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| Dual High Speed ECL Comparators ADCMP563/ADCMP564 FEATURES Differential ECL compatible outputs 700 ps propagation delay input to output 75 ps propagation delay dispersion Input common-mode range: -2.0 V to +3.0 V Robust input protection Differential latch control Internal latch pull-up resistors Power supply rejection greater than 85 dB 700 ps minimum pulse width 1.5 GHz equivalent input rise time bandwidth Typical output rise/fall time of 500 ps ESD protection > 4kV HBM, >200V MM Programmable hysteresis FUNCTIONAL BLOCK DIAGRAM HYS* NONINVERTING INPUT Q OUTPUT ADCMP563/ ADCMP564 INVERTING INPUT Q OUTPUT *ADCMP564 ONLY Figure 1. GND 1 QA 1 QA 2 GND 3 LEA 4 LEA 5 VEE 6 -INA 7 +INA 8 16 QB 15 QB 14 GND 04650-0-001 LATCH ENABLE INPUT LATCH ENABLE INPUT 20 19 18 GND QB QB GND LEB LEB VCC -INB 04650-0-012 QA 2 QA 3 GND 4 LEA 5 LEA 6 VEE 7 -INA 8 04650-0-002 APPLICATIONS Automatic test equipment High speed instrumentation Scope and logic analyzer front ends Window comparators High speed line receivers Threshold detection Peak detection High speed triggers Patient diagnostics Disk drive read channel detection Hand-held test instruments Zero crossing detectors Line receivers and signal restoration Clock drivers ADCMP564 TOP VIEW (Not to Scale) 17 16 15 14 13 12 11 ADCMP563 TOP VIEW (Not to Scale) 13 LEB 12 LEB 11 VCC 10 -INB 9 +INB +INA 9 HYSA 10 +INB HYSB Figure 2. ADCMP563 16-Lead QSOP Figure 3. ADCMP564 20-Lead QSOP GENERAL DESCRIPTION The ADCMP563/ADCMP564 are high speed comparators fabricated on Analog Devices' proprietary XFCB process. The devices feature a 700 ps propagation delay with less than 75 ps overdrive dispersion. Dispersion, a measure of the difference in propagation delay under differing overdrive conditions, is a particularly important characteristic of high speed comparators. A separate programmable hysteresis pin is available on the ADCMP564. A differential input stage permits consistent propagation delay with a wide variety of signals in the common-mode range from -2.0 V to +3.0 V. Outputs are complementary digital signals that are fully compatible with ECL 10 K and 10 KH logic families. The outputs provide sufficient drive current to directly drive transmission lines terminated in 50 to -2 V. A latch input, which is included, permits tracking, track-and-hold, or sample-and-hold modes of operation. The latch input pins contain internal pull-ups that set the latch in tracking mode when left open. The ADCMP563/ADCMP564 are specified over the industrial temperature range (-40C to +85C). Rev. A Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved. ADCMP563/ADCMP564 TABLE OF CONTENTS Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 5 Thermal Considerations.............................................................. 5 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ............................................. 8 Timing Information ....................................................................... 10 Application Information................................................................ 11 Clock Timing Recovery............................................................. 11 Optimizing High Speed Performance ..................................... 11 Comparator Propagation Delay Dispersion ........................... 11 Comparator Hysteresis .............................................................. 12 Minimum Input Slew Rate Requirement ................................ 12 Typical Application Circuits.......................................................... 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 14 REVISION HISTORY 7/04--Data Sheet Changed from Rev. 0 to Rev. A Changes to Specification Table ....................................................... 