NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 D D D D D NE555 . . . D, P, PS, OR PW PACKAGE SA555 . . . D OR P PACKAGE SE555 . . . D, JG, OR P PACKAGE (TOP VIEW) Timing From Microseconds to Hours Astable or Monostable Operation Adjustable Duty Cycle TTL-Compatible Output Can Sink or Source up to 200 mA Designed To Be Interchangeable With Signetics NE555, SA555, and SE555 GND TRIG OUT RESET 1 8 2 7 3 6 4 5 VCC DISCH THRES CONT description SE555 . . . FK PACKAGE (TOP VIEW) NC GND NC VCC NC These devices are precision timing circuits capable of producing accurate time delays or oscillation. In the time-delay or monostable mode of operation, the timed interval is controlled by a single external resistor and capacitor network. In the astable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor. NC TRIG NC OUT NC 4 3 2 1 20 19 18 5 17 6 16 7 15 8 14 NC DISCH NC THRES NC NC RESET NC CONT NC 9 10 11 12 13 The threshold and trigger levels normally are two-thirds and one-third, respectively, of VCC. These levels can be altered by use of the control-voltage terminal. When the trigger input falls below the trigger level, the flip-flop is set and NC - No internal connection the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level, the flip-flop is reset and the output is low. The reset (RESET) input can override all other inputs and can be used to initiate a new timing cycle. When RESET goes low, the flip-flop is reset and the output goes low. When the output is low, a low-impedance path is provided between discharge (DISCH) and ground. The output circuit is capable of sinking or sourcing current up to 200 mA. Operation is specified for supplies of 5 V to 15 V. With a 5-V supply, output levels are compatible with TTL inputs. The NE555 is characterized for operation from 0C to 70C. The SA555 is characterized for operation from -40C to 85C. The SE555 is characterized for operation over the full military range of -55C to 125C. AVAILABLE OPTIONS PACKAGE TA VTHRES MAX VCC = 15 V SMALL OUTLINE (D, PS) CHIP CARRIER (FK) CERAMIC DIP (JG) PLASTIC DIP (P) PLASTIC THIN SHRINK SMALL OUTLINE (PW) 0C to 70C 11.2 V NE555D NE555PS -- -- NE555P NE555PW -40C to 85C 11.2 V SA555D -- -- SA555P -- -55C to 125C 10.6 V SE555D SE555FK SE555JG SE555P -- The D package is available taped and reeled. Add the suffix R to the device type (e.g., NE555DR). The PS and PW packages are only available taped and reeled. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright 2002, Texas Instruments Incorporated PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. On products compliant to MIL-PRF-38535, all parameters are tested unless otherwise noted. On all other products, production processing does not necessarily include testing of all parameters. POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 1 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 FUNCTION TABLE RESET TRIGGER VOLTAGE THRESHOLD VOLTAGE OUTPUT DISCHARGE SWITCH Low Irrelevant Irrelevant Low On High <1/3 VDD Irrelevant High Off High >1/3 VDD >2/3 VDD Low On High >1/3 VDD <2/3 VDD As previously established Voltage levels shown are nominal. functional block diagram VCC 8 6 THRES 2 TRIG RESET 4 CONT 5 I I I I R1 R S 1 I I 3 II 7 1 GND Pin numbers shown are for the D, JG, P, PS, and PW packages. NOTE A: RESET can override TRIG, which can override THRES. 