V and +2V Input-Referred Noise Voltage Density 300 Description -3 dB Small-Signal Bandwidth, X or Y Min Typ 90 10 1.0 400 100 Max Test Level V V V I V Units MHz MHz dB V/s nV/Hz Test Circuit Note: For typical performance curves, RF = 0, RG = x, VS = 5V, RL = 5003/4, and CL = 15 pF unless otherwise noted. Typical Performance Curves Transfer Function of X Input for Various Y Inputs Transfer Function of Y Input for Various X Inputs 3 EL4450C EL4450C Wideband Four-Quadrant Multiplier Frequency Response for Various Feedback Divider Ratios Frequency Response for Various RL, CL VS = 5V Frequency Response for Various RL, CL VS = 15V X Input Frequency Response for Various Y DC Inputs Y Input Frequency Response for Various X DC Inputs -3 dB Bandwidth and Peaking vs Supply Voltage Change in Bandwidth and Peaking vs Temperature Total Harmonic Distortion of X Input vs Frequency Total Harmonic Distortion of Y Input vs Frequency 4 EL4450C EL4450C Wideband Four-Quadrant Multiplier Slew Rate vs Supply Voltage Slew Rate vs Die Temperature CMRR vs Frequency Input Voltage Noise vs Frequency Nonlinearity of X Input Nonlinearity of Y Input Bias Current vs Die Temperature Common-Mode Input Range vs Supply Voltage 5 EL4450C EL4450C Wideband Four-Quadrant Multiplier Supply Current vs Die Temperature Supply Current vs Supply Voltage 14-Pin Package Power Dissipation vs Ambient Temperature 6 EL4450C EL4450C Wideband Four-Quadrant Multiplier Applications Information The EL4450 is a complete four-quadrant multiplier with 90 MHz bandwidth. It has three sets of inputs; a differential multiplying X-input, a differential multiplying Yinput, and another differential input which is used to complete a feedback loop with the output. Here is a typical connection: Figure 1. The gain of the feedback divider is H, and H = RG/(RG + RF). The transfer function of the part is VOUT = AO x (1/2 x ((VINX+-VINX-) x (VINY+-VINY-)) + (VREF-VFB)). VFB is connected to VOUT through a feedback network, so V FB = H*V OUT . A O is the open-loop gain of the amplifier, and is about 600. The large value of AO drives (1/2 x ((VINX+-VINX-) x (VINY+-VINY-)) + (VREF-VFB))0. Rearranging and substituting for VREF VOUT = (1/2 x ((VINX+-VINX-) x (VINY+-VINY-)) +VREF)/H, or VOUT = (XY/2 + VREF)/H used to create more of a frequency-compensated divider. The value of the capacitor should scale with the parasitic capacitance at the FB input. It is also practical to place small capacitors across both the feedback resistors (whose values maintain the desired gain) to swamp out parasitics. For instance, two 10 pF capacitors across equal divider resistors for a maximum gain of 1 will dominate parasitic effects and allow a higher divider resistance. The REF pin can be used as the output's ground reference, or for DC offsetting of the output, or it can be used to sum in another signal. Thus the output is equal to one-half the product of X and Y inputs and offset by VREF, all gained up by the feedback divider ratio. The EL4450 is stable for a direct connection between VOUT and FB, and the feedback divider may be used for higher output gain, although with the traditional loss of bandwidth. It is important to keep the feedback divider's impedance at the FB terminal low so that stray capacitance does not diminish the loop's phase margin. The pole caused by the parallel impedance of the feedback resistors and stray capacitance should be at least 150 MHz; typical strays of 3 pF thus require a feedback impedance of 3603/4 or less, Alternatively, a small capacitor across RF can be 7 Input Connections The input transistors can be driven from resistive and capacitive sources, but are capable of oscillation when presented with an inductive input. It takes about 80 nH of series inductance to make the inputs actually oscillate, equivalent to four inches of unshielded wiring or about 6 of unterminated input transmission line. The oscillation has a characteristic frequency of 500 MHz. Placing one's finger (via a metal probe) or an oscilloscope probe on the input will kill the oscillation. Normal high-frequency construction obviates any such problems, where the input source is reasonably close to the input. If this is EL4450C EL4450C Wideband Four-Quadrant Multiplier not possible, one can insert series resistors of around to 513/4 to de-Q the inputs. * RPAR is the parallel of all resistors loading the output For instance, the EL4450C draws a maximum of 18 mA. With light loading, RPARx and the dissipation with 5V supplies is 180 mW. The maximum supply voltage that