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National
National

74LS121 Datasheet

Clear and Complementary Outputs


74LS121 Datasheet Preview


June 1989
54121 DM54121 DM74121 One-Shot with
Clear and Complementary Outputs
General Description
Y Jitter free Schmitt-trigger input
The DM54 74121 is a monostable multivibrator featuring
both positive and negative edge triggering with complemen-
Y Excellent noise immunity typically 1 2V
Y Stable pulse width up to 90% duty cycle
tary outputs An internal 2kX timing resistor is provided for Y TTL DTL compatible
design convenience minimizing component count and lay- Y Compensated for VCC and temperature variations
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-
msition rates as slow as 1 volt second A high immunity to
VCC noise of typically 1 5V is also provided by internal cir-
ocuitry at the input stage
To obtain optimum and trouble free operation please read
.coperating rules and NSC one-shot application notes careful-
ly and observe recommendations
Features
UY Triggered from active-high transition or active-low tran-
sition inputs
t4Y Variable pulse width from 30 ns to 28 seconds
Y Input clamp diodes
Y 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 RINT or an external resistor (RX) and
capacitor (CX) 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
RX and CX combinations There are three trigger inputs from
the device two negative edge-triggering (A) inputs one pos-
itive edge Schmitt-triggering (B) input
eConnection Diagram
eDual-In-Line Package
.DataShTL F 6538–1
wOrder Number 54121DMQB 54121FMQB
DM54121J DM54121W or DM74121N
wwSee NS Package Number J14A N14A or W14B
Function Table
Inputs
A1 A2
B
L XH
X LH
XXL
HHX
HvH
vH H
vv H
L Xu
X Lu
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
e A Positive Pulse
e A Negative Pulse
Outputs
QQ
LH
LH
LH
LH
C1995 National Semiconductor Corporation TL F 6538
www.DataSheet4U.comRRD-B30M105 Printed in U S A
Page 1

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
b55 C to a125 C
DM74
0 C to a70 C
Storage Temperature Range
b65 C to a150 C
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
Recommended Operating Conditions
Symbol
Parameter
DM54121
Min Nom Max
DM74121
Min Nom Max
Units
VCC
VTa
VTb
VTa
VTb
IOH
IOL
tW
dV dt
Supply Voltage
Positive-Going Input Threshold
Voltage at the A Input (VCC e Min)
Negative-Going Input Threshold
Voltage at the A Input (VCC e Min)
Positive-Going Input Threshold
Voltage at the B Input (VCC e Min)
Negative-Going Input Threshold
Voltage at the B Input (VCC 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)
45
5
5 5 4 75
5
5 25
14 2
14 2
V
V
08 14
08 14
V
15 2
15 2
V
08 13
08 13
V
b0 4
b0 4
mA
16 16 mA
40 40
ns
1 1 Vs
dV dt
Rate of Rise or Fall of
Logic Input (A) (Note 1)
1 1 V ms
REXT
External Timing Resistor (Note 1)
CEXT
External Timing Capacitance (Note 1)
DC
Duty Cycle (Note 1)
RT e 2 kX
RT e REXT (Max)
TA Free Air Operating Temperature
Note 1 TA e 25 C and VCC e 5V
14
0
b55
30
1000
67
90
125
14
0
0
40
1000
67
90
70
kX
mF
%
C
Electrical Characteristics over recommended operating free air temperature range (unless otherwise noted)
Symbol
Parameter
Conditions
VI
VOH
VOL
II
Input Clamp Voltage
High Level Output
Voltage
Low Level Output
Voltage
Input Current Max
Input Voltage
VCC e Min II e b12 mA
VCC e Min IOH e Max
VIL e Max VIH e Min
VCC e Min IOL e Max
VIH e Min VIL e Max
VCC e Max VI e 5 5V
IIH
High Level Input
VCC e Max
A1 A2
Current
VI e 2 4V
B
IIL
Low Level Input
VCC e Max
A1 A2
Current
VI e 0 4V
B
IOS Short Circuit
Output Current
VCC e Max
(Note 2)
DM54
DM74
ICC Supply Current
VCC e Max
Quiescent
Triggered
Note 1 All typicals are at VCC e 5V TA e 25 C
Note 2 Not more than one output should be shorted at a time
Min
24
b20
b18
Typ
(Note 1)
34
02
13
23
Max
b1 5
04
1
40
80
b1 6
b3 2
b55
b55
25
40
Units
V
V
V
mA
mA
mA
mA
mA
2
www.DataSheet4U.com
Page 2

Switching Characteristics at VCC e 5V and TA e 25 C (See Section 1 for Test Waveforms and Outout Load)
Symbol
Parameter
From (Input)
To (Output)
Conditions
Min Max Units
tPLH
tPLH
Propagation Delay Time
Low to High Level Output
Propagation Delay Time
Low to High Level Output
A1 A2
to Q
B to
Q
CEXT e 80 pF
RINT to VCC
CL e 15 pF
RL e 400X
70 ns
55 ns
tPHL
Propagation Delay Time
High to Low Level Output
A1 A2
to Q
80 ns
tPHL
Propagation Delay Time
High to Low Level Output
B
to Q
65 ns
tW(OUT)
tW(OUT)
tW(OUT)
Output Pulse
Width Using the
Internal Timing Resistor
Output Pulse
Width Using Zero
Timing Capacitance
Output Pulse
Width Using External
Timing Resistor
A1 A2 or B
to Q Q
A1 A2
to Q Q
A1 A2
to Q Q
A1 A2
to Q Q
CEXT e 80 pF
RINT to VCC
RL e 400X
CL e 15 pF
70 150
CEXT e 0 pF
RINT to VCC
RL e 400X
CL e 15 pF
50
CEXT e 100 pF
RINT e 10 kX
RL e 400X
600 800
CL e 15 pF
CEXT e 1 mF
RINT e 10 kX
RL e 400X
6
8
CL e 15 pF
ns
ns
ns
ms
Operating Rules
1 To use the internal 2 kX timing resistor connect the RINT
pin to VCC
2 An external resistor (RX) or the internal resistor (2 kX)
and an external capacitor (CX) are required for proper
operation The value of CX 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 RX and CX For CX k 1000 pF see Fig-
ure 1 design curves on TW as function of timing compo-
nents value For CX l1000 pF the output is defined as
tW e K RX CX
where RX is in Kilo-ohm
CX is in pico Farad
TW is in nano second
K 07
FIGURE 1
TL F 6538 – 2
4 If CX is an electrolytic capacitor a switching diode is often
required for standard TTL one-shots to prevent high in-
verse leakage current (Figure 2)
FIGURE 2
TL F 6538 – 3
3
Page 3
Part Number 74LS121
Manufactur National
Description Clear and Complementary Outputs
Total Page 6 Pages
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