Datasheet SA555, SE555 Datasheet (ST)

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1

2

3

45

6

7

8

Features

■ Low turn off time

■ Maximum operating frequency greater than

500kHz

■ Timing from microseconds to hours

■ Operates in both astable and monostable

modes

■ High output current can source or sink 200mA

■ Adjustable duty cycle

■ TTL compatible

■ Temperature stability of 0.005% per °C

Description

NE555

SA555 - SE555

General purpose single bipolar timers

N

DIP8

(Plastic package)

D

SO8

(Plastic micropackage)

The NE555 monolithic timing circuit is a highly
stable controller capab le of producing accurate
time delays or oscillation. In the time delay mode
of operation, the time is precisely controlled by
one external resistor and capacitor. For a stable
operation 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
wav eforms, and the output structure can source
or sink up to 200mA.

Pin connections

(top view)

1 - GND
2 - Trigger
3 - Output
4 - Reset

5 - Control voltage
6 - Threshold
7 - Discharge
8 - V

CC

March 2007 Rev 4 1/20

www.st.com

20

Contents NE555 - SA555 - SE555

Contents

1 Schematic diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Absolute maximum ratings and operating conditions . . . . . . . . . . . . . 4

3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.1 Monostable operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.2 Astable operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.3 Pulse width modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.4 Linear ramp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.5 50% duty cycle oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.6 Additional information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

6 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2/20

NE555 - SA555 - SE555 Schematic diagrams

T

1 Schematic diagrams

Figure 1. Block diagram

+

V

CC

5kΩ

THRESHOLD

CONTROL VOLTAGE

TRIGGER

COMP

5kΩ

COMP

5kΩ

R
FLIP-FLOP

S

INHIBIT/
RESET

Q

DISCHARGE

OUT

Figure 2. Schematic diagram

THRESHOLD

COMPARATOR

V

HRESHOLD

TRIGGER

RESET

DISCHARGE

G N D

CC

R1

4.7k

Q5 Q6 Q7 Q8 Q9

Q1

Q2

2

4

Q15

7

Q14

1

R2

R3

830

W

W

Q3

R5

10k

4.7k

Q4

Q10

W

RESET

W

R6

100k

Q11 Q12

W

S - 8086

R4

1k

W

Q13

100k

S

CONTROL
VOLTAGE

5

R8

5k

W

Q19

R11
5k

W

R9

5k

W

R7

W

D2

Q16 Q18

Q17

R10
5k

W

4.7k

R17

R12

6.8k

W

Q20

W

Q23

R16

100

Q21

OUTPUT

Q22

R13

3.9k

W

D1

R14

220

R15

4.7k

W

3

W

Q24

W

TRIGGER COMPARATOR FLIP FLOP

3/20

Absolute maximum ratings and operating conditions NE555 - SA555 - SE555

2 Absolute maximum ratings and operating conditions

Table 1. Absolute maximum ratings

Symbol Parameter Value Unit

V

CC

T

j

T

stg

Table 2. Operating conditions

Supply voltage 18 V
Junction temperature 150 °C
Storage temperature range -65 to 150 °C

Symbol Parameter Value Unit

Supply voltage

Vth, V

V

trig

CC

, Vcl, V

NE555
SA555
SE555

Maximum input voltage V

reset

4.5 to 16

4.5 to 16

4.5 to 18

CC

Operating free air temperature range

T

oper

NE555
SA555
SE555

0 to 70

-40 to 105

-55 to 125

V

V

°C

4/20

NE555 - SA555 - SE555 Electrical characteristics

3 Electrical characteristics

Table 3. T

= +25°C, VCC = +5V to +15V (unless otherwise specified)

amb

Symbol Parameter

Supply current (RL = ∝)

I

Low stage V

CC

High state V

= +5V

CC

VCC = +15V

= 5V

CC

Timing error (monostable)
(R

= 2k to 100kΩ, C = 0.1μF)

A

Initial accuracy

(1)

Drift with temperature
Drift with supply voltage

Timing error (astable)
(R

= 1kΩ to 100kΩ, C = 0.1μF, VCC = +15V)

A, RB

Initial accuracy -

(1)

Drift with temperature
Drift with supply voltage

Control voltage level

V

CL

VCC = +15V

= +5V

V

CC

Threshold voltage

V

th

V

CC

= +15V

VCC = +5V

Threshold current

I

th

(2)

Trigger voltage

V

V

I

trig

reset

trig

VCC = +15V

= +5V

V

CC

Trigger current (V
Reset voltage

(3)

