..LOW TURN OFF TIME NE555 SA555 - SE555 GENERAL PURPOSE SINGLE BIPOLAR TIMERS. MAXIMUM OPERATING FREQUENCY GREATER THAN 500kHz

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1 NE SA - SE GENERAL PURPOSE SINGLE BIPOLAR TIMERS..LOW TURN OFF TIME MAXIMUM OPERATING FREQUENCY GREATER THAN 00kHz. TIMING FROM MICROSECONDS TO HOURS. OPERATES IN BOTH ASTABLE AND MONOSTABLE MODES HIGH OUTPUT CURRENT CAN SOURCE OR SINK 00mA ADJUSTABLE DUTY CYCLE. TTL COMPATIBLE TEMPERATURE STABILITY OF 0.00% PER o C DESCRIPTION The NE monolithic timing circuit is a highly stable controller capableof producing accuratetime delays or oscillation. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor.for a stableoperation as an oscillator, the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output structure can source or sink up to 00mA. The NE is available in plastic and ceramic minidip package and in a 8-lead micropackage and in metal can package version. N DIP8 (Plastic Package) ORDER CODES D SO8 (Plastic Micropackage) Part Temperature Package Number Range N D NE 0 o C, 0 o C SA 0 o C, o C SE o C, o C PIN CONNECTIONS (top view) 8 - GND - Trigger - Output - Reset - Control voltage - Threshold - Discharge 8-VCC July 998 /

2 BLOCK DIAGRAM V + CC kω THRESHOLD CONTROL VOLTAGE COMP R DISCHARGE FLIP-FLOP kω Q TRIGGER COMP S INHIBIT/ RESET OUT kω RESET S S SCHEMATIC DIAGRAM THRESHOLD COMPARATOR CONTROL VOLTAGE OUTPUT V CC R.kΩ R 80Ω R.kΩ R kω R8 kω R.8kΩ Q Q Q Q8 Q9 Q9 Q0 Q Ρ Q THRESHOLD TRIGGER Q Q Q Q Q Q Q Q R9 kω Q R kω D R.kΩ Q8 Q R 0Ω.9kΩ D R 0Ω R.kΩ Q RES ET DISCHARGE Q Q GND Q R kω R 0kΩ R 0kΩ R kω TRIGGER COMPARATOR FLIP FLOP ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit V cc Supply Voltage 8 V Toper Operating Free Air Temperature Range for NE for SA for SE 0to0 0 to to Tj Junction Temperature 0 T stg Storage Temperature Range to 0 o C o C o C /

3 OPERATING CONDITIONS Symbol Parameter SE NE - SA Unit V CC Supply Voltage. to 8. to 8 V V th,v trig,v cl,v reset Maximum Input Voltage V CC V CC V ELECTRICAL CHARACTERISTICS Tamb = + o C, VCC = +V to +V (unless otherwise specified) Symbol Parameter I CC Supply Current (R L ) (- note ) Low State V CC =+V VCC = +V High State VCC = V VCL Vth Timing Error (monostable) (RA =k to 0kΩ, C = 0.µF) Initial Accuracy - (note ) Drift with Temperature Drift with Supply Voltage Timing Error (astable) (RA, RB=kΩto 0kΩ, C = 0.µF, VCC = +V) Initial Accuracy - (note ) Drift with Temperature Drift with Supply Voltage Control Voltage level VCC = +V VCC =+V Threshold Voltage VCC = +V VCC =+V SE NE - SA Min. Typ. Max. Min. Typ. Max Unit ma % ppm/ C %/V % ppm/ C %/V I th Threshold Current - (note ) µa V trig Trigger Voltage V CC = +V V CC =+V.8. I trig Trigger Current (V trig = 0V) µa Vreset Reset Voltage - (note ) V I reset VOL VOH Notes : Reset Current V reset = +0.V Vreset =0V Low Level Output Voltage V CC = +V, I O(sink) = ma I O(sink) = 0mA IO(sink) = 0mA IO(sink) = 00mA VCC = +V, IO(sink) = 8mA IO(sink) = ma High Level Output Voltage VCC = +V, IO(source) = 00mA IO(source) = 0mA VCC = +V, IO(source) = 0mA Supply current when output is high is typically ma less.. Tested at V CC = +V and V CC = +V.. This will determine the maximum value of RA +RB for +V operation the max total is R = 0MΩ and for V operation the max total R =.MΩ. V V V ma V V /

