HD74HC149 [HITACHI]
8-to-8-line Priority Encoder; 8到8行优先编码器
| 型号： | HD74HC149 |
| 厂家： | 
HITACHI SEMICONDUCTOR |
| 描述： | 8-to-8-line Priority Encoder |
| 文件： | 总9页 (文件大小：62K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
HD74HC149
8-to-8-line Priority Encoder
Description
The HD74HC149 is priority encoder which has 8 input lines (0 - 7) and 8 output lies (Y0 - Y7).
It is the logical combination of a HD74HC148 8-3 line priority encoder driving a HD74HC138 3-8 line
decoder.
Only one request output can be low at a time. The output that is low is dependent on the highest priority
request that is low. The order of priority is 7 highest and 0 lowest.
When E input is high, all outputs are high.
When a output (Y0 - Y7) is low, P output is low and this indicates active condition.
Features
•
•
•
•
•
High Speed Operation: tpd (0 - 7 to Y) = 16 ns typ (CL = 50 pF)
High Output Current: Fanout of 10 LSTTL Loads
Wide Operating Voltage: VCC = 2 to 6 V
Low Input Current: 1 µA max
Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
HD74HC149
Function Table
Inputs
Outputs
0
1
2
3
4
5
6
7
E
H
L
L
L
L
L
L
L
L
L
Y0
H
H
H
H
H
H
H
H
H
L
Y1 Y2
Y3
H
H
H
H
H
H
L
Y4 Y5
Y6
H
H
H
L
Y7
H
H
L
P
H
H
L
L
L
L
L
L
L
L
X
X
H
X
X
X
X
X
X
L
X
H
X
X
X
X
X
L
X
H
X
X
X
X
L
X
H
X
X
X
L
X
H
X
X
L
X
H
X
L
X
H
L
H
H
H
H
H
H
H
H
L
H
H
H
H
H
H
H
L
H
H
H
H
H
L
H
H
H
H
L
H
X
X
H
H
H
H
H
H
H
H
H
H
H
H
H
H
X
H
H
H
H
H
H
H
H
H
H
H
H
X
H
H
H
H
H
H
H
H
H
H
X
H
H
H
H
H
H
H
H
X
H
H
H
H
H
H
X
H
H
H
H
L
H
H
H :
High level
Low level
Irrelevant
L
:
:
X
Pin Arrangement
0
1
20 VCC
19 Y0
18 Y1
17 Y2
16 Y3
15 Y4
14 Y5
13 Y6
12 Y7
1
2
3
4
5
6
7
E
2
3
4
5
6
7
8
9
Inputs
Outputs
GND 10
11
P
(Top view)
2
HD74HC149
Logic Diagram
7
6
Y7
Y6
Y5
Y4
5
4
3
2
Y3
Y2
Y1
1
0
Y0
P
E
3
HD74HC149
DC Characteristics
Ta = –40 to
Ta = 25°C
+85°C
Item
Symbol VCC (V) Min Typ Max Min Max Unit Test Conditions
Input voltage
VIH
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
2.0
4.5
6.0
4.5
6.0
6.0
6.0
1.5
—
—
—
—
0.5
1.5
3.15
4.2
—
—
V
V
V
3.15 —
—
4.2
—
—
—
—
—
—
—
—
VIL
0.5
1.35
1.8
—
1.35 —
1.8
—
—
—
—
—
—
Output voltage
VOH
1.9 2.0
4.4 4.5
5.9 6.0
4.18 —
5.68 —
1.9
4.4
5.9
4.13
5.63
—
Vin = VIH or VIL IOH = –20 µA
—
—
—
IOH = –4 mA
IOH = –5.2 mA
—
VOL
—
—
—
—
—
—
—
0.0 0.1
0.0 0.1
0.0 0.1
0.1
0.1
0.1
0.33
0.33
V
Vin = VIH or VIL IOL = 20 µA
—
—
—
—
—
—
0.26 —
0.26 —
±0.1 —
4.0
IOL = 4 mA
IOL = 5.2 mA
Input current
Iin
±1.0 µA
40 µA
Vin = VCC or GND
Quiescent supply ICC
current
—
Vin = VCC or GND, Iout = 0 µA
4
HD74HC149
AC Characteristics (CL = 50 pF, Input tr = tf = 6 ns)
Ta = –40 to
+85°C
Ta = 25°C
Symbol VCC (V) Min Typ Max Min Max Unit Test Conditions
Item
Propagation delay tPLH
2.0
4.5
6.0
2.0
4.5
6.0
2.0
4.5
6.0
—
—
—
—
—
—
—
—
—
—
—
—
140 —
175 ns
0 - 7 to Y, P
time
tPHL
16 28
—
—
35
—
—
24
30
tPLH
tPHL
155 —
195 ns
E to Y, P
13 31
—
—
—
—
—
—
39
33
—
—
5
26
75
15
13
10
Output rise/fall
time
tTLH
tTHL
95
19
16
10
ns
—
5
Input capacitance Cin
pF
5
Unit: mm
24.50
25.40 Max
20
11
10
1
1.30
0.89
7.62
1.27 Max
+ 0.11
– 0.05
0.25
2.54 ± 0.25
0.48 ± 0.10
0° – 15°
Hitachi Code
JEDEC
EIAJ
DP-20N
—
Conforms
Weight (reference value) 1.26 g
Unit: mm
12.6
13 Max
11
10
20
1
+ 0.20
7.80
– 0.30
0.80 Max
1.15
0° – 8°
1.27
0.70 ± 0.20
*0.42 ± 0.08
0.40 ± 0.06
0.15
0.12 M
Hitachi Code
JEDEC
FP-20DA
—
EIAJ
Conforms
*Dimension including the plating thickness
Base material dimension
Weight (reference value) 0.31 g
Unit: mm
12.8
13.2 Max
11
10
20
1
+ 0.25
– 0.40
10.40
0.935 Max
1.45
0° – 8°
+ 0.57
– 0.30
1.27
0.70
*0.42 ± 0.08
0.40 ± 0.06
0.15
M
0.12
Hitachi Code
JEDEC
EIAJ
FP-20DB
Conforms
—
*Dimension including the plating thickness
