Part A
74HC139D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 4290 Stückzahl
- Package
- SOIC-16
- Series
- Logic.Signal Schalter, Multiplexer, Decoder
Replacement verdict
Not a drop-in replacement
The 74HC151D and 74HC139D are functionally dissimilar logic ICs and cannot serve as substitutes for one another. The 74HC151D is an 8-to-1 multiplexer with a single data output, while the 74HC139D is a dual 2-to-4 decoder/demultiplexer with four active-low outputs per section. Their logic functions, input/output configurations, and pin assignments differ fundamentally, making direct replacement impossible without circuit redesign.
Different logic function
Different output type
Different channel count
Different pinout
Parts at a glance
Part B
74HC151D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 3388 Stückzahl
- Package
- SOIC-16
- Series
- Logic.Signal Schalter, Multiplexer, Decoder
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC151D | 74HC139D | Why it matters |
|---|---|---|---|
| Logic Function | 8-to-1 multiplexer with complementary outputs | Dual 2-to-4 line decoder/demultiplexer | The core function determines whether the device can select one of many inputs (mux) or activate one of several outputs from an address (decoder), so they are not functionally interchangeable. |
| Number of Channels | 1 multiplexer | 2 decoders/demultiplexers | Channel count affects how many independent signal paths can be handled in a design. |
| Inputs per Channel | 8 data inputs plus 3 select inputs | 2 address inputs per decoder | The number of selectable inputs or address lines defines the selection range and routing capability. |
| Outputs per Channel | 2 complementary outputs (Y and Ybar) | 4 active-low outputs per decoder | Output count and polarity determine how many loads can be driven and whether external inversion is needed. |
| Output Type | Push-pull complementary | Active-low push-pull | Output polarity and drive style affect compatibility with downstream logic and whether pull-up resistors are required. |
| Enable/Strobe Input | Active-low enable (Ebar) | Two active-low enable inputs (one per decoder) | Enable inputs allow cascading and power-saving control; their number and polarity affect system-level design. |
| Propagation Delay (typical at 5 V) | Approximately 14 ns | Approximately 11 ns | Propagation delay influences maximum operating frequency and timing margins in synchronous systems. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | The supply range determines compatibility with 3.3 V and 5 V logic families and battery-powered designs. |
| Package | SO16 (SOIC-16) | SO16 (SOIC-16) | Package and pin count affect PCB footprint, assembly, and thermal characteristics. |
| Pin Count | 16 | 16 | Pin count must match the PCB footprint and available board space. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC139D | 74HC151D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Obsolete | Active |
| Type | Decoder/Demultiplexer | Multiplexer |
| Circuit | 1 x 2:4 | 1 x 8:1 |
| Independent Circuits | 2 | 1 |
| Current - Output High Low | 5.2mA, 5.2mA | 5.2mA, 5.2mA |
| Voltage Supply Source | Single Supply | Single Supply |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary functions of the 74HC151D and 74HC139D?
The 74HC151D is an 8-input multiplexer that selects one of eight data inputs based on a 3-bit select code and provides the selected data at a single output. The 74HC139D is a dual 2-to-4 line decoder/demultiplexer that decodes two independent 2-bit addresses into four mutually exclusive active-LOW outputs per section.
Can the 74HC151D and 74HC139D be used interchangeably in a design?
No. They perform different logic functions: the 74HC151D is a multiplexer, while the 74HC139D is a decoder/demultiplexer. They are not pin-compatible or functionally equivalent, so direct substitution is not possible without redesigning the surrounding circuitry.
What are the key differences in input and output configurations between the two devices?
The 74HC151D has eight data inputs (D0–D7), three select inputs (A, B, C), an active-LOW enable input, and complementary outputs (Y and Y-bar). The 74HC139D has two independent sections, each with two address inputs (A0, A1), one active-LOW enable input, and four active-LOW outputs (Y0–Y3).
Do the 74HC151D and 74HC139D operate at the same supply voltage and logic levels?
Yes. Both are 74HC-series CMOS devices typically specified for a supply voltage range of 2.0 V to 6.0 V, with standard CMOS input thresholds and rail-to-rail output swing compatible with 5 V and 3.3 V logic systems.
What are the typical propagation delays and drive capabilities of these devices?
Both devices are specified with typical propagation delays in the low nanosecond range at 5 V supply, and both provide standard CMOS output drive suitable for driving other CMOS inputs. Exact delay and drive values depend on supply voltage, load capacitance, and temperature, and should be taken from the manufacturer datasheet.
Are the 74HC151D and 74HC139D available in the same package type?
Both are commonly offered in SO16 (D) surface-mount packages, which have the same 16-pin count and footprint. However, pin assignments differ between the two functions, so board layout and signal routing must be designed accordingly.
Which device is better for expanding input selection versus address decoding?
The 74HC151D is intended for data selection and multiplexing, making it suitable for expanding input selection. The 74HC139D is intended for address decoding and demultiplexing, making it suitable for generating chip-select or enable signals from a binary address.
Can the 74HC139D be used to drive the select inputs of a 74HC151D?
Yes, in principle the active-LOW outputs of the 74HC139D can be used as logic signals, but the 74HC151D select inputs are not active-LOW enable inputs. Any interfacing must respect the required logic polarity and voltage levels, and the system timing must be validated against both datasheets.