Part A
74HC238D
東芝セミコンダクター・アンド・ストレージ
- Lifecycle
- Active
- Stock
- 5394 個数
- Package
- SOIC-16
- Series
- ロジック - 信号スイッチ、マルチプレクサ、デコーダ
Replacement verdict
Not a drop-in replacement
The 74HC238D and 74HC251D-Q100J are functionally dissimilar logic ICs: one is a 3-to-8 decoder/demultiplexer and the other is an 8-input multiplexer with 3-state outputs. They differ in logic function, output type, channel configuration, and package/pinout, so neither can directly substitute for the other in an existing design without circuit redesign.
Different logic function
Different output type
Different channel configuration
Different package and pinout
Parts at a glance
Part B
74HC251D-Q100J
ネクスペリアUSA株式会社
- Lifecycle
- Active
- Stock
- 6040 個数
- Package
- SOIC-16
- Series
- ロジック - 信号スイッチ、マルチプレクサ、デコーダ
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC238D | 74HC251D-Q100J | Why it matters |
|---|---|---|---|
| Function | 3-to-8 Line Decoder / Demultiplexer | 8-Input Multiplexer with 3-State Outputs | These devices perform fundamentally different logic functions, so they are not functionally substitutable in a circuit. |
| Logic Type | Decoder/Demultiplexer | Multiplexer | The logic type determines the input-to-output mapping and the role the IC plays in a design. |
| Number of Outputs | 8 | 1 | Output count affects how many downstream loads or signal paths the device can drive. |
| Number of Inputs | 3 (address) plus enable inputs | 8 data plus select inputs | Input count and type determine the selection/addressing scheme and overall interface complexity. |
| Output Type | Active-low outputs | 3-state | Output type affects bus sharing, drive capability, and whether outputs can be tied together. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both support the standard HC family supply range, allowing use in similar logic-level systems. |
| Package | SOIC-16 | SOIC-16 | Matching package and pin count can simplify PCB layout, though pin functions still differ. |
| Qualification | Standard commercial grade | AEC-Q100 automotive qualified | Automotive qualification indicates enhanced reliability and testing for harsh environments. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Similar temperature ratings mean both can operate in comparable industrial temperature environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC238D | 74HC251D-Q100J |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HC | Automotive, AEC-Q100, 74HC |
| Part Status | Active | Active |
| Type | Decoder/Demultiplexer | Multiplexer |
| Circuit | 1 x 3:8 | 1 x 8:1 |
| Independent Circuits | 1 | 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 ~ 125°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary functions of the 74HC238D and 74HC251D-Q100J?
The 74HC238D is a 3-to-8 line decoder/demultiplexer that accepts a 3-bit binary address and activates one of eight mutually exclusive outputs. The 74HC251D-Q100J is an 8-input multiplexer with 3-state outputs that selects one of eight data inputs based on a 3-bit select code and routes it to a single output.
Are the 74HC238D and 74HC251D-Q100J pin-compatible or functionally interchangeable?
No. The 74HC238D is a decoder/demultiplexer with eight outputs and three address inputs, while the 74HC251D-Q100J is a multiplexer with eight data inputs, three select inputs, one data output, and an output enable. Their pin functions and logic operations differ, so they are not direct substitutes.
What are the key differences in output configuration between these two devices?
The 74HC238D provides eight active-high outputs (with three enable inputs) that are mutually exclusive based on the address. The 74HC251D-Q100J provides a single 3-state output that can be high, low, or high-impedance, depending on the output enable and selected data input.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HC238D and 74HC251D-Q100J are HC-family CMOS devices typically specified for a supply voltage range of 2.0 V to 6.0 V, with 5 V being the nominal operating voltage for many designs.
What is the significance of the Q100 suffix on the 74HC251D-Q100J?
The Q100 suffix indicates that the device is qualified to the AEC-Q100 standard for automotive-grade integrated circuits. This means it meets stricter reliability and temperature requirements compared to standard commercial or industrial grade versions.
Can the 74HC238D be used to drive the 74HC251D-Q100J in a multiplexed system?
Yes, they can be used together. The 74HC238D can decode a 3-bit address to generate enable signals for multiple 74HC251D-Q100J multiplexers, allowing expansion of the number of data channels in a system. However, timing and logic level compatibility must be verified in the specific design.
What are the typical propagation delay and drive current specifications for these devices?
Both devices are standard HC-family logic. Typical propagation delay at 5 V is in the range of 10–20 ns, and output drive current is typically ±4 mA at 5 V. For exact limits, refer to the manufacturer datasheet for each specific part number.
Are both devices available in the same package type?
The 74HC238D is commonly offered in a SO16 (small outline) package. The 74HC251D-Q100J is also typically offered in a SO16 package. However, package variants can differ by manufacturer and ordering code, so the exact package drawing should be confirmed from the datasheet.