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54121 DM54121 DM74121 One-Shot with Clear and Complementary Outputs
June 1989
54121 DM54121 DM74121 One-Shot with
Clear and Complementary Outputs
General Description
The DM54 74121 is a monostable multivibrator featuring
both positive and negative edge triggering with complemen-
tary outputs An internal 2kX timing resistor is provided for
design convenience minimizing component count and lay-
out problems This device can be used with a single external
capacitor Inputs (A) are active-low trigger transition inputs
and input (B) is an active-high transition Schmitt-trigger in-
put that allows jitter-free triggering from inputs with tran-
sition rates as slow as 1 volt second A high immunity to
V
CC
noise of typically 1 5V is also provided by internal cir-
cuitry at the input stage
To obtain optimum and trouble free operation please read
operating rules and NSC one-shot application notes careful-
ly and observe recommendations
Y
Y
Y
Y
Y
Y
Y
Jitter free Schmitt-trigger input
Excellent noise immunity typically 1 2V
Stable pulse width up to 90% duty cycle
TTL DTL compatible
Compensated for V
CC
and temperature variations
Input clamp diodes
Alternate Military Aerospace device (54121) is avail-
able Contact a National Semiconductor Sales Office
Distributor for specifications
Functional Description
The basic output pulse width is determined by selection of
an internal resistor R
INT
or an external resistor (R
X
) and
capacitor (C
X
) Once triggered the output pulse width is in-
dependent of further transitions of the inputs and is a func-
tion of the timing components Pulse width can vary from a
few nano-seconds to 28 seconds by choosing appropriate
R
X
and C
X
combinations There are three trigger inputs from
the device two negative edge-triggering (A) inputs one pos-
itive edge Schmitt-triggering (B) input
Features
Y
Y
Triggered from active-high transition or active-low tran-
sition inputs
Variable pulse width from 30 ns to 28 seconds
Connection Diagram
Dual-In-Line Package
Function Table
Inputs
A1
L
X
X
H
H
A2
X
L
X
H
B
H
H
L
X
H
H
H
Q
L
L
L
L
Outputs
Q
H
H
H
H
v
H
v
v
L
X
H
L
X
TL F 6538 – 1
v
X
L
u
u
e
High Logic Level
e
Low Logic Level
e
Can Be Either Low or High
e
Positive Going Transition
e
Negative Going Transition
e
A Positive Pulse
e
A Negative Pulse
u
v
Order Number 54121DMQB 54121FMQB
DM54121J DM54121W or DM74121N
See NS Package Number J14A N14A or W14B
C
1995 National Semiconductor Corporation
TL F 6538
RRD-B30M105 Printed in U S A
Absolute Maximum Ratings
(Note)
If Military Aerospace specified devices are required
please contact the National Semiconductor Sales
Office Distributors for availability and specifications
Supply Voltage
Input Voltage
7V
5 5V
Note
The ‘‘Absolute Maximum Ratings’’ are those values
beyond which the safety of the device cannot be guaran-
teed The device should not be operated at these limits The
parametric values defined in the ‘‘Electrical Characteristics’’
table are not guaranteed at the absolute maximum ratings
The ‘‘Recommended Operating Conditions’’ table will define
the conditions for actual device operation
Operating Free Air Temperature Range
b
55 C to
a
125 C
DM54
DM74
0 C to
a
70 C
Storage Temperature Range
b
65 C to
a
150 C
Recommended Operating Conditions
Symbol
V
CC
V
T
a
V
T
b
V
T
a
V
T
b
I
OH
I
OL
t
W
dV dt
dV dt
R
EXT
