Part A
74HCT00D
Компания Toshiba Semiconductor и Storage
- Lifecycle
- Active
- Stock
- 1289 ПКС
- Package
- SOIC-20
- Series
- Логика - Ворота и инверторы
Replacement verdict
Not a drop-in replacement
The 74HCT00D and 74HCT245D,653 are not functionally interchangeable despite sharing the same 74HCT logic family and SOIC-14 package. The 74HCT00D is a quad 2-input NAND gate, while the 74HCT245D,653 is an octal bus transceiver with 3-state outputs and direction control. Their logic functions, channel counts, pinouts, and I/O characteristics differ fundamentally, so substituting one for the other is not possible without redesigning the surrounding circuit.
Different logic function
Different channel count
Different pinout
Different output type
Parts at a glance
Part B
74HCT245D,653
Компания NXP USA Inc.
- Lifecycle
- Active
- Stock
- 5860 ПКС
- Package
- SOIC-20
- Series
- Логика - буферы, драйверы, приемники, передатчики
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 | 74HCT245D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Quad 2-input NAND gate | Octal bus transceiver with 3-state outputs | The logic function defines the fundamental operation of the device; these two parts perform completely different functions and are not functionally interchangeable. |
| Number of Gates / Channels | 4 gates | 8 channels | The channel count determines how many independent signal paths the device can handle, affecting circuit density and board layout. |
| Output Type | Push-pull (totem-pole) | 3-state (tri-state) | 3-state outputs allow bus sharing by placing outputs in high-impedance mode, while push-pull outputs cannot be tied together; this affects bus architecture compatibility. |
| Direction Control | None (unidirectional logic) | Direction pin (DIR) for A-to-B or B-to-A | Bidirectional control is essential for bus transceiver applications; the NAND gate has no such capability. |
| Output Enable | Not applicable | Active-low output enable (OE) | Output enable allows the device to be disconnected from the bus, which is critical for multi-device bus systems. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both devices operate on standard 5 V TTL-compatible supply, so power supply compatibility is identical. |
| Logic Family | HCT (High-speed CMOS, TTL-compatible) | HCT (High-speed CMOS, TTL-compatible) | Same logic family ensures compatible input thresholds and output drive levels with other HCT devices. |
| Propagation Delay (typical) | ~9 ns at 5 V | ~12 ns at 5 V | Propagation delay affects timing margins in synchronous systems; differences may impact timing-critical designs. |
| Package | SO14 (14-pin SOIC) | SO20 (20-pin SOIC) | Different pin counts and package sizes mean they are not footprint-compatible and cannot be swapped on the same PCB pad layout. |
| Pin Count | 14 | 20 | Pin count determines board space and routing requirements; mismatched pin counts prevent direct substitution. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74HCT00D | 74HCT245D,653 |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74HCT | 74HCT |
| Part Status | Obsolete | Active |
| Logic Type | NAND Gate | Transceiver, Non-Inverting |
| Number of Elements | - | 1 |
| Number of Bits per Element | - | 8 |
| Output Type | - | 3-State |
| Current - Output High Low | 4mA, 4mA | 6mA, 6mA |
| Voltage - Supply | 4.5V ~ 5.5V | 4.5V ~ 5.5V |
| Operating Temperature | -40°C ~ 85°C | -40°C ~ 125°C (TA) |
| 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 74HCT245D,653?
The 74HCT00D is a quad 2-input NAND gate, providing four independent logic gates in a single package. The 74HCT245D,653 is an octal bus transceiver with 3-state outputs, designed for bidirectional data transfer between two buses. They serve fundamentally different logic and interface functions and are not functionally interchangeable.
Are the 74HCT00D and 74HCT245D,653 pin-compatible?
No. The 74HCT00D is typically supplied in a 14-pin SOIC package, while the 74HCT245D,653 is supplied in a 20-pin SOIC package. They have different pin counts, pin assignments, and PCB land patterns, so they cannot be used as drop-in replacements for each other.
Do both devices operate from the same supply voltage range?
Yes. Both the 74HCT00D and the 74HCT245D,653 are HCT-family CMOS devices specified for a nominal 5 V supply, with a recommended operating supply voltage range of 4.5 V to 5.5 V. This makes them compatible with TTL logic levels in 5 V systems.
Can the 74HCT245D,653 be used to drive a bus that the 74HCT00D also drives?
Only with proper system design. The 74HCT245D,653 has 3-state outputs that can be placed in high-impedance mode, allowing bus sharing. The 74HCT00D has standard totem-pole outputs without 3-state capability, so it cannot release the bus. Direct contention must be avoided by ensuring the 74HCT00D output is not active when the 74HCT245D,653 drives the same node.
What is the difference in output drive current between the two devices?
Both devices are specified with standard HCT-family output drive. The 74HCT00D provides ±4 mA output current at 5 V. The 74HCT245D,653 provides ±6 mA output current at 5 V. The higher drive of the 74HCT245D,653 makes it more suitable for bus driving, while the 74HCT00D is intended for general logic functions.
Are both devices available in the same package type?
Both are available in SOIC packages, but with different pin counts. The 74HCT00D is a 14-pin SOIC (D package). The 74HCT245D,653 is a 20-pin SOIC (D package). The "653" suffix on the 74HCT245D,653 indicates tape and reel packing. Package footprint and pin count differ, so they are not mechanically interchangeable.
Which device is better suited for bidirectional data bus applications?
The 74HCT245D,653 is specifically designed for bidirectional bus applications. It features an octal transceiver with direction control and output enable, allowing data to flow in either direction between two buses. The 74HCT00D is a fixed-function NAND gate array and has no bus transceiver capability, so it is not suitable for bidirectional bus interfacing.
Do both devices have the same propagation delay characteristics?
No. The 74HCT00D has a typical propagation delay of approximately 9 ns at 5 V. The 74HCT245D,653 has a typical propagation delay of approximately 10 ns at 5 V. While similar in magnitude, the exact timing parameters differ and should be verified from the respective manufacturer datasheets for critical timing analysis.