Philips Semiconductors
Product specification
Hex inverting Schmitt trigger
APPLICATION INFORMATION
The slow input rise and fall times cause additional power
dissipation, this can be calculated using the following
formula:
P
ad
= f
i
×
(t
r
×
I
CCa
+ t
f
×
I
CCa
)
×
V
CC
.
Where:
P
ad
f
i
t
r
t
f
I
CCa
= additional power dissipation (µW)
= input frequency (MHz)
= input rise time (µs); 10%
−
90%
= input fall time (µs); 10%
−
90%
= average additional supply current (µA)
74HC/HCT14
Average I
CCa
differs with positive or negative input
transitions, as shown in Figs 14 and 15.
Fig.14 Average I
CC
for HC Schmitt trigger devices;
linear change of V
i
between 0.1 V
CC
to
0.9 V
CC
HC/HCT14 used in a relaxation oscillator circuit, see
Fig.16.
Fig.15 Average I
CC
for HCT Schmitt trigger devices;
linear change of V
i
between 0.1 V
CC
to
0.9 V
CC
.
Note to Application information
All values given are typical unless otherwise specified.
1
1
HC : f
=
--
≈
------------------
-
-
T 0.8 RC
PACKAGE OUTLINES
See
“74HC/HCT/HCU/HCMOS Logic Package Outlines”.
1
1
HCT : f
=
--
≈
---------------------
-
-
T 0.67 RC
Fig.16 Relaxation oscillator using HC/HCT14.
September 1993
8
PHILIPS [ NXP SEMICONDUCTORS ]
