CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
D
D
D
D
D
D
D
D
E PACKAGE
(TOP VIEW)
Inputs Are TTL-Voltage Compatible
Speed of Bipolar F, AS, and S, With
Significantly Reduced Power Consumption
Designed Specifically for High-Speed
Memory Decoders and Data-Transmission
Systems
Incorporates Three Enable Inputs to
Simplify Cascading and/or Data Reception
Balanced Propagation Delays
±24-mA Output Drive Current
– Fanout to 15 F Devices
SCR-Latchup-Resistant CMOS Process and
Circuit Design
Exceeds 2-kV ESD Protection Per
MIL-STD-883, Method 3015
A
B
C
G2A
G2B
G1
Y7
GND
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
VCC
Y0
Y1
Y2
Y3
Y4
Y5
Y6
description/ordering information
The CD74ACT238 decoder/demultiplexer is designed for high-performance memory-decoding and data-routing
applications that require very short propagation-delay times. In high-performance memory systems, this
decoder can be used to minimize the effects of system decoding. When employed with high-speed memories
utilizing a fast enable circuit, the delay times of this decoder and the enable time of the memory usually are less
than the typical access time of the memory. This means that the effective system delay introduced by the
decoder is negligible.
The conditions at the binary-select inputs and the three enable inputs select one of eight output lines. Two
active-low and one active-high enable inputs reduce the need for external gates or inverters when expanding.
A 24-line decoder can be implemented without external inverters, and a 32-line decoder requires only one
inverter. An enable input can be used as a data input for demultiplexing applications (see Application
Information).
ORDERING INFORMATION
TA
PACKAGE†
ORDERABLE
PART NUMBER
TOP-SIDE
MARKING
–55°C to 125°C
PDIP – E
Tube
CD74ACT238E
CD74ACT238E
† Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines
are available at www.ti.com/sc/package.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright 2003, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
POST OFFICE BOX 655303
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1
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
FUNCTION TABLE
SELECT INPUTS
ENABLE INPUTS
G1
G2A
G2B
C
B
X
X
H
X
X
X
X
H
X
X
A
OUTPUTS
Y0
Y1
Y2
Y3
Y4
X
L
X
L
Y5
Y6
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
X
X
X
X
X
L
L
L
L
L
L
L
L
H
L
L
L
L
L
H
L
L
L
L
L
L
L
H
L
L
L
L
H
L
H
L
L
L
L
L
L
H
L
L
L
H
L
L
L
H
L
L
L
L
L
H
L
L
L
H
H
L
L
L
H
L
L
L
L
H
L
L
H
L
L
L
L
L
L
H
L
L
L
H
L
L
H
L
H
L
L
L
L
L
H
L
L
H
L
L
H
H
L
L
L
L
L
L
L
H
L
H
L
L
H
H
H
L
L
L
L
L
L
L
H
logic diagram (positive logic)
15
A
Y0
1
14
Y1
13
Select
Inputs
B
Y2
2
12
11
3
Y3
Data
Outputs
Y4
C
10
9
G2A
Enable
Inputs
G2B
G1
2
Y7
4
7
5
6
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Y5
Y6
Y7
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
absolute maximum ratings over operating free-air temperature range (unless otherwise noted)†
Supply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.5 V to 6 V
Input clamp current, IIK (VI < 0 V or VI > VCC) (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±20 mA
Output clamp current, IOK (VO < 0 V or VO > VCC) (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±50 mA
Continuous output current, IO (VO > 0 V or VO < VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±50 mA
Continuous current through VCC or GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±200 mA
Package thermal impedance, θJA (see Note 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67°C/W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –65°C to 150°C
† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. The input and output voltage ratings may be exceeded if the input and output current ratings are observed.