Base material dimension
Weight (reference value) 0.52 g
Cautions
1. Hitachi neither warrants nor grants licenses of any rights of Hitachi’s or any third party’s patent,
copyright, trademark, or other intellectual property rights for information contained in this document.
Hitachi bears no responsibility for problems that may arise with third party’s rights, including
intellectual property rights, in connection with use of the information contained in this document.
2. Products and product specifications may be subject to change without notice. Confirm that you have
received the latest product standards or specifications before final design, purchase or use.
3. Hitachi makes every attempt to ensure that its products are of high quality and reliability. However,
contact Hitachi’s sales office before using the product in an application that demands especially high
quality and reliability or where its failure or malfunction may directly threaten human life or cause risk
of bodily injury, such as aerospace, aeronautics, nuclear power, combustion control, transportation,
traffic, safety equipment or medical equipment for life support.
4. Design your application so that the product is used within the ranges guaranteed by Hitachi particularly
for maximum rating, operating supply voltage range, heat radiation characteristics, installation
conditions and other characteristics. Hitachi bears no responsibility for failure or damage when used
beyond the guaranteed ranges. Even within the guaranteed ranges, consider normally foreseeable
failure rates or failure modes in semiconductor devices and employ systemic measures such as fail-
safes, so that the equipment incorporating Hitachi product does not cause bodily injury, fire or other
consequential damage due to operation of the Hitachi product.
5. This product is not designed to be radiation resistant.
6. No one is permitted to reproduce or duplicate, in any form, the whole or part of this document without
written approval from Hitachi.
7. Contact Hitachi’s sales office for any questions regarding this document or Hitachi semiconductor
products.
Hitachi, Ltd.
Semiconductor & Integrated Circuits.
Nippon Bldg., 2-6-2, Ohte-machi, Chiyoda-ku, Tokyo 100-0004, Japan
Tel: Tokyo (03) 3270-2111 Fax: (03) 3270-5109
URL
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Europe
: http:semiconductor.hitachi.com/
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: http://www.hitachi.com.tw/E/Product/SICD_Frame.htm
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Japan
: http://www.hitachi.co.jp/Sicd/indx.htm
For further information write to:
Hitachi Semiconductor
(America) Inc.
Hitachi Europe GmbH
Hitachi Asia (Hong Kong) Ltd.
Group III (Electronic Components)
7/F., North Tower, World Finance Centre,
Harbour City, Canton Road, Tsim Sha Tsui,
Kowloon, Hong Kong
Tel: <852> (2) 735 9218
Fax: <852> (2) 730 0281
Hitachi Asia Pte. Ltd.
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Hitachi Tower
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Tel: 535-2100
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Germany
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3F, Hung Kuo Building. No.167,
Tun-Hwa North Road, Taipei (105)
Tel: <886> (2) 2718-3666
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Electronic Components Group.
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Berkshire SL6 8YA, United Kingdom
Tel: <44> (1628) 585000
Fax: <44> (1628) 778322
Copyright ' Hitachi, Ltd., 1999. All rights reserved. Printed in Japan.
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