2 OUT POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 DISCH NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 absolute maximum ratings over operating free-air temperature range (unless otherwise noted) Supply voltage, VCC (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V Input voltage (CONT, RESET, THRES, and TRIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC Output current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 mA Continuous total dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Dissipation Rating Table Package thermal impedance, JA (see Note 2): D package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97C/W P package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85C/W PS package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95C/W PW package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149C/W Case temperature for 60 seconds: FK package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds: D, P, PS, or PW package . . . . . . . . 260C Lead temperature 1,6 mm (1/16 inch) from case for 60 seconds: JG package . . . . . . . . . . . . . . . . . . . . 300C Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -65C to 150C Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. NOTES: 1. All voltage values are with respect to GND. 2. The package thermal impedance is calculated in accordance with JESD 51-7. DISSIPATION RATING TABLE PACKAGE TA 25C POWER RATING DERATING FACTOR ABOVE TA = 25C TA = 70C POWER RATING TA = 85C POWER RATING TA = 125C POWER RATING FK 1375 mW 11.0 mW/C 880 mW 715 mW 275 mW JG (SE555) 1050 mW 8.4 mW/C 672 mW 546 mW 210 mW recommended operating conditions VCC VI IO TA Supply voltage MIN MAX SA555, NE555 4.5 16 SE555 4.5 18 Input voltage (CONT, RESET, THRES, and TRIG) VCC 200 Output current Operating free-air temperature POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 NE555 0 SA555 -40 85 SE555 -55 125 UNIT V V mA 70 C 3 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 electrical characteristics, VCC = 5 V to 15 V, TA = 25C (unless otherwise noted) PARAMETER THRES voltage level VCC = 15 V VCC = 5 V TYP MAX MIN TYP MAX 9.4 10 10.6 8.8 10 11.2 2.7 3.3 4 2.4 3.3 4.2 30 250 30 250 5 5.2 4.5 5 5.6 1.1 1.67 2.2 0.5 2 0.7 1 4.8 TA = -55C to 125C TRIG voltage level TRIG current RESET voltage level RESET current 3 1.45 VCC = 5 V 0.3 TA = -55C to 125C RESET at VCC 9.6 TA = -55C to 125C TA = -55C to 125C VCC = 15 V, VCC = 5 V, IOL = 3.5 mA 0.1 0.4 0.1 0.4 -1 -0.4 -1.5 20 100 10 10.4 2.9 VCC = 15 V,, IOH = -100 mA VCC = 15 V, VCC = 5 V,, IOH = -100 mA 100 10 11 3.8 2.6 3.3 4 0.1 0.25 0.4 0.75 2 2.5 A V mA nA V 3.8 0.15 0.4 0.5 2 2.2 2.7 V 2.5 2.5 0.35 0.1 0.2 0.15 0.25 0.1 0.35 0.15 0.4 0.8 13 13.3 12.75 13.3 12 12.5 3 TA = -55C to 125C VCC = 15 V V 1 TA = -55C to 125C IOL = 200 mA TA = -55C to 125C IOH = -200 mA nA 0.2 TA = -55C to 125C IOL = 8 mA VCC = 5 V, 20 9 10.4 3.3 TA = -55C to 125C VCC = 5 V,, IOL = 5 mA 0.3 -0.4 TA = -55C to 125C VCC = 15 V,, IOL = 100 mA Output high, g No load 1 TA = -55C to 125C VCC = 15 V,, IOL = 50 mA Supply current 0.9 0.7 0.1 VCC = 15 V,, IOL = 10 mA Output low,, No load 0.5 9.6 2.9 VCC = 5 V 1.9 1.1 RESET at 0 V VCC = 15 V High-level output voltage 1.67 V 1.9 DISCH switch off-state current Low-level out output ut voltage 6 TA = -55C to 125C TRIG at 0 V CONT voltage (open circuit) UNIT MIN THRES current (see Note 3) VCC = 15 V NE555 SA555 SE555 TEST CONDITIONS V 12.5 3.3 2.75 3.3 2 VCC = 5 V VCC = 15 V 10 12 10 15 3 5 3 6 9 10 9 13 mA VCC = 5 V 2 4 2 5 NOTE 3: This parameter