2. The package thermal impedance is calculated in accordance with JESD 51-7.
recommended operating conditions (see Note 3)
TA = 25°C
–40°C to
85°C
UNIT
MIN
MAX
MIN
MAX
MIN
MAX
4.5
5.5
4.5
5.5
4.5
5.5
VCC
VIH
Supply voltage
VIL
VI
Low-level input voltage
Input voltage
0
VO
IOH
Output voltage
0
High-level output current
–24
IOL
∆t/∆v
Low-level output current
Input transition rise or fall rate
High-level input voltage
–55°C to
125°C
2
2
0.8
2
V
0.8
V
VCC
VCC
V
–24
–24
mA
24
24
24
mA
10
10
10
ns/V
VCC
VCC
0.8
V
0
0
VCC
VCC
0
0
V
NOTE 3: All unused inputs of the device must be held at VCC or GND to ensure proper device operation. Refer to the TI application report,
Implications of Slow or Floating CMOS Inputs, literature number SCBA004.
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3
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
electrical characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
VOH
VOL
VI = VIH or VIL
VI = VIH or VIL
II
ICC
VI = VCC or GND
VI = VCC or GND,
DICC‡
VI = VCC – 2.1 V
–55°C to
125°C
TA = 25°C
VCC
MAX
MIN
–40°C to
85°C
MAX
MIN
UNIT
MAX
IOH = –50 µA
IOH = –24 mA
4.5 V
4.4
4.5 V
3.94
IOH = –50 mA†
IOH = –75 mA†
5.5 V
IOL = 50 µA
IOL = 24 mA
IOL = 50 mA†
4.5 V
0.1
0.1
0.1
4.5 V
0.36
0.5
0.44
IOL = 75 mA†
5.5 V
IO = 0
4.4
4.4
3.7
3.8
V
3.85
5.5 V
3.85
5.5 V
1.65
V
1.65
5.5 V
±0.1
±1
±1
µA
5.5 V
8
160
80
µA
2.4
3
2.8
mA
4.5 V to
5.5 V
Ci
10
10
10
pF
† Test one output at a time, not exceeding 1-second duration. Measurement is made by forcing indicated current and measuring voltage to minimize
power dissipation. Test verifies a minimum 50-Ω transmission-line drive capability at 85°C and 75-Ω transmission-line drive capability at 125°C.
‡ Additional quiescent supply current per input pin, TTL inputs high, 1 unit load
ACT INPUT LOAD TABLE
INPUT
UNIT LOAD
A, B, or C
0.83
G2A or G2B
1
G1
0.42
Unit Load is ∆ICC limit specified in
electrical characteristics table
(e.g., 2.4 mA at 25°C).
switching characteristics over recommended operating free-air temperature range,
VCC = 5 V ± 0.5 V, CL = 50 pF (unless otherwise noted) (see Figure 1)
FROM
(INPUT)
TO
(OUTPUT)
tPLH
tPHL
A B
A,
B, C
Any Y
tPLH
tPHL
G1
Any Y
tPLH
tPHL
G2A G2B
G2A,
Any Y
PARAMETER
–55°C to
125°C
–40°C to
85°C
MIN
MAX
MIN
MAX
3.9
15.6
4
14.2
3.9
15.6
4
14.2
3.4
13.6
3.5
12.4
3.4
13.6
3.5
12.4
3.6
14.2
3.7
12.9
3.6
14.2
3.7
12.9
UNIT
ns
ns
ns
operating characteristics, VCC = 5 V, TA = 25°C
PARAMETER
Cpd
4
Power dissipation capacitance
POST OFFICE BOX 655303
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TYP
UNIT
110
pF
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
PARAMETER MEASUREMENT INFORMATION
S1
R1 = 500 Ω
From Output
Under Test
2 × VCC
Open
GND
CL = 50 pF
(see Note A)
R2 = 500 Ω
TEST
S1
tPLH/tPHL
tPLZ/tPZL
tPHZ/tPZH
Open
2 × VCC
GND
tw
3V
1.5 V
Input
LOAD CIRCUIT
1.5 V
0V
VOLTAGE WAVEFORMS
PULSE DURATION
CLR
Input
3V
Reference
Input
3V
1.5 V
1.5 V
0V
0V
trec
Data
Input
3V
1.5 V
CLK
th
tsu
1.5 V
10%
90%
90%
tr
0V
VOLTAGE WAVEFORMS
RECOVERY TIME
3V
1.5 V
10% 0 V
tf
VOLTAGE WAVEFORMS
SETUP AND HOLD AND INPUT RISE AND FALL TIMES
3V
Input
1.5 V
1.5 V
0V
tPLH
In-Phase
Output
50%
10%
90%
90%
tr
90%
1.5 V
1.5 V
0V
tPHL
tPHL
Out-of-Phase
Output
3V
Output
Control
VOH
50% VCC
10%
VOL
tf
tPLH
50% VCC
10%
tf
50%
10%
90%
VOH
VOL
tr
VOLTAGE WAVEFORMS
PROPAGATION DELAY AND OUTPUT TRANSITION TIMES
Output
Waveform 1
S1 at 2 × VCC
(see Note B)
tPLZ
tPZL
20% VCC
tPHZ
tPZH
Output
Waveform 2
S1 at GND
(see Note B)
≈VCC
20% VCC
VOL
80% VCC
VOH
80% VCC
≈0 V
VOLTAGE WAVEFORMS
OUTPUT ENABLE AND DISABLE TIMES
NOTES: A. CL includes probe and test-fixture capacitance.