= 0V) 0.5 0.9 0.5 2.0 µA

trig

Reset current

I

reset

V
V

reset
reset

= +0.4V
= 0V

Low level output voltage

= +15VI

V

CC

V

OL

VCC = +5V I

O(sink)

I

O(sink)

I

O(sink)

I

O(sink)
O(sink)

I

O(sink)

= 10mA
= 50mA
= 100mA
= 200mA
= 8mA
= 5mA

High level output voltage

V

= +15VI

V

OH

CC

V

CC

= +5V I

O(sink)

I

O(sink)
O(sink)

= 200mA
= 100mA
= 100mA

SE555 NE555 - SA555

Min. Typ. Max. Min. Typ. Max.

3

10

2

0.5
30

0.05

1.5
90

0.15

9.6

2.9103.33

9.4

2.7103.33

5

12

3

10

2

2

100

0.2

1

50

0.130.5

2.25
150

0.3

10.4

3.892.6103.33114

10.648.8

2.4103.33

6

15

ppm/°C

ppm/°C

11.2

4.2

0.1 0.25 0.1 0.25 µA

4.8

1.4551.67

5.2

1.9

4.5

1.151.67

5.6

2.2

0.4 0.7 1 0.4 0.7 1 V

13

0.1

0.4

0.1

0.4

2.5

0.1

0.05

12.5

13.3

3

3.3

0.4
1

0.15

0.5

2

2.2

0.1

0.4

0.1

0.4
2

0.4

1.5

0.25

0.75

2.5

2.5

0.25

0.2

0.3

0.25

0.4

0.35

12.5

12.75

2.75

13.3

3.3

Unit

mA

%

%/V

%

%/V

V

V

V

mA

V

V

5/20

Electrical characteristics NE555 - SA555 - SE555

Table 3. T

= +25°C, VCC = +5V to +15V (unless otherwise specified)

amb

SE555 NE555 - SA555

Symbol Parameter

Min. Typ. Max. Min. Typ. Max.

I

dis(off)

V

dis(sat)

t

1. Tested at VCC = +5V and VCC = +15V.

2. This will determine the maximum value of R
operation and 3.5MΩ for +5V operation.

3. Specified with trigger input high.

4. No protection against excessive pin 7 current is necessary, providing the package dissipation rating is not exceeded.

5. Time measured from a positive pulse (from 0V to 0.8xV
Output pin. Trigger is tied to Threshold.

Discharge pin leakage current
(output high) V

Discharge pin saturation voltage
(output low)

VCC = +15V, I
VCC = +5V, I

t

Output rise time

r

t

Output fall time

f

Turn off time

off

(4)

(5)

dis

dis

dis

(V

= 10V

= 15mA

= 4.5mA

= VCC)0.50.5µs

reset

+ RB for 15V operation. The maximum total (RA + RB) is 20MΩ for 15V

A

) on the Threshold pin to the transition from high to low on the

CC

20 100 20 100 nA

18080480

200

100
100

200
200

18080480

200

100
100

300
300

Unit

mV

ns

6/20

NE555 - SA555 - SE555 Electrical characteristics

Figure 3. Minimum pulse width required for

triggering

Figure 4. Supply current versus supply

voltage

Figure 5. Delay time versus temperature Figure 6. Low output voltage versus output

sink current

Figure 7. Low output voltage versus output

sink current

Figure 8. Low output voltage versus output

sink current

7/20

Electrical characteristics NE555 - SA555 - SE555

Figure 9. High output voltage drop versus

output

Figure 11. Propagation delay versus voltage

level of trigger value

Figure 10. Delay time versus supply voltage

8/20

NE555 - SA555 - SE555 Application information

4 Application information

4.1 Monostable operation

In the monostable mode, the timer generates a single pulse. As shown in Figure 12, the
external capacitor is initially held discharged by a transistor inside the timer.

Figure 12. Typical schematics in monostable operation

V

= 5 to 15V

CC

Reset

R1

4

8

Trigger

Output

The circuit triggers on a negative-going input signal when the level reaches 1/3 V

2

NE555

3

1

7

6

Control Voltage

5

0.01

C1

μF

. Once

CC

triggered, the circuit remains in this state until the set time has elapsed, e v en if it is triggered
again during this interval. The duration of the output HIGH state is given by t = 1.1 R

1C1

and

is easily determined by Figure 14.
Note that because the charge rate and the threshold level of the comparator are both

directly proportional to supply voltage, th e ti ming int e rval is inde pende nt of sup ply. Applying
a negative pulse simultaneously to the reset terminal (pin 4) and the trigger terminal (pin 2)
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 is applied, the output is driven to its LOW state.