4 Changes to Figure 14........................................................................ 9 Changes to Figure 21...................................................................... 12 Changes to Figure 23...................................................................... 13 4/04--Revision 0: Initial Version Rev. A | Page 2 of 16 ADCMP563/ADCMP564 SPECIFICATIONS VCC = +5.0 V, VEE = -5.2 V, TA = -40C to +85C. Typical values are at TA = +25C, unless otherwise noted. Table 1. Electrical Characteristics Parameter DC INPUT CHARACTERISTICS Input Voltage Range Input Differential Voltage Input Offset Voltage Input Offset Voltage Channel Matching Offset Voltage Tempco Input Bias Current Input Bias Current Tempco Input Offset Current Input Capacitance Input Resistance, Differential Mode Input Resistance, Common Mode Active Gain Common-Mode Rejection Ratio Hysteresis LATCH ENABLE CHARACTERISTICS Latch Enable Voltage Range Latch Enable Differential Input Voltage Latch Enable Input High Current Latch Enable Input Low Current LE Voltage, Open LE Voltage, Open Latch Setup Time Latch Hold Time Latch to Output Delay Latch Minimum Pulse Width DC OUTPUT CHARACTERISTICS Output Voltage--High Level Output Voltage--Low Level Rise Time Fall Time AC PERFORMANCE Propagation Delay Propagation Delay Tempco Prop Delay Skew--Rising Transition to Falling Transition Within Device Propagation Delay Skew-- Channel-to-Channel Overdrive Dispersion Slew Rate Dispersion Pulse Width Dispersion Duty Cycle Dispersion Common-Mode Voltage Dispersion Symbol Conditions Min -2.0 -5 -10.0 Typ Max 3.0 +5 +10.0 Unit V V mV mV V/C A nA/C A pF k k dB dB mV V V A A V V ps ps ps ps V V ps ps ps ps ps/C ps ps ps ps ps ps ps ps VOS VOS/dT IBC VCM = 0 V @ -IN = -2 V, +IN = +3 V -10.0 CIN AV CMRR VCM = -2.0 V to +3.0 V RHYS = -2.0 0.4 -300 -300 -0.2 -2.8 2.0 2.0 2.0 3 0.5 1.0 0.75 750 1800 63 80 1.0 +10.0 tS tH tPLOH, tPLOL tPL VOH VOL tR tF tPD tPD /dT @ 0.0 V @ -2.0 V Latch inputs not connected Latch inputs not connected VOD = 250 mV VOD = 250 mV VOD = 250 mV VOD = 250 mV ECL 50 to -2.0 V ECL 50 to -2.0 V 10% to 90% 10% to 90% VOD = 1 V VOD = 20 mV VOD = 1 V VOD = 1 V VOD = 1 V 20 mV VOD 100 mV 100 mV VOD 1.5 V 0.4 V/ns SR 1.33 V/ns 750ps PW 10ns 33 MHz, 1 V/ns, 0.5 V 1 V swing, -1.5 V VCM +2.5 V 0 -2.6 200 200 500 500 0 2.0 +300 +300 +0.1 -2.4 -1.15 -1.95 530 450 700 830 0.25 50 50 75 75 50 25 10 10 -0.81 -1.54 Rev. A | Page 3 of 16 ADCMP563/ADCMP564 Parameter AC PERFORMANCE (continued) Equivalent Input Rise Time Bandwidth1 Maximum Toggle Rate Minimum Pulse Width RMS Random Jitter Unit to Unit Propagation Delay Skew POWER SUPPLY Positive Supply Current Negative Supply Current Positive Supply Voltage Negative Supply Voltage Power Dissipation DC Power Supply Rejection Ratio--VCC DC Power Supply Rejection Ratio--VEE HYSTERESIS (ADCMP564 Only) Hysteresis Symbol BWEQ PWMIN Conditions 0 V to 1 V swing, 2 V/ns >50% output swing, 50% duty cycle tPD < 25 ps VOD = 400 mV, 1.3 V/ns, 312 MHz, 50% duty cycle Min Typ 1500 800 700 1.0 100 IVCC IVEE VCC VEE PD PSRRVCC PSRRVEE RHYS = 23.5 k RHYS = 9.0 k @ +5.0 V @ -5.2 V Dual Dual Dual, without load Dual, with load 2 10 4.75 -4.96 90 150 3.2 19 5.0 -5.2 120 180 85 85 20 70 5 25 5.25 -5.45 150 230 Max Unit MHz MHz ps ps ps mA mA V V mW mW dB dB mV mV 1 Equivalent input rise time bandwidth assumes a first-order input response and is calculated by the following formula: BWEQ = 0.22/(trCOMP2 - trIN2), where trIN is the 20/80 input transition time applied to the comparator and trCOMP is the effective transition time, as digitized by the comparator input. Rev. A | Page 4 of 16 ADCMP563/ADCMP564 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter Supply Voltages Positive Supply Voltage (VCC to GND) Negative Supply Voltage (VEE to GND) Ground Voltage