B. Waveform 1 is for an output with internal conditions such that the output is low except when disabled by the output control.
Waveform 2 is for an output with internal conditions such that the output is high except when disabled by the output control.
C. All input pulses are supplied by generators having the following characteristics: PRR ≤ 1 MHz, ZO = 50 Ω, tr = 3 ns, tf = 3 ns.
Phase relationships between waveforms are arbitrary.
D. For clock inputs, fmax is measured with the input duty cycle at 50%.
E. The outputs are measured one at a time with one input transition per measurement.
F. tPLH and tPHL are the same as tpd.
G. tPZL and tPZH are the same as ten.
H. tPLZ and tPHZ are the same as tdis.
I. All parameters and waveforms are not applicable to all devices.
Figure 1. Load Circuit and Voltage Waveforms
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• DALLAS, TEXAS 75265
5
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
APPLICATION INFORMATION
CD74ACT238
BIN/OCT
1
2
3
VCC
0
1
1
2
2
4
6
3
&
4
4
EN
5
5
6
7
15
14
13
12
11
10
9
7
0
1
2
3
4
5
6
7
CD74ACT238
BIN/OCT
1
A0
2
A1
3
A2
1
2
2
4
6
A3
0
1
3
&
4
4
A4
EN
5
5
6
7
15
14
13
12
11
10
9
7
8
9
10
11
12
13
14
15
CD74ACT238
BIN/OCT
1
2
3
6
0
1
1
2
2
4
3
&
4
4
5
EN
5
6
7
Figure 2. 24-Bit Decoding Scheme
6
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• DALLAS, TEXAS 75265
15
14
13
12
11
10
9
7
16
17
18
19
20
21
22
23
CD74ACT238
3-LINE TO 8-LINE DECODER/DEMULTIPLEXER
SCHS330 –FEBRUARY 2003
APPLICATION INFORMATION
CD74ACT238
BIN/OCT
1
A0
2
A1
3
A2
1
1
2
2
4
6
VCC
0
3
&
4
4
A3
EN
5
A4
5
6
7
15
14
13
12
11
10
9
7
0
1
2
3
4
5
6
7
CD74ACT238
BIN/OCT
1
2
3
0
1
1
2
2
4
6
3
&
4
4
EN
5
5
6
7
15
14
13
12
11
10
9
7
8
9
10
11
12
13
14
15
CD74ACT238
BIN/OCT
1
2
3
0
1
1
2
2
4
6
3
&
4
4
EN
5
5
6
7
15
14
13
12
11
10
9
7
16
17
18
19
20
21
22
23
CD74ACT238
BIN/OCT
1
2
3
6
0
1
1
2
2
4
3
&
4
4
5
EN
5
6
7
15
14
13
12
11
10
9
7
24
25
26
27
28
29
30
31
Figure 3. 32-Bit Decoding Scheme
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7
PACKAGE OPTION ADDENDUM
www.ti.com
12-Jan-2006
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
CD74ACT238E
ACTIVE
PDIP
N
16
25
Pb-Free
(RoHS)
CU NIPDAU
N / A for Pkg Type
CD74ACT238EE4
ACTIVE
PDIP
N
16
25
Pb-Free
(RoHS)
CU NIPDAU
N / A for Pkg Type
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
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