PLM393LVDR datasheet(18/29 Pages) TI1

18 / 29 page

100 kŸ

100 pF

100 kŸ

VCC

100 kŸ

OUT

1 MŸ

100 kŸ

RPU

10 kŸ

LM393LV-Q1

SNOSDB3 – JUNE 2020

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Typical Applications (continued)

Figure 12. Square-Wave Oscillator Output Waveform

10.2.3 Adjustable Pulse Width Generator

Figure 13 is a variation on the square wave oscillator that allows adjusting the pulse widths.

R4 and R5 provide separate charge and discharge paths for the capacitor C depending on the output state.

Figure 13. Adjustable Pulse Width Generator

The charge path is set through R5 and D2 when the output is high. Similarly, the discharge path for the capacitor

is set by R4 and D1 when the output is low.

The pulse width t1 is determined by the RC time constant of R5 and C. Thus, the time t2 between the pulses can

be changed by varying R4, and the pulse width can be altered by R5. The frequency of the output can be

changed by varying both R4 and R5. At low voltages, the effects of the diode forward drop (0.8 V, or 0.15 V for

Shottky) must be taken into account by altering output high and low voltages in the calculations. RPU should be at

least 10x less than the smallest value of R4 or R5.

10.2.4 Time Delay Generator

The circuit shown in Figure 14 provides output signals at a prescribed time interval from a time reference and

automatically resets the output low when the input returns to 0V. This is useful for sequencing a "power on"

signal to trigger a controlled start-up of power supplies.

PLM393LVDR Datasheet(PDF) 18 Page - Texas Instruments