Differential Input Voltages Input Common-Mode Voltage Differential Input Voltage Input Voltage, Latch Controls Output Output Current Temperature Operating Temperature, Ambient Operating Temperature, Junction Storage Temperature Range Rating -0.5 V to +6.0 V -6.0 V to +0.5 V -0.5 V to +0.5 V -3.0 V to +4.0 V -7.0 V to +7.0 V VEE to +0.5 V 30 mA -40C to +85C 125C -65C to +150C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL CONSIDERATIONS The ADCMP563 QSOP 16-lead package option has a JA (junction-to-ambient thermal resistance) of 104C/W in still air. The ADCMP564 QSOP 20-lead package option has a JA (junction-to-ambient thermal resistance) of 80C/W in still air. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. A | Page 5 of 16 ADCMP563/ADCMP564 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS GND 1 QA 1 QA 2 GND 3 LEA 4 LEA 5 VEE 6 -INA 7 +INA 8 16 QB 15 QB 14 GND 20 19 18 GND QB QB GND LEB LEB VCC -INB 04650-0-012 QA 2 QA 3 GND 4 LEA 5 LEA 6 VEE 7 -INA 8 04650-0-002 ADCMP564 TOP VIEW (Not to Scale) 17 16 15 14 13 12 11 ADCMP563 TOP VIEW (Not to Scale) 13 LEB 12 LEB 11 VCC 10 -INB 9 +INB +INA 9 HYSA 10 +INB HYSB Figure 4. ADCMP563 16-Lead QSOP Pin Configuration Figure 5. ADCMP564 20-Lead QSOP Pin Configuration Table 3. Pin Function Descriptions Pin No. ADCMP563 ADCMP564 1 1 2 Mnemonic GND QA Function Analog Ground. One of two complementary outputs for Channel A. QA is logic high if the analog voltage at the noninverting input is greater than the analog voltage at the inverting input (provided the comparator is in compare mode). See the description of Pin LEA for more information. One of two complementary outputs for Channel A. QA is logic low if the analog voltage at the noninverting input is greater than the analog voltage at the inverting input (provided the comparator is in compare mode). See the description of Pin LEA for more information. Analog Ground. One of two complementary inputs for Channel A Latch Enable. In compare mode (logic high), the output tracks changes at the input of the comparator. In latch mode (logic low), the output reflects the input state just prior to the comparator being placed in the latch mode. LEA must be driven in conjunction with LEA. If left unconnected, the comparator defaults to compare mode. One of two complementary inputs for Channel A Latch Enable. In compare mode (logic low), the output tracks changes at the input of the comparator. In latch mode (logic high), the output reflects the input state just prior to the comparator being placed in the latch mode. LEA must be driven in conjunction with LEA. If left unconnected, the comparator defaults to compare mode. Negative Supply Terminal. Inverting Analog Input of the Differential Input Stage for Channel A. The inverting A input must be driven in conjunction with the noninverting A input. Noninverting Analog Input of the Differential Input Stage for Channel A. The noninverting A input must be driven in conjunction with the inverting A input. Programmable Hysteresis Input. Programmable Hysteresis Input. Noninverting Analog Input of the Differential Input Stage for Channel B. The noninverting B input must be driven in conjunction with the inverting B input. Inverting Analog Input of the Differential Input Stage for Channel B. The inverting B input must be driven in conjunction with the noninverting B input. Positive Supply Terminal. One of two complementary inputs for Channel B Latch Enable. In compare mode (logic low), the output tracks changes at the input of the comparator. In latch mode (logic high), the output reflects the input state just prior to the comparator being placed in the latch mode. LEB must be driven in conjunction with LEB. If left unconnected, the comparator defaults to compare mode. 2 3 QA 3 4 4 5 GND LEA 5 6 LEA 6 