...the analog plus company TM XR-0A Precision Waveform Generator FEATURES APPLICATIONS June 1- Low Frequency Drift, 50ppm/ C, Typical Simultaneous, Triangle, and Outputs Low Distortion - THD 1% High FM and Triangle Linearity Wide Frequency Range 0.001Hz to 00KHz Variable Duty Cycle, % to % Low Distortion Variation with Temperature Precision Waveform Generation Sweep and FM Generation Tone Generation Instrumentation and Test Equipment Design Precision PLL Design GENERAL DESCRIPTION The XR-0A is a precision waveform generator IC capable of producing sine, square, triangular, sawtooth, and pulse waveforms, with a minimum number of external components and adjustments. The XR-0A allows the elimination of the external distortion adjusting resistor which greatly improves the temperature drift of distortion, as well as lowering external parts count. Its operating frequency can be selected over eight decades of frequency, from 0.001Hz to 00kHz, by the choice of external R-C components. The frequency of oscillation is highly stable over a wide range of temperature and supply voltage changes. Both full frequency sweeping as well as smaller frequency variations (FM) can be accomplished with an external control voltage. Each of the three basic waveform outputs, (i.e., sine, triangle and square) are simultaneously available from independent output terminals. The XR-0A monolithic waveform generator uses advanced processing technology and Schottky-barrier diodes to enhance its frequency performance. ORDERING INFORMATION Operating Part No. Package Temperature Range XR-0ACP 14 Lead 00 mil PDIP 0 C to 0 C 1 EXAR Corporation, 40 Kato Road, Fremont, CA 45 (5) 66-000 FAX (5) 66-01 1
6 Timing Capacitor Triangle Wave Output Adjust 1 1 DCA1 DCA FM Sweep 4 5 Ia / Buffer Output Square Wave Output FM Bias Switch S Ib C External 1/ Comp1 Comp Flip Flop Figure 1. XR-0A Block Diagram
PIN CONFIGURATION SA1 SWO TWO DCA1 DCA FMBI 1 4 5 6 14 NC 1 NC 1 SA TC SQO FMSI 14 Lead PDIP (0.00 ) PIN DESCRIPTION Pin # Symbol Type Description 1 Á SA1 I ÁÁ Wave Form Adjust Input 1. Á SWO O ÁÁ Output. Á TWO O ÁÁ Triangle Wave Output. 4 Á DCA1 I ÁÁ Duty Cycle Adjustment Input. 5 Á DCA I ÁÁ Duty Cycle Adjustment Input. 6 ÁÁ Positive Power Supply. Á FMBI I ÁÁ Frequency Modulation Input. Á FMSI I ÁÁ Frequency Sweep Input. Á SQO O ÁÁ Output. Á TC I ÁÁ Timing Capacitor Input. ÁÁ Negative Power Supply. 1 Á SA I ÁÁ Wave Form Adjust Input. 1 ÁÁ NC No Connect. 14 ÁÁ NC No Connect.
DC ELECTRICAL CHARACTERISTICS Test Conditions: V S = +5V to +15V, T A = 5 C, R L = 1M, R A = R B = k, C 1 = 00pF, S 1 closed, unless otherwise specified. (See Figure.) Parameter Min. Typ. Max. Unit Conditions General Characteristics Supply Voltage, V S Single Supply 0 V Dual Supplies +5 +15 V Supply Current 1 0 ma V S = +V 1 Frequency Characteristics (Measured at Pin ) Range of Adjustment Max. Operating Frequency 00 khz R A = R B, = 1.5k, C 1 = 60pF; R L = K Lowest Practical Frequency 0.001 Hz R A = R B = 1M, C 1 = 500F (Low Leakage Capacitor) Max. Sweep Frequency of FM Input 0 khz FM Sweep Range 00:1 S 1 Open, FM Linearity :1 Ratio 0. % S 1 Open Range of Timing Resistors 0.5 00 K Values of R A and R B Temperature Stability 50 PPM/ C T A = 0 C to 0 C Power Supply Stability 0.05 %/V V V S 0V or +5V V S 15V Output Characteristics Square-Wave Measured at Pin Amplitude (Peak-to-Peak) 0. 0. x V SPLY R L = 0k Saturation Voltage 0. 0.5 V I SINK = ma Rise Time 0 ns R L = 4.k Fall Time 40 ns R L = 4.k Duty Cycle Adjustment % Triangle/Sawtooth/Ramp Measured at Pin Amplitude (Peak-to-Peak) 0. 0. x V SPLY R L = 0k Linearity 0.1 % Notes 1 Currents through R A and R B not included. V SUPPLY = 0V. Apply sweep voltage at Pin. - (1/ V SUPPLY - ) V PIN V SUPPLY = Total Supply Voltage across the IC Specifications are subject to change without notice 4