the device can run on for a given PD and the other parameters is VS,max = (PD + VO2/RPAR)/(2IS + VO/RPAR) Signal Amplitudes Signal input common-mode voltage must be between (V-) + 2.5V and (V+) -2.5V to ensure linearity. Additionally, the differential voltage on any input stage must be limited to 6V to prevent damage. The differential signal range is 2V in the EL4450C. The input range is substantially constant with temperature. The maximum dissipation a package can offer is PD,max = (TJ,max-TA,max)/JA The Ground Pin The ground pin draws only 6 A maximum DC current, and may be biased anywhere between (V-) +2.5V and (V+) -3.5V. The ground pin is connected to the IC's substrate and frequency compensation components. It serves as a shield within the IC and enhances input stage CMRR over frequency, and if connected to a potential other than ground, it must be bypassed. Where TJ,max is the maximum junction temperature, 150C for reliability, less to retain optimum electrical performance TA,max is the ambient temperature, 70C for commercial and 85C for industrial range JA is the thermal resistance of the mounted package, obtained from data sheet dissipation curves The more difficult case is the SO-14 package. With a maximum junction temperature of 150C and a maxim u m a m b i e n t t e m pe r a t u r e o f 8 5 C , t he 6 5 C temperature rise and package thermal resistance of 120/W gives a dissipation of 542 mW at 85C. This allows the full maximum operating supply voltage unloaded, but reduced if loaded significantly. Power Supplies The EL4450C works well on supplies from 3V to 15V. The supplies may be of different voltages as long as the requirements of the GND pin are observed (see the Ground Pin section for a discussion). The supplies should be bypassed close to the device with short leads. 4.7 F tantalum capacitors are very good, and no smaller bypasses need be placed in parallel. Capacitors as low as 0.01 F can be used if small load currents flow. Single-polarity supplies, such as +12V with +5V can be used, where the ground pin is connected to +5V and Vto ground. The inputs and outputs will have to have their levels shifted above ground to accommodate the lack of negative supply. The power dissipation of the EL4450C increases with power supply voltage, and this must be compatible with the package chosen. This is a close estimate for the dissipation of a circuit: PD =2*IS,max*VS + (VS-VO)*VO/RPAR Output Loading The output stage is very powerful. It typically can source 85 mA and sink 120 mA. Of course, this is too much current to sustain and the part will eventually be destroyed by excessive dissipation or by metal traces on the die opening. The metal traces are completely reliable while delivering the 30 mA continuous output given in the Absolute Maximum Ratings table in this data sheet, or higher purely transient currents. Gain accuracy degrades only 0.2% from no load to 1003/4 load. Heavy resistive loading will degrade frequency response and video distortion for loads < 1003/4. Capacitive loads will cause peaking in the frequency response. If a capacitive load must be driven, a smallvalued series resistor can be used to isolate it. 123/4 to 513/4 should suffice. A 223/4 series resistor will limit peaking to 2.5 dB with even a 220 pF load. where * IS,max is the maximum supply current * VS is the supply voltage (assumed equal) * VO is the output voltage 8 EL4450C EL4450C Wideband Four-Quadrant Multiplier Mixer Applications Because of its lower distortion levels, the Y input is the better choice for a mixer's signal port. The X input would receive oscillator amplitudes of about 1V RMS maximum. Carrier suppression is initially limited by the offset voltage of the Y input, 20 mV maximum, and is about 37 dB worst-case. Better suppression can be obtained by nulling the offset of the X input. Similarly, nulling the offset of the Y input will improve signal-port suppression. Driving an input differentially will also maximize feedthrough suppression at frequencies beyond 10 MHz. AC Level Detectors Square-law converters are commonly used to convert AC signals to DC voltages corresponding to the original amplitude in subsystems like automatic gain controls (AGC's) and amplitude-stabilized oscillators. Due to the controlled AC amplitudes, the inputs of the multiplier will see a relatively constant signal level. Best performance will be obtained for inputs between 200 mVRMS and 1 VRMS. The traditional use of the EL4450C as an AGC detector and control loop would be: Figure 2. Traditional