Retriggerable Monostable Circuit

CD 4047 is the low power Monostable / Astable Multivibrator that requires only an external capacitor and a resistor to give the output pulses.
The values of these components determine the output pulse width in the Monostable mode and output frequency in the Astable mode.

Monostable mode

Monostable mode can be obtained by triggering the + input of the IC using a low to high pulse or by a high to low pulse at the – input. The IC can be retriggered by applying simultaneous low to high pulse in both the + and – inputs.

Astable mode

This can be obtained by keeping a high / low level at the Astable input. Output frequency depends on the timing components.

Pin connections of CD4047

CD 4047 is a low power CMOS IC that can operate between 3 to 15 volts DC.

Retriggerable Monostable Circuit diagram

retriggerable monostable

The circuit diagram is the typical application of the IC CD4047 in the Monostable mode. The timing elements are the capacitor C1 connected between the pins 1 and 3and the resistor R1 between pins 2 and 3. When a low to high pulse is applied to its pin 8 and 12, output pulse will be available from pins 10 and 11.

Output pulse width depends on the values of R1 and C1 which can be determined using the formula 2.48 R.C. R1 should be between 10k and 10M. Design of CD4047 in different modes is given in the function table of the data sheet provided.

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