7 8 7 8 9 10 11 12 13 14 15 VEE -INA +INA HYSA HYSB +INB -INB VCC LEB 9 10 11 12 Rev. A | Page 6 of 16 ADCMP563/ADCMP564 Pin No. ADCMP563 ADCMP564 13 16 Mnemonic LEB Function One of two complementary inputs for Channel B Latch Enable. In compare mode (logic high), the output tracks changes at the input of the comparator. In latch mode (logic low), the output reflects the input state just prior to the comparator being placed in the latch mode. LEB must be driven in conjunction with LEB. If left unconnected, the comparator defaults to compare mode. Analog Ground. One of two complementary outputs for Channel B. QB is logic low if the analog voltage at the noninverting input is greater than the analog voltage at the inverting input (provided the comparator is in compare mode). See the description of Pin LEB for more information. One of two complementary outputs for Channel B. QB is logic high if the analog voltage at the noninverting input is greater than the analog voltage at the inverting input (provided the comparator is in compare mode). See the description of Pin LEB for more information. Analog Ground. 14 15 17 18 GND QB 16 19 QB 20 GND Rev. A | Page 7 of 16 ADCMP563/ADCMP564 TYPICAL PERFORMANCE CHARACTERISTICS VCC = 3.3 V, TA = 25C, unless otherwise noted. 3.0 2.5 2.80 2.78 +IN INPUT BIAS CURRENT (A) (+IN = 3V, -IN = 0V) 04650-0-013 2.76 2.74 2.72 2.70 2.68 2.66 2.64 2.62 2.60 -40 -20 0 20 40 60 80 04650-0-016 INPUT BIAS CURRENT (A) 2.0 1.5 1.0 0.5 0 -0.5 -1.0 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 NONINVERTING INPUT VOLTAGE (INVERTING VOLTAGE = 0V) TEMPERATURE (C) Figure 6. Input Bias Current vs. Input Voltage 2.00 1.95 1.90 1.85 1.80 1.75 1.70 1.65 1.60 04650-0-014 Figure 9. Input Bias Current vs. Temperature -0.8 -1.0 OUTPUT RISE AND FALL (V) OFFSET VOLTAGE (mV) -1.2 -1.4 -1.6 1.55 1.50 -40 -20 0 20 40 60 80 -2.0 0 0.25 0.50 0.75 1.00 TIME (ns) 1.25 1.50 1.75 2.00 TEMPERATURE (C) Figure 7. Input Offset Voltage vs. Temperature 550 545 540 535 475 470 465 460 Figure 10. Rise and Fall of Outputs vs. Time TIME (ps) TIME (ps) 530 525 520 515 510 04650-0-015 455 450 445 440 435 430 425 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 04650-0-018 505 500 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 TEMPERATURE (C) TEMPERATURE (C) Figure 8. Rise Time vs. Temperature Figure 11. Fall Time vs. Temperature Rev. A | Page 8 of 16 04650-0-017 -1.8 ADCMP563/ADCMP564 720 715 PROPAGATION DELAY (ps) 04650-0-019 705 704 703 702 701 700 699 698 697 -2 04650-0-022 PROPAGATION DELAY (ps) 710 705 700 695 690 685 680 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 -1 0 1 2 3 TEMPERATURE (C) INPUT COMMON-MODE VOLTAGE (V) Figure 12. Propagation Delay vs. Temperature 140 120 100 Figure 15. Propagation Delay vs. Common-Mode Voltage 25 PROPAGATION DELAY ERROR (ps) PROPAGATION DELAY ERROR (ps) 20 15 80 60 40 20 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 OVERDRIVE VOLTAGE (V) 10 5 04650-0-020 -5 0.7 1.7 2.7 3.7 4.7 5.7 6.7 7.7 8.7 9.7 PULSE WIDTH (ns) Figure 13. Propagation Delay vs. Overdrive Voltage 160 140 PROGRAMMED HYSTERESIS (mV) Figure 16. Propagation Delay Error vs. Pulse Width 160 140 PROGRAMMED HYSTERESIS (mV) 120 100 80 60 40 04650-0-021 120 100 80 60 40 20 0 0 50 100 IHYS (A) 150 04650-0-024 20 0 50 40 30 RHYS (k) 20 10 0 Figure 14. Comparator Hysteresis vs. RHYS Figure 17. Comparator Hysteresis vs. IHYS Rev. A | Page 9 of 16 04650-0-023 0 ADCMP563/ADCMP564 TIMING INFORMATION LATCH ENABLE 50% LATCH ENABLE tS tH tPL DIFFERENTIAL INPUT VOLTAGE VIN VOD VREF VOS tPDL Q OUTPUT tPLOH 50% tPDH tF 50% 04650-0-003 Q OUTPUT tPLOL tR Figure 18. System Timing Diagram Figure 18 shows the compare and latch features of the ADCMP563. Table 4 describes the terms in the diagram. Table 4. Timing Descriptions Symbol tPDH tPDL