Operating Rules
(Continued)
5 Output pulse width versus V
CC
and operation tempera-
tures
Figure 3
depicts the relationship between pulse
width variation versus V
CC
Figure 4
depicts pulse width
variation versus ambient temperature
6 The ‘‘K’’ coefficient is not a constant but varies as a
function of the timing capacitor C
X
Figure 5
details this
characteristic
TL F 6538 – 6
TL F 6538 – 4
FIGURE 3
TL F 6538 – 5
FIGURE 4
FIGURE 5
7 Under any operating condition C
X
and R
X
must be kept
as close to the one-shot device pins as possible to mini-
mize stray capacitance to reduce noise pick-up and to
reduce I
c
R and Ldi dt voltage developed along their
connecting paths If the lead length from C
X
to pins (10)
and (11) is greater than 3 cm for example the output
pulse width might be quite different from values predicted
from the appropriate equations A non-inductive and low
capacitive path is necessary to ensure complete dis-
charge of C
X
in each cycle of its operation so that the
output pulse width will be accurate
8 V
CC
and ground wiring should conform to good high-fre-
quency standards and practices so that switching tran-
sients on the V
CC
and ground return leads do not cause
interaction between one-shots A 0 01
mF
to 0 10
mF
by-
pass capacitor (disk ceramic or monolithic type) from V
CC
to ground is necessary on each device Furthermore the
bypass capacitor should be located as close to the V
CC
-
pin as space permits
For further detailed device characteristics and output performance please
refer to the NSC one-shot application note AN-366
4
NSC [ NATIONAL SEMICONDUCTOR ]
