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DM74121N

Part # DM74121N
Description IC, Monostable MultivibratorTTL, 14Pin Plastic Dip
Category IC
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National Semiconductor Corp
Date Code: 8934
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

© 1999 Fairchild Semiconductor Corporation DS006538 www.fairchildsemi.com
June 1989
Revised November 1999
DM74121 One-Shot with Clear and Complementary Outputs
DM74121
One-Shot with Clear and Complementary Outputs
General Description
The DM74121 is a monostable multivibrator featuring both
positive and negative edge triggering with complementary
outputs. An internal 2k timing resistor is provided for
design convenience minimizing component count and lay-
out problems. this device can be used with a single exter-
nal capacitor. Inputs (A) are active-LOW trigger transition
inputs and input (B) is and 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
circuitry at the input stage.
To obtain optimum and trouble free operation please read
operating rules and one-shot application notes carefully
and observe recommendations.
Features
Triggered from active-HIGH transition or active-LOW
transition inputs
Variable pulse width from 30 ns to 28 seconds
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
Ordering Code:
Connection Diagram Function Table
H = HIGH Logic Level = Positive Going Transition
L = LOW Logic Level = Negative Going Transition
X = Can Be Either LOW or HIGH
= A Positive Pulse
= A Negative Pulse
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
independent of further transitions of the inputs and is 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 positive edge Schmitt-triggering (B) input.
Order Number Package Number Package Description
DM74121N N14A 14-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Inputs Outputs
A1 A2 B Q Q
LXHLH
XLHLH
XXLLH
HHXLH
H H
HH
↓↓H
LX
XL
www.fairchildsemi.com 2
DM74121
Operating Rules
1. To use the internal 2 k timing resistor, connect the
R
INT
pin to V
CC
.
2. An external resistor (R
X
) or the internal resistor (2 k)
and an external capacitor (C
X
) are required for proper
operation. The value of C
X
may vary from 0 to any nec-
essary value. For small time constants use high-quality
mica, glass, polypropylene, polycarbonate, or polysty-
rene capacitors. For large time constants use solid tan-
talum 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 repre-
sent the pulse width the device generates.
3. The pulse width is essentially determined by external
timing components R
X
and C
X
. For C
X
< 1000 pF see
Figure 1 design curves on t
W
as function of timing com-
ponents value. For C
X
> 1000 pF the output is defined
as:
t
W
= 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 0.7]
4. If C
X
is an electrolytic capacitor a switching diode is
often required for standard TTL one-shots to prevent
high inverse leakage current Figure 2.
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.
7. Under any operating condition C
X
and R
X
must be kept
as close to the one-shot device pins as possible to min-
imize stray capacitance, to reduce noise pick-up, and
to reduce I X 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 val-
ues 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 accu-
rate.
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 µF to 0.10
µF bypass capacitor (disk ceramic or monolithic type)
from V
CC
to ground is necessary on each device. Fur-
thermore, the bypass capacitor should be located as
close to the V
CC
-pin as space permits.
For further detailed device characteristics and output per-
formance please refer to the one-shot application note, AN-
366.
FIGURE 1.
FIGURE 2.
FIGURE 3.
FIGURE 4.
FIGURE 5.
3 www.fairchildsemi.com
DM74121
Absolute Maximum Ratings(Note 1)
Note 1: 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 tables are not guaranteed at the absolute maximum ratings.
The Recommended Operating Conditions table will define the conditions
for actual device operation.
Recommended Operating Conditions
Note 2: T
A
= 25°C and V
CC
= 5V
Electrical Characteristics
over recommended operating free air temperature range (unless otherwise noted)
Note 3: All typicals are at V
CC
= 5V, T
A
= 25°C.
Note 4: Not more than one output should be shorted at a time.
Supply Voltage 7V
Input Voltage 5.5V
Operating Free Air Temperature Range 0°C to +70°C
Storage Temperature Range 65°C to +150°C
Symbol Parameter Min Nom Max Units
V
CC
Supply Voltage 4.75 5 5.25 V
V
T+
Positive-Going Input Threshold Voltage
1.4 2 V
at the A Input (V
CC
= Min)
V
T
Negative-Going Input Threshold Voltage
0.8 1.4 V
at the A Input (V
CC
= Min)
V
T+
Positive-Going Input Threshold Voltage
1.5 2 V
at the B Input (V
CC
= Min)
V
T
Negative-Going Input Threshold Voltage
0.8 1.3 V
at the B Input (V
CC
= Min)
I
OH
HIGH Level Output Current 0.4 mA
I
OL
LOW Level Output Current 16 mA
t
W
Input Pulse Width (Note 2) 40 ns
dV/dt Rate of Rise or Fall of
1V/s
Schmidt Input (B) (Note 2)
dV/dt Rate of Rise or Fall of
1V/µs
Schmidt Input (A) (Note 2)
R
EXT
External Timing Resistor (Note 2) 1.4 40 k
C
EXT
External Timing Capacitance (Note 2) 0 1000 µF
DC Duty Cycle (Note 2) R
T
= 2 k 67
%
R
T
= R
EXT
(Max) 90
T
A
Free Air Operating Temperature 0 70 °C
Symbol Parameter Conditions Min
Typ
(Note 3)
Max Units
V
I
Input Clamp Voltage V
CC
= Min, I
I
= 12 mA 1.5 V
V
OH
HIGH Level Output V
CC
= Min, I
OH
= Max,
2.4 3.4 V
Voltage V
IL
= Max, V
IH
= Min
V
OL
LOW Level Output V
CC
= Min, I
OL
= Max,
0.2 0.4 V
Voltage V
IH
= Max, V
IL
= Min
I
I
Input Current @
V
CC
= Max, V
I
= 5.5V 1 mA
Max Input Voltage
I
IH
HIGH Level V
CC
= Max, A1, A2 40
µA
Input Current V
I
= 2.4V B 80
I
IL
LOW Level V
CC
= Max, A1, A2 1.6
mA
Input Current V
I
= 0.4V B 3.2
I
OS
Short Circuit Output Current V
CC
= Max (Note 4) 18 55 mA
I
CC
Supply Current V
CC
= Max Quiescent 13 25
mA
Triggered 23 40
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