When a negative trigger pulse is applied to pin 2, the f lip-flop is set, releasing the short­circuit across the external capacitor and driving the output HIGH. The voltage across the
capacitor increases exponentially with the time co nsta nt t = R
the capacitor equals 2/3 V

, the comparator resets the flip-flop which then discharges the

CC

. When the voltage across

1C1

capacitor rapidly and drives the output to its LOW state.

Figure 13 shows the actual waveforms generated in this mode of operation.

When Reset is not used, it should be tied high to avoid any possibility of unwanted
triggering.

9/20

Application information NE555 - SA555 - SE555

CAPACITOR VOLTAGE = 2.0V/div

t = 0.1 ms / div

INPUT = 2.0V/div

OUTPUT VOLTAGE = 5.0V/div

R1 = 9.1kΩ, C1 = 0.01μF, R = 1kΩ

L

C

(μF)

10

1.0

0.1

0.01

0.001
10 100 1.0 10 100 10 (t )

d

μs μs

ms ms ms s

10M

Ω

1M

Ω

1

00

k

Ω

10k

Ω

R1

=

1k

Ω

Figure 13. Waveforms in monostable operation

Figure 14. Pulse duration versus R1C1

4.2 Astable operation

When the circuit is connected as shown in Figure 15 (pin 2 and 6 connected) it triggers itself
and free runs as a multi-vibrator. The external capacitor charges through R
discharges through R
of these two resistors.

In the astable mode of oper ation, C
As in the triggered mode, the charge and discharge times and, therefore, frequency are
independent of the supply voltage.

10/20

and R2 and

only. Thus the duty cycle can be set accurately by adjusting the ratio

2

charges and discharges between 1/3 VCC and 2/3 VCC.

1

1

NE555 - SA555 - SE555 Application information

Figure 15. Typical schematics in astable operation

= 5 to 15V

V

CC

R1

4

8

Output

0.01μF

Control

Voltage

3

NE555

5

1

7

R2

6

2

C1

Figure 16 shows the actual waveforms generated in this mode of operation.

The charge time (output HIGH) is given by:

t1 = 0.693 (R

+ R2) C

1

1

and the discharge time (output LOW) by:

t2 = 0.693 (R

2

) C

1

Thus the total period T is given by:

T = t1 + t2 = 0.693 (R1 + 2R2) C1

The frequency of oscillation is then:

f =

1

---

T

1.44

-------------------------------------- -=

R1 2R2+()C1

It can easily be found from Figure 17.
The duty cycle is given by:

------------------------- -=

R1 2R2+

R2

D

11/20

Application information NE555 - SA555 - SE555

t = 0.5 ms / div

OUTPUT VOLTAGE = 5.0V/div

CAPACITOR VOLTAGE = 1.0V/div

R1 = R2 = 4.8kΩ, C1= 0.1μF, R = 1kΩ

L

C

(μF)

10

1.0

0.1

0.01

0.001

0.1 1 10 100 1k 10k f (Hz)

o

1

M

Ω

R

1

+

R

2

=

1

0

M

Ω

1

0

0

k

Ω

1

0

k

Ω

1

k

Ω

Figure 16. Waveforms in astable operation

Figure 17. Free running frequency versus R

, R2 and C

1

1

12/20

NE555 - SA555 - SE555 Application information

Trigger

Output

C

NE555

2

4

3

1

5

6

7

8

E

V

CC

0.01μF

R2

R1

R

2N4250

or equiv.

4.3 Pulse width modulator

When the timer is connected in the monostab le mode a nd triggered with a cont inuous pulse
train, the output pulse width can be m odulated by a signal applied to pin 5. Figure 18 shows
the circuit.

Figure 18. Pulse width modulator

V

CC

R

A

4

8

Trigger

Output

4.4 Linear ramp

When the pull-up resistor, RA, in the monostable circuit is replaced by a constant current
source, a linear ramp is generated. Figure 19 shows a circuit configuration that will perform
this function.

Figure 19. Linear ramp

2

NE555

3

1

7

6

Modulation

Input

5

C

13/20

Application information NE555 - SA555 - SE555

Figure 20 shows the waveforms generator by the linear ramp.

