HIGH PERFORMANCE VOLTAGE COMPARATORS

Size: px

Start display at page:

Download "HIGH PERFORMANCE VOLTAGE COMPARATORS"

Morgan Atkins
6 years ago
Views:

1 Order this document by LM/D The ability to operate from a single power supply of. V to V or ± V split supplies, as commonly used with operational amplifiers, makes the LM/LM a truly versatile comparator. Moreover, the inputs of the device can be isolated from system ground while the output can drive loads referenced either to ground, the or the supply. This flexibility makes it possible to drive DTL, RTL, TTL, or MOS logic. The output can also switch voltages to V at currents to ma. Thus the LM/LM can be used to drive relays, lamps or solenoids. HIGH PERFORMANCE VOLTAGE COMPARATORS SEMICONDUCTOR TECHNICAL DATA Typical Comparator Design Configurations Split Power Supply with Offset Balance Single Supply. k. k 6 GroundReferred Load Load Referred to Negative Supply N SUFFIX PLASTIC PACKAGE CASE 66 D SUFFIX PLASTIC PACKAGE CASE (SO) Input polarity is reversed when Gnd pin is used as an output. Load Referred to Positive Supply Input polarity is reversed when Gnd pin is used as an output. Strobe Capability Gnd PIN CONNECTIONS (Top View) 6 Balance/Strobe Balance 6 TTL Strobe Device ORDERING INFORMATION Operating Temperature Range Package. k LMD LMD LMN TA = to C TA = to C SO SO Plastic DIP MOTOROLA ANALOG IC DEVICE DATA Motorola, Inc. 996 Rev

2 LM LM MAXIMUM RATINGS (TA = C, unless otherwise noted.) Rating Symbol LM LM Unit Total Supply Voltage 6 6 Vdc to Negative Supply Voltage VO Vdc Ground to Negative Supply Voltage Vdc Input Differential Voltage VID ± ± Vdc Input Voltage (Note ) Vin ± ± Vdc Voltage at Strobe Pin to to Vdc Power Dissipation and Thermal Characteristics Plastic DIP PD 6 mw Derate Above TA = C /θja. mw/ C Operating Ambient Temperature Range TA to to C Operating Junction Temperature TJ(max) C Storage Temperature Range Tstg 6 to 6 to C ELECTRICAL CHARACTERISTICS ( = V, = V, TA = C, unless otherwise noted [Note ].) LM LM Characteristic Symbol Min Typ Max Min Typ Max Unit Input Offset Voltage (Note ) VIO mv RS kω, TA = C.... RS kω, Tlow TA Thigh*. Input Offset Current (Note ) TA = C IIO.. na Tlow TA Thigh* Input Bias Current TA = C IIB na Tlow TA Thigh* Voltage Gain AV V/mV Response Time (Note ) ns Saturation Voltage VOL V VID. mv, IO = ma, TA = C.. VID mv, IO = ma, TA = C... V, =, Tlow TA Thigh* VID 6. mv, Isink. ma.. VID mv, Isink. ma.. Strobe On Current (Note ) IS.. ma Leakage Current VID. mv, VO= V, TA = C, Istrobe=. ma. na VID mv, VO= V, TA = C, Istrobe=. ma. na VID. mv, VO= V, Tlow TA Thigh*.. µa Input Voltage Range (Tlow TA Thigh*) VICR.. to.... to.. V Positive Supply Current ICC ma Negative Supply Current IEE.... ma * T low = C for LM T high = C for LM = C for LM = C for LM NOTES:. Offset voltage, offset current and bias current specifications apply for a supply voltage range from a single. V supply up to ± V supplies.. This rating applies for ± V supplies. The positive input voltage limit is V above the negative supply. The negative input voltage limit is equal to the negative supply voltage or V below the positive supply, whichever is less.. The offset voltages and offset currents given are the maximum values required to drive the output within a volt of either supply with a. ma load. Thus, these parameters define an error band and take into account the worst case effects of voltage gain and input impedance.. The response time specified is for a mv input step with. mv overdrive.. Do not short the strobe pin to ground; it should be current driven at. ma to. ma. MOTOROLA ANALOG IC DEVICE DATA

3 LM LM Figure. Circuit Schematic Balance Balance/Strobe. k 6. k. k. k. k. k. k 9. k. k 6 Gnd, INPUT BIAS CURRENT (na) I IB Figure. Input Bias Current Normal Pins & 6 Tied to = V = V, INPUT OFFSET CURRENT (na) I IO..... Figure. Input Offset Current Pins & 6 Tied to Normal = V = V, INPUT BIAS CURRENT (na) I IB 6 Figure. Input Bias Current versus Differential Input Voltage DIFFERENTIAL INPUT VOLTAGE (V) = V = V TA = C COMMON MODE LIMITS (V)..... Figure. Common Mode Limits Referred to Supply Voltages MOTOROLA ANALOG IC DEVICE DATA

