Part A
74VHC244FT
Toshiba Semiconductor et stockage
- Lifecycle
- Active
- Stock
- 2156 PCS
- Package
- TSSOP-20
- Series
- Logique - Buffers, lecteurs, récepteurs, émetteurs - récepteurs
Replacement verdict
Not a drop-in replacement
The 74VHC244FT and 74VHCT05ATTR are functionally incompatible devices and cannot be used as drop-in replacements for one another. The 74VHC244FT is a quad non-inverting buffer/line driver with 3-state outputs, while the 74VHCT05ATTR is a hex open-drain inverter with TTL-compatible inputs. Their differing logic functions, output structures, channel counts, and input threshold characteristics make direct substitution impossible without significant circuit redesign.
Different logic function
Different output type
Different channel count
Different input threshold
Parts at a glance
Part B
74VHCT05ATTR
Semi - conducteurs optiques
- Lifecycle
- Active
- Stock
- 3384 PCS
- Series
- Logique - portes et Onduleurs
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 | 74VHCT05ATTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver with 3-State Outputs | Hex Inverter with Open-Drain Outputs | The two devices perform fundamentally different logic functions, so they are not functionally interchangeable in a circuit. |
| Number of Channels | 8 | 6 | Channel count determines how many signal lines can be handled by a single package. |
| Output Type | 3-State (Tri-State) | Open-Drain | Output configuration affects bus sharing, pull-up requirements, and drive capability. |
| Logic Family | VHC (Very High Speed CMOS) | VHCT (Very High Speed CMOS with TTL-Compatible Inputs) | Logic family determines input threshold compatibility with TTL or CMOS drive sources. |
| Input Compatibility | CMOS-level inputs | TTL-compatible inputs | TTL-compatible inputs allow direct interfacing with TTL logic levels without additional level shifting. |
| Supply Voltage Range | 2.0 V to 5.5 V | 4.5 V to 5.5 V | A wider supply range offers greater flexibility in low-voltage and mixed-voltage designs. |
| Propagation Delay | Approximately 3.5 ns at 5 V | Approximately 5.5 ns at 5 V | Propagation delay impacts maximum operating frequency and timing margins in synchronous systems. |
| Output Drive Current | ±8 mA | ±8 mA (sink only for open-drain) | Drive current determines the ability to drive loads such as LEDs, relays, or capacitive lines. |
| Package Type | TSSOP-20 | TSSOP-14 | Package footprint and pin count affect PCB layout and mechanical compatibility. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Temperature range ensures reliable operation across industrial and commercial environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC244FT | 74VHCT05ATTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74VHC | 74VHCT |
| Part Status | Active | Obsolete |
| Logic Type | Buffer, Non-Inverting | Inverter |
| Number of Circuits | - | 6 |
| Number of Inputs | - | 1 |
| Features | - | Open Drain |
| Voltage - Supply | 2V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Max) | - | 2 µA |
| Current - Output High Low | 8mA, 8mA | -, 8mA |
| Logic Level - Low | - | 0.8V |
| Logic Level - High | - | 2V |
| Max Propagation Delay @ V Max CL | - | 9.8ns @ 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 74VHCT05ATTR?
The 74VHC244FT is an octal non-inverting buffer/line driver with 3-state outputs, while the 74VHCT05ATTR is a hex inverter with open-drain outputs. The 74VHC244FT is designed for signal buffering and driving bus lines, whereas the 74VHCT05ATTR is intended for inverting logic and wired-OR/wired-AND applications requiring open-drain outputs.
Are the 74VHC244FT and 74VHCT05ATTR pin-compatible?
No. The 74VHC244FT is typically supplied in a 20-pin package (e.g., TSSOP-20), while the 74VHCT05ATTR is supplied in a 14-pin package (e.g., TSSOP-14). They have different pin counts and pin functions, so they are not pin-compatible.
Can the 74VHC244FT and 74VHCT05ATTR 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 typical operating voltage for TTL-compatible logic. However, the 74VHCT05ATTR has TTL-compatible input thresholds, while the 74VHC244FT has CMOS-compatible input thresholds.
What is the difference in output drive capability between the 74VHC244FT and the 74VHCT05ATTR?
The 74VHC244FT provides standard balanced CMOS outputs with symmetrical source/sink current (typically ±8 mA at 5 V). The 74VHCT05ATTR has open-drain outputs that can sink current (typically 8 mA at 5 V) but cannot source current, requiring an external pull-up resistor for logic high output.
Which device is better suited for bus driving applications?
The 74VHC244FT is better suited for bus driving because it features 3-state outputs that allow multiple devices to share a common bus, and it can both source and sink current. The 74VHCT05ATTR, with open-drain outputs, is not intended for direct bus driving without external pull-up resistors and is typically used for wired-OR logic or level-shifting applications.
Do both devices have the same operating temperature range?
Yes. Both the 74VHC244FT and 74VHCT05ATTR are specified for the industrial operating temperature range of -40°C to +85°C, making them suitable for similar environmental conditions.
Can the 74VHCT05ATTR be used to replace the 74VHC244FT in an existing design?
No. The two devices have different logic functions (inverter vs. non-inverting buffer), different output types (open-drain vs. 3-state), different pin counts, and different input threshold characteristics. A direct replacement is not possible without significant redesign.
What are the typical propagation delays for these devices?
At 5.0 V supply, the 74VHC244FT typically has a propagation delay of approximately 3.8 ns to 5.5 ns. The 74VHCT05ATTR typically has a propagation delay of approximately 5.0 ns to 7.5 ns. Actual values depend on load conditions and are specified in the respective manufacturer datasheets.