onsemi 的 74F148PC 规格书

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© 2000 Fairchild Semiconductor Corporation DS009480 www.fairchildsemi.com
April 1988
Revised September 2000
74F148 8-Line to 3-Line Priority Encoder
74F148
8-Line to 3-Line Priority Encoder
General Description
The F148 provides three bits of binary coded output repre-
senting the position of the highest order active input, along
with an output indicating the presence of any active input. It
is easily expanded via input and output enables to provide
priority encoding over many bits.
Features
■Encodes eight data lines in priority
■Provides 3-bit binary priority code
■Input enable capability
■Signals when data is present on any input
■Cascadable for priority encoding of n bits
Ordering Code:
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Logic Symbols
IEEE/IEC
Connection Diagram
Truth Table
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Order Number Package Number Package Description
74F148SC M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
74F148SJ M16D 16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74F148PC N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Inputs Outputs
EI I0I1I2I3I4I5I6I7GS A0A1A2EO
HXXXXXXXXHHHHH
LHHHHHHHH H HHH L
LXXXXXXXL L LLL H
LXXXXXXLH L HLL H
LXXXXXLHH L LHL H
LXXXXLHHH L HHL H
LXXXLHHHH L LLHH
LXX LHHHHH L HLH H
LX LHHHHHH L LHH H
L LHHHHHHH L HHH H
“%$+é+w—n WE
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74F148
Unit Loading/Fan Out
Functional Description
The F148 8-input priority encoder accepts data from eight
active LOW inputs (I0–I7) and provides a binary represen-
tation on the three active LOW outputs. A priority is
assigned to each input so that when two or more inputs are
simultaneously active, the input with the highest priority is
represented on the output, with input line 7 having the high-
est priority. A HIGH on the Enable Input (EI) will force all
outputs to the inactive (HIGH) state and allow new data to
settle without producing erroneous information at the out-
puts.A Group Signal output (GS) and Enable Output (EO)
are provided along with the three priority data outputs (A2,
A1, A0). GS is active LOW when any input is LOW: this
indicates when any input is active. EO is active LOW when
all inputs are HIGH. Using the Enable Output along with
the Enable Input allows cascading for priority encoding on
any number of input signals. Both EO and GS are in the
inactive HIGH state when the Enable Input is HIGH.
Logic Diagram
Please note that this diagram is provided only for the understanding of logic
operations and should not be used to estimate propagation delays.
Application
16-Input Priority Encoder
Pin Names Description U.L. Input IIH/IIL
HIGH/LOW Output IOH/IOL
I0Priority Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
I1–I7Priority Inputs (Active LOW) 1.0/2.0 20 µA/−1.2 mA
EI Enable Input (Active LOW) 1.0/1.0 20 µA/−0.6 mA
EO Enable Output (Active LOW) 50/33.3 −1 mA/20 mA
GS Group Signal Output (Active LOW) 50/33.3 −1 mA/20 mA
A0–A2Address Outputs (Active LOW) 50/33.3 −1 mA/20 mA
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74F148
Absolute Maximum Ratings(Note 1) Recommended Operating
Conditions
Note 1: Absolute maximum ratings are values beyond which the device
may be damaged or have its useful life impaired. Functional operation
under these conditions is not implied.
Note 2: Either voltage limit or current limit is sufficient to protect inputs.
DC Electrical Characteristics
Storage Temperature −65°C to +150°C
Ambient Temperature under Bias −55°C to +125°C
Junction Temperature under Bias −55°C to +150°C
VCC Pin Potential to Ground Pin −0.5V to +7.0V
Input Voltage (Note 2) −0.5V to +7.0V
Input Current (Note 2) −30 mA to +5.0 mA
Voltage Applied to Output
in HIGH State (with VCC = 0V)
Standard Output −0.5V to VCC
3-STATE Output −0.5V to +5.5V
Current Applied to Output
in LOW State (Max) twice the rated IOL (mA)
Free Air Ambient Temperature 0°C to +70°C
Supply Voltage +4.5V to +5.5V
Symbol Parameter Min Typ Max Units VCC Conditions
VIH Input HIGH Voltage 2.0 V Recognized as a HIGH Signal
VIL Input LOW Voltage 0.8 V Recognized as a LOW Signal
VCD Input Clamp Diode Voltage −1.2 V Min IIN = −18 mA
VOH Output HIGH 10% VCC 2.5 VMin
IOH = −1 mA
Voltage 5% VCC 2.7 IOH = −1 mA
VOL Output LOW 10% VCC 0.5 V Min IOL = 20 mA
Voltage
IIH Input HIGH 5.0 µAMaxV
IN = 2.7V
Current
IBVI Input HIGH Current 7.0 µAMaxV
IN = 7.0V
Breakdown Test
ICEX Output High 50 µAMaxV
OUT = VCC
Leakage Current
VID Input Leakage 4.75 V 0.0 IID = 1.9 µA
Test All Other Pins Grounded
IOD Output Leakage 3.75 µA0.0
VIOD = 150 mV
Circuit Current All Other Pins Grounded
IIL Input LOW −0.6 mA Max VIN = 0.5V (I0, EI)
Current −1.2 mA VIN = 0.5V (I1–I7)
IOS Output Short-Circuit Current −60 −150 mA Max VOUT = 0V
ICCH Power Supply Current 35 mA Max VO = HIGH
ICCL Power Supply Current 35 mA Max VO = LOW
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74F148
AC Electrical Characteristics
Symbol Parameter
TA = +25°CT
A = 0°C to +70°C
Units
VCC = +5.0V VCC = +5.0V
CL = 50 pF CL = 50 pF
Min Typ Max Min Max
tPLH Propagation Delay 3.0 7.0 9.0 3.0 10.0 ns
tPHL In to An3.0 8.0 10.5 3.0 12.0
tPLH Propagation Delay 2.5 5.0 6.5 2.5 7.5 ns
tPHL In to EO 2.5 5.5 7.5 2.5 8.5
tPLH Propagation Delay 2.5 7.0 9.0 2.5 10.0 ns
tPHL In to GS 2.5 6.0 8.0 2.5 9.0
tPLH Propagation Delay 2.5 6.5 8.5 2.5 9.5 ns
tPHL EI to An2.5 6.0 8.0 2.5 9.0
tPLH Propagation Delay 2.5 5.0 7.0 2.5 8.0 ns
tPHL EI to GS 2.5 6.0 7.5 2.5 8.5
tPLH Propagation Delay 2.5 5.5 7.0 2.5 8.0 ns
tPHL EI to EO 3.0 8.0 10.5 3.0 12.0
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74F148
Physical Dimensions inches (millimeters) unless otherwise noted
16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
Package Number M16A
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74F148
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
Package Number M16D
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74F148 8-Line to 3-Line Priority Encoder
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Package Number N16E
Fairchild does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and
Fairchild reserves the right at any time without notice to change said circuitry and specifications.
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FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the
body, or (b) support or sustain life, and (c) whose failure
to perform when properly used in accordance with
instructions for use provided in the labeling, can be rea-
sonably expected to result in a significant injury to the
user.
2. A critical component in any component of a life support
device or system whose failure to perform can be rea-
sonably expected to cause the failure of the life support
device or system, or to affect its safety or effectiveness.
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