Part A
74HC245D
東芝セミコンダクター・アンド・ストレージ
- Lifecycle
- Active
- Stock
- 4218 個数
- Package
- SOIC-14
- Series
- ロジック - バッファ、ドライバ、レシーバ、トランシーバ
Replacement verdict
Not a drop-in replacement
The 74HC245D and 74HC251D-Q100J are functionally unrelated devices: the former is an octal bidirectional bus transceiver with 3-state outputs, while the latter is a single 8-channel multiplexer with 3-state complementary outputs. They differ in logic function, channel configuration, output behavior, and package/pinout, so neither can directly substitute for the other in an existing design without significant circuit redesign.
Different logic function
Different channel configuration
Different output type
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 | 74HC245D | 74HC251D-Q100J | Why it matters |
|---|---|---|---|
| Function | Octal bus transceiver with 3-state outputs | 8-input multiplexer with 3-state outputs | These devices perform fundamentally different logic functions, so they are not functionally interchangeable in a circuit. |
| Logic Type | Bidirectional transceiver | Multiplexer | The logic type determines the signal routing behavior and cannot be substituted without redesigning the surrounding circuit. |
| Number of Channels | 8 | 1 (8:1 multiplexer) | Channel count affects how many signals can be handled simultaneously and the required board layout. |
| Direction Control | Direction pin (DIR) selects A-to-B or B-to-A | Not applicable; select inputs choose one of eight inputs | Direction control is essential for bus transceiver operation but has no equivalent in a multiplexer. |
| Output Type | 3-state | 3-state | Both offer 3-state outputs, but the control logic and data path differ significantly. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Compatible supply voltage ranges allow both to operate in similar logic-level systems. |
| Package | SOIC-20 | SOIC-16 | Different package sizes and pin counts prevent direct drop-in replacement on the same PCB footprint. |
| Pin Count | 20 | 16 | Pin count mismatch means the devices cannot share the same socket or land pattern. |
| Qualification | Standard commercial | AEC-Q100 qualified | AEC-Q100 qualification indicates the multiplexer is suitable for automotive applications, while the transceiver is not. |
| Propagation Delay | Typically 8 ns at 5 V | Typically 11 ns at 5 V | Different propagation delays affect timing margins in high-speed digital designs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC245D | 74HC251D-Q100J |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HC | Automotive, AEC-Q100, 74HC |
| Part Status | Active | Active |
| Type | - | Multiplexer |
| Circuit | - | 1 x 8:1 |
| Independent Circuits | - | 1 |
| Current - Output High Low | 7.8mA, 7.8mA | 5.2mA, 5.2mA |
| Voltage Supply Source | - | Single Supply |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | Transceiver, Non-Inverting | - |
| Number of Elements | 1 | - |
| Number of Bits per Element | 8 | - |
| Output Type | 3-State | - |
Frequently asked questions
What are the primary functions of the 74HC245D and 74HC251D-Q100J?
The 74HC245D is an octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74HC251D-Q100J is an 8-input multiplexer with 3-state outputs, used to select one of eight data inputs based on a 3-bit binary address.
Are the 74HC245D and 74HC251D-Q100J pin-compatible?
No. The 74HC245D is typically supplied in a 20-pin SOIC package, while the 74HC251D-Q100J is supplied in a 16-pin SOIC package. They have different pin counts and pin functions, so they are not pin-compatible.
Can the 74HC245D and 74HC251D-Q100J operate at the same supply voltage range?
Yes. Both devices are members of the 74HC logic family and typically operate over a supply voltage range of 2.0 V to 6.0 V, with nominal 5 V operation. However, always verify the specific datasheet for the exact part number and manufacturer.
What is the difference in logic function between the 74HC245D and 74HC251D-Q100J?
The 74HC245D provides bidirectional data transfer between two buses with direction and output-enable control. The 74HC251D-Q100J selects one of eight input signals and routes it to a single output, with an output-enable control. They serve different roles: bus interfacing versus data selection.
Does the 74HC251D-Q100J have automotive qualification?
Yes. The suffix "-Q100" indicates that the 74HC251D-Q100J is qualified to the AEC-Q100 standard for automotive applications. The 74HC245D, as a standard logic part, does not carry this automotive qualification unless explicitly stated by the manufacturer.
Can the 74HC245D be used as a direct replacement for the 74HC251D-Q100J?
No. The two devices have different logic functions, pin counts, and package sizes. The 74HC245D cannot perform multiplexing, and the 74HC251D-Q100J cannot perform bidirectional bus transceiving. They are not interchangeable.
What are the typical output drive capabilities of these devices?
Both devices typically provide standard CMOS output drive, often specified as ±4 mA or ±6 mA at 5 V, depending on the manufacturer and test conditions. For exact drive strength, consult the respective manufacturer datasheet.
Are both devices available in SOIC packages?
Yes. The 74HC245D is commonly available in a 20-pin SOIC package, and the 74HC251D-Q100J is commonly available in a 16-pin SOIC package. Package designations may vary slightly by manufacturer.