LM555 LM555 Timer Literature Number: SNAS548B LM555 Timer General Description Features The LM555 is a highly stable device for generating accurate time delays or oscillation. Additional terminals are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running frequency and duty cycle are accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output circuit can source or sink up to 200mA or drive TTL circuits. n n n n n n n n n Direct replacement for SE555/NE555 Timing from microseconds through hours Operates in both astable and monostable modes Adjustable duty cycle Output can source or sink 200 mA Output and supply TTL compatible Temperature stability better than 0.005% per C Normally on and normally off output Available in 8-pin MSOP package Applications n n n n n n n Precision timing Pulse generation Sequential timing Time delay generation Pulse width modulation Pulse position modulation Linear ramp generator Schematic Diagram 00785101 (c) 2006 National Semiconductor Corporation DS007851 www.national.com LM555 Timer July 2006 LM555 Connection Diagram Dual-In-Line, Small Outline and Molded Mini Small Outline Packages 00785103 Top View Ordering Information Package 8-Pin SOIC 8-Pin MSOP 8-Pin MDIP www.national.com Part Number Package Marking Media Transport LM555CM LM555CM Rails LM555CMX LM555CM 2.5k Units Tape and Reel LM555CMM Z55 1k Units Tape and Reel LM555CMMX Z55 3.5k Units Tape and Reel LM555CN LM555CN Rails 2 NSC Drawing M08A MUA08A N08E Soldering Information Dual-In-Line Package If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Soldering (10 Seconds) +18V (SOIC and MSOP) 1180 mW LM555CMM 613 mW Storage Temperature Range Vapor Phase (60 Seconds) 215C Infrared (15 Seconds) 220C See AN-450 "Surface Mounting Methods and Their Effect on Product Reliability" for other methods of soldering surface mount devices. Operating Temperature Ranges LM555C 260C Small Outline Packages Power Dissipation (Note 3) LM555CM, LM555CN LM555 Absolute Maximum Ratings (Note 2) 0C to +70C -65C to +150C Electrical Characteristics (Notes 1, 2) (TA = 25C, VCC = +5V to +15V, unless othewise specified) Parameter Conditions Limits Units LM555C Min Supply Voltage Supply Current Typ 4.5 Max 16 V 6 15 mA VCC = 5V, RL = VCC = 15V, RL = (Low State) (Note 4) 3 10 1 % RA = 1k to 100k, 50 ppm/C Timing Error, Monostable Initial Accuracy Drift with Temperature C = 0.1F, (Note 5) Accuracy over Temperature 1.5 % Drift with Supply 0.1 %/V 2.25 % 150 ppm/C 3.0 % Timing Error, Astable Initial Accuracy Drift with Temperature RA, RB = 1k to 100k, C = 0.1F, (Note 5) Accuracy over Temperature Drift with Supply 0.30 %/V Threshold Voltage 0.667 x VCC VCC = 15V 5 V VCC = 5V 1.67 Trigger Voltage Trigger Current 0.5 Reset Voltage 0.4 Reset Current Threshold Current Control Voltage Level (Note 6) VCC = 15V VCC = 5V 9 2.6 Pin 7 Leakage Output High V 0.9 A 0.5 1 V 0.1 0.4 mA 0.1 0.25 A 10 3.33 11 4 V 1 100 nA Pin 7 Sat (Note 7) Output Low VCC = 15V, I7 = 15mA 180 Output Low VCC = 4.5V, I7 = 4.5mA 80 3 mV 200 mV www.national.com LM555 Electrical Characteristics (Notes 1, 2) (Continued) (TA = 25C, VCC = +5V to +15V, unless othewise specified) Parameter Conditions Limits Units LM555C Min Output Voltage Drop (Low) Typ Max ISINK = 10mA 0.1 0.25 V ISINK = 50mA 0.4 0.75 V ISINK = 100mA 2 2.5 V ISINK = 200mA 2.5 VCC = 15V V VCC = 5V ISINK = 8mA V ISINK = 5mA 0.25 ISOURCE = 200mA, VCC = 15V 12.5 V 12.75 13.3 V 2.75 3.3 V Rise Time of Output 100 ns Fall Time of Output 100 ns Output Voltage Drop (High) ISOURCE = 100mA, VCC = 15V VCC = 5V 0.35 V Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified. Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 3: For operating at elevated temperatures the device must be derated above 25C based on a +150C maximum junction temperature and a thermal resistance of 106C/W (DIP), 170C/W (S0-8), and 204C/W (MSOP) junction to ambient. Note 4: Supply current when output high typically 1 mA less at VCC = 5V. Note 5: Tested at VCC = 5V and VCC = 15V. Note 6: This will determine the maximum value of RA + RB for 15V operation. The maximum total (RA + RB) is 20M. Note 7: No protection against excessive pin 7 current is necessary providing the package dissipation rating will not be exceeded. Note 8: Refer to RETS555X drawing of military LM555H and LM555J versions for specifications. www.national.com 4 LM555 Typical Performance Characteristics Minimuim Pulse Width Required for Triggering Supply Current vs. Supply Voltage 00785119 00785104 High Output Voltage vs. Output Source Current Low Output Voltage vs. Output Sink Current 00785121 00785120 Low Output Voltage vs. Output Sink Current Low Output Voltage vs. Output Sink Current 00785123 00785122 5 www.national.com LM555 Typical Performance Characteristics (Continued) Output Propagation Delay vs. Voltage Level of Trigger Pulse Output Propagation Delay vs. Voltage Level of Trigger Pulse 00785125 00785124 Discharge Transistor (Pin 7) Voltage vs. Sink Current Discharge Transistor (Pin 7) Voltage vs. Sink Current 00785127 00785126 www.national.com 6 MONOSTABLE OPERATION When the reset function is not in use, it is recommended that it be connected to VCC to avoid any possibility of false triggering. In this mode of operation, the timer functions as a one-shot (Figure 1). The external capacitor is initially held discharged by a transistor inside the timer. Upon application of a negative trigger pulse of less than 1/3 VCC to pin 2, the flip-flop is set which both releases the short circuit across the capacitor and drives the output high. Figure 3 is a nomograph for easy determination of R, C values for various time delays. NOTE: In monostable operation, the trigger should be driven high before the end of timing cycle. 00785105 00785107 FIGURE 1. Monostable FIGURE 3. Time Delay The voltage across the capacitor then increases exponentially for a period of t = 1.1 RA C, at the end of which time the voltage equals 2/3 VCC. The comparator then resets the flip-flop which in turn discharges the capacitor and drives the output to its low state. Figure 2 shows the waveforms generated in this mode of operation. Since the charge and the threshold level of the comparator are both directly proportional to supply voltage, the timing interval is independent of supply. ASTABLE OPERATION If the circuit is connected as shown in Figure 4 (pins 2 and 6 connected) it will trigger itself and free run as a multivibrator. The external capacitor charges through RA + RB and discharges through RB. Thus the duty cycle may be precisely set by the ratio of these two resistors. 00785106 VCC = 5V Top Trace: Input 5V/Div. TIME = 0.1 ms/DIV. RA = 9.1k Middle Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 2V/Div. C = 0.01F 00785108 FIGURE 2. Monostable Waveforms FIGURE 4. Astable During the timing cycle when the output is high, the further application of a trigger pulse will not effect the circuit so long as the trigger input is returned high at least 10s before the end of the timing interval. However the circuit can be reset In this mode of operation, the capacitor charges and discharges between 1/3 VCC and 2/3 VCC. As in the triggered mode, the charge and discharge times, and therefore the frequency are independent of the supply voltage. 7 www.national.com LM555 during this time by the application of a negative pulse to the reset terminal (pin 4). The output will then remain in the low state until a trigger pulse is again applied. Applications Information LM555 Applications Information FREQUENCY DIVIDER (Continued) The monostable circuit of Figure 1 can be used as a frequency divider by adjusting the length of the timing cycle. Figure 7 shows the waveforms generated in a divide by three circuit. Figure 5 shows the waveforms generated in this mode of operation. 