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NE555
SA555 - SE555
General-purpose single bipolar timers
Features
■ Low turn-off time
■ Maximum operating frequency greater than
500 kHz
■ Timing from microseconds to hours
■ Operates in both astable and monostable
modes
■ Output can source or sink up to 200 mA
■ Adjustable duty cycle
■ TTL compatible
■ Temperature stability of 0.005% per °C
Description
The NE555, SA555, and SE555 monolithic timing
circuits are highly stable controllers capable 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
waveforms, and the output structure can source
or sink up to 200 mA.
N
DIP8
(Plastic package)
D
SO8
(Plastic micropackage)
Pin connections
(top view)
1
2
3
4
1 - GND
2 - Trigger
3 - Output
4 - Reset
8
7
6
5
5 - Control voltage
6 - Threshold
7 - Discharge
8 - VCC
January 2012
Doc ID 2182 Rev 6
1/20
www.st.com
20
1 page
NE555 - SA555 - SE555
Electrical characteristics
Table 3.
Symbol
Tamb = +25° C, VCC = +5 V to +15 V (unless otherwise specified) (continued)
Parameter
SE555
NE555 - SA555
Min. Typ. Max. Min. Typ. Max.
Unit
VOH
High level output voltage
VCC = +15 VIO(sink) = 200 mA
IO(sink) = 100 mA
VCC = +5 V IO(sink) = 100 mA
12.5
13 13.3
3 3.3
12.7
5
2.75
12.5
13.3
3.3
V
Idis(off)
Discharge pin leakage current
(output high) Vdis = 10 V
Vdis(sat)
Discharge pin saturation voltage
(output low) (4)
VCC = +15V, Idis = 15 mA
VCC = +5V, Idis = 4.5 mA
tr Output rise time
tf Output fall time
toff Turn off time (5) (Vreset = VCC)
20 100
180 480
80 200
100 200
100 200
0.5
20 100 nA
180 480
80 200
100 300
100 300
0.5
mV
ns
µs
1. Tested at VCC = +5 V and VCC = +15 V.
2. This will determine the maximum value of RA + RB for 15 V operation. The maximum total (RA + RB) is 20 MΩ for +15 V
operation and 3.5 MΩ for +5 V 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 0 V to 0.8 x VCC) on the threshold pin to the transition from high to low on the
output pin. Trigger is tied to threshold.
Doc ID 2182 Rev 6
5/20
5 Page
NE555 - SA555 - SE555
Figure 16. Waveforms in astable operation
t = 0.5 ms / div
OUTPUT VOLTAGE = 5.0V/div
Application information
CAPACITOR VOLTAGE = 1.0V/div
R1 = R2 = 4.8kΩ, C1= 0.1μF, RL = 1kΩ
Figure 17. Free running frequency versus R1, R2 and C1
C
(μF)
10
1.0
0.1
0.01
R1
+
R2
=
1MΩ100k1Ω0kΩ1kΩ
10MΩ
0.001
0.1 1 10 100 1k 10k fo(Hz)
Doc ID 2182 Rev 6
11/20
11 Page
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