influences the maximum value of the timing resistors RA and RB in the circuit of Figure 12. For example, when VCC = 5 V, the maximum value is R = RA + RB 3.4 M, and for VCC = 15 V, the maximum value is 10 M. 4 POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 operating characteristics, VCC = 5 V and 15 V TEST CONDITIONS PARAMETER Initial error of timing interval Each timer, monostable Each timer, astable Temperature coefficient of timing interval Each timer, monostable Each timer, astable TA = MIN to MAX Supply-voltage y g sensitivityy of timing interval Each timer, monostable Each timer, astable TA = 25C TA = 25C NE555 SA555 SE555 MIN TYP MAX 0.5% 1.5%* 1.5% 30 UNIT TYP MAX 1% 3% 2.25% 100* 90 0.05 MIN 50 ppm/C 150 0.2* 0.15 0.1 0.5 0.3 %/V Output-pulse rise time CL = 15 pF, TA = 25C 100 200* 100 300 ns Output-pulse fall time CL = 15 pF, TA = 25C 100 200* 100 300 ns * On products compliant to MIL-PRF-38535, this parameter is not production tested. For conditions shown as MIN or MAX, use the appropriate value specified under recommended operating conditions. Timing interval error is defined as the difference between the measured value and the average value of a random sample from each process run. Values specified are for a device in a monostable circuit similar to Figure 9, with the following component values: RA = 2 k to 100 k, C = 0.1 F. Values specified are for a device in an astable circuit similar to Figure 12, with the following component values: RA = 1 k to 100 k, C = 0.1 F. POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 5 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 TYPICAL CHARACTERISTICS LOW-LEVEL OUTPUT VOLTAGE vs LOW-LEVEL OUTPUT CURRENT 4 2 1 0.7 0.4 IIII IIII IIII IIII IIII IIII IIII IIII IIII IIIII IIIII IIIII 10 7 VCC = 5 V TA = -55C TA = 25C IIIII TA = 125C 0.2 0.1 0.07 0.04 VOL - Low-Level Output Voltage - V VOL - Low-Level Output Voltage - V 10 7 LOW-LEVEL OUTPUT VOLTAGE vs LOW-LEVEL OUTPUT CURRENT 0.02 VCC = 10 V 4 2 TA = 25C 1 0.7 TA= -55C TA = 125C 0.4 0.2 0.1 0.07 0.04 0.02 0.01 0.01 1 2 4 7 10 20 40 70 100 1 2 IOL - Low-Level Output Current - mA Figure 1 TA = -55C 1 0.7 TA = 25C 0.2 TA = 125C 0.04 1.6 1.2 0.8 0.6 0.4 0.01 0 4 7 10 20 40 70 100 TA = 125C 1 0.2 2 IIIIII VCC = 5 V to 15 V 1 IOL - Low-Level Output Current - mA Figure 3 2 4 7 10 20 40 70 100 IOH - High-Level Output Current - mA Figure 4 Data for temperatures below 0C and above 70C are applicable for SE555 circuits only. 6 70 100 TA = 25C 1.4 0.02 1 40 TA = -55C 1.8 2 0.1 0.07 20 IIII IIII IIII IIII 2.0 VCC = 15 V 0.4 10 DROP BETWEEN SUPPLY VOLTAGE AND OUTPUT vs HIGH-LEVEL OUTPUT CURRENT ( VCC - VOH) - Voltage Drop - V VOL - Low-Level Output Voltage - V 4 IIII IIII 7 Figure 2 LOW-LEVEL OUTPUT VOLTAGE vs LOW-LEVEL OUTPUT CURRENT 10 7 4 IOL - Low-Level Output Current - mA POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 TYPICAL CHARACTERISTICS NORMALIZED OUTPUT PULSE DURATION (MONOSTABLE OPERATION) vs SUPPLY VOLTAGE SUPPLY CURRENT vs SUPPLY VOLTAGE Pulse Duration Relative to Value at VCC = 10 V 10 Output Low, No Load 9 I CC - Supply Current - mA 8 TA = 25C 7 6 5 TA = -55C 4 TA = 125C 3 2 1 0 5 6 7 8 9 10 11 12 13 14 1.015 1.010 1.005 1 0.995 0.990 0.985 15 0 5 VCC - Supply Voltage - V Figure 5 PROPAGATION DELAY TIME vs LOWEST VOLTAGE LEVEL OF TRIGGER PULSE 1.015 300 VCC = 10 V TA = 125C tpd - Propagation Delay Time - ns Pulse Duration Relative to Value at TA = 25 C 20 Figure 