DC ELECTRICAL CHARACTERISTICS (CONT D) Test Conditions: V S = +5V to +15V, T A = 5 C, R L = 1M, R A = R B = k, C 1 = 00pF, S 1 closed, unless otherwise specified. (See Figure.) Parameter Min. Typ. Max. Unit Conditions Output Characteristics (Cont d) Output Impedance 00 I OUT = 5mA -Wave Amplitude (Peak-to-Peak) 0. 0. x V SPLY R L = 0k Distortion 0. % R L = 1M 4,5 Unadjusted 0.5 % R L = 1M 4,5 Adjusted 0. % Notes 4 Triangle duty cycle set at 50%, use R A and R B. 5 As R L is decreased distortion will increase, R L min 50K. Bold face parameters are covered by production test and guaranteed over operating temperature range. Specifications are subject to change without notice ABSOLUTE MAXIMUM RATINGS Power Supply............................... 6V Power Dissipation (package limitation) Plastic Package.................. 65mW Derate Above +5 C............. 5mW/ C Storage Temperature Range...... -65 C to +150 C 5
SYSTEM DESCRIPTION The XR-0A precision waveform generator produces highly stable and sweepable square, triangle, and sine waves across eight frequency decades. The device time base employs resistors and a capacitor for frequency and duty cycle determination. The generator contains dual comparators, a flip-flop driving a switch, current sources, buffers, and a sine wave convertor. Three identical frequency outputs are simultaneously available. Supply voltage can range from V to 0V, or ±5V to ±15V with dual supplies. Unadjusted sine wave distortion is typically less than 0.% with the sine wave distortion adjust pin (Pin 1) open. Distortion levels may be improved by including a 0kΩ potentiometer between the supplies, with the wiper connected to Pin 1. Small frequency deviation (FM) is accomplished by applying modulation voltage to Pins and ; large frequency deviation (sweeping) is accomplished by applying voltage to Pin only. Sweep range is typically 00:1. The square wave output is an open collector transistor; output amplitude swing closely approaches the supply voltage. Triangle output amplitude is typically 1/ of the supply, and sine wave output reaches 0. of the supply voltage. +15V R A R B 4 5 1 1 6 R L DCA1 DCA SA1 SA C1 TC Timing Circuitry SWO S1 FMBI FMSI U1 TWO SQO Triangle Wave XR-0A 15V Figure. Generalized Test Circuit 6
R A R K Buffer 4 I A SWITCH S R 1 40K C R B Buffer 5 I B Figure. Detailed View of Current Sources I A and I B. WAVEFORM ADJUSTMENT The symmetry of all waveforms can be adjusted with the external timing resistors. Two possible ways to accomplish this are shown in Figure 4, Figure 5, and Figure 6. Best results are obtained by keeping the timing resistors R A and R B separate (Figure 4.) R A controls the rising portion of the triangle and sine wave and the low state of the square wave. The magnitude of the triangle waveform is set at 1/ ; therefore, the duration of the rising proportion of the triangle is: t 1 C V I A C - 1 5R A 5 R A C The duration of the falling portion of the triangle and sine wave and the low state of the square wave is: t C V C V CC- 1 V CC 5 I B -I V A CC - R A R B C R A -R B 5R 5R B A Thus a 50% duty cycle is achieved when R A = R B If the duty-cycle is to be varied over a small range about 50%, the connection shown in Figure 5 is slightly more convenient. If no adjustment of the duty cycle is desired, pins 4 and 5 can be shorted together, as shown in Figure 6. This connection, however, carries an inherently larger variation of the duty cycle. With two separate timing resistors the frequency is given by: f 1 t 1 t or, if R A = R B = R f 0. RC 1 5 R AC1 R B (for Figure 4. ) R A R B If a single timing resistor is used (Figure 5 and Figure 6), the frequency is: f 0.15 RC The frequency of oscillation is independent of supply voltage, even though none of the voltages are regulated inside the integrated circuit. This is due to the fact that both currents and thresholds are direct, linear function of the supply voltage and thus their effects cancel.