The time interval is given by:

(2/3 Vcc RE (R1+R2) C

--------------------------------------------------------------- -

T =

R1 Vcc - VBE (R1+R2)

VBE = 0.6V

Figure 20. Linear ramp

V

= 5V

CC

Time:
20µs/DIV

+ 47kΩ

R

1

R2 = 100kΩ

= 2.7kΩ

R

E

C = 0.01µF

4.5 50% duty cycle oscillator

For a 50% duty cycle, the resistors RA and RE can be connected as in figure 19. The time
period for the output hi gh is th e sam e a s for astable operation (see Section 4.2 on page 10):

t1 = 0.693 R

For the output low it is

Thus the frequency of oscillation is:

C

A

t2[(R. RB)/(RA+RB)].C.Ln

=

Top trace: input 3V/DIV
Middle trace: output 5V/DIV
Bottom trace: output 5V/DIV
Bottom trace: capacitor voltage 1V/DIV

RB 2RA–

-------------------------- -

2RB RA–

1

f

---------------- -=

t1 t2+

14/20

NE555 - SA555 - SE555 Application information

Figure 21. 50% duty cycle oscillator

V

CC

4

2

8

R

7

B

22kΩ

R

A

51kΩ

V

CC

Out

3

Note that this circuit will not oscillate if R
and R

cannot bring pin 2 down to 1/3 VCC and trigger the lower comparator.

B

4.6 Additional information

Adequate power supply by passing is necessary to protect associated circuitry. The
minimum recommended is 0.1µF in parallel with 1µF electrolytic.

NE55

1

is greater than 1/2 RA because the junction of RA

B

6

5

0.01μF
C

0.01μF

15/20

Package information NE555 - SA555 - SE555

5 Package information

In order to meet environmental requirements, STMicroelectronics offers these devices in
ECOPACK
category of second level interconnect is marke d on the pa ckage and on the inner box label,
in compliance with JEDEC Standard JESD97. The maximum ratings related t o soldering
conditions are also marked on the inner box label. ECOPACK is an STMicroelectronics
trademark. ECOPACK specifications are available at: www.st.com

®

packages. These packages have a lead-free second level interconnect. The

.

16/20

NE555 - SA555 - SE555 Package information

Figure 22. DIP8 package mechanical data

Dimensions

Ref.

Min. Typ. Max. Min. Typ. Max.

A5.330.210
A1 0.38 0.015
A2 2.92 3.30 4.95 0.115 0.130 0.195

b 0.36 0.46 0.56 0.014 0.018 0.022
b2 1.14 1.52 1.78 0.045 0.060 0.070

c 0.20 0.25 0.36 0.008 0.010 0.014
D 9.02 9.27 10.16 0.355 0.365 0.400
E 7.62 7.87 8.26 0.300 0.310 0.325

E1 6.10 6.35 7.11 0.240 0.250 0.280

e 2.54 0.100

eA 7.62 0.300
eB 10.92 0.430

L 2.92 3.30 3.81 0.115 0.130 0.150

Millimeters Inches

17/20

Package information NE555 - SA555 - SE555

Figure 23. SO8 package mechanical data

Dimensions

Ref.

Min. Typ. Max. Min. Typ. Max.

A1.750.069

A1 0.10 0.25 0.004 0.010
A2 1.25 0.049

b 0.28 0.48 0.011 0.019

c 0.17 0.23 0.007 0.010
D 4.80 4.90 5.00 0.189 0.193 0.197
H 5.80 6.00 6.20 0.228 0.236 0.244

E1 3.80 3.90 4.00 0.150 0.154 0.157

e 1.27 0.050
h 0.25 0.50 0.010 0.020
L 0.40 1.27 0.016 0.050

k1°8°1°8°

ccc 0.10 0.004

Millimeters Inches

18/20

NE555 - SA555 - SE555 Ordering information

6 Ordering information

Table 4. Order codes

Part number Temperature range Package Packing Marking

NE555N

0°C, +70°C

NE555D/DT SO8 Tube or tape & reel NE555
SA555N

-40°C, +105°C

SA555D/DT SO8 Tube or tape & reel SA555
SE555N

-55°C, + 125°C

SE555D/DT SO8 Tube or tape & reel SE555

7 Revision history

Date Revision Changes

1-Jun-2003 1 Initial release.

2004-2006 2-3 Internal revisions

15-Mar-2007 4

DIP8 Tube NE555N

DIP8 Tube SA555N

DIP8 Tube SE555N

Expanded order code table.
Template update.

19/20

NE555 - SA555 - SE555

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20/20