00785109 VCC = 5V Top Trace: Output 5V/Div. TIME = 20s/DIV. Bottom Trace: Capacitor Voltage 1V/Div. 00785111 VCC = 5V Top Trace: Input 4V/Div. RA = 3.9k TIME = 20s/DIV. Middle Trace: Output 2V/Div. RB = 3k RA = 9.1k Bottom Trace: Capacitor 2V/Div. C = 0.01F C = 0.01F FIGURE 5. Astable Waveforms FIGURE 7. Frequency Divider The charge time (output high) is given by: t1 = 0.693 (RA + RB) C And the discharge time (output low) by: t2 = 0.693 (RB) C Thus the total period is: T = t1 + t2 = 0.693 (RA +2RB) C The frequency of oscillation is: PULSE WIDTH MODULATOR When the timer is connected in the monostable mode and triggered with a continuous pulse train, the output pulse width can be modulated by a signal applied to pin 5. Figure 8 shows the circuit, and in Figure 9 are some waveform examples. Figure 6 may be used for quick determination of these RC values. The duty cycle is: 00785112 FIGURE 8. Pulse Width Modulator 00785110 FIGURE 6. Free Running Frequency www.national.com 8 LM555 Applications Information (Continued) 00785113 VCC = 5V 00785115 Top Trace: Modulation 1V/Div. TIME = 0.2 ms/DIV. VCC = 5V Bottom Trace: Output Voltage 2V/Div. Top Trace: Modulation Input 1V/Div. TIME = 0.1 ms/DIV. RA = 9.1k Bottom Trace: Output 2V/Div. RA = 3.9k C = 0.01F RB = 3k C = 0.01F FIGURE 9. Pulse Width Modulator FIGURE 11. Pulse Position Modulator PULSE POSITION MODULATOR This application uses the timer connected for astable operation, as in Figure 10, with a modulating signal again applied to the control voltage terminal. The pulse position varies with the modulating signal, since the threshold voltage and hence the time delay is varied. Figure 11 shows the waveforms generated for a triangle wave modulation signal. LINEAR RAMP When the pullup resistor, RA, in the monostable circuit is replaced by a constant current source, a linear ramp is generated. Figure 12 shows a circuit configuration that will perform this function. 00785116 00785114 FIGURE 12. FIGURE 10. Pulse Position Modulator Figure 13 shows waveforms generated by the linear ramp. The time interval is given by: VBE . 0.6V 9 www.national.com LM555 Applications Information (Continued) 00785117 VCC = 5V Top Trace: Input 3V/Div. TIME = 20s/DIV. Middle Trace: Output 5V/Div. R1 = 47k Bottom Trace: Capacitor Voltage 1V/Div. 00785118 R2 = 100k RE = 2.7 k FIGURE 14. 50% Duty Cycle Oscillator C = 0.01 F Note that this circuit will not oscillate if RB is greater than 1/2 RA because the junction of RA and RB cannot bring pin 2 down to 1/3 VCC and trigger the lower comparator. FIGURE 13. Linear Ramp 50% DUTY CYCLE OSCILLATOR For a 50% duty cycle, the resistors RA and RB may be connected as in Figure 14. The time period for the output high is the same as previous, t1 = 0.693 RA C. For the output low it is t2 = ADDITIONAL INFORMATION Adequate power supply bypassing is necessary to protect associated circuitry. Minimum recommended is 0.1F in parallel with 1F electrolytic. Lower comparator storage time can be as long as 10s when pin 2 is driven fully to ground for triggering. This limits the monostable pulse width to 10s minimum. Delay time reset to output is 0.47s typical. Minimum reset pulse width must be 0.3s, typical. Thus the frequency of oscillation is Pin 7 current switches within 30ns of the output (pin 3) voltage. www.national.com 10 LM555 Physical Dimensions inches (millimeters) unless otherwise noted Small Outline Package (M) NS Package Number M08A 8-Lead (0.118" Wide) Molded Mini Small Outline Package NS Package Number MUA08A 11 www.national.com LM555 Timer Physical Dimensions inches (millimeters) unless otherwise noted (Continued) Molded Dual-In-Line Package (N) NS Package Number N08E National 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. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/quality/green. Lead free products are RoHS compliant. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP(R) Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page www.ti.com/video e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2011, Texas Instruments Incorporated