74F148 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

74F148

8-input priority encoder

Philips Electronics 

Philips Semiconductors

8-input priority encoder

Product specification

74F148

FEATURES

• Code conversions

• Multi-channel D/A converter

• Decimal-to-BCD converter

• Cascading for priority encoding of “N” bits

• Input enable capability

• Priority encoding-automatic selection of highest priority input line

• Output enable-active Low when all inputs are High

• Group signal output-active when any input is Low

DESCRIPTION

The 74F148 8-input priority encoder accepts data from eight

active-Low inputs and provides a binary representation 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 I7 having

the highest 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 outputs. A Group

Signal (GS) output and an Enable Output (EO) are provided with the

three data outputs. The GS is active-Low when any input is Low:

this indicates when any input is active. The EO is active-Low when

all inputs are High. Using the Enable Output along with the Enable

Input allows priority encoding of N input signals. Both EO and GS

are active-High when the Enable Input is High.

PIN CONFIGURATION

I4 1

I5 2

I6 3

I7 4

EI 5

A2 6

A1 7

GND 8

16 VCC

15 EO

14 GS

13 I3

12 I2

11 I1

10 I0

9 A0

SF00181

TYPE

74F148

TYPICAL

PROPAGATION

DELAY

6.0ns

TYPICAL

SUPPLY CURRENT

(TOTAL)

23mA

ORDERING INFORMATION

DESCRIPTION

COMMERCIAL RANGE

VCC = 5V ±10%,

Tamb = 0°C to +70°C

16-pin plastic DIP

N74F148N

16-pin plastic SO

N74F148D

PKG DWG #

SOT38-4

SOT109-1

INPUT AND OUTPUT LOADING AND FAN-OUT TABLE

PINS

DESCRIPTION

74F (U.L.) HIGH/LOW

I1 – I7

Priority inputs (active Low)

1.0/2.0

I0

Priority input (active Low)

1.0/1.0

EI

Enable input (active Low)

1.0/2.0

EO

Enable output (active Low)

50/33

GS

Group select output (active Low)

50/33

A0 – A2

Address outputs (active Low)

50/33

NOTE: One (1.0) FAST unit load is defined as: 20µA in the High state and 0.6mA in the Low state.

LOAD VALUE HIGH/LOW

20µA/1.2mA

20µA/0.6mA

20µA/1.2mA

1.0mA/20mA

1.0mA/20mA

1.0mA/20mA

March 1, 1990

2

853–0345 98994

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