Part A
74HCT00D
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 1289 Stückzahl
- Package
- SOIC-20
- Series
- Logic-Gates und Wechselrichter
Replacement verdict
Not a drop-in replacement
The 74HCT00D and 74HCT221D,118 are not functionally interchangeable despite sharing the 74HCT logic family and SO14 package. The 74HCT00D is a quad 2-input NAND gate, while the 74HCT221D,118 is a dual monostable multivibrator with Schmitt-trigger inputs. Their internal logic functions, pin assignments, and application roles differ fundamentally, so substituting one for the other is not feasible without redesigning the surrounding circuit.
Different logic function
Different pin assignment
Different output behavior
Different application role
Parts at a glance
Part B
74HCT221D,118
Nexperia USA Inc.
- Lifecycle
- Active
- Stock
- 9432 Stückzahl
- Package
- SOIC-16
- Series
- Logic-Multivibrators
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT00D | 74HCT221D,118 | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate | Dual monostable multivibrator (one-shot) | The logic function defines the fundamental behavior of the device; different functions are not functionally substitutable. |
| Number of Circuits | 4 | 2 | The number of independent channels determines how many signals can be processed simultaneously. |
| Number of Inputs per Circuit | 2 | 2 (A and B trigger inputs) | Input count affects the logic capability and the way signals are combined or triggered. |
| Number of Outputs per Circuit | 1 | 2 (Q and Q-bar) | Output configuration determines available signal polarities and fan-out options. |
| Supply Voltage Range | 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. |
| Propagation Delay | Typically 9 ns at 5 V | Typically 25 ns at 5 V | Propagation delay affects timing margins and maximum operating frequency in a circuit. |
| Output Drive Current | ±4 mA | ±4 mA | Drive current determines the ability to drive loads such as LEDs or other logic inputs. |
| Package Type | SO14 (SOIC-14) | SO16 (SOIC-16) | Package footprint and pin count must match the PCB layout for physical interchangeability. |
| Pin Count | 14 | 16 | Different pin counts mean the devices are not pin-to-pin compatible and cannot be swapped directly. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both support industrial temperature ranges, so thermal compatibility is equivalent. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT00D | 74HCT221D,118 |
|---|---|---|
| Supplier | - | Nexperia USA Inc. |
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NAND 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 | 17ns @ 5.5V, 50pF | - |
Frequently asked questions
What are the primary functional differences between the 74HCT00D and the 74HCT221D,118?
The 74HCT00D is a quad 2-input NAND gate, while the 74HCT221D,118 is a dual non-retriggerable monostable multivibrator. The 74HCT00D performs combinational logic, whereas the 74HCT221D,118 generates output pulses with a duration determined by external timing components.
Are the 74HCT00D and 74HCT221D,118 pin-compatible?
No. The 74HCT00D is typically supplied in a 14-pin SOIC package with a standard quad-gate pinout, while the 74HCT221D,118 is supplied in a 16-pin SOIC package with a different pinout for timing, trigger, and reset functions. They are not drop-in replacements.
Can the 74HCT00D be used to replace the 74HCT221D,118 in a pulse-generation circuit?
No. The 74HCT00D is a logic gate and cannot generate a controlled pulse width without additional external circuitry. The 74HCT221D,118 is specifically designed as a monostable multivibrator with an output pulse width set by an external resistor and capacitor.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT00D and the 74HCT221D,118 are HCT-family devices and operate from a nominal 5 V supply, with a specified operating range typically from 4.5 V to 5.5 V.
What is the function of the 74HCT221D,118 that the 74HCT00D cannot perform?
The 74HCT221D,118 provides a non-retriggerable monostable output with a pulse width determined by an external resistor and capacitor. The 74HCT00D cannot provide this timing function because it is a fixed-function NAND gate.
Are both devices compatible with TTL logic levels?
Yes. Both the 74HCT00D and the 74HCT221D,118 are HCT-type devices, which means they have TTL-compatible input thresholds while operating from a 5 V CMOS supply.
Which device is better suited for debouncing a mechanical switch?
The 74HCT221D,118 is better suited for switch debouncing because its monostable output can generate a clean, fixed-width pulse from a noisy input. The 74HCT00D would require additional external components to achieve a similar debouncing function.
Do the 74HCT00D and 74HCT221D,118 have the same output drive capability?
Both devices are standard HCT-family logic parts and typically provide symmetrical CMOS output drive. However, exact output current ratings should be verified from the respective manufacturer datasheets, as they may differ between logic gates and multivibrators.