DISTORTION ADJUSTMENT To minimize sine wave distortion, two potentiometers can be connected as shown in Figure. This configuration allows a reduction of sine wave distortion close to 0.5%. +15V R A R B 4 5 1 1 6 R L C1 TC FMBI FMSI DCA1 Timing Circuitry U1 DCA SA1 SA SWO TWO SQO Triangle Wave XR-0A 15V Figure 4. Possible Connection for External Duty Cycle Adjust +15V Frequency TC Duty Cycle FMBI FMSI 4 5 1 1 6 DCA1 DCA Timing Circuitry U1 SA1 SA SWO TWO SQO XR-0A R L Triangle Wave 15V Figure 5. Single Potentiometer for External Duty Cycle Adjust
+15V R C1 TC FMBI FMSI DCA1 4 5 1 1 6 Timing Circuitry U1 DCA SA1 SA SWO TWO SQO XR-0A R L Triangle Wave 15V Figure 6. No Duty Cycle Adjust +15V 0K R A R B 0K C1 DCA1 DCA TC Timing Circuitry FMBI FMSI 4 5 1 1 6 U1 SA1 SA SWO TWO SQO R L 15V Triangle Wave XR-0A 15V Figure. Minimum Distortion
SELECTING TIMING COMPONENTS For any given output frequency, there is a wide range of R and C combinations that will work. However, certain constraints are placed upon the magnitude of the charging current for optimum performance. At the low end, currents of less than 0.1A are undesirable because circuit leakages will contribute significant errors at high temperatures. At higher currents (1 > 5mA), transistor betas and saturation voltages will contribute increasingly large errors. Optimum performance will be obtained for charging currents of 1A to 1mA. If pins and are shorted together, the magnitude of the charging current due to R A can be calculated from: I R 1 (R 1 R ) 1 R A 5R A A similar calculation holds for R B. When the duty cycle is greater than 60%, the device may not oscillate every time, unless: 1. The rise times of the V+ are X times slower than R A C T.. A 0.1F capacitor is tied from pin and to ground. NOTE: - This is only needed if the duty cycle is powered up with R A >>R B. SINGLE-SUPPLY AND SPLIT-SUPPLY OPERATION The waveform generator can be operated either from a single power supply (V to 0V) or a dual power supply (+5V to +15V). With a single power supply the average levels of the triangle and sine wave are at exactly one half of the supply voltage, while the square wave alternates between + and ground. A split power supply has the advantage that all waveforms move symmetrically about ground. The square wave output is not committed. A load resistor can be connected to a different power supply, as long as the applied voltage remains within the breakdown capability of the waveform generator (0V). In this way, the square wave output will be TTL compatible (load resistor connected to +5V) while the waveform generator itself is powered from a higher supply voltage. FREQUENCY MODULATION AND SWEEP The frequency of the waveform generator is an inverse function of the dc voltage at pin (measured from + ). By altering this voltage, frequency modulation is performed. For small deviations (e.g., +%), the modulating signal can be applied to pin by merely providing ac coupling with a capacitor, as shown in Figure. An external resistor between pins and is not necessary, but it can be used to increase input impedance. Without it (i.e. pins and connected together), the input impedance is K); with it, this impedance increases to (R // K For larger FM deviations or for frequency sweeping, the modulating signal is applied between the positive supply voltage and pin (Figure.) In this way the entire bias for the current sources is created by the modulating signal and a very large (e.g. 00:1) sweep range is obtained (f=0 at V SWEEP =0). Care must be taken, however, to regulate the supply voltage; in this configuration the charge current is no longer a function of the supply voltage (yet the trigger thresholds still are) and thus the frequency becomes dependent on the supply voltage. The potential on pin may be swept from to / -V.
+15V R A R B 4 5 1 1 6 R L C1 TC DCA1 Timing Circuitry DCA SA1 SA SWO FMBI U1 TWO Triangle Wave FM FMSI SQO XR-0A 15V Figure. Frequency Modulator +15V R A R B R L C1 TC FMBI DCA1 4 5 1 1 6 Timing Circuitry U1 DCA SA1 SA SWO TWO FMSI Sweep Voltage SQO - (V SUP - ) < = V IN & < = XR-0A Triangle Wave 15V Figure. Frequency Sweep
0 1.0 1.0 Current Consumption 15-55 C 5 C 15 C Normalized Frequency 1.01 1.00 0. 0. 5 5 15 0 5 0 Supply Voltage Figure. Power Dissipation vs. Supply Voltage 5 15 0 5 0 Supply Voltage Figure. Frequency Drift vs. Power Supply 1 Distortion % 6 4 Unadjusted Adjusted 0 Hz 0Hz 1kHz khz 0kHz 1MHz Frequency Figure 1. THD vs. Frequency 1
14 LEAD PLASTIC DUAL-IN-LINE (00 MIL PDIP) Rev. 1.00 14 1 E 1 D E Seating Plane A L B e B 1 A 1 A α e A e B C INCHES MILLIMETERS SYMBOL MIN MAX MIN MAX A 0.145 0..6 5. A 1 0.015 0.00 0. 1. A 0.5 0.15. 4.5 B 0.014 0.04 0.6 0.56 B 1 0.00 0.00 0.6 1. C 0.00 0.014 0.0 0. D 0.5 0.5 1.4 0.1 E 0.00 0.5.6.6 E 1 0.40 0.0 6.. e 0.0 BSC.54 BSC e A 0.00 BSC.6 BSC e B 0. 0.40.. L 0.5 0.160. 4.06 α 0 15 0 15 Note: The control dimension is the inch column 1
Notes 14
Notes 15
NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Copyright 1 EXAR Corporation Datasheet June 1 Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. 16