4 ELECTRICAL CHARACTERISTICS (continued) Symbol I dis(off) V dis(sat) tr t f Notes : Parameter Discharge Pin Leakage Current (output high) (V dis = V) Discharge pin Saturation Voltage (output low) - (note ) VCC = +V, Idis = ma VCC = +V, Idis =.ma Output Rise Time Output Fall Time SE NE - SA Min. Typ. Max. Min. Typ. Max. Unit na toff Turn off Time - (note ) (Vreset = VCC) µs. No protection against excessive Pin current is necessary, providing the package dissipation rating will not be exceeded.. Time mesaured from a positive going input pulse from 0 to 0.8x VCC into the threshold to the drop from high to low of the output trigger is tied to treshold mv ns Figure : Minimum Pulse Width Required for Trigering Figure : Supply Current versus Supply Voltage Figure : Delay Time versus Temperature Figure : Low Output Voltage versus Output Sink Current /

5 Figure : Low Output Voltage versus Output Sink Current Figure : Low Output Voltage versus Output Sink Current Figure : High Output Voltage Drop versus Output Figure 8 : Delay Time versus Supply Voltage Figure 9 : Propagation Delay versus Voltage Level of Trigger Value /

6 APPLICATION INFORMATION MONOSTABLE OPERATION In the monostable mode, the timer functions as a one-shot. Referring to figure the external capacitor is initially held discharged by a transistor inside the timer. Figure Figure t = 0. ms / div INPUT =.0V/div OUTPUT VOLTAGE =.0V/div V CC = to V Reset R 8 Trigger Output NE C Control Voltage 0.0µF CAPACITOR VOLTAGE =.0V/div R = 9.kΩ, C = 0.0µF, R = kω L Figure The circuit triggers on a negative-going input signal when the level reaches / Vcc. Once triggered, the circuit remains in this state until the set time has elapsed, even if it is triggered again during this interval. The duration of the output HIGH stateis given by t =. R C and is easily determined by figure. Notice that since the charge rate and the threshold level of the comparator are both directly proportional to supply voltage, the timing interval is independent of supply. Applying a negativepulse simultaneously to the reset terminal (pin ) and the trigger terminal (pin ) during the timing cycle discharges the external capacitor and causes the cycle to start over. The timing cycle now starts on the positive edge of the reset pulse. During the time the reset pulse in applied, the output is driven to its LOW state. When a negativetrigger pulse is applied to pin, the flip-flop is set, releasing the short circuit across the external capacitor and driving the output HIGH. The voltage across the capacitor increases exponentially with the time constantτ =RC. When the voltage across the capacitor equals/ V cc, the comparatorresets the flip-flop which then discharge the capacitor rapidly and drivers the output to its LOW state. Figure shows the actual waveforms generatedin this mode of operation. When Reset is not used, it should be tied high to avoid any possibly or false triggering. C (µf) R= kω kω 0kΩ MΩ MΩ 0.00 µs 0 µs.0 ms ms 0 ms s (t d) ASTABLE OPERATION When the circuit is connected as shown in figure (pin and connected)it triggers itself and free runs as a multivibrator. The external capacitor charges through R and R and discharges through R only. Thus the duty cycle may beprecisely set by the ratio of these two resistors. In the astable mode of operation, C charges and discharges between / Vcc and / Vcc. As in the triggeredmode, the chargeand discharge times and therefore frequency are independent of the supply voltage. /

