Part A
74VHC244FT
東芝電晶體與存儲
- Lifecycle
- Active
- Stock
- 2156 件
- Package
- TSSOP-20
- Series
- 邏輯-緩衝器、驅動器、接收器、收發器
Replacement verdict
Not a drop-in replacement
The 74VHC244FT and 74VHCT04ATTR are functionally incompatible devices and cannot be used as drop-in replacements for each other. The 74VHC244FT is a quad non-inverting buffer with 3-state outputs, while the 74VHCT04ATTR is a hex inverting inverter with standard push-pull outputs. They differ in logic function, channel count, output configuration, and input threshold technology, making direct substitution impossible without circuit redesign.
Different logic function
Different channel count
Different output type
Different input threshold
Parts at a glance
Part B
74VHCT04ATTR
意法半導體
- Lifecycle
- Active
- Stock
- 6592 件
- Series
- 邏輯-門和逆變器
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74VHC244FT | 74VHCT04ATTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver (3-state, non-inverting) | Hex Inverter (unbuffered) | The two devices perform fundamentally different logic functions, so they are not direct substitutes in a circuit. |
| Number of Channels | 8 | 6 | Channel count determines how many independent signal lines can be handled by a single package. |
| Output Type | 3-state | Push-pull | 3-state outputs allow bus sharing and high-impedance isolation, while push-pull outputs always drive the line. |
| Logic Family | VHC (Very High-speed CMOS) | VHCT (Very High-speed CMOS, TTL-compatible) | VHCT inputs are TTL-voltage compatible, while VHC inputs are CMOS-level, affecting interfacing with different logic levels. |
| Input Compatibility | CMOS-level inputs | TTL-level compatible inputs | TTL-compatible inputs allow direct interfacing with 5 V TTL logic without additional level shifting. |
| Propagation Delay (typical) | ~3.5 ns at 5 V | ~5.5 ns at 5 V | Propagation delay affects maximum operating frequency and timing margins in synchronous designs. |
| Supply Voltage Range | 2.0 V to 5.5 V | 4.5 V to 5.5 V | A wider supply range offers more flexibility for low-voltage and mixed-voltage systems. |
| Output Drive Current | ±8 mA | ±8 mA | Drive current determines the ability to drive capacitive loads and fan-out to other gates. |
| Package | TSSOP-20 | TSSOP-14 | Different pin counts and package sizes affect PCB layout, footprint, and board space. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | The temperature range must cover the application environment for reliable operation. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC244FT | 74VHCT04ATTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74VHC | 74VHCT |
| Part Status | Active | Obsolete |
| Logic Type | Buffer, Non-Inverting | Inverter |
| Number of Circuits | - | 6 |
| Number of Inputs | - | 1 |
| Voltage - Supply | 2V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | - | 2 µA |
| Current - Output High Low | 8mA, 8mA | 8mA, 8mA |
| Logic Level - Low | - | 0.8V |
| Logic Level - High | - | 2V |
| Max Propagation Delay @ V Max CL | - | 7.7ns @ 5V, 50pF |
| Operating Temperature | -40°C ~ 125°C (TA) | -55°C ~ 125°C |
| Mounting Type | Surface Mount | Surface Mount |
| Number of Elements | 2 | - |
| Number of Bits per Element | 4 | - |
| Output Type | 3-State | - |
Frequently asked questions
What are the primary functional differences between the 74VHC244FT and the 74VHCT04ATTR?
The 74VHC244FT is an octal non-inverting buffer/line driver with 3-state outputs, while the 74VHCT04ATTR is a hex inverting inverter. The 74VHC244FT provides eight buffer channels with tri-state control, whereas the 74VHCT04ATTR provides six inverting channels without tri-state capability.
Are the 74VHC244FT and 74VHCT04ATTR pin-to-pin compatible?
No. The 74VHC244FT is typically supplied in a TSSOP-20 package, while the 74VHCT04ATTR is typically supplied in a TSSOP-14 package. They have different pin counts, pin assignments, and package footprints, so they are not drop-in replacements for each other.
What logic families do the 74VHC244FT and 74VHCT04ATTR belong to?
The 74VHC244FT belongs to the VHC (Very High Speed CMOS) family. The 74VHCT04ATTR belongs to the VHCT (Very High Speed CMOS with TTL-compatible inputs) family. The VHCT variant is designed to accept TTL-level input voltages while maintaining CMOS output drive characteristics.
Can the 74VHC244FT and 74VHCT04ATTR operate from the same supply voltage?
Yes. Both devices are specified for a nominal supply voltage range of 2.0 V to 5.5 V, with 5.0 V being the most common operating condition. However, the 74VHCT04ATTR input thresholds are TTL-compatible, while the 74VHC244FT input thresholds are CMOS-level.
Does the 74VHC244FT have 3-state outputs while the 74VHCT04ATTR does not?
Yes. The 74VHC244FT features 3-state outputs controlled by two active-low output enable pins (1OE and 2OE), allowing the outputs to be placed in a high-impedance state. The 74VHCT04ATTR has standard push-pull outputs and does not provide a high-impedance disable function.
What are the typical propagation delay characteristics of these two devices?
At a 5.0 V supply, the 74VHC244FT typically exhibits a propagation delay of approximately 3.5 ns to 5.0 ns. The 74VHCT04ATTR typically exhibits a propagation delay of approximately 4.0 ns to 6.0 ns. Exact values depend on load capacitance, temperature, and supply voltage as specified in the respective manufacturer datasheets.
Are the 74VHC244FT and 74VHCT04ATTR interchangeable in a design without modification?
No. They differ in function (buffer vs. inverter), channel count (8 vs. 6), package type (TSSOP-20 vs. TSSOP-14), and control features (3-state vs. non-3-state). Direct substitution would require significant design changes including PCB layout, logic polarity, and control signal routing.
Which device is better suited for bus driving applications?
The 74VHC244FT is better suited for bus driving applications because it provides eight non-inverting buffer channels with 3-state outputs, allowing multiple devices to share a common bus. The 74VHCT04ATTR is intended for signal inversion and is not designed for bus-oriented tri-state applications.