Part A
74HCT02D
東芝セミコンダクター・アンド・ストレージ
- Lifecycle
- Active
- Stock
- 5658 個数
- Package
- SOIC-16
- Series
- ロジック - ゲートおよびインバータ
Replacement verdict
Not a drop-in replacement
The 74HCT245D and 74HCT02D are not functionally interchangeable. The 74HCT245D is an octal bus transceiver with 3-state outputs and directional control, while the 74HCT02D is a quad 2-input NOR gate. Their logic functions, pin configurations, and I/O structures are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different channel count
Different pinout
Different output type
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT245D | 74HCT02D | Why it matters |
|---|---|---|---|
| Logic Function | Octal bus transceiver with 3-state outputs | Quad 2-input NOR gate | The core logic function determines whether the devices are functionally interchangeable; these are entirely different functions and cannot substitute for each other. |
| Number of Channels / Gates | 8 channels (bidirectional) | 4 gates (2-input NOR) | Channel/gate count affects how many signals can be processed, directly impacting circuit design and board layout. |
| Output Type | 3-state (tri-state) outputs | Push-pull (totem-pole) outputs | 3-state outputs allow bus sharing and high-impedance disconnection, while push-pull outputs cannot be tied together, affecting bus architectures. |
| Direction Control | Direction pin (DIR) and Output Enable (OE) | None (unidirectional logic gate) | Direction control enables bidirectional data flow, a feature absent in simple logic gates, affecting data bus interfacing. |
| Propagation Delay (tpd) | Typical 12 ns at 5 V | Typical 10 ns at 5 V | Propagation delay influences maximum operating speed and timing margins in synchronous systems. |
| Supply Voltage Range (VCC) | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both operate in the standard 5 V TTL-compatible range, so supply compatibility is not a differentiator here. |
| Output Drive Current (IOH/IOL) | ±6 mA (typical) | ±4 mA (typical) | Drive current determines the ability to drive loads such as LEDs or other logic inputs without buffering. |
| Package Type | SOIC-20 (D suffix) | SOIC-14 (D suffix) | Package footprint and pin count affect PCB layout and cannot be interchanged without redesign. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both meet industrial temperature requirements, so thermal compatibility is equivalent. |
| Input Compatibility | TTL-compatible inputs | TTL-compatible inputs | TTL compatibility ensures direct interfacing with 5 V TTL logic families without additional level shifting. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT02D | 74HCT245D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NOR Gate | Transceiver, Non-Inverting |
| Number of Circuits | 4 | - |
| Number of Inputs | 2 | - |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | 1 µA | - |
| Current - Output High Low | 4mA, 4mA | 6mA, 6mA |
| Logic Level - Low | 0.8V | - |
| Logic Level - High | 2V | - |
| Max Propagation Delay @ V Max CL | 16ns @ 5.5V, 50pF | - |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | - | 3-State |
Frequently asked questions
What are the primary functions of the 74HCT245D and 74HCT02D?
The 74HCT245D is an octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74HCT02D is a quad 2-input NOR gate, providing four independent logic gates for general-purpose logic inversion and combination.
Can the 74HCT245D and 74HCT02D be used interchangeably in a design?
No. They are functionally different devices. The 74HCT245D is a bus transceiver with direction control and 3-state outputs, while the 74HCT02D is a logic gate array. They cannot be substituted for one another without a complete redesign of the circuit function.
Do both devices operate on the same supply voltage range?
Yes. Both the 74HCT245D and 74HCT02D are HCT-family devices and operate with a nominal supply voltage of 5 V, typically within the recommended range of 4.5 V to 5.5 V as specified in their respective manufacturer datasheets.
Are the 74HCT245D and 74HCT02D compatible with TTL logic levels?
Yes. Both devices are members of the HCT logic family, which features TTL-compatible input thresholds when operated at 5 V, allowing direct interfacing with TTL outputs while maintaining CMOS output drive characteristics.
What are the package and pin count differences between the 74HCT245D and 74HCT02D?
The 74HCT245D is typically supplied in a 20-pin SOIC package (the "D" suffix indicates SOIC), while the 74HCT02D is typically supplied in a 14-pin SOIC package. The pin counts and pin functions differ due to their distinct internal architectures.
Which device is suitable for driving a shared data bus?
The 74HCT245D is suitable for shared data bus applications because it provides octal bidirectional transceiver functionality with 3-state outputs, allowing multiple devices to share a common bus. The 74HCT02D does not have 3-state outputs or bus-driving capability and is not intended for bus multiplexing.
Do both devices have the same output drive current capability?
No. The 74HCT245D is specified with output drive currents suitable for bus driving, typically ±6 mA at 5 V in standard HCT logic. The 74HCT02D has standard HCT gate output drive, typically ±4 mA at 5 V. Exact values should be verified from the specific manufacturer datasheet.
Are the 74HCT245D and 74HCT02D available in automotive-qualified versions?
Automotive qualification depends on the specific manufacturer and part number variant. Standard commercial 74HCT245D and 74HCT02D devices are not automatically automotive-qualified. Designers must verify AEC-Q100 qualification status from the manufacturer's datasheet or product page for the exact ordering code.