LMC555CMM datasheet(7/12 Pages) NSC

7 / 12 page

Application Information (Continued)

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.

50% DUTY CYCLE OSCILLATOR

The frequency of oscillation is

f = 1/(1.4 R

CC)

micro SMD Marking Orientation

Top View

00866923

Bumps are numbered counter-clockwise

00866915

VCC = 5V

Top Trace: Modulation 1 V/Div.

TIME = 0.2 ms/Div.

Bottom Trace: Output Voltage 2 V/Div.

RA = 9.1 kΩ

C = 0.01 µF

FIGURE 9. Pulse Width Modulator Waveforms

00866921

FIGURE 10. Pulse Position Modulator

00866916

VCC = 5V

Top Trace: Modulation Input 1 V/Div.

TIME = 0.1 ms/Div.

Bottom Trace: Output Voltage 2 V/Div.

RA = 3.9 kΩ

RB =3kΩ

C = 0.01 µF

FIGURE 11. Pulse Position Modulator Waveforms

00866906

FIGURE 12. 50% Duty Cycle Oscillator

LMC555CMM Datasheet(PDF) 7 Page - National Semiconductor (TI)