Part A
74HC139D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 4290 PCS
- Package
- SOIC-16
- Series
- Logic - Signal Switches, Multiplexers, Decoders
Replacement verdict
Not a drop-in replacement
The 74HC157D and 74HC139D are not functionally interchangeable despite sharing the same 74HC logic family and SOIC-16 package. The 74HC157D is a quad 2-to-1 non-inverting multiplexer with three-state outputs, while the 74HC139D is a dual 1-of-4 inverting decoder/demultiplexer. Their internal logic functions, pin assignments, and output configurations differ fundamentally, so direct substitution is not possible without circuit redesign.
Different logic function
Different output type
Different pin assignment
Different channel configuration
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC157D | 74HC139D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input multiplexer | Dual 2-to-4 line decoder/demultiplexer | The core function determines whether the device selects between data inputs or decodes a binary address, so they are not functionally interchangeable. |
| Number of Channels | 4 | 2 | Channel count affects how many independent signals can be processed simultaneously in a design. |
| Output Type | Non-inverting | Inverting | Output polarity must match the intended logic to avoid inverted or incorrect signal behavior. |
| Number of Outputs | 4 | 4 | Although both provide four outputs, the mapping from inputs to outputs differs due to the different logic functions. |
| Input Type | Data and select inputs | Address and enable inputs | The input semantics define how the device is controlled and whether it can be substituted in a given circuit. |
| Enable/Strobe Control | Active-low enable (G) | Two active-low enables (1G, 2G) | Enable control affects when outputs are active or forced to a defined state, impacting system timing and bus sharing. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Matching supply voltage ranges ensures both devices can operate in the same logic family and power environment. |
| Package | SO16 | SO16 | Identical package and pin count simplify PCB layout and may allow the same footprint, though pinout differences still prevent direct substitution. |
| Logic Family | HC | HC | Same logic family generally means compatible voltage levels, speed, and drive characteristics. |
| Pinout Compatibility | Multiplexer pinout | Decoder/demultiplexer pinout | Different internal functions result in different pin assignments, so they cannot be dropped into the same socket without redesign. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC139D | 74HC157D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Obsolete | Active |
| Type | Decoder/Demultiplexer | Multiplexer |
| Circuit | 1 x 2:4 | 4 x 2:1 |
| 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 ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary functions of the 74HC157D and 74HC139D?
The 74HC157D is a quad 2-input multiplexer that selects one of two 4-bit data sources based on a common select input. The 74HC139D is a dual 2-to-4 line decoder/demultiplexer that decodes two binary inputs into four mutually exclusive active-LOW outputs per section.
Can the 74HC157D and 74HC139D be used interchangeably in a design?
No. They perform different logic functions: the 74HC157D 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 supply voltage and logic family specifications for both devices?
Both are 74HC-series high-speed CMOS devices. They typically operate over a supply voltage range of 2.0 V to 6.0 V, with standard 74HC input and output characteristics. Verify exact limits and timing parameters in the respective manufacturer datasheets.
What package type do the 74HC157D and 74HC139D use?
Both the 74HC157D and 74HC139D are commonly offered in a 16-pin SOIC package, indicated by the "D" suffix in many manufacturer part numbering systems. Always confirm the package code and mechanical dimensions from the specific manufacturer datasheet.
How many outputs does each device provide?
The 74HC157D provides four multiplexed outputs, one for each 2-input multiplexer channel. The 74HC139D provides eight outputs total, consisting of two independent 2-to-4 decoders, each with four active-LOW outputs.
What are the key control inputs for the 74HC157D and 74HC139D?
The 74HC157D has a common select input and an active-LOW enable/strobe input that forces all outputs LOW when disabled. The 74HC139D has two independent address inputs per decoder and one active-LOW enable input per decoder; when enabled, one of four outputs is pulled LOW based on the address.
Are the 74HC157D and 74HC139D compatible with 74LS or 74HCT logic levels?
74HC devices are CMOS logic and their input thresholds are typically compatible with 74LS outputs under the same supply voltage, but they are not identical to 74HCT devices, which are specifically designed for TTL voltage compatibility. Verify logic level compatibility in the datasheet before mixing logic families.
What are typical applications for the 74HC157D versus the 74HC139D?
The 74HC157D is typically used for data selection, signal routing, and multiplexing multiple data sources onto a common bus. The 74HC139D is typically used for address decoding, memory or peripheral chip selection, and demultiplexing a single data line to one of several destinations.