Switching Characteristics
Symbol
t
PLH
t
PLH
t
PHL
t
PHL
t
W(OUT)
Parameter
Propagation Delay Time
Low to High Level Output
Propagation Delay Time
Low to High Level Output
Propagation Delay Time
High to Low Level Output
Propagation Delay Time
High to Low Level Output
Output Pulse
Width Using the
Internal Timing Resistor
Output Pulse
Width Using Zero
Timing Capacitance
Output Pulse
Width Using External
Timing Resistor
at V
CC
e
5V and T
A
e
25 C (See Section 1 for Test Waveforms and Outout Load)
From (Input)
To (Output)
A1 A2
to Q
B to
Q
A1 A2
to Q
B
to Q
A1 A2 or B
to Q Q
C
EXT
e
80 pF
R
INT
to V
CC
R
L
e
400X
C
L
e
15 pF
C
EXT
e
0 pF
R
INT
to V
CC
R
L
e
400X
C
L
e
15 pF
C
EXT
e
100 pF
R
INT
e
10 kX
R
L
e
400X
C
L
e
15 pF
C
EXT
e
1
mF
R
INT
e
10 kX
R
L
e
400X
C
L
e
15 pF
Conditions
C
EXT
e
80 pF
R
INT
to V
CC
C
L
e
15 pF
R
L
e
400X
Min
Max
70
55
80
65
Units
ns
ns
ns
ns
70
150
ns
t
W(OUT)
A1 A2
to Q Q
50
ns
t
W(OUT)
A1 A2
to Q Q
600
800
ns
A1 A2
to Q Q
6
8
ms
Operating Rules
1 To use the internal 2 kX timing resistor connect the R
INT
pin to V
CC
2 An external resistor (R
X
) or the internal resistor (2 kX)
and an external capacitor (C
X
) are required for proper
operation The value of C
X
may vary from 0 to any neces-
sary value For small time constants use high-quality
mica glass polypropylene polycarbonate or polystyrene
capacitors For large time constants use solid tantalum or
special aluminum capacitors If the timing capacitors
have leakages approaching 100 nA or if stray capaci-
tance from either terminal to ground is greater than 50 pF
the timing equations may not represent the pulse width
the device generates
3 The pulse width is essentially determined by external tim-
ing components R
X
and C
X
For C
X
k
1000 pF see
Fig-
ure 1
design curves on T
W
as function of timing compo-
nents value For C
X
l
1000 pF the output is defined as
t
W
e
K R
X
C
X
where R
X
is in Kilo-ohm
C
X
is in pico Farad
T
W
is in nano second
K
07
TL F 6538 – 2
FIGURE 1
4 If C
X
is an electrolytic capacitor a switching diode is often
required for standard TTL one-shots to prevent high in-
verse leakage current
(Figure 2)
TL F 6538 – 3
FIGURE 2
3
NSC [ NATIONAL SEMICONDUCTOR ]
