74HCT14 Datasheet, PDF (17/23 Pages) NXP Semiconductors – Hex inverting Schmitt trigger

Philips Semiconductors
Hex inverting Schmitt trigger
Product specification
74HC14; 74HCT14
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_CC(AV) + t_f × I_CC(AV)) × V_CC.
Where:
P_ad = additional power dissipation (µW);
f_i = input frequency (MHz);
t_r = input rise time (µs); 10% to 90%;
t_f = input fall time (µs); 10% to 90%;
I_CC(AV) = average additional supply current (µA).
I_CC(AV) differs with positive or negative input transitions, as
shown in Figs 16 and 17.
For 74HC/HCT14 used in a relaxation oscillator circuit,
see Fig.18.
Note to application information
All values given are typical unless otherwise specified.
400
handbook, halfpage
ICC(AV)
(µA)
300
MNA852
200
100
0
0
positive - going
edge
negative - going
edge
2
4 _{VCC (V)} 6
Linear change of V_I between 0.1V_CC to 0.9V_CC
Fig.16 Average I_CC for 74HC14 Schmitt trigger
devices.
400
handbook, halfpage
ICC(AV)
(µA)
300
200
100
MNA853
positive - going
egddge
negative - going
egddge
0
0
2
4 _{VCC (V)} 6
Linear change of V_I between 0.1V_CC to 0.9V_CC.
Fig.17 Average I_CC for HCT Schmitt trigger
devices.
2003 Oct 30
handbook, halfpage
R
C
MNA854
74HC14 : f = _T-1-- ≈ _{0----.-8---1---R----C---}
74HCT14 : f = _T-1-- ≈ _{0----.-6----7-1----R-----C--}
Fig.18 Relaxation oscillator using 74HC/HCT14.
17