hcf4047 STMicroelectronics, hcf4047 Datasheet - Page 8

• Manufacturer Part Number: hcf4047
• Description: Low Power Monostable/astable Multivibrator
• Manufacturer: STMicroelectronics

HCF4047B
Where tM = monostable mode pulse width. Values
for tM are as follows :
Typ : V
Min : V
Max : V
Thus if t
variation will be (+ 9.3%, - 0.0%).
Note : In the astable mode, the first positive half
cycle has a duration of T
are t
In addition to variations from unit to unit, the
monostable pulse width may vary as a function of
frequency with respect to V
4 - RETRIGGER MODE
The HCF4047B can be used in the retrigger mode
FIGURE A : Retrigger-mode waveforms
5 - EXTERNAL COUNTER OPTION
Time t
use of external counting circuitry. Advantages
include digitally controlled pulse duration, small
timing capacitors for long time periods, and
extremely fast recovery time.
FIGURE B : Implementation of external counter option
8/12
A
/2.
M
TR
TR
TR
can be extended by any amount with the
M
= 0.5 V
= 0.33 V
= 0.67 V
= 2.48 RC is used, the maximum
DD
DD
DD
t
M
t
M
t
M
= 2.48 RC
= 2.71 RC
M
= 2.48 RC
; succeeding durations
DD
and temperature.
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 terminals 8 and 12, and the
output is taken from terminal 10 or 11. As shown in
fig.A normal monostable action is obtained when
one retrigger pulse is applied. Extended pulse
duration is obtained when more than one pulse is
applied. For two input pulses, t
For more than two pulses, t
terminates at some variable time t
termination of the last retrigger pulse. t
because t
second positive edge of the oscillator output
appears at flip-flop 4 (see logic diagram).
A typical implementation is shown in fig. B. The
pulse duration at the output is
text = (N - 1) (t
Where text = pulse duration of the circuitry, and N
is the number of counts used.
RE
(Q OUTPUT) terminates after the
A
) + (t
M
+ t
A
/2)
RE
RE
= t
(Q OUTPUT)
1
D
D
’ + t
is variable
after the
1
+ 2t
2
.