tPLOH tPLOL tH tPL tS tR tF VOD Timing Input to Output High Delay Input to Output Low Delay Latch Enable to Output High Delay Latch Enable to Output Low Delay Minimum Hold Time Minimum Latch Enable Pulse Width Minimum Setup Time Output Rise Time Output Fall Time Voltage Overdrive Description Propagation delay measured from the time the input signal crosses the reference ( the input offset voltage) to the 50% point of an output low-to-high transition. Propagation delay measured from the time the input signal crosses the reference ( the input offset voltage) to the 50% point of an output high-to-low transition. Propagation delay measured from the 50% point of the latch enable signal low-to-high transition to the 50% point of an output low-to-high transition. Propagation delay measured from the 50% point of the latch enable signal low-to-high transition to the 50% point of an output high-to-low transition. Minimum time after the negative transition of the latch enable signal that the input signal must remain unchanged to be acquired and held at the outputs. Minimum time the latch enable signal must be high to acquire an input signal change. Minimum time before the negative transition of the latch enable signal that an input signal change must be present to be acquired and held at the outputs. Amount of time required to transition from a low to a high output as measured at the 20% and 80% points. Amount of time required to transition from a high to a low output as measured at the 20% and 80% points. Difference between the differential input and reference input voltages. Rev. A | Page 10 of 16 ADCMP563/ADCMP564 APPLICATION INFORMATION The ADCMP563/ADCMP564 comparators are very high speed devices. Consequently, high speed design techniques must be employed to achieve the best performance. The most critical aspect of any ADCMP563/ADCMP564 design is the use of a low impedance ground plane. A ground plane, as part of a multilayer board, is recommended for proper high speed performance. Using a continuous conductive plane over the surface of the circuit board can create this, allowing breaks in the plane only for necessary signal paths. The ground plane provides a low inductance ground, eliminating any potential differences at different ground points throughout the circuit board caused by ground bounce. A proper ground plane also minimizes the effects of stray capacitance on the circuit board. It is also important to provide bypass capacitors for the power supply in a high speed application. A 1 F electrolytic bypass capacitor should be placed within 0.5 inches of each power supply pin to ground. These capacitors reduce any potential voltage ripples from the power supply. In addition, a 10 nF ceramic capacitor should be placed as close as possible from the power supply pins on the ADCMP563/ADCMP564 to ground. These capacitors act as a charge reservoir for the device during high frequency switching. The LATCH ENABLE input is active low (latched). If the latching function is not used, the LATCH ENABLE input may be left open or may be grounded (ground is an ECL logic high) The complementary input, LATCH ENABLE, may be left open or may be tied to -2.0 V. Leaving the latch inputs unconnected or providing the proper voltages disables the latching function. Occasionally, one of the two comparator stages within the ADCMP563/ADCMP564 is not used. The inputs of the unused comparator should not be allowed to float. The high internal gain may cause the output to oscillate (possibly affecting the comparator that is being used) unless the output is forced into a fixed state. This is easily accomplished by ensuring that the two inputs are at least one diode drop apart, while also appropriately connecting the LATCH ENABLE and LATCH ENABLE inputs as described