AGC Detector/DC Feedback Circuit The EL4450C simply provides an output equal to the square of the input signal and an integrator filters out the AC component, while comparing the DC component to an amplitude reference. The integrator output is the DC control voltage to the variable-gain sections of the AGC (not shown). If a negative polarity of reference is required, one of the multiplier input terminal pairs is reversed, inverting the multiplier output. Input bias current will cause input voltage offsets due to source impedances; putting a compensating resistor in series with the grounded inputs of the EL4450C will reduce this offset greatly. This control system will attempt to force VIN,RMS2/4=VREF. The extra op-amp can be eliminated by using this circuit: 9 EL4450C EL4450C Wideband Four-Quadrant Multiplier Figure 3. Simplified AGC Detector/DC Feedback Circuit Here the internal op-amp of the EL4450C replaces the external amplifier. The feedback capacitor CF does not provide a perfect integration action; a zero occurs at a frequency of 1/21/4RCF. This is canceled by including another RCF pair at the AGC control output. If the reference voltage must be negative, the resistor at pin 11 is connected to ground rather than the reference and pin 10 connected to the reference. The amplitude reference will have to support some AC currents flowing through R. If this is a problem, several changes can be made to eliminate it. The reference is connected to pin 10 and the resistor R connected to pin 11 reconnected to ground, and one of the multiplier input connections are reversed. Square-law detectors have a restricted input range, about 10:1, because the output rapidly disappears into the DC errors as signal amplitudes reduce. This circuit gives a multiplier output that is the absolute value of the input, thus increasing range to 100:1: 10 EL4450C EL4450C Wideband Four-Quadrant Multiplier Figure 4. Absolute-Value Input Circuitry An ECL comparator produces an output corresponding to the sign of the input, which when multiplied by the input produces an effective absolute-value function. The RC product connected to the X inputs simply emulates the time delay of the compa rator to m aintain c ircuit ac curac y at higher frequencies. 11 EL4450C EL4450C Wideband Four-Quadrant Multiplier Nonlinear Function Generation The REF pin of the EL4450C can be used to sum in various quantities of polynomial function generators. For instance, this sum of REF allows a linear signal path which can have various amounts of squared signal added: Figure 5. Polynomial Function Generator The polarity of the squared signal can be reversed by swapping one of the X or Y input pairs. The REF and FB pins also simplify feedback schemes that allow square-rooting: The diode and I pulldown assure that the output will always produce the positive square-root of the input signal. Ipulldown should be large enough to assure that the diode be forward-biased for any load current. In this configuration, the bandwidth of the circuit will reduce for smaller input signals. Figure 6. Square-Rooter 12 EL4450C EL4450C Wideband Four-Quadrant Multiplier The REF and FB terminals can also be used to implement division: The output frequency response reduces for smaller values of VX, but is not affected by VREF. Figure 7. Divider Connection 13 EL4450C EL4450C Wideband Four-Quadrant Multiplier General Disclaimer Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes in the circuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. WARNING - Life Support Policy January 1996 Rev B Elantec, Inc. 1996 Tarob Court Milpitas, CA 95035 Telephone: (408) 945-1323 (800) 333-6314 Fax: (408) 945-9305 European Office: 44-71-482-4596 14 Elantec, Inc. products are not authorized for and should not be used within Life Support Systems without the specific written consent of Elantec, Inc. Life Support systems are equipment intended to support or sustain life and whose failure to perform when properly used in accordance with instructions provided can be reasonably expected to result in significant personal injury or death. Users contemplating application of Elantec, Inc. Products in Life Support Systems are requested to contact Elantec, Inc. factory headquarters to establish suitable terms & conditions for these applications. Elantec, Inc.'s warranty is limited to replacement of defective components and does not cover injury to persons or property or other consequential damages. Printed in U.S.A. |
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