Part A
74HCT00D
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 1289 PCS
- Package
- SOIC-20
- Series
- Logic - Gates and Inverters
Replacement verdict
Not a drop-in replacement
The 74HCT245D and 74HCT00D are not functionally interchangeable despite sharing the same 74HCT logic family and SOIC-16 package. The 74HCT245D is an octal bus transceiver with 3-state non-inverting outputs and direction control, while the 74HCT00D is a quad 2-input NAND gate with standard push-pull outputs. Their internal logic functions, pin assignments, and signal flow architectures are fundamentally different, making direct substitution impossible without complete circuit redesign.
Different logic function
Different output type
Different pin assignment
Different channel count
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 | 74HCT00D | Why it matters |
|---|---|---|---|
| Logic Function | Octal bus transceiver with 3-state outputs | Quad 2-input NAND gate | Defines the fundamental logic operation; these devices perform completely different functions and are not functionally interchangeable. |
| Number of Channels / Gates | 8 channels (bidirectional) | 4 gates (2-input NAND) | Determines how many independent signal paths or logic operations the device can handle in a circuit. |
| 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 on a shared bus. |
| Direction Control | Direction pin (DIR) and Output Enable (OE) | None (unidirectional logic) | The transceiver can route data in either direction under control, whereas the NAND gate has fixed signal flow. |
| Supply Voltage Range (VCC) | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both are HCT-family devices designed for 5 V TTL-compatible systems; matching supply range ensures electrical compatibility. |
| Logic Family | HCT (High-speed CMOS, TTL-compatible) | HCT (High-speed CMOS, TTL-compatible) | Same logic family means compatible input thresholds, output drive, and noise margins when used in the same design. |
| Package | SOIC-20 (D suffix) | SOIC-14 (D suffix) | Package footprint and pin count differ, so they are not drop-in replacements on a PCB despite sharing the SOIC family. |
| Pin Count | 20 pins | 14 pins | Different pin counts mean incompatible footprints and pinouts; substitution requires board redesign. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Both support industrial temperature ranges, suitable for the same environmental conditions. |
| Propagation Delay (typical) | ~12 ns at 5 V | ~9 ns at 5 V | Timing differences affect signal integrity and maximum operating frequency in synchronous designs. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT00D | 74HCT245D |
|---|---|---|
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NAND 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 | 17ns @ 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 functional differences between the 74HCT245D and the 74HCT00D?
The 74HCT245D is an octal bus transceiver with 3-state outputs, designed for bidirectional asynchronous communication between data buses. The 74HCT00D is a quad 2-input NAND gate, providing four independent logic gates for general-purpose logic inversion and gating functions. They serve fundamentally different roles: one is for bus interfacing, the other for logic implementation.
Are the 74HCT245D and 74HCT00D pin-compatible or package-compatible?
No. The 74HCT245D is typically supplied in a 20-pin SOIC package (D suffix), while the 74HCT00D is typically supplied in a 14-pin SOIC package. They have different pin counts, pinouts, and package dimensions, so they are not drop-in replacements for each other on a PCB.
Can the 74HCT245D and 74HCT00D operate from the same power supply voltage?
Yes. Both devices are members of the 74HCT logic family and are specified for a nominal supply voltage of 5 V, with a recommended operating range typically from 4.5 V to 5.5 V. They are compatible with TTL logic levels when powered from a 5 V supply.
Does the 74HCT245D have any functionality that the 74HCT00D lacks?
Yes. The 74HCT245D provides bidirectional data transfer with direction control (DIR) and output enable (OE) inputs, plus 3-state outputs for bus isolation. The 74HCT00D does not have 3-state outputs, direction control, or bus transceiver capability; it only performs fixed 2-input NAND logic.
Can the 74HCT00D be used to replace the 74HCT245D in a bus transceiver application?
No. The 74HCT00D cannot replicate the 74HCT245D's bidirectional bus interface, 3-state output control, or direction management. A direct substitution would require additional external logic and would not match the original bus drive, isolation, or timing characteristics.
Are both the 74HCT245D and 74HCT00D available in the same SOIC package type?
Both are commonly available in SOIC packages, but with different pin counts: the 74HCT245D in a 20-pin SOIC (D package) and the 74HCT00D in a 14-pin SOIC (D package). The package family is similar, but the physical footprint and pin arrangement differ.
Which device is more suitable for driving heavy bus loads?
The 74HCT245D is specifically designed for bus-oriented applications and typically provides symmetrical output drive suitable for driving moderate bus capacitance. The 74HCT00D is a general-purpose logic gate with standard output drive and is not intended for direct bus driving or bidirectional bus interfacing.
Do the 74HCT245D and 74HCT00D have the same propagation delay characteristics?
No. Propagation delays differ because the devices implement different internal functions and signal paths. The 74HCT245D includes bus transceiver circuitry with direction and enable controls, while the 74HCT00D is a simple NAND gate. For exact timing specifications, refer to the respective manufacturer datasheets.