HCF4047M013TR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
HCF4047M013TR Datasheet PDF : 12 Pages
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HCF4047B
Where tM = monostable mode pulse width. Values
for tM are as follows :
Typ : VTR = 0.5 VDD tM = 2.48 RC
Min : VTR = 0.33 VDD tM = 2.71 RC
Max : VTR = 0.67 VDD tM = 2.48 RC
Thus if tM = 2.48 RC is used, the maximum
variation will be (+ 9.3%, - 0.0%).
Note : In the astable mode, the first positive half
cycle has a duration of TM ; succeeding durations
are tA/2.
In addition to variations from unit to unit, the
monostable pulse width may vary as a function of
frequency with respect to VDD and temperature.
4 - RETRIGGER MODE
The HCF4047B can be used in the retrigger mode
FIGURE A : Retrigger-mode waveforms
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, tRE = t1’ + t1 + 2t2.
For more than two pulses, tRE (Q OUTPUT)
terminates at some variable time tD after the
termination of the last retrigger pulse. tD is variable
because tRE (Q OUTPUT) terminates after the
second positive edge of the oscillator output
appears at flip-flop 4 (see logic diagram).
5 - EXTERNAL COUNTER OPTION
Time tM can be extended by any amount with the
use of external counting circuitry. Advantages
include digitally controlled pulse duration, small
timing capacitors for long time periods, and
extremely fast recovery time.
A typical implementation is shown in fig. B. The
pulse duration at the output is
text = (N - 1) (tA) + (tM + tA/2)
Where text = pulse duration of the circuitry, and N
is the number of counts used.
FIGURE B : Implementation of external counter option
8/12
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