LMC555CMM National Semiconductor, LMC555CMM Datasheet - Page 6

• Manufacturer Part Number: LMC555CMM
• Description: Timer IC
• Manufacturer: National Semiconductor

Specifications of LMC555CMM

• Frequency: 3MHz
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Supply Voltage: 15V
• Current Rating: 150A
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Timer Type: Timer
• Package / Case: 8-MSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Information
V
TIME = 20 µs/Div.
R
R
C = 0.01 µF
The charge time (output high) is given by
And the discharge time (output low) by:
Thus the total period is:
The frequency of oscillation is:
Figure 6 may be used for quick determination of these RC
Values. The duty cycle, as a fraction of total period that the
output is low, is:
CC
A
B
= 3.9 kΩ
= 9 kΩ
= 5V
FIGURE 6. Free Running Frequency
FIGURE 5. Astable Waveforms
T = t
Top Trace: Output 5 V/Div.
Bottom Trace: Capacitor Voltage 1 V/Div.
t
1
1
+ t
= 0.693 (R
t
2
2
= 0.693 (R
= 0.693 (R
A
+ R
B
)C
A
B
+ R
)C
B
(Continued)
)C
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FREQUENCY DIVIDER
The monostable circuit of Figure 1 can be used as a fre-
quency divider by adjusting the length of the timing cycle.
Figure 7 shows the waveforms generated in a divide by three
circuit.
V
TIME = 20 µs/Div. Middle Trace: Output 2 V/Div.
R
C = 0.01 µF
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 the Control
Voltage Terminal. Figure 8 shows the circuit, and in Figure 9
are some waveform examples.
CC
A
= 9.1 kΩ
= 5V
FIGURE 7. Frequency Divider Waveforms
FIGURE 8. Pulse Width Modulator
Top Trace: Input 4 V/Div.
Bottom Trace: Capacitor 2 V/Div.
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