Part A
74HCT02D
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 5658 PCS
- Package
- SOIC-16
- Series
- Logique - portes et Onduleurs
Replacement verdict
Not a drop-in replacement
The 74HCT02D and 74HCT221D,118 are not functionally interchangeable despite sharing the 74HCT logic family and SO14 package. The 74HCT02D is a quad 2-input NOR gate, while the 74HCT221D,118 is a dual monostable multivibrator with Schmitt-trigger inputs. Their logic function, input/output behavior, and timing characteristics are fundamentally different, so the 74HCT221D,118 cannot directly replace the 74HCT02D in existing designs without significant circuit redesign.
Different logic function
Different output behavior
Different timing function
Different input type
Parts at a glance
Part B
74HCT221D,118
Nexperia USA Inc.
- Lifecycle
- Active
- Stock
- 9432 PCS
- Package
- SOIC-16
- Series
- Logique - multivibrateurs
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT02D | 74HCT221D,118 | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NOR gate | Dual non-retriggerable monostable multivibrator with reset | The logic function defines the fundamental behavior of the device; these parts perform completely different operations and are not functionally interchangeable. |
| Number of Circuits | 4 | 2 | The number of independent channels determines how many signals can be processed simultaneously in a design. |
| Number of Inputs per Circuit | 2 | 2 (trigger inputs A0, A1) plus reset | Input count per element affects the logic capability and the way the device interfaces with surrounding circuitry. |
| Output Type | Push-pull (standard CMOS totem-pole) | Push-pull (standard CMOS totem-pole) | Output type determines drive capability and whether external pull-up or pull-down resistors are required. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | The supply voltage range must match the system power rail for the device to operate reliably. |
| Propagation Delay (typical) | 9 ns at 5 V | 45 ns at 5 V (trigger to output) | Propagation delay affects timing margins and maximum operating frequency in synchronous designs. |
| Output Current (High/Low) | ±4 mA | ±4 mA | Output current capability determines how many loads or what type of loads the device can drive directly. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | The temperature range must cover the application environment to ensure reliable operation. |
| Package / Mounting Type | SO-14 (SOIC-14), surface mount | SO-16 (SOIC-16), surface mount | Package and pin count must match the PCB footprint; different packages are not drop-in compatible. |
| Pin Count | 14 | 16 | Pin count determines board layout compatibility and cannot be substituted without a redesign. |
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 | 74HCT02D | 74HCT221D,118 |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NOR Gate | Monostable |
| Independent Circuits | - | 2 |
| Schmitt Trigger Input | - | Yes |
| Propagation Delay | - | 31 ns |
| Current - Output High Low | 4mA, 4mA | 4mA, 4mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5 V ~ 5.5 V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Circuits | 4 | - |
| Number of Inputs | 2 | - |
| Current - Quiescent (Max) | 1 µA | - |
| Logic Level - Low | 0.8V | - |
| Logic Level - High | 2V | - |
| Max Propagation Delay @ V Max CL | 16ns @ 5.5V, 50pF | - |
Frequently asked questions
What are the primary functional differences between the 74HCT02D and the 74HCT221D,118?
The 74HCT02D is a quad 2-input NOR gate, while the 74HCT221D,118 is a dual monostable multivibrator. The 74HCT02D performs combinational logic, whereas the 74HCT221D,118 generates output pulses with a duration determined by external timing components.
Are the 74HCT02D and 74HCT221D,118 pin-compatible?
No. The 74HCT02D is typically supplied in a 14-pin SOIC package, and the 74HCT221D,118 is supplied in a 16-pin SOIC package. They have different pin counts and pin functions, so they are not pin-compatible.
Can the 74HCT02D be used as a direct substitute for the 74HCT221D,118 in a monostable circuit?
No. The 74HCT02D is a logic gate and does not contain the internal timing and pulse-generation circuitry of the 74HCT221D,118. A direct substitution would not provide the monostable function.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT02D and the 74HCT221D,118 are HCT-family devices and are specified for a nominal 5 V supply, with operation typically characterized over the 4.5 V to 5.5 V range.
Which device is suitable for debouncing a mechanical switch?
The 74HCT221D,118 is suitable for switch debouncing because its monostable output can generate a clean, fixed-width pulse from a noisy input. The 74HCT02D can be used in a latch or flip-flop configuration for debouncing, but it does not provide a single-component monostable solution.
Are both devices available in SOIC packages?
Yes. The 74HCT02D is commonly available in a 14-pin SOIC package, and the 74HCT221D,118 is commonly available in a 16-pin SOIC package. Package type alone does not make them interchangeable.
What timing components does the 74HCT221D,118 require that the 74HCT02D does not?
The 74HCT221D,118 requires external resistors and capacitors to set the output pulse width. The 74HCT02D does not require external timing components because it is a combinational logic gate.
Can both devices be used in the same 5 V HCT logic system?
Yes. Both are HCT-family devices and are intended for 5 V logic systems with TTL-compatible input thresholds. They can coexist in the same system when each is used according to its own function and pinout.