NE555 데이터 시트보기 (PDF) - Fairchild Semiconductor
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NE555 Datasheet PDF : 14 Pages
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LM555/NE555/SA555
Application Information
Table 1 below is the basic operating table of 555 timer:
Table 1. Basic Operating Table
Threshold Voltage
(Vth)(PIN 6)
Trigger Voltage
(Vtr)(PIN 2)
Reset(PIN 4) Output(PIN 3)
Discharging Tr.
(PIN 7)
Don't care
Don't care
Low
Low
ON
Vth > 2Vcc / 3
Vth > 2Vcc / 3
High
Low
ON
Vcc / 3 < Vth < 2 Vcc / 3 Vcc / 3 < Vth < 2 Vcc / 3
High
-
-
Vth < Vcc / 3
Vth < Vcc / 3
High
High
OFF
When the low signal input is applied to the reset terminal, the timer output remains low regardless of the threshold voltage or
the trigger voltage. Only when the high signal is applied to the reset terminal, the timer's output changes according to
threshold voltage and trigger voltage.
When the threshold voltage exceeds 2/3 of the supply voltage while the timer output is high, the timer's internal discharge Tr.
turns on, lowering the threshold voltage to below 1/3 of the supply voltage. During this time, the timer output is maintained
low. Later, if a low signal is applied to the trigger voltage so that it becomes 1/3 of the supply voltage, the timer's internal
discharge Tr. turns off, increasing the threshold voltage and driving the timer output again at high.
1. Monostable Operation
Trigger
RL
4
RESET
2 TRIG
8
Vcc
DISCH 7
THRES 6
3 OUT
GND
1
CONT 5
+Vcc
RA
C1
C2
Figure 1. Monoatable Circuit
102
101
=1kΩ
R AA
10kΩ
100kΩ
1MΩ
10MΩ
100
10-1
10-2
10-3
10-5
10-4
10-3
10-2
10-1
100
101
102
Time Delay(s)
Figure 2. Resistance and Capacitance vs.
Time delay(td)
Figure 3. Waveforms of Monostable Operation
4
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