Fairchild 74VHC138 service manual
74VHC138
3-to-8 Decoder/Demultiplexer
74VHC138 3-to-8 Decoder/Demultiplexer
November 1992
Revised April 1999
General Description
The VHC138 is an advanced high speed CMOS 3-to-8
decoder/demultiplexer fabricated with silicon gate CMOS
technology. It achieves the high speed op eration simil ar to
equivalent Bipolar Schottky TTL while maintaining the
CMOS low power dissipation.
When the device is enabled, 3 bina ry select inpu ts (A
and A2) determine which one of the outputs (O0–O7) will go
LOW. When enable input E
is held HIGH, decoding function is inhibited and all outputs
go HIGH. E
cade connection and for use as an address decode r for
memory systems. An input protection cir cuit ensures that
, E1 and E2 inputs are provided to ease cas-
3
is held LOW or either E1 or E
3
0V to 7V can be applied to the inpu t pins withou t regard to
the supply voltage. This device can be used to interface 5V
to 3V systems and two supply systems such as battery
back up. This circuit prevents device destruction due to
mismatched supply and input voltages.
Features
, A
0
1
■ High Speed: tPD = 5.7ns (typ) at TA = 25°C
■ Low power dissipation: I
2
■ High noise immunity: V
■ Power down protection provided on all inputs
■ Pin and function compatible with 74HC138
= 4 µA (max.) at TA = 25°C
CC
= V
NIH
= 28% VCC (min.)
NIL
Ordering Code:
Order Number Package Number Package Description
74VHC138M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150” Narrow
74VHC138SJ M16D 16-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm Wide
74VHC138MTC MTC16 16-Lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153, 4.4mm Wide
74VHC138N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300” Wide
Surface mount pack ages are also available on Tape and Reel. Specify by appending the suffix letter “X” to the or dering code.
Logic Symbols
Connection Diagram
IEEE/IEC
Pin Descriptions
Pin Names Description
A
0–A2
E
1–E2
E
3
O
0–O7
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Address Inputs
Enable Inputs
Enable Input
Outputs
Truth Table
74VHC138
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Inputs Outputs
E
1E2E3A0A1A2O0O1O2O3O4O5O6O7
HXXXXXHHHHHHHH
XHXXXXHHHHHHHH
XXLXXXHHHHHHHH
LLHLLLLHHHHHHH
LLHHL LHLHHHHHH
LLHLHLHHLHHHHH
LLHHHLHHHLHHHH
LLHL LHHHHHLHHH
LLHHLHHHHHHLHH
LLHLHHHHHHHHLH
LLHHHHHHHHHHHL
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Absolute Maximum Ratings(Note 1) Recommended Operating
Supply Voltage (VCC) −0.5V to +7.0V
DC Input Voltage (V
DC Output Voltage (V
Input Diode Current (I
Output Diode Current (I
DC Output Current (I
/GND Current (ICC) ±75 mA
DC V
CC
Storage Temperature (T
Lead Temperature (T
) −0.5V to +7.0V
IN
) −0.5V to VCC + 0.5V
OUT
) −20 mA
IK
) ±20 mA
OK
) ±25 mA
OUT
) −65°C to +150°C
STG
)
L
(Soldering, 10 seconds) 260°C
Conditions
Supply Voltage (V
Input Voltage (V
Output Voltage (V
Operating Temperature (T
Input Rise and Fall Time (t
= 3.3V ± 0.3V 0 ∼ 100 ns/V
V
CC
= 5.0V ± 0.5V 0 ∼ 20 ns/V
V
CC
Note 1: Absolute Maximum Ratings are valu es beyond whic h the device
may be damaged or ha ve its useful life impaire d. The datab ook specific ations should be met, without exception, to ensure that the system design is
reliable over its p ower supp ly, temperature, and o utput/input loading variables. Fairchild does not recommend operation outside databook specifications.
Note 2: Unused inputs must be held HIGH or LOW. They may not float.
(Note 2)
)2.0V to +5.5V
CC
)0V to +5.5V
IN
)0V to V
OUT
) −40°C to +85°C
OPR
, tf)
r
DC Electrical Characteristics
Symbol Parameter
V
IH
V
IL
V
OH
V
OL
I
IN
I
CC
HIGH Level Input Voltage 2.0 1.50 1.50
LOW Level Input Voltage 2.0 0.50 0.50
HIGH Level Output Voltage 2.0 1.9 2.0 1.9 VIN = VIHIOH = −50 µA
LOW Level Output Voltage 2.0 0.0 0.1 0.1 VIN = VIHIOL = 50 µA
Input Leakage Current 0 − 5.5 ±0.1 ±1.0 µAVIN = 5.5V or GND
Quiescent Supply Current 5.5 4.0 40.0 µAVIN = VCC or GND
V
CC
(V)
3.0 − 5.5 0.7 V
3.0 − 5.5 0.3 V
3.0 2.9 3.0 2.9 V or V
4.5 4.4 4.5 4.4
3.0 2.58 2.48
4.5 3.94 3.80 IOH = −8 mA
3.0 0.0 0.1 0.1 V or V
4.5 0.0 0.1 0.1
3.0 0.36 0.44
4.5 0.36 0.44 IOL = 8 mA
TA = 25°CT
Min Typ Max Min Max
CC
CC
= −40°C to +85°C
A
0.7 V
CC
0.3 V
Units Conditions
V
V
CC
V
V
74VHC138
CC
IL
IOH = −4 mA
IL
IOL = 4 mA
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