LM555CN

LM555 Timer July 2006 LM555 Timer General Description 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. Features 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 © 2006 National Semiconductor Corporation DS007851 www.national.com 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 Part Number LM555CM LM555CMX LM555CMM LM555CMMX LM555CN Package Marking LM555CM LM555CM Z55 Z55 LM555CN Media Transport Rails 2.5k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel Rails NSC Drawing M08A MUA08A N08E www.national.com 2 LM555 Absolute Maximum Ratings (Note 2) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Power Dissipation (Note 3) LM555CM, LM555CN LM555CMM Operating Temperature Ranges LM555C Storage Temperature Range 0˚C to +70˚C −65˚C to +150˚C 1180 mW 613 mW +18V Soldering Information Dual-In-Line Package Soldering (10 Seconds) Small Outline Packages (SOIC and MSOP) Vapor Phase (60 Seconds) Infrared (15 Seconds) 215˚C 220˚C 260˚C See AN-450 “Surface Mounting Methods and Their Effect on Product Reliability” for other methods of soldering surface mount devices. Electrical Characteristics (Notes 1, 2) (TA = 25˚C, VCC = +5V to +15V, unless othewise specified) Parameter Conditions Min Supply Voltage Supply Current VCC = 5V, RL = ∞ VCC = 15V, RL = ∞ (Low State) (Note 4) 4.5 3 10 Limits LM555C Typ Max 16 6 15 V mA Units Timing Error, Monostable Initial Accuracy Drift with Temperature Accuracy over Temperature Drift with Supply Timing Error, Astable Initial Accuracy Drift with Temperature Accuracy over Temperature Drift with Supply Threshold Voltage Trigger Voltage Trigger Current Reset Voltage Reset Current Threshold Current Control Voltage Level Pin 7 Leakage Output High Pin 7 Sat (Note 7) Output Low Output Low VCC = 15V, I7 = 15mA VCC = 4.5V, I7 = 4.5mA 180 80 200 mV mV (Note 6) VCC = 15V VCC = 5V 9 2.6 0.4 VCC = 15V VCC = 5V RA, RB = 1k to 100kΩ, C = 0.1µF, (Note 5) 3.0 0.30 0.667 5 1.67 0.5 0.5 0.1 0.1 10 3.33 1 0.9 1 0.4 0.25 11 4 100 % %/V x VCC V V µA V mA µA V nA 2.25 150 % ppm/˚C RA = 1k to 100kΩ, C = 0.1µF, (Note 5) 1.5 0.1 % %/V 1 50 % ppm/˚C 3 www.national.com LM555 Electrical Characteristics (Notes 1, 2) Parameter (Continued) (TA = 25˚C, VCC = +5V to +15V, unless othewise specified) Conditions Min Limits LM555C Typ 0.1 0.4 2 2.5 Max 0.25 0.75 2.5 V V V V V 0.25 12.5 12.75 2.75 13.3 3.3 100 100 0.35 V V V V ns ns Units Output Voltage Drop (Low) VCC = 15V ISINK = 10mA ISINK = 50mA ISINK = 100mA ISINK = 200mA VCC = 5V ISINK = 8mA ISINK = 5mA Output Voltage Drop (High) ISOURCE = 200mA, VCC = 15V ISOURCE = 100mA, VCC = 15V VCC = 5V Rise Time of Output Fall Time of Output 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 25˚C based on a +150˚C maximum junction temperature and a thermal resistance of 106˚C/W (DIP), 170˚C/W (S0-8), and 204˚C/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 20MΩ. 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 00785104 00785119 High Output Voltage vs. Output Source Current Low Output Voltage vs. Output Sink Current 00785120 00785121 Low Output Voltage vs. Output Sink Current Low Output Voltage vs. Output Sink Current 00785122 00785123 5 www.national.com LM555 Typical Performance Characteristics Output Propagation Delay vs. Voltage Level of Trigger Pulse (Continued) Output Propagation Delay vs. Voltage Level of Trigger Pulse 00785124 00785125 Discharge Transistor (Pin 7) Voltage vs. Sink Current Discharge Transistor (Pin 7) Voltage vs. Sink Current 00785126 00785127 www.national.com 6 LM555 Applications Information MONOSTABLE OPERATION 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. 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. When the reset function is not in use, it is recommended that it be connected to VCC to avoid any possibility of false triggering. 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 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. FIGURE 3. Time Delay 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 TIME = 0.1 ms/DIV. RA = 9.1kΩ C = 0.01µF Top Trace: Input 5V/Div. Middle Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 2V/Div. 00785108 FIGURE 2. Monostable Waveforms 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 10µs before the end of the timing interval. However the circuit can be reset FIGURE 4. Astable 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 Applications Information (Continued) FREQUENCY DIVIDER 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 TIME = 20µs/DIV. RA = 3.9kΩ RB = 3kΩ C = 0.01µF Top Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 1V/Div. VCC = 5V TIME = 20µs/DIV. RA = 9.1kΩ C = 0.01µF Top Trace: Input 4V/Div. Middle Trace: Output 2V/Div. 00785111 Bottom Trace: Capacitor 2V/Div. FIGURE 5. Astable Waveforms 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: FIGURE 7. Frequency Divider 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 TIME = 0.2 ms/DIV. RA = 9.1kΩ C = 0.01µF Top Trace: Modulation 1V/Div. Bottom Trace: Output Voltage 2V/Div. 00785115 VCC = 5V TIME = 0.1 ms/DIV. RA = 3.9kΩ RB = 3kΩ C = 0.01µF Top Trace: Modulation Input 1V/Div. Bottom Trace: Output 2V/Div. 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 TIME = 20µs/DIV. R1 = 47kΩ R2 = 100kΩ RE = 2.7 kΩ C = 0.01 µF Top Trace: Input 3V/Div. Middle Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 1V/Div. 00785118 FIGURE 14. 50% Duty Cycle Oscillator 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. ADDITIONAL INFORMATION Adequate power supply bypassing is necessary to protect associated circuitry. Minimum recommended is 0.1µF in parallel with 1µF electrolytic. Lower comparator storage time can be as long as 10µs when pin 2 is driven fully to ground for triggering. This limits the monostable pulse width to 10µs minimum. Delay time reset to output is 0.47µs typical. Minimum reset pulse width must be 0.3µs, typical. Pin 7 current switches within 30ns of the output (pin 3) voltage. 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 = Thus the frequency of oscillation is 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. 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