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 74HC244D and 74HC238D are not functionally interchangeable despite sharing the same 74HC logic family and SOIC-16 package. The 74HC244D is an octal non-inverting buffer/line driver with 3-state outputs, while the 74HC238D is a 3-to-8 line decoder/demultiplexer with active-high outputs. Their internal logic functions, pin assignments, and signal flow are fundamentally different, so substituting one for the other in an existing design is not feasible without redesigning the surrounding circuitry.
Different logic function
Different output type
Different pin assignment
Different channel count
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC244D | 74HC238D | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state outputs | 3-to-8 line decoder/demultiplexer | The core function differs fundamentally; one buffers signals while the other decodes addresses, so they are not functionally interchangeable. |
| Number of Outputs | 8 | 8 | Both provide eight outputs, but the output activation logic differs (buffered data vs. one-of-eight decoded selection). |
| Output Type | 3-state | Active-low (non-3-state) | 3-state outputs allow bus sharing, while the decoder's standard outputs cannot be tri-stated, affecting bus interfacing. |
| Control Inputs | Two active-low output enable pins (1OE, 2OE) | Three enable inputs (two active-low, one active-high) | Different enable schemes change how the device is gated and cascaded in a system. |
| Input Configuration | 8 data inputs | 3 address inputs | The number and role of inputs determine the device's application; buffering uses parallel data, decoding uses binary address lines. |
| Supply Voltage Range | 2.0 V to 6.0 V | 2.0 V to 6.0 V | Both operate over the standard HC-family supply range, so power compatibility is identical. |
| Logic Family | 74HC (high-speed CMOS) | 74HC (high-speed CMOS) | Same logic family ensures comparable input thresholds, noise margins, and drive characteristics. |
| Package | SO14 (D suffix) | SO16 (D suffix) | Different pin counts and footprints prevent direct drop-in replacement on the same PCB pad layout. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature ratings mean both suit the same industrial and automotive environments. |
| Propagation Delay (typical at 5 V) | ~11 ns | ~14 ns | Timing differences affect signal integrity and maximum operating frequency in synchronous designs. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC238D | 74HC244D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Type | Decoder/Demultiplexer | - |
| Circuit | 1 x 3:8 | - |
| Independent Circuits | 1 | - |
| Current - Output High Low | 5.2mA, 5.2mA | 7.8mA, 7.8mA |
| Voltage Supply Source | Single Supply | - |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 85°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | - | Buffer, Non-Inverting |
| Number of Elements | - | 2 |
| Number of Bits per Element | - | 4 |
| Output Type | - | 3-State |