LM555CM National Semiconductor, LM555CM Datasheet - Page 9

• Manufacturer Part Number: LM555CM
• Description: IC, TIMER, SINGLE, 16V, 8-SOIC
• Manufacturer: National Semiconductor

Specifications of LM555CM

• Operating Mode: Astable / Monostable
• No. Of Timers: 1
• Clock External Input: Yes
• Supply Voltage Range: 4.5V To 16V
• Digital Ic Case Style: SOIC
• No. Of Pins: 8
• Operating Temperature Range: 0°C To +70°C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Applications Information
V
TIME = 0.2 ms/DIV. Bottom Trace: Output Voltage 2V/Div.
R
C = 0.01µF
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.
CC
A
= 9.1kΩ
= 5V
FIGURE 10. Pulse Position Modulator
FIGURE 9. Pulse Width Modulator
Top Trace: Modulation 1V/Div.
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V
TIME = 0.1 ms/DIV.
R
R
C = 0.01µF
LINEAR RAMP
When the pullup resistor, R
replaced by a constant current source, a linear ramp is
generated. Figure 12 shows a circuit configuration that will
perform this function.
Figure 13 shows waveforms generated by the linear ramp.
The time interval is given by:
CC
A
B
= 3.9kΩ
= 3kΩ
= 5V
FIGURE 11. Pulse Position Modulator
Top Trace: Modulation Input 1V/Div.
Bottom Trace: Output 2V/Div.
FIGURE 12.
V
BE
. 0.6V
A
, in the monostable circuit is
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