6 NORMALIZED OUTPUT PULSE DURATION (MONOSTABLE OPERATION) vs FREE-AIR TEMPERATURE 1.010 1.005 1 0.995 0.990 0.985 -75 15 10 VCC - Supply Voltage - V 250 TA = 70C TA = 25C 200 150 TA = 0C 100 TA = -55C 50 0 -50 -25 0 25 50 75 100 125 TA - Free-Air Temperature - C 0 0.1 x VCC 0.2 x VCC 0.3 x VCC 0.4 x VCC Lowest Voltage Level of Trigger Pulse Figure 7 Figure 8 Data for temperatures below 0C and above 70C are applicable for SE555 series circuits only. POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 7 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION monostable operation For monostable operation, any of these timers can be connected as shown in Figure 9. If the output is low, application of a negative-going pulse to the trigger (TRIG) sets the flip-flop (Q goes low), drives the output high, and turns off Q1. Capacitor C then is charged through RA until the voltage across the capacitor reaches the threshold voltage of the threshold (THRES) input. If TRIG has returned to a high level, the output of the threshold comparator resets the flip-flop (Q goes high), drives the output low, and discharges C through Q1. IIIII IIIII IIIII IIIII RA = 9.1 k CL = 0.01 F RL = 1 k See Figure 9 RA 5 I 4 7 6 Input 2 8 CONT VCC RL RESET DISCH OUT 3 Input Voltage Voltage - 2 V/div VCC (5 V to 15 V) Output Output Voltage THRES TRIG IIIIII GND 1 Capacitor Voltage Pin numbers shown are for the D, JG, P, PS, and PW packages. Time - 0.1 ms/div Figure 9. Circuit for Monostable Operation Applying a negative-going trigger pulse simultaneously to RESET and TRIG during the timing interval discharges C and reinitiates the cycle, commencing on the positive edge of the reset pulse. The output is held low as long as the reset pulse is low. To prevent false triggering, when RESET is not used, it should be connected to VCC. 8 POST OFFICE BOX 655303 10 RA = 10 M 1 tw - Output Pulse Duration - s Monostable operation is initiated when TRIG voltage falls below the trigger threshold. Once initiated, the sequence ends only if TRIG is high at the end of the timing interval. Because of the threshold level and saturation voltage of Q1, the output pulse duration is approximately tw = 1.1RAC. Figure 11 is a plot of the time constant for various values of RA and C. The threshold levels and charge rates both are directly proportional to the supply voltage, VCC. The timing interval is, therefore, independent of the supply voltage, so long as the supply voltage is constant during the time interval. Figure 10. Typical Monostable Waveforms RA = 1 M 10-1 10-2 10-3 RA = 100 k RA = 10 k 10-4 RA = 1 k 10-5 0.001 0.01 0.1 1 10 100 C - Capacitance - F Figure 11. Output Pulse Duration vs Capacitance * DALLAS, TEXAS 75265 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION astable operation As shown in Figure 12, adding a second resistor, RB, to the circuit of Figure 9 and connecting the trigger input to the threshold input causes the timer to self-trigger and run as a multivibrator. The capacitor C charges through RA and RB and then discharges through RB only. Therefore, the duty cycle is controlled by the values of RA and RB. This astable connection results in capacitor C charging and discharging between the threshold-voltage level (0.67 x VCC) and the trigger-voltage level (0.33 x VCC). As in the monostable circuit, charge and discharge times (and, therefore, the frequency and duty cycle) are independent of the supply voltage. IIIIIIIIII