LM809/LM810 3-Pin Microprocessor Reset Circuits
LM809/LM810 3-Pin Microprocessor Reset Circuits
LM809/LM810 3-Pin Microprocessor Reset Circuits
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<strong>LM809</strong>/<strong>LM810</strong>3-<strong>Pin</strong> <strong>Microprocessor</strong> <strong>Reset</strong> <strong>Circuits</strong>General DescriptionThe <strong>LM809</strong>/810 microprocessor supervisory circuits can beused to monitor the power supplies in microprocessor anddigital systems. They provide a reset to the microprocessorduring power-up, power-down and brown-out conditions.The function of the <strong>LM809</strong>/810 is to monitor the V CC supplyvoltage, and assert a reset signal whenever this voltagedeclines below the factory-programmed reset threshold. Thereset signal remains asserted for 240ms after V CC risesabove the threshold. The <strong>LM809</strong> has an active-low RESEToutput, while the <strong>LM810</strong> has an active-high RESET output.Seven standard reset voltage options are available, suitablefor monitoring 5V, 3.3V, and 3V supply voltages.With a low supply current of only 15µA, the <strong>LM809</strong>/810 areideal for use in portable equipment. The <strong>LM809</strong>/<strong>LM810</strong> areavailable in the 3-pin SOT23 package.Typical Application CircuitFeaturesn Precise monitoring of 3V, 3.3V, and 5V supply voltagesn Superior upgrade to MAX809/810n Fully specified over temperaturen 140ms min. Power-On <strong>Reset</strong> pulse width, 240ms typicalActive-low RESET Output (<strong>LM809</strong>)Active-high RESET Output (<strong>LM810</strong>)n Guaranteed RESET Output valid for V CC ≥1Vn Low Supply Current, 15µA typ.n Power supply transient immunityApplicationsn <strong>Microprocessor</strong> Systemsn Computersn Controllersn Intelligent Instrumentsn Portable/Battery-Powered Equipmentn AutomotiveConnection DiagramApril 2001<strong>LM809</strong>/<strong>LM810</strong> 3-<strong>Pin</strong> <strong>Microprocessor</strong> <strong>Reset</strong> <strong>Circuits</strong>( ) are for <strong>LM810</strong>1010570210105701© 2001 National Semiconductor Corporation DS101057 www.national.com
<strong>LM809</strong>/<strong>LM810</strong>Ordering Information<strong>Reset</strong> Threshold(V)<strong>LM809</strong> Supplied as 1000units, tape & reel<strong>LM809</strong> Supplied as 3000units, tape & reelPackageTop Mark4.63 <strong>LM809</strong>M3-4.63 <strong>LM809</strong>M3X-4.63 S8B4.38 <strong>LM809</strong>M3-4.38 <strong>LM809</strong>M3X-4.38 S7B4.00 <strong>LM809</strong>M3-4.00 <strong>LM809</strong>M3X-4.00 S6B3.08 <strong>LM809</strong>M3-3.08 <strong>LM809</strong>M3X-3.08 S5B2.93 <strong>LM809</strong>M3-2.93 <strong>LM809</strong>M3X-2.93 S4B2.63 <strong>LM809</strong>M3-2.63 <strong>LM809</strong>M3X-2.63 S3B2.45 <strong>LM809</strong>M3-2.45 <strong>LM809</strong>M3X-2.45 SFBPackageTypeSOT23-3NSC PackageM03B<strong>Reset</strong> Threshold(V)<strong>LM810</strong> Supplied as 1000units, tape & reel<strong>LM810</strong> Supplied as 3000units, tape & reelPackageTop Mark4.63 <strong>LM810</strong>M3-4.63 <strong>LM810</strong>M3X-4.63 SEBPackageTypeNSC Package4.38 <strong>LM810</strong>M3-4.38 <strong>LM810</strong>M3X-4.38 SDB4.00 <strong>LM810</strong>M3-4.00 <strong>LM810</strong>M3X-4.00 SCB3.08 <strong>LM810</strong>M3-3.08 <strong>LM810</strong>M3X-3.08 SBBSOT23-3 M03B2.93 <strong>LM810</strong>M3-2.93 <strong>LM810</strong>M3X-2.93 SAB2.63 <strong>LM810</strong>M3-2.63 <strong>LM810</strong>M3X-2.63 S9BCustom voltages and improved accuracies are available, subject to minimum orders. Contact your local National Semiconductor Sales Office for information.<strong>Pin</strong> DescriptionPIN NAME FUNCTION1 GND Ground reference2RESET (<strong>LM809</strong>)Active-low output. RESET remains low while V CC is below the reset threshold, andfor 240ms after V CC rises above the reset threshold.RESET (<strong>LM810</strong>)Active-high output. RESET remains high while V CC is below the reset threshold, andfor 240ms after V CC rises above the reset threshold.3 V CC Supply Voltage (+5V, +3.3V, or +3.0V)www.national.com 2