7 Figure Figure : Free Running Frequency versus R, R and C V CC = to V Output 8 R C (µf) NE kω kω 0.0µF Control Voltage R C R + R = MΩ MΩ 0kΩ Figure shows actual waveforms generatedin this mode of operation. The charge time (output HIGH) is given by : t = 0.9 (R +R )C and the discharge time (output LOW) by : t = 0.9 (R)C Thus the total period T is given by : T=t+t = 0.9 (R +R)C The frequency ofoscillation is them : f = T =. (R + R ) C and may be easily found by figure. The duty cycle is given by : R D = R + R Figure t = 0. ms / div OUTPUT VOLTAGE =.0V/div k k f o(hz) 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 modulatedby a signal applied to pin. Figure shows the circuit. Figure : Pulse Width Modulator. Trigger Output NE 8 Modulation Input RA C V CC CAPACITOR VOLTAGE =.0V/div R = R =.8kΩ, C= 0.µF, R = kω L /

8 LINEAR RAMP When the pullup resistor, RA, in the monostable circuit is replaced by a constant current source, a linear ramp is generated. Figure shows a circuit configuration that will perform this function. Figure. Trigger Output NE 8 R E N0 or equiv. C 0.0µF Figure 8 shows waveforms generator by the linear ramp. The time interval is given by : T = (/ V CC R E (R + R ) C R V CC V BE (R + R ) V BE = 0.V Figure 8 : Linear Ramp. R R V CC 0% DUTY CYCLE OSCILLATOR For a 0% duty cycle the resistors RA and RE may beconnected as in figure9. The time preriod for the output high is the same as previous, t = 0.9 R A C. For the output low it is t = [(R A R B ) (R A + R B )] CLn R B R A R B R A Thus the frequency of oscillation is f = t + t Note that this circuit will not oscillate if R B is greater Figure 9 : 0% Duty Cycle Oscillator. Out NE V CC 8 R B kω 0.0µF V CC R A kω C 0.0µF than / RA because the junction of RA and RB cannot bring pin down to / VCC andtrigger the lower comparator. ADDITIONAL INFORMATION Adequate power supply bypassing is necessary to protect associated circuitry. Minimum recommended is 0.µF in parallel with µf electrolytic. VCC = V Time = 0µs/DIV R = kω R = 0kΩ RE =.kω C = 0.0µF Top trace : input V/DIV Middle trace : output V/DIV Bottom trace : output V/DIV Bottom trace : capacitor voltage V/DIV 8/

9 PACKAGE MECHANICAL DATA 8 PINS - PLASTIC DIP PM-DIP8.EPS Dimensions Millimeters Inches Min. Typ. Max. Min. Typ. Max. A. 0. a B b b D E e. 0.0 e e F. 00 i L Z DIP8.TBL 9/

10 PACKAGE MECHANICAL DATA 8 PINS - PLASTIC MICROPACKAGE (SO) PM-SO8.EPS Dimensions Millimeters Inches Min. Typ. Max. Min. Typ. Max. A a a. 0.0 a b b C c o (typ.) D E e e F L M S 8 o (max.) SO8.TBL Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a trademark of STMicroelectronics 998 STMicroelectronics Printed in Italy All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco The Netherlands - Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdo m - U.S.A. ORDER CODE : /

.LOWTURNOFFTIME .MAXIMUM OPERATING FREQUENCY .TIMING FROM MICROSECONDS TO HOURS .OPERATES IN BOTH ASTABLE AND .HIGH OUTPUT CURRENT CAN SOURCE OR

.LOWTURNOFFTIME .MAXIMUM OPERATING FREQUENCY .TIMING FROM MICROSECONDS TO HOURS .OPERATES IN BOTH ASTABLE AND .HIGH OUTPUT CURRENT CAN SOURCE OR NE SA- SE GENERAL PURPOSE SINGLE BIPOLAR TIMERS.LOWTURNOFFTIME.MAXIMUM OPERATING FREQUENY GREATER THAN 00kHz.TIMING FROM MIROSEONDS TO HOURS.OPERATES IN BOTH ASTABLE AND MONOSTABLE MODES.HIGH OUTPUT URRENT