TL/F/6545
DM54148 Priority Encoder
June 1989
DM54148 Priority Encoder
General Description
This TTL encoder features priority decoding of the input
data to ensure that only the highest-order data line is en-
coded. The DM54148 encodes eight data lines to three-line
(4-2-1) binary (octal). Cascading circuitry (enable input E1
and enable output E0) has been provided to allow octal ex-
pansion without the need for external circuitry. For all types,
data inputs and outputs are active at the low logic level.
Features
YEncodes 8 data lines to 3-line binary (octal)
YApplications include:
N-bit encoding
Code converters and generators
Connection Diagram
Dual-In-Line Package
TL/F/6545–1
Order Number DM54148J or DM54148W
See NS Package Number J16A or W16A
Function Table
DM54148
Inputs Outputs
E1 0 1 2 3 4 5 6 7 A2 A1 A0 GS E0
H XXXXXXXX H H H H H
L HHHHHHHH H H H H L
L XXXXXXXL L L L L H
L XXXXXXLH L L H L H
L XXXXXLHH L H L L H
L XXXXLHHH L H H L H
L XXXLHHHH H L L L H
L XX LHHHHH H L H L H
L XLHHHHHH H H L L H
L LHHHHHHH H H H L H
H
e
High Logic Level, L eLow Logic Level, X eDon’t Care
C1995 National Semiconductor Corporation RRD-B30M105/Printed in U. S. A.
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§Ctoa
125§C
Storage Temperature Range b65§Ctoa
150§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 DM54148 Units
Min Nom Max
VCC Supply Voltage 4.5 5 5.5 V
VIH High Level Input Voltage 2 V
VIL Low Level Input Voltage 0.8 V
IOH High Level Output Current b0.8 mA
IOL Low Level Output Current 16 mA
TAFree Air Operating Temperature b55 125 §C
Electrical Characteristics over recommended operating free air temperature range (unless otherwise noted)
Symbol Parameter Conditions Min Typ Max Units
(Note 1)
VIInput Clamp Voltage VCC eMin, IIeb
12 mA b1.5 V
VOH High Level Output VCC eMin, IOH eMax 2.4 V
Voltage VIL eMax, VIH eMin
VOL Low Level Output VCC eMin, IOL eMax 0.4 V
Voltage VIH eMin, VIL eMax
IIInput Current @Max VCC eMax, VIe5.5V 1mA
Input Voltage
IIH High Level Input VCC eMax 0 Input 40 mA
Current VIe2.4V Others 80
IIL Low Level Input VCC eMax 0 Input b1.6 mA
Current VIe0.4V Others b3.2
IOS Short Circuit VCC eMax (Note 2) b35 b85 mA
Output Current
ICC1 Supply Current VCC eMax (Note 3) 40 60 mA
ICC2 Supply Current VCC eMax (Note 4) 35 55 mA
Note 1: All typicals are at VCC e5V, TAe25§C.
Note 2: Not more than one output should be shorted at a time.
Note 3: ICC1 is measured with inputs E1 and 7 grounded, other inputs and outputs open.
Note 4: ICC2 is measured with all inputs and all outputs open.
2
Switching Characteristics at VCC e5V and TAe25§C (See Section 1 for Test Waveforms and Output Load)
Symbol Parameter From (Input) Waveform RLe400X,C
Le15 pF Units
To (Output) Min Max
tPLH Propagation Delay Time 0 thru 7 15 ns
Low to High Level Output to A0, 1, 2 In-Phase
tPHL Propagation Delay Time 0 thru 7 Output
14 ns
High to Low Level Output to A0, 1, 2
tPLH Propagation Delay Time 0 thru 7 19 ns
Low to High Level Output to A0, 1, 2 Out-of-Phase
tPHL Propagation Delay Time 0 thru 7 Output
19 ns
High to Low Level Output to A0, 1, 2
tPLH Propagation Delay Time 0 thru 7 10 ns
Low to High Level Output to E0 Out-of-Phase
tPHL Propagation Delay Time 0 thru 7 Output
25 ns
High to Low Level Output to E0
tPLH Propagation Delay Time 0 thru 7 30 ns
Low to High Level Output to GS In-Phase
tPHL Propagation Delay Time 0 thru 7 Output
25 ns
High to Low Level Output to GS
tPLH Propagation Delay Time E1 to 16 ns
Low to High Level Output A0, 1, 2 In-Phase
tPHL Propagation Delay Time E1 to Output
15 ns
High to Low Level Output A0, 1, 2
tPLH Propagation Delay Time E1 to GS 13 ns
Low to High Level Output In-Phase
tPHL Propagation Delay Time E1 to GS
Output
15 ns
High to Low Level Output
tPLH Propagation Delay Time E1 to E0 15 ns
Low to High Level Output In-Phase
tPHL Propagation Delay Time E1 to E0
Output
30 ns
High to Low Level Output
3
Logic Diagram
TL/F/6545–2
4
Physical Dimensions inches (millimeters)
16-Lead Ceramic Dual-In-Line Package (J)
Order Number DM54148J
NS Package Number J16A
5
DM54148 Priority Encoder
Physical Dimensions inches (millimeters) (Continued)
16-Lead Ceramic Flat Package (W)
Order Number DM54148W
NS Package Number W16A
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failure to perform, when properly used in accordance support device or system, or to affect its safety or
with instructions for use provided in the labeling, can effectiveness.
be reasonably expected to result in a significant injury
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