4 LM LM V INPUT VOLTAGE (mv) in, V, OUTPUT VOLTAGE (V) O..... mv Figure 6. Response Time for Various Input Overdrives. mv. mv ttlh, RESPONSE TIME (µs) V in. V Ω V O = V = V TA = C V INPUT VOLTAGE (mv) in, V, OUTPUT VOLTAGE (V) O..... mv Figure. Response Time for Various Input Overdrives. mv. mv tthl, RESPONSE TIME (µs) V in = V = V TA = C. V Ω V O V INPUT VOLTAGE (mv) in, V, OUTPUT VOLTAGE (V) O.. Figure. Response Time for Various Input Overdrives mv. mv. mv V in V EE V CC V O. k = V = V TA = C Figure 9. Response Time for Various Input Overdrives.... ttlh, RESPONSE TIME (µs) tthl, RESPONSE TIME (µs) V INPUT VOLTAGE (mv) in, V, OUTPUT VOLTAGE (V) O.. mv. mv. mv V in V CC V EE = V = V TA = C V O. k OUTPUT SHORT CIRCUIT CURRENT (ma) Figure. Short Circuit Current Characteristics and Power Dissipation Power Dissipation TA = C. VO, OUTPUT VOLTAGE (V) Short Circuit Current , POWER DISSIPATION (W) PD V OL, SATURATION VOLTAGE (V) Figure. Saturation Voltage versus Current TA = C TA = C TA = C. 6 6 IO, OUTPUT CURRENT (ma) MOTOROLA ANALOG IC DEVICE DATA

5 LM LM Figure. Leakage Current Figure. Power Supply Current versus Supply Voltage OUTPUT LEAKAGE CURRENT (ma).. = V = V VO = V (LM/ only) POWER SUPPLY CURRENT (ma) TA = C Positive Supply Low Positive and Negative Power Supply H igh. 6., POWER SUPPLY VOLTAGE (V) SUPPLY CURRENT (ma) Figure. Power Supply Current Postive Supply Low Positive and Negative Supply High = V = V. APPLICATIONS INFORMATION Figure. Improved Method of Adding Hysteresis Without Applying Positive Feedback to the V Figure 6. Conventional Technique for Adding Hysteresis V. k. k. k. µf. k C k. µf. k Input R C R 6 LM. µf. k Input R C R C 6 LM V. µf. M V k. µf MOTOROLA ANALOG IC DEVICE DATA

6 LM LM TECHNIQUES FOR AVOIDING OSCILLATIONS IN COMPARATOR APPLICATIONS When a high speed comparator such as the LM is used with high speed input signals and low source impedances, the output response will normally be fast and stable, providing the power supplies have been bypassed (with. µf disc capacitors), and that the output signal is routed well away from the inputs (Pins and ) and also away from Pins and 6. However, when the input signal is a voltage ramp or a slow sine wave, or if the signal source impedance is high (. kω to kω), the comparator may burst into oscillation near the crossingpoint. This is due to the high gain and wide bandwidth of comparators like the LM series. To avoid oscillation or instability in such a usage, several precautions are recommended, as shown in Figure. The trim pins (Pins and 6) act as unwanted auxiliary inputs. If these pins are not connected to a trimpot, they should be shorted together. If they are connected to a trimpot, a. µf capacitor (C) between Pins and 6 will minimize the susceptibility to AC coupling. A smaller capacitor is used if Pin is used for positive feedback as in Figure. For the fastest response time, tie both balance pins to. Certain sources will produce a cleaner comparator output waveform if a pf to pf capacitor (C) is connected directly across the input pins. When the signal source is applied through a resistive network, R, it is usually advantageous to choose R of the same value, both for DC and for dynamic (AC) considerations. Carbon, tinoxide, and metalfilm resistors have all been used with good results in comparator input circuitry, but inductive wirewound resistors should be avoided. When comparator circuits use input resistors (e.g., summing resistors), their value and placement are particularly important. In all cases the body of the resistor should be close to the device or socket. In other words, there should be a very short lead length or printedcircuit foil run between comparator and resistor to radiate or pick up signals. The same applies to capacitors, pots, etc. For example, if R = kω, as little as inches of lead between the resistors and the input pins can result in oscillations that are very hard to dampen. Twisting these input leads tightly is the best alternative to placing resistors close to the comparator. Since feedback to almost any pin of a comparator can result in oscillation, the printedcircuit layout should be engineered thoughtfully. Preferably there should be a groundplane under the LM circuitry (e.g., one side of a double layer printed circuit board). Ground, positive supply or negative supply foil should extend between the output and the inputs to act as a guard. The foil connections for the inputs should be as small and compact as possible, and should be essentially surrounded by ground foil on all sides to guard against capacitive coupling from any fast highlevel signals (such as the output). If Pins and 6 are not used, they should be shorted together. If they are connected to a trimpot, the trimpot should be located no more than a few inches away from the LM, and a. µf capacitor should be installed across Pins and 6. If this capacitor cannot be used, a shielding printedcircuit foil may be advisable between Pins 6 and. The power supply bypass capacitors should be located within a couple inches of the LM. A standard procedure is to add hysteresis to a comparator to prevent oscillation, and to avoid excessive noise on the output. In the circuit of Figure 6, the feedback resistor of kω from the output to the positive input will cause about. mv of hysteresis. However, if R is larger than Ω, such as kω, it would not be practical to simply increase the value of the positive feedback resistor proportionally above kω to maintain the same amount of hysteresis. When both inputs of the LM are connected to active signals, or if a highimpedance signal is driving the positive input of the LM so that positive feedback would be disruptive, the circuit of Figure is ideal. The positive feedback is applied to Pin (one of the offset adjustment pins). This will be sufficient to cause. mv to. mv hysteresis and sharp transitions with input triangle waves from a few Hz to hundreds of khz. The positivefeedback signal across the Ω resistor swings mv below the positive supply. This signal is centered around the nominal voltage at Pin, so this feedback does not add to the offset voltage of the comparator. As much as. mv of offset voltage can be trimmed out, using the. kω pot and. kω resistor as shown. Figure. ZeroCrossing Detector Driving CMOS Logic Figure. Relay Driver with Strobe Capability = V Input Balance Adjust Balance. k. k LM = V Gnd k to CMOS Logic Gnd LM Balance/Strobe N Q or Equiv. k TTL Strobe *D *Zener Diode D protects the comparator from inductive kickback and voltage transients on the supply line. 6 MOTOROLA ANALOG IC DEVICE DATA