C
EXT
DC
T
A
Supply Voltage
Positive-Going Input Threshold
Voltage at the A Input (V
CC
e
Min)
Negative-Going Input Threshold
Voltage at the A Input (V
CC
e
Min)
Positive-Going Input Threshold
Voltage at the B Input (V
CC
e
Min)
Negative-Going Input Threshold
Voltage at the B Input (V
CC
e
Min)
High Level Output Current
Low Level Output Current
Input Pulse Width (Note 1)
Rate of Rise or Fall of
Schmidt Input (B) (Note 1)
Rate of Rise or Fall of
Logic Input (A) (Note 1)
External Timing Resistor (Note 1)
External Timing Capacitance (Note 1)
Duty Cycle (Note 1)
R
T
e
2 kX
R
T
e
R
EXT
(Max)
Free Air Operating Temperature
b
55
Note 1
T
A
e
25 C and V
CC
e
5V
Parameter
Min
45
DM54121
Nom
5
14
08
14
15
08
13
b
0 4
DM74121
Max
55
2
08
2
08
Min
4 75
Nom
5
14
14
15
13
b
0 4
Units
Max
5 25
2
V
V
V
2
V
V
mA
mA
ns
1
1
V s
V
ms
kX
mF
%
C
16
40
1
1
14
0
30
1000
67
90
125
0
14
0
40
16
40
1000
67
90
70
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Symbol
V
I
V
OH
V
OL
I
I
I
IH
I
IL
I
OS
I
CC
Parameter
Input Clamp Voltage
High Level Output
Voltage
Low Level Output
Voltage
Input Current
Input Voltage
Max
Conditions
V
CC
e
Min I
I
e b
12 mA
V
CC
e
Min
V
IL
e
Max
I
OH
e
Max
V
IH
e
Min
24
34
02
04
1
40
80
b
1 6
b
3 2
b
20
b
18
b
55
b
55
Min
Typ
(Note 1)
Max
b
1 5
Units
V
V
V
mA
mA
mA
mA
mA
V
CC
e
Min I
OL
e
Max
V
IH
e
Min V
IL
e
Max
V
CC
e
Max V
I
e
5 5V
V
CC
e
Max
V
I
e
2 4V
V
CC
e
Max
V
I
e
0 4V
V
CC
e
Max
(Note 2)
V
CC
e
Max
A1 A2
B
A1 A2
B
DM54
DM74
Quiescent
Triggered
High Level Input
Current
Low Level Input
Current
Short Circuit
Output Current
Supply Current
13
23
25
40
Note 1
All typicals are at V
CC
e
5V T
A
e
25 C
Note 2
Not more than one output should be shorted at a time
2
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
Operating Rules
(Continued)
5 Output pulse width versus V
CC
and operation tempera-
tures
Figure 3
depicts the relationship between pulse
width variation versus V
CC
Figure 4
depicts pulse width
variation versus ambient temperature
6 The ‘‘K’’ coefficient is not a constant but varies as a
function of the timing capacitor C
X
Figure 5
details this
characteristic
TL F 6538 – 6
TL F 6538 – 4
FIGURE 3
TL F 6538 – 5
FIGURE 4
FIGURE 5
7 Under any operating condition C
X
and R
X
must be kept
as close to the one-shot device pins as possible to mini-
mize stray capacitance to reduce noise pick-up and to
reduce I
c
R and Ldi dt voltage developed along their
connecting paths If the lead length from C
X
to pins (10)
and (11) is greater than 3 cm for example the output
pulse width might be quite different from values predicted
from the appropriate equations A non-inductive and low
capacitive path is necessary to ensure complete dis-
charge of C
X
in each cycle of its operation so that the
output pulse width will be accurate
8 V
CC
and ground wiring should conform to good high-fre-
quency standards and practices so that switching tran-
sients on the V
CC
and ground return leads do not cause
interaction between one-shots A 0 01
mF
to 0 10
mF
by-
pass capacitor (disk ceramic or monolithic type) from V
CC
to ground is necessary on each device Furthermore the
bypass capacitor should be located as close to the V
CC
-
pin as space permits
For further detailed device characteristics and output performance please
refer to the NSC one-shot application note AN-366
4
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