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74HCT6323AD,118

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22
Nexperia
74HC6323A; 74HCT6323A
Programmable ripple counter with oscillator; 3-state
Measurement points are given in Table 8
V
OL
and V
OH
are typical voltage output levels that occur with the output load.
Figure 6. The input MR to output OUT, 3-state enable and disable times
aaa-028602
V
M
t
W
t
rec
MR INPUT
V
I
GND
X1 INPUT
V
M
V
I
GND
Measurement points are given in Table 8
V
OL
and V
OH
are typical voltage output levels that occur with the output load.
Figure 7. The MR minimum pulse width and MR to X1 recovery time.
Table 8. Measurement points
Input OutputType
V
I
V
M
V
M
V
X
V
Y
74HC6323A GND to V
CC
0.5 x V
CC
0.5 x V
CC
0.1 x V
CC
0.9 x V
CC
74HCT6323A GND to 3 V 1.3 V 1.3 V 0.1 x V
CC
0.9 x V
CC
74HC_HCT6323A All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2018. All rights reserved.
Product data sheet Rev. 4 — 9 July 2018
13 / 22
Nexperia
74HC6323A; 74HCT6323A
Programmable ripple counter with oscillator; 3-state
001aah768
t
W
t
W
t
r
t
r
t
f
V
M
V
I
negative
pulse
GND
V
I
positive
pulse
GND
10 %
90 %
90 %
10 %
V
M
V
M
V
M
t
f
V
CC
DUT
R
T
V
I
V
O
C
L
G
Test data is given in Table 9.
Definitions test circuit:
R
T
= Termination resistance should be equal to output impedance Z
o
of the pulse generator.
C
L
= Load capacitance including jig and probe capacitance.
Figure 8. Test circuit for measuring switching times
Table 9. Test data
Input LoadType
V
I
t
r
, t
f
C
L
74HC6323A GND to V
CC
6 ns 15 pF, 50 pF
74HCT6323A GND to 3 V 6 ns 15 pF, 50 pF
12 Application information
12.1 Typical Crystal Oscillator
In Figure 9, R2 is the power limiting resistor. For starting and maintaining oscillation a
minimum transconductance is necessary, so R2 should not be too large. A practical value
for R2 is 2.2 kΩ.
The oscillator has been designed to operate over a wide frequency spectrum, for quartz
crystals operating in the fundamental mode and in the overtone mode. The circuit is
a Pierce type oscillator and requires a minimum of external components. There are
two on-chip capacitors, X1 and X2, of approximately 7 pF. Together with the stray and
input capacitance the value becomes 12 pF for 8-pin SO packages. These values are
convenient and make it possible to run the oscillator in the third overtone without external
capacitors applied. If a certain frequency is chosen, the IC parameters, as forward
transconductance, and the crystal parameters such as the motional resistances R1
(fundamental), R3 (third overtone) and R5 (fifth overtone), are of paramount importance.
Also the values of the external components as R
s
(series resistance) and the crystal load
capacitances play an important role. Especially in overtone mode oscillations, R
b
(bias
resistance) and the load capacitance values are very important.
74HC_HCT6323A All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2018. All rights reserved.
Product data sheet Rev. 4 — 9 July 2018
14 / 22
Nexperia
74HC6323A; 74HCT6323A
Programmable ripple counter with oscillator; 3-state
12.2 Considerations for Fundamental Oscillator:
In the fundamental oscillator mode, the R
b
has only the function of biasing the inverter
stage, so that it operates as an amplifier with a phase shift of approximately 180°. The
value must be high, i.e. 100 kΩ up to 10 MΩ. The load capacitors C1 and C2, must
have a value that is suitable for the crystal being used. The crystal is designed for
a certain frequency having a specific load capacitance. C1 can be used to trim the
oscillation frequency. The series resistance reduces the total loop gain. One function of
it is therefore to reduce the power dissipation in the crystal. R
s
also suppresses overtone
oscillations and introduces a phase shift over a broad frequency range. This is of less
concern provided R
s
is not too high a value.
Note: A combination of a small load capacitor value and a small series resistance, may
cause a third overtone oscillation.
12.3 Considerations for Third-overtone Oscillator:
In the overtone configuration, series resistance is no longer applied. This is essential
otherwise the gain for third overtone can be too small for oscillation. A simple solution
to suppress the fundamental oscillation, is to spoil the crystal fundamental activity.
By dramatically reducing the value of the bias resistor of the inverting stage, and
applying small load capacitors, it is possible to have an insufficient phase in the total
loop for fundamental oscillation. However the phase for third overtone is good. It can
be explained by the R
b
× C
l
time constant. During oscillation the crystal with the load
capacitors cause a phase shift of 180°. Because R
b
is parallel with the crystal (no R
s
),
R
b
spoils the phase for fundamental. R
b
× C
l
must be of a value, that it is not spoiling the
phase for third overtone too much. Because third overtone is a 3 times higher frequency
than the fundamental, the R
b
× C
l
cannot 'maintain' the higher third overtone frequency,
which results in a less spoiled overtone phase.
74HC_HCT6323A All information provided in this document is subject to legal disclaimers. © Nexperia B.V. 2018. All rights reserved.
Product data sheet Rev. 4 — 9 July 2018
15 / 22
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P22

74HCT6323AD,118

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