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HD74HC688
8-bit Magnitude Comparator
Description
The HD74HC688 compares bit for bit two 8-bit words and indicates whether or not they are equal. The
P=Q output indicates equality when it is low.
A single active low enable is provided to facilitate cascading of several packages and enable comparison of
words greater than 8-bits.
This device is useful in memory block decoding applications, where memory block enable signals must be
generated from computer address information.
Features
• High Speed Operation: tpd (P or Q to Output) = 17 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)
Function Table
Input
Data P, Q Enable G P=Q
P=Q L L
P>Q L H
P<Q L H
XH H
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HD74HC688
Pin Arrangement
G
1
P
2
0
20
19
V
CC
P=Q
Q
P
Q
P
Q
P
Q
GND
3
0
4
1
5
1
6
2
7
2
8
3
9
3
10
18
17
16
15
14
13
12
11
Q
7
P
7
Q
6
P
6
Q
5
P
5
Q
4
Q
4
(Top view)
2
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Block Diagram
HD74HC688
P
0
Q
0
P
1
Q
1
P
2
Q
2
P
3
Q
3
P
4
P=Q
Q
4
P
5
Q
5
P
6
Q
6
P
7
Q
7
G
3
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HD74HC688
DC Characteristics
Ta = –40 to
Ta = 25°C
Item Symbol V
Input voltage V
IH
(V) Min Typ Max Min Max Unit Test Conditions
CC
2.0 1.5 — — 1.5 — V
4.5 3.15 — — 3.15 —
6.0 4.2 — — 4.2 —
V
IL
2.0 — — 0.5 — 0.5 V
4.5 — — 1.35 — 1.35
6.0 — — 1.8 — 1.8
Output voltage V
OH
2.0 1.9 2.0 — 1.9 — V Vin = VIH or VILIOH = –20 µA
4.5 4.4 4.5 — 4.4 —
6.0 5.9 6.0 — 5.9 —
4.5 4.18 — — 4.13 — IOH = –4 mA
6.0 5.68 — — 5.63 — IOH = –5.2 mA
V
OL
2.0 — 0.0 0.1 — 0.1 V Vin = VIH or VILIOL = 20 µA
4.5 — 0.0 0.1 — 0.1
6.0 — 0.0 0.1 — 0.1
4.5 — — 0.26 — 0.33 IOL = 4 mA
6.0 — — 0.26 — 0.33 IOL = 5.2 mA
Input current Iin 6.0 — — ±0.1 — ±1.0 µA Vin = VCC or GND
Quiescent supply
I
CC
6.0 — — 4.0 — 40 µA Vin = VCC or GND, Iout = 0 µA
current
+85°C
4
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AC Characteristics (CL = 50 pF, Input tr = tf = 6 ns)
Ta = –40 to
Ta = 25°C
Item Symbol V
Propagation delay t
time t
PLH
PHL
(V) Min Typ Max Min Max Unit Test Conditions
CC
2.0 — — 210 — 265 ns P or Q to output
4.5 — 17 42 — 53
6.0 — — 36 — 45
t
PLH
t
PHL
2.0 — — 120 — 150 ns Enable to P=Q
4.5 — 9 24 — 30
6.0 — — 20 — 26
Output rise/fall t
time t
TLH
THL
2.0 — — 75 — 95 ns
4.5 — 5 15 — 19
6.0 — — 13 — 16
Input capacitance Cin — — 5 10 — 10 pF
+85°C
HD74HC688
5
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24.50
25.40 Max
Unit: mm
1120
6.30
1
0.89
1.27 Max
2.54 ± 0.25
1.30
10
0.48 ± 0.10
7.00 Max
0.51 Min
2.54 Min 5.08 Max
Hitachi Code
JEDEC
EIAJ
Weight
7.62
+ 0.11
0.25
– 0.05
0° – 15°
(reference value)
DP-20N
—
Conforms
1.26 g
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20
Unit: mm
12.6
13 Max
11
5.5
1
0.80 Max
1.27
*0.42 ± 0.08
0.40 ± 0.06
*Dimension including the plating thickness
Base material dimension
10
0.12
0.10 ± 0.10
0.15
M
2.20 Max
7.80
0.20 ± 0.04
*0.22 ± 0.05
0.70 ± 0.20
Hitachi Code
JEDEC
EIAJ
Weight
(reference value)
+ 0.20
– 0.30
1.15
0° – 8°
FP-20DA
—
Conforms
0.31 g
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20
Unit: mm
12.8
13.2 Max
11
7.50
1
0.935 Max
1.27
*0.42 ± 0.08
0.40 ± 0.06
*Dimension including the plating thickness
Base material dimension
10
0.12
0.20 ± 0.10
0.15
M
2.65 Max
10.40
0.25 ± 0.04
*0.27 ± 0.05
0.70
Hitachi Code
JEDEC
EIAJ
Weight
(reference value)
+ 0.25
– 0.40
1.45
+ 0.57
– 0.30
0° – 8°
FP-20DB
Conforms
—
0.52 g
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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 failsafes, 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.
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