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TL/F/6538
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 complementary outputs. An internal 2kX timing resistor is provided for
design convenience minimizing component count and layout 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 input that allows jitter-free triggering from inputs with transition 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 carefully and observe recommendations.
Features
Y
Triggered from active-high transition or active-low transition inputs
Y
Variable pulse width from 30 ns to 28 seconds
Y
Jitter free Schmitt-trigger input
Y
Excellent noise immunity typically 1.2V
Y
Stable pulse width up to 90% duty cycle
Y
TTL, DTL compatible
Y
Compensated for VCCand temperature variations
Y
Input clamp diodes
Y
Alternate Military/Aerospace device (54121) is available. 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 (RX) and
capacitor (C
X
). Once triggered the output pulse width is independent of further transitions of the inputs and is a function of the timing components. Pulse width can vary from a
few nano-seconds to 28 seconds by choosing appropriate
R
X
and CXcombinations. There are three trigger inputs from
the device, two negative edge-triggering (A) inputs, one positive edge Schmitt-triggering (B) input.
Connection Diagram
Dual-In-Line Package
TL/F/6538– 1
Order Number 54121DMQB, 54121FMQB,
DM54121J, DM54121W or DM74121N
See NS Package Number J14A, N14A or W14B
Function Table
Inputs Outputs
A1 A2 B Q Q
LXHL H
XLH L H
XXL L H
HHX L H
H
v
HÉß
v
HHÉß
vv
H Éß
LX
u
Éß
XL
u
Éß
H
e
High Logic Level
L
e
Low Logic Level
X
e
Can Be Either Low or High
u
e
Positive Going Transition
v
e
Negative Going Transition
É
e
A Positive Pulse
ß
e
A Negative Pulse
C
1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.
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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 7V
Input Voltage 5.5V
Operating Free Air Temperature Range
DM54
b
55§Ctoa125§C
DM74 0
§
Ctoa70§C
Storage Temperature Range
b
65§Ctoa150§C
Note:
The ‘‘Absolute Maximum Ratings’’ are those values
beyond which the safety of the device cannot be guaranteed. 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.
Recommended Operating Conditions
Symbol Parameter
DM54121 DM74121
Units
Min Nom Max Min Nom Max
V
CC
Supply Voltage 4.5 5 5.5 4.75 5 5.25 V
V
T
a
Positive-Going Input Threshold
1.4 2 1.4 2 V
Voltage at the A Input (V
CC
e
Min)
V
T
b
Negative-Going Input Threshold
0.8 1.4 0.8 1.4 V
Voltage at the A Input (V
CC
e
Min)
V
T
a
Positive-Going Input Threshold
1.5 2 1.5 2 V
Voltage at the B Input (V
CC
e
Min)
V
T
b
Negative-Going Input Threshold
0.8 1.3 0.8 1.3 V
Voltage at the B Input (V
CC
e
Min)
I
OH
High Level Output Current
b
0.4
b
0.4 mA
I
OL
Low Level Output Current 16 16 mA
t
W
Input Pulse Width (Note 1) 40 40 ns
dV/dt
Rate of Rise or Fall of
1 1 V/s
Schmidt Input (B) (Note 1)
dV/dt
Rate of Rise or Fall of
11V/ms
Logic Input (A) (Note 1)
R
EXT
External Timing Resistor (Note 1) 1.4 30 1.4 40 kX
C
EXT
External Timing Capacitance (Note 1) 0 1000 0 1000 mF
DC Duty Cycle (Note 1) R
T
e
2kX 67 67
%
R
T
e
R
EXT
(Max) 90 90
T
A
Free Air Operating Temperature
b
55 125 0 70
§
C
Note 1: T
A
e
25§C and V
CC
e
5V.