7 LM LM OUTLINE DIMENSIONS B N SUFFIX PLASTIC PACKAGE CASE 66 ISSUE K NOTES:. DIMENSION L TO CENTER OF LEAD WHEN FORMED PARALLEL.. PACKAGE CONTOUR OPTIONAL (ROUND OR SQUARE CORNERS).. DIMENSIONING AND TOLERANCING PER ANSI Y.M, 9. NOTE T SEATING PLANE H F A L C J N M D K G. (.) M T A M B M MILLIMETERS INCHES DIM MIN MAX MIN MAX A B C.9... D.... F.... G. BSC. BSC H.6... J.... K.9... L.6 BSC. BSC M N.6... D SUFFIX PLASTIC PACKAGE CASE (SO) ISSUE R A E B C A e D B H A. M C B S A S. M B M SEATING PLANE. h X C L NOTES:. DIMENSIONING AND TOLERANCING PER ASME Y.M, 99.. DIMENSIONS ARE IN MILLIMETERS.. DIMENSION D AND E DO NOT INCLUDE MOLD PROTRUSION.. MAXIMUM MOLD PROTRUSION. PER SIDE.. DIMENSION B DOES NOT INCLUDE MOLD PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE. TOTAL IN EXCESS OF THE B DIMENSION AT MAXIMUM MATERIAL CONDITION. MILLIMETERS DIM MIN MAX A.. A.. B..9 C.. D.. E.. e. BSC H. 6. h.. L.. MOTOROLA ANALOG IC DEVICE DATA

8 LM LM Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters which may be provided in Motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including Typicals must be validated for each customer application by customer s technical experts. Motorola does not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal Opportunity/Affirmative Action Employer. How to reach us: USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; JAPAN: Nippon Motorola Ltd.; TatsumiSPDJLDC, 6F SeibuButsuryuCenter, P.O. Box 9; Phoenix, Arizona 6. or 6 Tatsumi KotoKu, Tokyo, Japan. MFAX: RMFAX@ .sps.mot.com TOUCHTONE 6669 ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; B Tai Ping Industrial Park, INTERNET: Ting Kok Road, Tai Po, N.T., Hong Kong MOTOROLA ANALOG IC DEVICE LM/D DATA

MARKING DIAGRAMS PIN CONNECTIONS ORDERING INFORMATION PDIP 8 N SUFFIX CASE 626 LM311D AWL YYWW SO 8 98 Units/Rail

MARKING DIAGRAMS PIN CONNECTIONS ORDERING INFORMATION PDIP 8 N SUFFIX CASE 626 LM311D AWL YYWW SO 8 98 Units/Rail The ability to operate from a single power supply of 5.0 V to 30 V or 15 V split supplies, as commonly used with operational amplifiers, makes the LM211/LM311 a truly versatile comparator. Moreover, the