Part A
74HCT04D
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 4496 PCS
- Package
- SOIC-16
- Series
- Logic - Gates and Inverters
Replacement verdict
Not a drop-in replacement
The 74HCT04D and 74HCT646D,653 are not functionally interchangeable. The 74HCT04D is a hex inverting gate, while the 74HCT646D,653 is an octal bus transceiver/register with 3-state outputs. They differ in logic function, channel count, pin configuration, and control architecture, so direct substitution is not possible without a complete circuit redesign.
Different logic function
Different channel count
Different pin configuration
Different control architecture
Parts at a glance
Part B
74HCT646D,653
NXP USA Inc.
- Lifecycle
- Active
- Stock
- 3630 PCS
- Package
- SOIC-24
- Series
- Logic - Buffers, Drivers, Receivers, Transceivers
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74HCT04D | 74HCT646D,653 | Why it matters |
|---|---|---|---|
| Logic Function | Hex Inverter | Octal Bus Transceiver/Register | The two devices perform fundamentally different logic functions, so they are not functionally interchangeable in a circuit. |
| Number of Channels | 6 | 8 | Channel count determines how many independent signal lines the device can process. |
| Direction Control | Unidirectional | Bidirectional (with direction pin) | Bidirectional capability allows the transceiver to route data in either direction, which the inverter cannot do. |
| Output Type | Inverting | Non-inverting (3-state) | Inverting versus non-inverting outputs changes the logic polarity, affecting signal integrity and circuit behavior. |
| 3-State Outputs | No | Yes | 3-state outputs allow the device to be disconnected from a bus, enabling shared bus architectures. |
| Package | SOIC-14 | SOIC-24 | Different package sizes and pin counts affect PCB layout and cannot be directly swapped. |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | Both devices operate from the same standard 5 V TTL-compatible supply range. |
| Logic Family | HCT | HCT | Same logic family ensures compatible input thresholds and output drive characteristics. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +125 °C | Identical temperature ratings mean both can be used in the same environmental conditions. |
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 | 74HCT04D | 74HCT646D,653 |
|---|---|---|
| Supplier | - | NXP USA Inc. |
| Series | 74HCT | 74HCT |
| Part Status | Active | Obsolete |
| Logic Type | Inverter | 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 ~ 125°C | -40°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Circuits | 6 | - |
| Number of Inputs | 1 | - |
| 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 74HCT04D and the 74HCT646D,653?
The 74HCT04D is a hex inverter containing six independent NOT gates, while the 74HCT646D,653 is an octal bus transceiver and register with 3-state outputs. The 74HCT04D provides simple logic inversion, whereas the 74HCT646D,653 supports bidirectional data transfer, data registration, and bus interfacing.
Are the 74HCT04D and 74HCT646D,653 pin-compatible?
No. The 74HCT04D is typically supplied in a 14-pin SOIC package, while the 74HCT646D,653 is supplied in a 24-pin SOIC package. Pin counts, pin functions, and package dimensions differ, so they are not drop-in replacements.
Can the 74HCT04D be used as a direct substitute for the 74HCT646D,653 in an existing design?
No. The devices perform fundamentally different logic functions and have different pinouts and package sizes. Substitution would require a complete redesign of the surrounding circuitry and PCB layout.
What are the key electrical characteristics of the 74HCT04D?
The 74HCT04D operates over a supply voltage range of 4.5 V to 5.5 V, features TTL-compatible input thresholds, and provides typical propagation delay of 12 ns at 5 V. It has standard push-pull CMOS outputs capable of driving 4 mA at 5 V.
What are the key electrical characteristics of the 74HCT646D,653?
The 74HCT646D,653 operates over a supply voltage range of 4.5 V to 5.5 V, features TTL-compatible inputs, and provides 3-state outputs for bus-oriented applications. It includes an 8-bit register and control circuitry for direction and output enable, with typical propagation delay of 20 ns at 5 V.
Do both devices support the same operating temperature range?
Yes. Both the 74HCT04D and 74HCT646D,653 are specified for the industrial temperature range of -40 °C to +125 °C, as documented in their respective manufacturer datasheets.
Which device is more suitable for bus interface applications?
The 74HCT646D,653 is specifically designed for bus interface applications due to its 3-state outputs, bidirectional data flow, and integrated registers. The 74HCT04D is a general-purpose inverter and is not intended for bus driving or data registration.