previously. The best performance is achieved with the use of proper ECL terminations. The open emitter outputs of the ADCMP563/ ADCMP564 are designed to be terminated through 50 resistors to -2.0 V, or any other equivalent ECL termination. If a -2.0 V supply is not available, an 82 resistor to ground and a 130 resistor to -5.2 V provide a suitable equivalent. If high speed ECL signals must be routed more than a centimeter, microstrip or stripline techniques may be required to ensure proper transition times and prevent output ringing. CLOCK TIMING RECOVERY Comparators are often used in digital systems to recover clock timing signals. High speed square waves transmitted over a distance, even tens of centimeters, can become distorted due to stray capacitance and inductance. Poor layout or improper termination can also cause reflections on the transmission line, further distorting the signal waveform. A high speed comparator can be used to recover the distorted waveform while maintaining a minimum of delay. OPTIMIZING HIGH SPEED PERFORMANCE As with any high speed comparator amplifier, proper design and layout techniques should be used to ensure optimal performance from the ADCMP563/ADCMP564. The performance limits of high speed circuitry can easily be a result of stray capacitance, improper ground impedance, or other layout issues. Minimizing resistance from source to the input is an important consideration in maximizing the high speed operation of the ADCMP563/ADCMP564. Source resistance, in combination with equivalent input capacitance, could cause a lagged response at the input, thus delaying the output. The input capacitance of the ADCMP563/ADCMP564, in combination with stray capacitance from an input pin to ground, could result in several picofarads of equivalent capacitance. A combination of 3 k source resistance and 5 pF input capacitance yields a time constant of 15 ns, which is significantly slower than the 750 ps capability of the ADCMP563/ADCMP564. Source impedances should be significantly less than 100 for best performance. Sockets should be avoided due to stray capacitance and inductance. If proper high speed techniques are used, the devices should be free from oscillation when the comparator input signal passes through the switching threshold. COMPARATOR PROPAGATION DELAY DISPERSION The ADCMP563/ADCMP564 have been specifically designed to reduce propagation delay dispersion over an input overdrive range of 100 mV to 1.5 V. Propagation delay overdrive dispersion is the change in propagation delay that results from a change in the degree of overdrive (how far the switching point is exceeded by the input). The overall result is a higher degree of timing accuracy because the ADCMP563/ADCMP564 are far less sensitive to input variations than most comparator designs. Rev. A | Page 11 of 16 ADCMP563/ADCMP564 Propagation delay dispersion is important in critical timing applications such as ATE, bench instruments, and nuclear instrumentation. Overdrive dispersion is defined as the variation in propagation delay as the input overdrive conditions are changed (Figure 19). For the ADCMP563/ADCMP564, overdrive dispersion is typically 75 ps as the overdrive is changed from 100 mV to 1.5 V. This specification applies for both positive and negative overdrive because the ADCMP563 and the ADCMP564 have equal delays for positive and negative going inputs. 