January 1995

12

Philips Semiconductors

Product specification

Monostable/astable multivibrator

HEF4047B

MSI

3. Retrigger mode operation

The HEF4047B can be used in the retrigger mode to extend the output pulse duration, or to compare the frequency of

an input signal with that of the internal oscillator. In the retrigger mode the input pulse is applied to pins 8 and 12, and

the output is taken from pin 10 or 11. Normal monostable action is obtained when one retrigger pulse is applied (Fig.8).

flip-flop 4.

4. External counter option

controlled pulse duration, small timing capacitors for long time periods, and extremely fast recovery time. A typical

implementation is shown in Fig.9.

The pulse duration at the output is:

Fig.8 Retrigger mode waveforms.

t

ext

N1

–

() t

A

()

t

M

12 t

A

⁄

+

()

+

=

Fig.9 Implementation of external counter option.