NSC 54LS168DMQB

54LS168 Synchronous Bi-Directional
BCD Decade Counter
General Description
The 54LS168 is a fully synchronous 4-state up/down counter featuring a preset capability for programmable operation,
carry lookahead for easy cascading and a U/D input to control the direction of counting. It counts in the BCD (8421)
sequence and all state changes, whether in counting or parallel loading, are initiated by the LOW-to-HIGH transition of
the clock.
Connection Diagram
Logic Symbol
Dual-In-Line Package
TL/F/10207 – 1
TL/F/10207 – 2
Order Number 54LS168DMQB,
54LS168FMQB or 54LS168LMQB
See NS Package Number
E20A, J16A or W16A
Pin Names
CEP
CET
CP
P0–P3
PE
U/D
Q0–Q3
TC
C1995 National Semiconductor Corporation
TL/F/10207
VCC e Pin 16
GND e Pin 8
Description
Count Enable Parallel Input (Active LOW)
Count Enable Trickle Input (Active LOW)
Clock Pulse Input (Active Rising Edge)
Parallel Data Inputs
Parallel Enable Input (Active LOW)
Up-Down Count Control Input
Flip-Flop Outputs
Terminal Count Output (Active LOW)
RRD-B30M105/Printed in U. S. A.
54LS168 Synchronous Bi-Directional BCD Decade Counter
June 1989
Absolute Maximum Ratings
(Note)
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.
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
b 55§ C to a 125§ C
54LS
b 65§ C to a 150§ C
Storage Temperature Range
Recommended Operating Conditions
Symbol
54LS168
Parameter
Units
Min
Nom
Max
4.5
5
5.5
VCC
Supply Voltage
VIH
High Level Input Voltage
VIL
Low Level Input Voltage
IOH
High Level Output Current
IOL
Low Level Output Current
TA
Free Air Operating Temperature
ts (H)
ts (L)
Setup Time HIGH or LOW
Pn, CEP or CET to CP
15
15
ns
th (H)
th (L)
Hold Time HIGH or LOW
Pn, CEP or CET to CP
5
5
ns
ts (H)
ts (L)
Setup Time HIGH or LOW
PE to CP
20
20
ns
th (H)
th (L)
Hold Time HIGH or LOW
PE to CP
0
0
ns
ts (H)
ts (L)
Setup Time HIGH or LOW
U/D to CP
25
25
ns
th (H)
th (L)
Hold Time HIGH or LOW
U/D to CP
0
0
ns
tw (H)
tw (L)
CP Pulse Width HIGH or LOW
20
20
ns
2
b 55
2
V
V
0.7
V
b 0.4
mA
4
mA
125
§C
Electrical Characteristics over recommended operating free air temperature range (unless otherwise noted)
Symbol
Parameter
Conditions
VI
Input Clamp Voltage
VCC e Min, II e b18 mA
VOH
High Level Output Voltage
VCC e Min, IOH e Max,
VIL e Max, VIH e Min
VOL
Low Level Output Voltage
VCC e Min, IOL e Max,
VIH e Min, VIL e Max
II
Input Current @ Max
Input Voltage
VCC e Max, VI e 10.0V
IIH
High Level Input Current
VCC e Max, VI e 2.7V
IIL
Low Level Input Current
IOS
ICC
VCC e Max, VI e 0.5V
Short Circuit Output Current
VCC e Max (Note 2)
Supply Current
VCC e Max (Note 3)
Typ
(Note 1)
Min
Max
Units
b 1.5
V
2.5
V
0.4
V
0.1
mA
Inputs
20
CET
40
mA
Data
b 0.5
b 400
CP, PE, U/D, CEP
b 30
b 400
CET
b 60
b 800
b 20
b 100
mA
34
mA
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, and the duration should not exceed one second.
Note 3: ICC is measured with all outputs open and all inputs grounded.
Switching Characteristics
VCC e a 5.0V, TA e a 25§ C (See Section 1 for test waveforms and output load)
54LS168
Symbol
Parameter
CL e 15 pF
Min
Units
Max
fMax
Maximum Clock Frequency
25
tPLH
tPHL
Propagation Delay
CP to Qn
20
20
ns
tPLH
tPHL
Propagation Delay
CP to TC
30
30
ns
tPLH
tPHL
Propagation Delay
CET to TC
15
20
ns
tPLH
tPHL
Propagation Delay
U/D to TC
25
25
ns
3
MHz
mA
Functional Description
The ’LS168 uses edge-triggered D-type flip-flops and has
no constraints on changing the control or data input signals
in either state of the Clock. The only requirement is that the
various inputs attain the desired state at least a setup time
before the rising edge of the clock and remain valid for the
recommended hold time thereafter. The parallel load operation takes precedence over the other operations, as indicated in the Mode Select Table. When PE is LOW, the data on
the P0 – P3 inputs enters the flip-flops on the next rising
edge of the Clock. In order for counting to occur, both CEP
and CET must be LOW and PE must be HIGH. The U/D
input then determines the direction of counting. The Terminal Count (TC) output is normally HIGH and goes LOW,
provided that CET is LOW, when a counter reaches zero in
the COUNT DOWN mode or reaches 9 in the COUNT UP
mode. The TC output state is not a function of the Count
Enable Parallel (CEP) input level. The TC output of the
’LS168 decade counter can also be LOW in the illegal
states 11, 13 and 15, which can occur when power is turned
on or via parallel loading. If an illegal state occurs, the
’LS168 will return to the legitimate sequence within two
counts. Since the TC signal is derived by decoding the flipflop states, there exists the possibility of decoding spikes on
TC. For this reason the use of TC as a clock signal is not
recommended (see logic equation below).
1. Count Enable e CEP # CET # PE
’LS168 Mode Select Table
PE
CEP
CET
U/D
L
H
H
H
H
X
L
L
H
X
X
L
L
X
H
X
H
L
X
X
Action on Rising Clock Edge
Load (Pn x Qn)
Count Up (Increment)
Count Down (Decrement)
No Change (Hold)
No Change (Hold)
H e HIGH Voltage Level
L e LOW Voltage Level
X e Immaterial
State Diagram
2. Up: TC e Q0 # Q3 # (U/D) # CET
3. Down: TC e Q0 # Q1 # Q2 # Q3 # (U/D) # CET
TL/F/10207 – 3
Logic Diagram
TL/F/10207 – 4
4
Physical Dimensions inches (millimeters)
Ceramic Leadless Chip Carrier Package (E)
Order Number 54LS168LMQB
NS Package Number E20A
16-Lead Ceramic Dual-In-Line Package (J)
Order Number 54LS168DMQB
NS Package Number J16A
5
54LS168 Synchronous Bi-Directional BCD Decade Counter
Physical Dimensions inches (millimeters) (Continued)
16-Lead Ceramic Flat Package (W)
Order Number 54LS168FMQB
NS Package Number W16A
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