W W W IIIIIIIIII IIIIIIIIII VCC (5 V to 15 V) RA = 5 k RB = 3 k C = 0.15 F RA II 4 7 RB 8 VCC CONT 6 2 RL RESET DISCH 3 OUT Output tH THRES TRIG Output Voltage tL GND C Voltage - 1 V/div 0.01 F Open (see Note A) 5 RL = 1 k See Figure 12 1 Pin numbers shown are for the D, JG, P, PS, and PW packages. NOTE A: Decoupling CONT voltage to ground with a capacitor can improve operation. This should be evaluated for individual applications. Figure 12. Circuit for Astable Operation POST OFFICE BOX 655303 Capacitor Voltage Time - 0.5 ms/div Figure 13. Typical Astable Waveforms * DALLAS, TEXAS 75265 9 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION astable operation (continued) Figure 13 shows typical waveforms generated during astable operation. The output high-level duration tH and low-level duration tL can be calculated as follows: 100 k + 0.693 (RA ) RB) C H t + 0.693 (R C L B) RA + 2 RB = 1 k Other useful relationships are shown below. + tH ) tL + 0.693 (RA ) 2RB) C 1.44 frequency [ (R ) 2R ) C period A Output driver duty cycle B + t t)L t + R )RB2R H L A B Output waveform duty cycle t R H B 1- t t R 2R H L A B R t B L Low- t o-high ratio t R R H A B + ) + + 10 ) + ) POST OFFICE BOX 655303 f - Free-Running Frequency - Hz t RA + 2 RB = 10 k 10 k RA + 2 RB = 100 k 1k 100 10 1 RA + 2 RB = 1 M RA + 2 RB = 10 M 0.1 0.001 0.01 0.1 1 10 C - Capacitance - F Figure 14. Free-Running Frequency * DALLAS, TEXAS 75265 100 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION missing-pulse detector The circuit shown in Figure 15 can be used to detect a missing pulse or abnormally long spacing between consecutive pulses in a train of pulses. The timing interval of the monostable circuit is retriggered continuously by the input pulse train as long as the pulse spacing is less than the timing interval. A longer pulse spacing, missing pulse, or terminated pulse train permits the timing interval to be completed, thereby generating an output pulse as shown in Figure 16. VCC (5 V to 15 V) Input 2 8 VCC OUT 0.01 F 3 TRIG DISCH 5 RL CONT THRES GND VCC = 5 V RA = 1 k C = 0.1 F See Figure 15 RA III Output 7 6 Voltage - 2 V/div 4 RESET IIIII IIIII IIIII IIIII Input Voltage IIIII IIIII C Output Voltage 1 A5T3644 Capacitor Voltage Pin numbers shown are shown for the D, JG, P, PS, and PW packages. Figure 15. Circuit for Missing-Pulse Detector POST OFFICE BOX 655303 Time - 0.1 ms/div Figure 16. Completed-Timing Waveforms for Missing-Pulse Detector * DALLAS, TEXAS 75265 11 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION frequency divider By adjusting the length of the timing cycle, the basic circuit of Figure 9 can be made to operate as a frequency divider. Figure 17 shows a divide-by-three circuit that makes use of the fact that retriggering cannot occur during the timing cycle. IIIII IIIII IIIII IIIII Voltage - 2 V/div VCC = 5 V RA = 1250 C = 0.02 F See Figure 9 Input Voltage Output Voltage Capacitor Voltage Time - 0.1 ms/div Figure 17. Divide-by-Three Circuit Waveforms pulse-width modulation The operation of the timer can be modified by modulating the internal threshold and trigger voltages, which is accomplished by applying an external voltage (or current) to CONT. Figure 18 shows a circuit for pulse-width modulation. A continuous input pulse train triggers the monostable circuit, and a control signal modulates the threshold voltage. Figure 19 shows the resulting output pulse-width modulation. While a