Absolute Maximum Ratings (Note 1)If Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.V CC −0.3V to 6.0VRESET, RESET−0.3V to (V CC + 0.3V)Input Current, V CC <strong>Pin</strong>20mAOutput Current, RESET, RESET<strong>Pin</strong>20mARate of Rise, V CC100V/µsESD Rating (Note 2)2kVContinuous Power Dissipation (T A = +70˚C)SOT-23 (Note 3)320mWAmbient Temperature Range−40˚C to +105˚CMaximum Junction Temperature125˚CStorage Temperature Range−65˚C to +160˚CLead Temperature (soldering,10sec)+300˚C<strong>LM809</strong>/<strong>LM810</strong>Electrical CharacteristicsV CC = full range, T A = −40˚C to +105˚C, unless otherwise noted. Typical values are at T A = +25˚C, V CC = 5V for4.63/4.38/4.00 versions, V CC = 3.3V for 3.08/2.93 versions, and V CC = 3V for 2.63/2.45 version. (Note 4)Symbol Parameter Conditions Min Typ Max UnitsI CCV CC RangeSupply CurrentT A = 0˚C to +70˚C 1.0 5.5T A = −40˚C to +105˚C 1.2 5.5T A = −40˚C to+85˚CT A = +85˚C to+105˚CV CC
<strong>LM809</strong>/<strong>LM810</strong>Electrical Characteristics (Continued)V CC = full range, T A = −40˚C to +105˚C, unless otherwise noted. Typical values are at T A = +25˚C, V CC = 5V for4.63/4.38/4.00 versions, V CC = 3.3V for 3.08/2.93 versions, and V CC = 3V for 2.63/2.45 version. (Note 4)Symbol Parameter Conditions Min Typ Max UnitsV OLV OHV OLV OHRESET Output Voltage Low(<strong>LM809</strong>)RESET Output Voltage High(<strong>LM809</strong>)RESET Output Voltage Low(<strong>LM810</strong>)RESET Output Voltage High(<strong>LM810</strong>)V CC =V TH min, I SINK = 1.2mA,<strong>LM809</strong>-2.45/2.63/2.93/3.08V CC =V TH min, I SINK = 3.2mA,0.4<strong>LM809</strong>-4.63/4.38/4.00V CC> 1.0V, I SINK = 50µA 0.3V CC> V TH max, I SOURCE = 500µA,<strong>LM809</strong>-2.45/2.63/2.93/3.08V CC> V TH max, I SOURCE = 800µA,<strong>LM809</strong>-4.63/4.38/4.00V CC =V TH max, I SINK = 1.2mA,<strong>LM810</strong>-2.63/2.93/3.08V CC =V TH max, I SINK = 3.2mA,<strong>LM810</strong>-4.63/4.38/4.001.8V < V CC< V TH min, I SOURCE = 150µA0.30.8V CCVV CC −1.50.30.40.8V CC VVVNote 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which the device operatescorrectly. Operating ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the ElectricalCharacteristics.Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin.Note 3: Production testing done at T A = +25˚C, over temperature limits guaranteed by design only.Note 4: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-3 package must be derated at 4mW/˚Cat ambient temperatures above 70˚C. The device has internal thermal protection.Note 5: RESET Output for <strong>LM809</strong>, RESET output for <strong>LM810</strong>.www.national.com 4
Typical Performance CharacteristicsSupply Current vs Temperature(No Load, LM8_ _-2.63/2.93/3.08)Supply Current vs Temperature(No Load, LM8_ _-4.63/4.38)Power-Down <strong>Reset</strong> Delay vs Temp(LM8_ _-2.63/2.93/3.08)<strong>LM809</strong>/<strong>LM810</strong>10105703 10105704 10105705Power-Down <strong>Reset</strong> Delay vsTemperature (LM8_ _-4.63/4.38)Power-Up <strong>Reset</strong> Timeout vsTemperatureNormalized <strong>Reset</strong> Threshold vsTemperature1010570610105708101057075www.national.com
<strong>LM809</strong>/<strong>LM810</strong>Applications InformationBenefits of Precision <strong>Reset</strong> ThresholdsA microprocessor supply supervisor must provide a resetoutput within a predictable range of the supply voltage. Acommon threshold range is between 5% and 10% below thenominal supply voltage. The 4.63V and 3.08V options of the<strong>LM809</strong>/810 use highly accurate circuitry to ensure that thereset threshold occurs only within this range (for 5V and 3.3Vsupplies). The other voltage options have the same tighttolerance to ensure a reset signal for other narrow monitorranges. See Table 1 for examples of how the standard resetthresholds