1.5V OVERDRIVE A current source can also be used with the HYS pin. The relationship between the current applied to the HYS pin and the resulting hysteresis is shown in Figure 17. -VH 2 0V INPUT 1 +VH 2 INPUT VOLTAGE 0 20mV OVERDRIVE 04650-0-005 VREF VOS OUTPUT DISPERSION Q OUTPUT 03633-0-004 Figure 20. Comparator Hysteresis Transfer Function 160 140 PROGRAMMED HYSTERESIS (mV) Figure 19. Propagation Delay Dispersion 120 100 80 60 40 20 0 50 04650-0-021 COMPARATOR HYSTERESIS The addition of hysteresis to a comparator is often useful in a noisy environment, or where it is not desirable for the comparator to toggle between states when the input signal is at the switching threshold. The transfer function for a comparator with hysteresis is shown in Figure 20. If the input voltage approaches the threshold from the negative direction, the comparator switches from a 0 to a 1 when the input crosses +VH/2. The new switching threshold becomes -VH/2. The comparator remains in a 1 state until the threshold -VH/2 is crossed coming from the positive direction. In this manner, noise centered on 0 V input does not cause the comparator to switch states unless it exceeds the region bounded by VH/2. Positive feedback from the output to the input is often used to produce hysteresis in a comparator (Figure 24). The major problem with this approach is that the amount of hysteresis varies with the output logic levels, resulting in a hysteresis that is not symmetrical around zero. In the ADCMP564, hysteresis is generated through the programmable hysteresis pin. A resistor from the HYS pin to GND creates a current into the part that is used to generate hysteresis. Hysteresis generated in this manner is independent of output swing and is symmetrical around the trip point. The hysteresis versus resistance curve is shown in Figure 21. 40 30 RHYS (k) 20 10 0 Figure 21. Comparator Hysteresis vs. RHYS MINIMUM INPUT SLEW RATE REQUIREMENT As for all high speed comparators, a minimum slew rate must be met to ensure that the device does not oscillate when the input crosses the threshold. This oscillation is due in part to the high input bandwidth of the comparator and the parasitics of the package. Analog Devices recommends a slew rate of 1 V/s or faster to ensure a clean output transition. If slew rates less than 1 V/s are used, hysteresis should be added to reduce the oscillation. Rev. A | Page 12 of 16 ADCMP563/ADCMP564 TYPICAL APPLICATION CIRCUITS VIN VREF ADCMP563/ ADCMP564 VIN OUTPUTS ADCMP564 VREF HYS OUTPUTS 0 TO 80k LATCH ENABLE INPUTS -2.0V 046500-007 -2.0V ALL RESISTORS 50, UNLESS OTHERWISE NOTED ALL RESISTORS 50 Figure 22. High Speed Sampling Circuits Figure 24. Adding Hysteresis Using the HYS Control Pin +VREF VIN 30 50 ADCMP563/ ADCMP564 OUTPUTS VIN ADCMP563/ ADCMP564 127 30 127 50 -2V -5.2V -VREF ADCMP563/ ADCMP564 OUTPUTS Figure 25. How to Interface an ECL Output to an Instrument with a 50 to Ground Input ALL RESISTORS 50 UNLESS OTHERWISE NOTED Figure 23. High Speed Window Comparator 04650-0-008 LATCH ENABLE INPUTS -2V Rev. A | Page 13 of 16 04650-0-011 04650-0-009 ADCMP563/ADCMP564 OUTLINE DIMENSIONS 0.193 BSC 16 9 0.154 BSC 1 8 0.236 BSC PIN 1 0.065 0.049 0.069 0.053 0.010 0.025 0.004 BSC COPLANARITY 0.004 0.012 0.008 SEATING PLANE 0.010 0.006 8 0 0.050 0.016 COMPLIANT TO JEDEC STANDARDS MO-137AB Figure 26. 16-Lead Shrink Small Outline Package [QSOP] (RQ-16) Dimensions shown in inches 0.341 BSC 20 11 0.154 BSC 1 10 0.236 BSC PIN 1 0.065 0.049 0.069 0.053 0.010 0.004 COPLANARITY 0.004 0.025 BSC 0.012 0.008 SEATING PLANE 0.010 0.006 8 0 0.050 0.016 COMPLIANT TO JEDEC STANDARDS MO-137AD Figure 27. 20-Lead Shrink Small Outline Package [QSOP] (RQ-20) Dimensions shown in inches ORDERING GUIDE Model ADCMP563BRQ ADCMP564BRQ Temperature Range -40C to +85C -40C to +85C Package Description 16-Lead QSOP 20-Lead QSOP Package Option RQ-16 RQ-20 Rev. A | Page 14 of 16 ADCMP563/ADCMP564 NOTES Rev. A | Page 15 of 16 ADCMP563/ADCMP564 NOTES (c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04650-0-7/04(A) Rev. A | Page 16 of 16 This datasheet has been download from: www..com Datasheets for electronics components. |
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