sine-wave modulation signal is illustrated, any wave shape could be used. 12 POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION IIIII IIIII IIIII VCC (5 V to 15 V) RESET 2 Clock Input RL 8 VCC OUT TRIG 5 CONT Output 7 THRES IIIIIII IIIIIII IIIIIII IIIIIII Modulation Input Voltage 3 DISCH Modulation Input (see Note A) RA Voltage - 2 V/div 4 RA = 3 k C = 0.02 F RL = 1 k See Figure 18 6 Clock Input Voltage IIIII IIIII IIIIII GND C 1 Output Voltage Pin numbers shown are for the D, JG, P, PS, and PW packages. NOTE A: The modulating signal can be direct or capacitively coupled to CONT. For direct coupling, the effects of modulation source voltage and impedance on the bias of the timer should be considered. Capacitor Voltage Time - 0.5 ms/div Figure 19. Pulse-Width-Modulation Waveforms Figure 18. Circuit for Pulse-Width Modulation pulse-position modulation As shown in Figure 20, any of these timers can be used as a pulse-position modulator. This application modulates the threshold voltage and, thereby, the time delay, of a free-running oscillator. Figure 21 shows a triangular-wave modulation signal for such a circuit; however, any wave shape could be used. VCC (5 V to 15 V) 8 RESET 2 Modulation Input 5 (see Note A) VCC OUT RL RA = 3 k RB = 500 RL = 1 k See Figure 20 RA 3 Output TRIG CONT DISCH 7 THRES 6 RB GND C Pin numbers shown are for the D, JG, P, PS, and PW packages. NOTE A: The modulating signal can be direct or capacitively coupled to CONT. For direct coupling, the effects of modulation source voltage and impedance on the bias of the timer should be considered. Figure 20. Circuit for Pulse-Position Modulation POST OFFICE BOX 655303 Voltage - 2 V/div 4 IIIIII IIIIII IIIIII IIIIII IIIIIIII IIIIIIII Modulation Input Voltage IIIIII IIIIII IIIIII IIIIII Output Voltage Capacitor Voltage Time - 0.1 ms/div Figure 21. Pulse-Position-Modulation Waveforms * DALLAS, TEXAS 75265 13 NE555, SA555, SE555 PRECISION TIMERS SLFS022C - SEPTEMBER 1973 - REVISED FEBRUARY 2002 APPLICATION INFORMATION sequential timer Many applications, such as computers, require signals for initializing conditions during start-up. Other applications, such as test equipment, require activation of test signals in sequence. These timing circuits can be connected to provide such sequential control. The timers can be used in various combinations of astable or monostable circuit connections, with or without modulation, for extremely flexible waveform control. Figure 22 shows a sequencer circuit with possible applications in many systems, and Figure 23 shows the output waveforms. VCC 4 RESET 2 8 VCC OUT TRIG S DISCH 5 0.01 F CONT 4 RESET RA 33 k 3 2 0.001 F 7 1 6 TRIG CONT 0.01 F CA CA = 10 F RA = 100 k RB THRES GND 1 CB 2 0.001 F 0.01 F Output B CB = 4.7 F RB = 100 k Pin numbers shown are for the D, JG, P, PS, and PW packages. NOTE A: S closes momentarily at t = 0. Figure 22. Sequential Timer Circuit IIIII II IIIII See Figure 22 Voltage - 5 V/div Output A III III Output B tw A IIIIII III III IIIII twA = 1.1 RACA tw B twB = 1.1 RBCB III II IIIII Output C tw C twC = 1.1 RCCC III t=0 t - Time - 1 s/div Figure 23. Sequential Timer Waveforms 14 POST OFFICE BOX 655303 * DALLAS, TEXAS 75265 8 VCC OUT TRIG DISCH 5 6 Output A 4 RESET 33 k 3 DISCH 7 5 THRES GND 8 VCC OUT CONT THRES GND 1 RC 3 7 6 CC CC = 14.7 F RC = 100 k Output C 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. 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