apply to 3V, 3.3V, and 5V nominal supply voltages.Negative-Going V CC TransientsThe <strong>LM809</strong>/810 are relatively immune to shortnegative-going transients or glitches on V CC . Figure 2 showsthe maximum pulse width a negative-going V CC transientcan have without causing a reset pulse. In general, as themagnitude of the transient increases, going further below thethreshold, the maximum allowable pulse width decreases.Typically, for the 4.63V and 4.38V version of the <strong>LM809</strong>/810,aV CC transient that goes 100mV below the reset thresholdand lasts 20µs or less will not cause a reset pulse. A 0.1 µFbypass capacitor mounted as close as possible to the V CCpin will provide additional transient rejection.TABLE 1. <strong>Reset</strong> Thresholds Related to CommonSupply Voltages<strong>Reset</strong>Threshold3.0V 3.3V 5.0V4.63 ± 3% 90 - 95%4.38 ± 3% 85 - 90%4.00 ± 3% 78 - 82%3.08 ± 3% 90 - 95%2.93 ± 3% 86 - 90%2.63 ± 3% 85 - 90% 77 - 81%2.45 ± 3% 79 - 84% 72 - 76%Ensuring a Valid <strong>Reset</strong> Output Down to V CC =0VWhen V CC falls below 1V, the <strong>LM809</strong> RESET output nolonger sinks current. A high-impedance CMOS logic inputconnected to RESET can therefore drift to undeterminedvoltages. To prevent this situation, a 100kΩ resistor shouldbe connected from the RESET output to ground, as shown inFigure 1.A 100kΩ pull-up resistor to V CC is also recommended for the<strong>LM810</strong>, if RESET is required to remain valid for V CC< 1V.10105709FIGURE 2. Maximum Transient Duration withoutCausing a <strong>Reset</strong> Pulse vs. <strong>Reset</strong> ComparatorOverdriveInterfacing to µPs with Bidirectional <strong>Reset</strong> <strong>Pin</strong>s<strong>Microprocessor</strong>s with bidirectional reset pins, such as theMotorola 68HC11 series, can be connected to the <strong>LM809</strong>RESET output. To ensure a correct output on the <strong>LM809</strong>even when the microprocessor reset pin is in the oppositestate, connect a 4.7kΩ resistor between the <strong>LM809</strong> RESEToutput and the µP reset pin, as shown in Figure 3. Buffer the<strong>LM809</strong> RESET output to other system components.10105710FIGURE 1. RESET Valid to V CC = Ground Circuit10105711FIGURE 3. Interfacing to <strong>Microprocessor</strong>s withBidirectional <strong>Reset</strong> I/Owww.national.com 6
Physical Dimensions inches (millimeters)unless otherwise noted3-Lead SOT23-3For Ordering, refer to Ordering Information tableNS Package Number M03B<strong>LM809</strong>/<strong>LM810</strong> 3-<strong>Pin</strong> <strong>Microprocessor</strong> <strong>Reset</strong> <strong>Circuits</strong>LIFE SUPPORT POLICYNATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORTDEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERALCOUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:1. Life support devices or systems are devices orsystems which, (a) are intended for surgical implantinto the body, or (b) support or sustain life, andwhose failure to perform when properly used inaccordance with instructions for use provided in thelabeling, can be reasonably expected to result in asignificant injury to the user.2. A critical component is any component of a lifesupport device or system whose failure to performcan be reasonably expected to cause the failure ofthe life support device or system, or to affect itssafety or effectiveness.National SemiconductorCorporationAmericasTel: 1-800-272-9959Fax: 1-800-737-7018Email: support@nsc.comwww.national.comNational SemiconductorEuropeFax: +49 (0) 180-530 85 86Email: europe.support@nsc.comDeutsch Tel: +49 (0) 69 9508 6208English Tel: +44 (0) 870 24 0 2171Français Tel: +33 (0) 1 41 91 8790National SemiconductorAsia Pacific CustomerResponse GroupTel: 65-2544466Fax: 65-2504466Email: ap.support@nsc.comNational SemiconductorJapan Ltd.Tel: 81-3-5639-7560Fax: 81-3-5639-7507National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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