Electrical Characteristics over recommended operating free air temperature range (unless otherwise noted)
Symbol Parameter Conditions Min
Typ
Max Units
(Note 1)
V
I
Input Clamp Voltage V
CC
e
Min, I
I
eb
12 mA
b
1.5 V
V
OH
High Level Output V
CC
e
Min, I
OH
e
Max,
2.4 3.4 V
Voltage V
IL
e
Max, V
IH
e
Min
V
OL
Low Level Output V
CC
e
Min, I
OL
e
Max,
0.2 0.4 V
Voltage V
IH
e
Min, V
IL
e
Max
I
I
Input Current@Max V
CC
e
Max, V
I
e
5.5V
1mA
Input Voltage
I
IH
High Level Input V
CC
e
Max A1, A2 40
mA
Current V
I
e
2.4V
B80
I
IL
Low Level Input V
CC
e
Max A1, A2
b
1.6
mA
Current V
I
e
0.4V
B
b
3.2
I
OS
Short Circuit V
CC
e
Max DM54
b
20
b
55
mA
Output Current (Note 2)
DM74
b
18
b
55
I
CC
Supply Current V
CC
e
Max Quiescent 13 25
mA
Triggered 23 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.
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Switching Characteristics at V
CC
e
5V and T
A
e
25§C (See Section 1 for Test Waveforms and Outout Load)
Symbol Parameter
From (Input)
Conditions Min Max Units
To (Output)
t
PLH
Propagation Delay Time A1, A2 C
EXT
e
80 pF
70 ns
Low to High Level Output to Q R
INT
to V
CC
t
PLH
Propagation Delay Time B to
C
L
e
15 pF
55 ns
Low to High Level Output Q
R
L
e
400X
t
PHL
Propagation Delay Time A1, A2
80 ns
High to Low Level Output to Q
t
PHL
Propagation Delay Time B
65 ns
High to Low Level Output to Q
t
W(OUT)
Output Pulse A1, A2 or B C
EXT
e
80 pF
Width Using the to Q, Q
R
INT
to V
CC
70 150 ns
Internal Timing Resistor R
L
e
400X
C
L
e
15 pF
t
W(OUT)
Output Pulse A1, A2 C
EXT
e
0pF
Width Using Zero to Q, Q
R
INT
to V
CC
50 ns
Timing Capacitance R
L
e
400X
C
L
e
15 pF
t
W(OUT)
Output Pulse A1, A2 C
EXT
e
100 pF
Width Using External to Q, Q
R
INT
e
10 kX
600 800 ns
Timing Resistor R
L
e
400X
C
L
e
15 pF
A1, A2 C
EXT
e
1 mF
to Q, Q
R
INT
e
10 kX
68ms
R
L
e
400X
C
L
e
15 pF
Operating Rules
1. To use the internal 2 kX timing resistor, connect the R
INT
pin to VCC.
2. An external resistor (RX) 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 necessary 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 capacitance 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 timing components R
X
and CX. For C
X
k
1000 pF see
Fig-
ure 1
design curves on TWas function of timing compo-
nents value. For C
X
l
1000 pF the output is defined as:
t
W
e
KRXC
X
where[RXis in Kilo-ohm
]
[
CXis in pico Farad
]
[
TWis in nano second
]
[
K&0.7
]
TL/F/6538– 2
FIGURE 1
4. If CXis an electrolytic capacitor a switching diode is often
required for standard TTL one-shots to prevent high inverse leakage current
(Figure 2)
.
TL/F/6538– 3
FIGURE 2
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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.
TL/F/6538– 4
FIGURE 3
TL/F/6538– 5
FIGURE 4
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
FIGURE 5
7. Under any operating condition CXand RXmust be kept
as close to the one-shot device pins as possible to minimize 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 discharge 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-frequency standards and practices so that switching transients on the V
CC
and ground return leads do not cause
interaction between one-shots. A 0.01 mF to 0.10 mF bypass 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.
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Physical Dimensions inches (millimeters)
14-Lead Ceramic Dual-In-Line Package (J)
Order Number 54121DMQB or DM54121J
NS Package Number J14A
14-Lead Molded Dual-In-Line Package (N)
Order Number DM74121N
NS Package Number N14A
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54121/DM54121/DM74121 One-Shot with Clear and Complementary Outputs
Physical Dimensions inches (millimeters) (Continued)
14-Lead Ceramic Flat Package (W)
Order Number 54121FMQB or DM54121W
NS Package Number W14B
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