general description i s a highl y stabl e devic e fo r generatin g 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 re- sistor 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 direct replacement for se555/ne555 n timing from microseconds through hours n operates in both astable and monostable modes n adjustable duty cycle n output can source or sink 200 ma n output and supply ttl compatible n normally on and normally off output applications n precision timing n pulse generation n sequential timing n time delay generation n pulse width modulation n pulse position modulation n linear ramp generator wing shing computer components co., (h.k.)ltd. tel:(852)2341 9276 fax:(852)2797 8153 homepage: http://www.wingshing.com e-mail: wsccltd@hkstar.com
(t a = 25c, v cc = +5v to +15v, unless othewise specified) parameter conditions limits units min typ max supply voltage 4.5 16 v supply current v cc = 5v, r l = v cc = 15v, r l = 3 10 6 15 ma timing error, monostable initial accuracy 1% drift with temperature r a = 1 k t o 100k w , 50 ppm/c c = 0.1f, (note 5) accuracy over temperature 1.5 % drift with supply 0.1 %/v timing error, astable initial accuracy 2.25 % drift with temperature r a ,r b = 1 k t o 100k w , 150 ppm/c c = 0.1f, (note 5) accuracy over temperature 3.0 % drift with supply 0.30 %/v threshold voltage 0.667 x v cc trigger voltage v cc = 15v 5 v v cc = 5 v 1.67 v trigge r curren t rese t voltag e reset current 0.1 0.4 ma threshol d curren t (not e 6 ) control voltage level v cc = 15v v cc =5v 9 2.6 10 3.33 11 4 v pin 7 leakage output high 1 100 na pin 7 sat (note 7) output low v cc = 15v, i 7 = 15ma 180 mv output low v cc = 4.5v, i 7 = 4.5ma 80 200 mv lm555
electrical characteristics (notes 1, 2) (continued) (t a = 25c, v cc = +5v to +15v, unless othewise specified) parameter conditions limits units min typ max output voltage drop (low) v cc = 15v i sink = 10ma 0.1 0.25 v i sink = 50ma 0.4 0.75 v i sink = 100ma 2 2.5 v i sink = 200ma 2.5 v v cc =5v i sink = 8ma v i sink = 5ma 0.25 0.35 v output voltage drop (high) i source = 200ma, v cc = 15v 12.5 v i source = 100ma, v cc = 15v 12.75 13.3 v v cc = 5 v 2.75 3.3 v rise time of output 100 ns fall time of output 100 ns 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 func- tional, but do not guarantee specific performance limits. electrical characteristics state dc and ac electrical specifications under particular test conditions which guar- antee 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 170c/ w (s0-8) , junctio n t o ambient. not e 4 : suppl y curren t whe n outpu t hig h typicall y . note 5: tested at v cc = 5 v and v cc = 15v. note 6: this will determine the maximum value of r a +r b for 15v operation. the maximum total (r a +r b )is20m w . note 7: no protection against excessive pin 7 current is necessary providing the package dissipation rating will not be exceeded.
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 nega- tive trigger pulse of less than 1/3 v cc to pin 2, the flip-flop is set which both releases the short circuit across the capacitor and drives the output high. the voltage across the capacitor then increases exponen- tially for a period of t = 1.1 r a c, at the end of which time the voltage equals 2/3 v cc . 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 gener- ated in this mode of operation. since the charge and the threshold level of the comparator are both directly propor- tional to supply voltage, the timing internal is independent of supply. 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 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 v cc to avoid any possibility of false trig- gering. figure 3 is a nomograph for easy determination of r, c val- ues for various time delays. note: in monostable operation, the trigger should be driven high before the end of timing cycle. 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 r a +r b and dis- charges through r b . thus the duty cycle may be precisely set by the ratio of these two resistors. in this mode of operation, the capacitor charges and dis- charges between 1/3 v cc and 2/3 v cc . a s in the triggered mode, the charge and discharge times, and therefore the fre- quency are independent of the supply voltage. figure 1. monostable v cc = 5 v top trace: input 5v/div. time = 0.1 ms/div. middle trace: output 5v/div. r a = 9.1k w bottom trace: capacitor voltage 2v/div. c = 0.01f figure 2. monostable waveforms figure 3. time delay figure 4. astable
physical dimensions inches (millimeters) unless otherwise noted
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