Part A
74HC244D
東芝セミコンダクター・アンド・ストレージ
- Lifecycle
- Active
- Stock
- 7745 個数
- Package
- SOIC-20
- 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 74HC244D and 74HC251D-Q100J serve fundamentally different logic functions—one is an octal non-inverting buffer with 3-state outputs, while the other is an 8-input multiplexer with 3-state outputs—so they are not functionally interchangeable despite sharing the 74HC logic family and SOIC-16 footprint. The 74HC251D-Q100J is also an automotive-qualified device, adding further differentiation. Designers must not treat these as substitutes.
Different logic function
Different input configuration
Different output behavior
Different qualification grade
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 | 74HC244D | 74HC251D-Q100J | Why it matters |
|---|---|---|---|
| Logic Function | Octal buffer/line driver with 3-state outputs | 8-input multiplexer with 3-state outputs | The core logic function differs, so these parts are not functionally interchangeable in a circuit. |
| Number of Channels | 8 buffers | 1 multiplexer (8:1) | Channel count and signal routing capability determine how many signals can be handled. |
| Control Inputs | Two output enable pins (1OE, 2OE) | Three select inputs (S0, S1, S2) and one output enable | Different control schemes affect how the device is driven and integrated into a design. |
| Output Type | 3-state non-inverting | 3-state non-inverting (multiplexed) | Both have 3-state outputs, but the multiplexer selects one of eight inputs rather than buffering eight independent lines. |
| Package | SOIC-20 (D suffix) | SOIC-16 (D suffix) | Different pin counts and package sizes affect PCB layout and footprint compatibility. |
| Pin Count | 20 pins | 16 pins | Pin count mismatch prevents direct drop-in replacement on the same footprint. |
| 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 voltage compatibility is equivalent. |
| Qualification | Standard commercial/industrial | AEC-Q100 automotive qualified | The Q100J variant is automotive-grade, which affects reliability requirements and target applications. |
| Propagation Delay (typical) | ~13 ns at 4.5 V | ~14 ns at 4.5 V | Timing differences can matter in high-speed or timing-critical designs. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C (automotive grade) | Both cover the industrial range, but the Q100J part is additionally qualified for automotive use. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC244D | 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 ~ 85°C (TA) | -40°C ~ 125°C |
| 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 | - |
Frequently asked questions
What are the primary functional differences between the 74HC244D and the 74HC251D-Q100J?
The 74HC244D is an octal non-inverting buffer/line driver with 3-state outputs, featuring eight independent channels controlled by two active-low output enable pins. The 74HC251D-Q100J is an 8-input multiplexer with 3-state outputs, which selects one of eight data inputs based on a 3-bit binary address and routes it to a single output. They serve fundamentally different logic functions: buffering versus data selection/multiplexing.
Are the 74HC244D and 74HC251D-Q100J pin-compatible?
No. The 74HC244D is typically housed in a 20-pin package (SO20) with a specific pinout for eight buffers and two enable pins. The 74HC251D-Q100J is typically housed in a 16-pin package (SO16) with a different pinout for eight inputs, three address selects, one enable, and one output. They are not pin-to-pin compatible and cannot be interchanged without PCB redesign.
What are the key electrical specifications of the 74HC244D?
The 74HC244D operates over a supply voltage range of 2.0 V to 6.0 V, with typical propagation delay of 11 ns at 4.5 V and 25°C. It provides ±6 mA output drive at 4.5 V and features 3-state outputs with high-impedance state when disabled. It is specified for operation from -40°C to +125°C.
What are the key electrical specifications of the 74HC251D-Q100J?
The 74HC251D-Q100J operates over a supply voltage range of 2.0 V to 6.0 V, with typical propagation delay of 14 ns at 4.5 V and 25°C. It provides ±5.2 mA output drive at 4.5 V and features 3-state outputs. The -Q100J suffix indicates AEC-Q100 qualification for automotive applications, with an operating temperature range of -40°C to +125°C.
Can the 74HC244D be used as a drop-in replacement for the 74HC251D-Q100J in an existing design?
No. The two devices have different logic functions, pin counts, and pinouts. The 74HC244D cannot perform multiplexing, and the 74HC251D-Q100J cannot perform octal buffering. A direct substitution is not possible without changing the circuit design and PCB layout.
What is the significance of the -Q100J suffix on the 74HC251D-Q100J?
The -Q100J suffix indicates that the device is qualified to AEC-Q100, the automotive electronics council standard for stress test qualification of integrated circuits. This makes the 74HC251D-Q100J suitable for automotive applications requiring higher reliability and temperature robustness compared to standard commercial-grade parts.
What are the typical applications for each device?
The 74HC244D is typically used for bus driving, memory address driving, and signal buffering in digital systems. The 74HC251D-Q100J is typically used for data selection, multiplexing multiple signal sources onto a single line, and function generation in automotive and industrial control systems.
Do both devices feature 3-state outputs?
Yes. Both the 74HC244D and the 74HC251D-Q100J feature 3-state outputs, allowing their outputs to be placed in a high-impedance state for bus sharing and multiplexed connections. However, the control logic for enabling/disabling the outputs differs between the two devices.