LM555H - National Semiconductor

LM555/LM555C

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 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 200 mA or drive

TTL circuits.

Features

nDirect replacement for SE555/NE555

nTiming from microseconds through hours

nOperates in both astable and monostable modes

nAdjustable duty cycle

nOutput can source or sink 200 mA

nOutput and supply TTL compatible

nTemperature stability better than 0.005%per ˚C

nNormally on and normally off output

nAvailable in 8 pin MSOP package

Applications

nPrecision timing

nPulse generation

nSequential timing

nTime delay generation

nPulse width modulation

nPulse position modulation

nLinear ramp generator

Schematic Diagram

DS007851-1

May 1997

LM555/LM555C Timer

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 +18V

Power Dissipation (Note 3)

LM555H, LM555CH 760 mW

LM555, LM555CN 1180 mW

LM555CMM 613 mW

Operating Temperature Ranges

LM555C 0˚C to +70˚C

LM555 −55˚C to + 125˚C

Storage Temperature Range −65˚C to +150˚C

Soldering Information

Dual-In-Line Package

Soldering (10 Seconds) 260˚C

Small Outline Packages

(SOIC and MSOP)

Vapor Phase (60 Seconds) 215˚C

Infrared (15 Seconds) 220˚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)

=25˚C, V

=+5V to +15V, unless othewise specified)

Limits

Parameter Conditions LM555 LM555C Units

Min Typ Max Min Typ Max

Supply Voltage 4.5 18 4.5 16 V

Supply Current V

=5V, R

=∞35 36mA

=15V, R

=∞10 12 10 15 mA

(Low State) (Note 4)

Timing Error, Monostable

Initial Accuracy 0.5 1 %

Drift with Temperature R

=1k to 100 kΩ, 30 50 ppm/˚C

C=0.1 µF, (Note 5)

Accuracy over Temperature 1.5 1.5 %

Drift with Supply 0.05 0.1 %/V

Timing Error, Astable

Initial Accuracy 1.5 2.25 %

Drift with Temperature R

=1k to 100 kΩ, 90 150 ppm/˚C

C=0.1 µF, (Note 5)

Accuracy over Temperature 2.5 3.0 %

Drift with Supply 0.15 0.30 %/V

Threshold Voltage 0.667 0.667 x V

Trigger Voltage V

=15V 4.8 5 5.2 5 V

=5V 1.45 1.67 1.9 1.67 V

Trigger Current 0.01 0.5 0.5 0.9 µA

Reset Voltage 0.4 0.5 1 0.4 0.5 1 V

Reset Current 0.1 0.4 0.1 0.4 mA

Threshold Current (Note 6) 0.1 0.25 0.1 0.25 µA

Control Voltage Level V

=15V 9.6 10 10.4 9 10 11 V

=5V 2.9 3.33 3.8 2.6 3.33 4 V

Pin 7 Leakage Output High 1 100 1 100 nA

Pin 7 Sat (Note 7)

Output Low V

=15V, I

=15 mA 150 180 mV

Output Low V

=4.5V, I

=4.5 mA 70 100 80 200 mV

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Electrical Characteristics (Notes 1, 2) (Continued)

=25˚C, V

=+5V to +15V, unless othewise specified)

Limits

Parameter Conditions LM555 LM555C Units

Min Typ Max Min Typ Max

Output Voltage Drop (Low) V

=15V

SINK

=10 mA 0.1 0.15 0.1 0.25 V

SINK

=50 mA 0.4 0.5 0.4 0.75 V

SINK

=100 mA 2 2.2 2 2.5 V

SINK

=200 mA 2.5 2.5 V

=5V

SINK

=8 mA 0.1 0.25 V

SINK

=5 mA 0.25 0.35 V

Output Voltage Drop (High) I

SOURCE

=200 mA, V

=15V 12.5 12.5 V

SOURCE

=100 mA, V

=15V 13 13.3 12.75 13.3 V

=5V 3 3.3 2.75 3.3 V

Rise Time of Output 100 100 ns

Fall Time of Output 100 100 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 andAC 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 25˚C based on a +150˚C maximum junction temperature and a thermal resistance

of 164˚C/W (T0-5), 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+R

Bfor 15V operation. The maximum total (RA+R

)is20MΩ.

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.

Connection Diagrams

Metal Can Package

DS007851-2

Top View

Order Number LM555H or LM555CH

See NS Package Number H08C

Dual-In-Line, Small Outline

and Molded Mini Small Outline Packages

DS007851-3

Top View

Order Number LM555J, LM555CJ,

LM555CM, LM555CMM or LM555CN

See NS Package Number J08A, M08A, MUA08A or

N08E

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Typical Performance Characteristics

Minimuim Pulse Width

Required for Triggering

DS007851-4

Supply Current vs

Supply Voltage

DS007851-19

High Output Voltage vs

Output Source Current

DS007851-20

Low Output Voltage vs

Output Sink Current

DS007851-21

Low Output Voltage vs

Output Sink Current

DS007851-22

Low Output Voltage vs

Output Sink Current

DS007851-23

Output Propagation Delay vs

Voltage Level of Trigger Pulse

DS007851-24

Output Propagation Delay vs

Voltage Level of Trigger Pulse

DS007851-25

Discharge Transistor (Pin 7)

Voltage vs Sink Current

DS007851-26

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Typical Performance Characteristics (Continued)

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

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

C, at the end of which time the

voltage equals 2/3 V

. 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 10 µs 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

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.

