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National Semiconductor Electronic Components Datasheet

DM74161 Datasheet

Synchronous 4-Bit Counters

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October 1992
DM54161 DM74161 DM74163
Synchronous 4-Bit Counters
General Description
These synchronous presettable counters feature an inter-
nal carry look-ahead for application in high-speed counting
designs The 161 and 163 are 4-bit binary counters The
carry output is decoded by means of a NOR gate thus pre-
venting spikes during the normal counting mode of opera-
tion Synchronous operation is provided by having all flip-
flops clocked simultaneously so that the outputs change co-
incident with each other when so instructed by the count-
enable inputs and internal gating This mode of operation
eliminates the output counting spikes which are normally
associated with asynchronous (ripple clock) counters A
buffered clock input triggers the four flip-flops on the rising
(positive-going) edge of the clock input waveform
These counters are fully programmable that is the outputs
may be preset to either level As presetting is synchronous
setting up a low level at the load input disables the counter
and causes the outputs to agree with the setup data after
the next clock pulse regardless of the levels of the enable
input The clear function for the 161 is asynchronous and a
low level at the clear input sets all four of the flip-flop out-
puts low regardless of the levels of clock load or enable
inputs The clear function for the 163 is synchronous and a
low level at the clear input sets all four of the flip-flop out-
puts low after the next clock pulse regardless of the levels
of the enable inputs This synchronous clear allows the
count length to be modified easily as decoding the maxi-
mum count desired can be accomplished with one
external NAND gate The gate output is connected to the
clear input to synchronously clear the counter to all low out-
puts Low-to-high transitions at the clear input of the 163 are
also permissible regardless of the logic levels on the clock
enable or load inputs
The carry look-ahead circuitry provides for cascading coun-
ters for n-bit synchronous applications without additional
gating Instrumental in accomplishing this function are two
count-enable inputs and a ripple carry output Both count-
enable inputs (P and T) must be high to count and input T is
fed forward to enable the ripple carry output The ripple car-
ry output thus enabled will produce a high-level output pulse
with a duration approximately equal to the high-level portion
of the QA output This high-level overflow ripple carry pulse
can be used to enable successive cascaded stages High-
to-low-level transitions at the enable P or T inputs of the 161
through 163 may occur regardless of the logic level on the
clock
Features
Y Synchronously programmable
Y Internal look-ahead for fast counting
Y Carry output for n-bit cascading
Y Synchronous counting
Y Load control line
Y Diode-clamped inputs
Connection Diagram
Dual-In-Line Package
Order Number DM54161J DM54161W
DM74161N or DM74163N
See NS Package Number J16A N16E or W16A
TL F 6551 – 1
C1995 National Semiconductor Corporation TL F 6551
RRD-B30M105 Printed in U S A


National Semiconductor Electronic Components Datasheet

DM74161 Datasheet

Synchronous 4-Bit Counters

No Preview Available !

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
VCC
VIH
VIL
IOH
IOL
fCLK
tW
tSU
tH
TA
Parameter
Supply Voltage
High Level Input Voltage
Low Level Input Voltage
High Level Output Current
Low Level Output Current
Clock Frequency (Note 6)
Pulse Width
(Note 6)
Clock
Clear
Setup Time
(Note 6)
Data
Enable P
Load
Clear (Note 5)
Hold Time (Note 6)
Free Air Operating Temperature
Min
45
2
0
25
20
20
34
25
20
0
b55
DM54161
Nom
5
Max
55
08
b0 8
16
25
125
DM74161 and 163
Min Nom Max
4 75 5
5 25
2
08
b0 8
16
0 25
25
20
20
34
25
20
0
0 70
Units
V
V
V
mA
mA
MHz
ns
ns
ns
C
Electrical Characteristics
Over recommended operating free air temperature range (unless otherwise noted)
Symbol
VI
VOH
VOL
II
IIH
IIL
Parameter
Input Clamp Voltage
High Level Output
Voltage
Low Level Output
Voltage
Input Current Max
Input Voltage
High Level Input
Current
Low Level Input
Current
Conditions
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
VCC e Max
VI e 2 4V
VCC e Max
VI e 0 4V
Enable T
Clock
Others
Enable T
Clock
Others
Min
24
Typ
(Note 1)
34
02
Max
b1 5
04
1
80
80
40
b3 2
b3 2
b1 6
Units
V
V
V
mA
mA
mA
2


Part Number DM74161
Description Synchronous 4-Bit Counters
Maker National Semiconductor
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DM74161 Datasheet PDF






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