Part A
74HC02D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 1347 Stückzahl
- Package
- SOIC-14
- Series
- Logic-Gates und Wechselrichter
Replacement verdict
Not a drop-in replacement
The 74HC03D and 74HC02D are not functionally interchangeable despite sharing the same 74HC CMOS logic family and SOIC-14 package. The 74HC03D provides open-drain outputs requiring external pull-up resistors, while the 74HC02D features standard push-pull outputs. This fundamental output architecture difference, combined with divergent logic functions and electrical characteristics, makes direct substitution inadvisable without circuit redesign.
Different output type
Different logic function
External pull-up may be required
Different drive characteristics
Parts at a glance
Part B
74HC03D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 3334 Stückzahl
- Package
- SOIC-14
- Series
- Logic-Gates und Wechselrichter
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HC03D | 74HC02D | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate with open-drain outputs | Quad 2-input NOR gate | The fundamental logic function differs, so these parts are not functionally interchangeable in a circuit. |
| Output Type | Open-drain | Push-pull (totem-pole) | Open-drain outputs require external pull-up resistors and allow wired-AND configurations, while push-pull outputs drive both high and low actively. |
| Supply Voltage Range | 2 V to 6 V | 2 V to 6 V | Both parts operate over the same supply range, allowing use in similar 2 V to 6 V logic systems. |
| Number of Gates | 4 | 4 | Both devices contain four independent gates, matching the logic density per package. |
| Number of Inputs per Gate | 2 | 2 | Both devices use 2-input gates, so the input count per gate is identical. |
| Package | SO14 (SOIC-14) | SO14 (SOIC-14) | Identical package and pin count simplify PCB footprint and assembly compatibility. |
| Pin Count | 14 | 14 | Same pin count supports similar board layout considerations. |
| Logic Family | 74HC | 74HC | Both belong to the HC CMOS family, sharing similar input thresholds and noise margins. |
| Output Drive Current | Sink current only (open-drain); no active high drive | Balanced sink and source current | The 74HC03D can only pull low and relies on a pull-up for high, while the 74HC02D actively drives both logic states. |
| Typical Propagation Delay | Approximately 9 ns at 4.5 V (open-drain, with pull-up) | Approximately 7 ns at 4.5 V | Timing differs due to output structure, which can affect speed-sensitive designs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HC02D | 74HC03D |
|---|---|---|
| Series | 74HC | 74HC |
| Part Status | Active | Active |
| Logic Type | NOR Gate | NAND Gate |
| Number of Circuits | 4 | 4 |
| Number of Inputs | 2 | 2 |
| Voltage - Supply | 2V ~ 6V | 2V ~ 6V |
| Current - Quiescent (Max) | 1 µA | 1 µA |
| Current - Output High Low | 5.2mA, 5.2mA | -, 5.2mA |
| Logic Level - Low | 0.5V ~ 1.8V | 0.5V ~ 1.8V |
| Logic Level - High | 1.5V ~ 4.2V | 1.5V ~ 4.2V |
| Max Propagation Delay @ V Max CL | 16ns @ 6V, 50pF | 13ns @ 6V, 50pF |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Features | - | Open Drain |
Frequently asked questions
What is the primary functional difference between the 74HC03D and the 74HC02D?
The 74HC03D contains four 2-input NAND gates with open-drain outputs, while the 74HC02D contains four 2-input NOR gates with standard push-pull (totem-pole) outputs. The logic function and output stage type are the key differentiators.
Can the 74HC03D and 74HC02D be used interchangeably in a design?
No. They implement different logic functions (NAND vs NOR) and have different output structures (open-drain vs push-pull). Direct substitution without redesigning the surrounding circuitry is not possible.
What are the output drive characteristics of the 74HC03D?
The 74HC03D features open-drain outputs, meaning it can sink current but cannot source current. It requires an external pull-up resistor to achieve a logic HIGH state. This allows wired-AND connections and level shifting when the pull-up voltage differs from VCC.
What are the output drive characteristics of the 74HC02D?
The 74HC02D has standard CMOS push-pull outputs, capable of both sourcing and sinking current. It does not require external pull-up resistors for normal logic operation and provides rail-to-rail output swing.
Do the 74HC03D and 74HC02D share the same pinout?
Yes. Both devices are offered in the SO14 package (the "D" suffix in 74HC03D and 74HC02D typically denotes SO14). They share the same 14-pin configuration with identical power supply and ground pins, and each contains four 2-input gates with the same input pin assignments. However, the output stage behavior differs as noted above.
What are the recommended operating conditions for the 74HC03D and 74HC02D?
Both devices are 74HC series CMOS logic ICs typically specified for a supply voltage range of 2.0 V to 6.0 V, with a nominal 5 V operation. They operate over the standard industrial temperature range of -40 °C to +125 °C, depending on the specific manufacturer's datasheet.
Which device is better for wired-AND or open-drain bus applications?
The 74HC03D is the appropriate choice for wired-AND or open-drain bus applications because its open-drain outputs can be tied together with a single pull-up resistor. The 74HC02D's push-pull outputs cannot be directly tied together without risking contention and excessive current.
Are the 74HC03D and 74HC02D available in the same package options?
Both are commonly available in SO14 (D suffix) and other standard packages such as DIP-14 and TSSOP-14, depending on the manufacturer. Package availability may vary by supplier, so the specific orderable part number should be verified against the manufacturer datasheet.