Discharge Transistor (Pin 7)

Voltage vs Sink Current

DS007851-27

DS007851-5

FIGURE 1. Monostable

DS007851-6

VCC =5V Top Trace: Input 5V/Div.

TIME =0.1 ms/DIV. Middle Trace: Output 5V/Div.

RA=9.1 kΩBottom Trace: Capacitor Voltage 2V/Div.

C=0.01 µF

FIGURE 2. Monostable Waveforms

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Applications Information (Continued)

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

and dis-

charges through R

. 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

and 2/3 V

. As in the triggered

mode, the charge and discharge times, and therefore the fre-

quency are independent of the supply voltage.

Figure 5

shows the waveforms generated in this mode of

operation.

The charge time (output high) is given by:

=0.693 (R

And the discharge time (output low) by:

=0.693 (R

Thus the total period is:

T=t

=0.693 (R

+2R

The frequency of oscillation is:

Figure 6

may be used for quick determination of these RC

values.

The duty cycle is:

FREQUENCY DIVIDER

The monostable circuit of

Figure 1

can be used as a fre-

quency divider by adjusting the length of the timing cycle.

Figure 7

shows the waveforms generated in a divide by three

circuit.

DS007851-7

FIGURE 3. Time Delay

DS007851-8

FIGURE 4. Astable

DS007851-9

VCC =5V Top Trace: Output 5V/Div.

TIME =20 µs/DIV. Bottom Trace: Capacitor Voltage 1V/Div.

RA=3.9 kΩ

RB=3kΩ

C=0.01 µF

FIGURE 5. Astable Waveforms

DS007851-10

FIGURE 6. Free Running Frequency

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Applications Information (Continued)

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

shows the circuit, and in

Figure 9

are some waveform

examples.

PULSE POSITION MODULATOR

This application uses the timer connected for astable opera-

tion, 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, R

, in the monostable circuit is re-

placed by a constant current source, a linear ramp is gener-

ated.

Figure 12

shows a circuit configuration that will perform

this function.

DS007851-11

VCC =5V Top Trace: Input 4V/Div.

TIME =20 µs/DIV. Middle Trace: Output 2V/Div.

RA=9.1 kΩBottom Trace: Capacitor 2V/Div.

C=0.01 µF

FIGURE 7. Frequency Divider

DS007851-12

FIGURE 8. Pulse Width Modulator

DS007851-13

VCC =5V Top Trace: Modulation 1V/Div.

TIME =0.2 ms/DIV. Bottom Trace: Output Voltage 2V/Div.

RA=9.1 kΩ

C=0.01 µF

FIGURE 9. Pulse Width Modulator

DS007851-14

FIGURE 10. Pulse Position Modulator

DS007851-15

VCC =5V Top Trace: Modulation Input 1V/Div.

TIME =0.1 ms/DIV. Bottom Trace: Output 2V/Div.

RA=3.9 kΩ

RB=3kΩ

C=0.01 µF

FIGURE 11. Pulse Position Modulator

DS007851-16

FIGURE 12.

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Applications Information (Continued)

Figure 13

shows waveforms generated by the linear ramp.

The time interval is given by:

≅0.6V

50%DUTY CYCLE OSCILLATOR

Fora50

%duty cycle, the resistors R

and R

may be con-

nected as in

Figure 14

. The time period for the output high is

the same as previous, t

=0.693 R

C. For the output low it

is t

Thus the frequency of oscillation is

Note that this circuit will not oscillate if R

is greater than 1/2

because the junction of R

and R

cannot bring pin 2

down to 1/3 V

and trigger the lower comparator.

ADDITIONAL INFORMATION

Adequate power supply bypassing is necessary to protect

associated circuitry. Minimum recommended is 0.1 µF in par-

allel with 1 µF electrolytic.

Lower comparator storage time can be as long as 10 µs

when pin 2 is driven fully to ground for triggering. This limits

the monostable pulse width to 10 µs minimum.

Delay time reset to output is 0.47 µs typical. Minimum reset

pulse width must be 0.3 µs, typical.

Pin 7 current switches within 30 ns of the output (pin 3) volt-

age.

DS007851-17

VCC =5V Top Trace: Input 3V/Div.

TIME =20 µs/DIV. Middle Trace: Output 5V/Div.

R1=47 kΩBottom Trace: Capacitor Voltage 1V/Div.

R2=100 kΩ

RE=2.7 kΩ

C=0.01 µF

FIGURE 13. Linear Ramp

DS007851-18

FIGURE 14. 50%Duty Cycle Oscillator

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Physical Dimensions inches (millimeters)

Metal Can Package (H)

Order Number LM555H or LM555CH

NS Package Number H08C

Ceramic Dual-In-Line Package (J)

Order Number LM555J or LM555CJ

NS Package Number J08A

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Physical Dimensions inches (millimeters) (Continued)

Small Outline Package (M)

Order Number LM555CM

NS Package Number M08A

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Physical Dimensions inches (millimeters) (Continued)

8-Lead (0.118” Wide) Molded Mini Small Outline Package

Order Number LM555CMM

NS Package Number MUA08A

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Physical Dimensions inches (millimeters) (Continued)

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1. Life support devices or systems are devices or sys-

tems which, (a) are intended for surgical implant into

the body, or (b) support or sustain life, and whose fail-

ure 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 in any component of a life support

device or system whose failure to perform can be rea-

sonably expected to cause the failure of the life support

device or system, or to affect its safety or effectiveness.

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Molded Dual-In-Line Package (N)

Order Number LM555CN

NS Package Number N08E

LM555/LM555C Timer

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