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Teilenummer | 555 |
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Beschreibung | General-purpose single bipolar timers | |
Hersteller | STMicroelectronics | |
Logo | ||
Gesamt 20 Seiten 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
Electrical characteristics
NE555 - SA555 - SE555
Figure 3. Minimum pulse width required for Figure 4. Supply current versus supply
triggering
voltage
Figure 5. Delay time versus temperature
Figure 6. Low output voltage versus output
sink current
Figure 7. Low output voltage versus output Figure 8. Low output voltage versus output
sink current
sink current
6/20 Doc ID 2182 Rev 6
6 Page Application information
NE555 - SA555 - SE555
4.3 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 18 shows
the circuit.
Figure 18. Pulse width modulator
Trigger
4
2
8
7
VCC
RA
Output
3
NE555
1
6
Modulation
Input
5
C
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
Trigger
48
RE
27
NE555
2N4250
or equiv.
6
VCC
R1
C
Output
3
5
0.01μF
R2
1
12/20
Doc ID 2182 Rev 6
12 Page | ||
Seiten | Gesamt 20 Seiten | |
PDF Download | [ 555 Schematic.PDF ] |
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