CD74HC123, CD74HCT123, CD74HC423, CD74HCT423
Test Circuits and Waveforms
A
A
B = LOW
A = HIGH
B
R
t
W
Q
t
W
t
W
V
S
t
W
V
S
Q
t
W
t
W
B
R
V
S
t
W
V
S
B = LOW
A = HIGH
FIGURE 1. OUTPUT PULSE CONTROL USING RESET INPUT
(R) PULSE FOR 123
FIGURE 2. OUTPUT PULSE CONTROL USING RESET INPUT
(R) FOR 423
A
B
B
A
t
rT
Q
V
S
t
W
t
W
t
W
t
W
(R = HIGH)
NOTE: Output pulse control using retrigger pulse for 123 and 423.
FIGURE 3. TRIGGERING OF ONE SHOT BY INPUT A OR INPUT B FOR A PERIOD t
W
8
6
4
2
10
3
8
6
4
2
0
10
k
Ω
0.9
EXTERNAL CAPACITANCE (C
X
) = 10nF
0.8
0.7
“K” FACTOR
0.6
0.5
0.4
0.3
0.2
0.1
HCT
EXTERNAL RESISTANCE (R
X
) = 10kΩ TO 100kΩ
AMBIENT TEMPERATURE (T
A
) = 25
o
C
OUTPUT PULSE WIDTH (µs)
R
X
=
10
2
8
6
4
2
10
1
8
6
4
2
10
3
2
R
X
=1
0k
Ω
DC SUPPLY VOLTAGE (V
CC
) = 5V
AMBIENT TEMPERATURE (T
A
) = 25
o
C
4 68
2 4 68
2 4 68
2
10
5
10
4
10
6
EXTERNAL CAPACITANCE (C
X
) - pF
4 68
10
7
1
2
3
4
5
6
7
8
9
DC SUPPLY VOLTAGE (V
CC
) - VOLTS
10
11
FIGURE 4. TYPICAL OUTPUT PULSE WIDTH AS A FUNCTION
OF C
X
FOR R
X
= 10kΩ AND 100kΩ
FIGURE 5. TYPICAL “K” FACTOR AS A FUNCTION OF V
CC
7
HARRIS [ HARRIS CORPORATION ]
