Part A
74VHC245FT
Toshiba Semiconductor and Storage
- Lifecycle
- Active
- Stock
- 4188 PCS
- Package
- TSSOP-20
- Series
- Logic - Buffers, Drivers, Receivers, Transceivers
Replacement verdict
Not a drop-in replacement
The 74VHC245FT and 74VHCT05ATTR are functionally unrelated devices and cannot serve as substitutes for one another. The 74VHC245FT is an octal bidirectional transceiver with 3-state outputs, while the 74VHCT05ATTR is a hex inverter with open-drain outputs. They differ in logic function, output configuration, channel count, and package type, making direct replacement impossible without redesigning the surrounding circuit.
Different logic function
Different output type
Different channel count
Different package type
Parts at a glance
Part B
74VHCT05ATTR
STMicroelectronics
- Lifecycle
- Active
- Stock
- 3384 PCS
- Series
- Logic - Gates and Inverters
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | 74VHC245FT | 74VHCT05ATTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Bus Transceiver, 3-State | Hex Inverter, Open-Drain | The two devices perform fundamentally different logic functions, so they are not direct functional substitutes 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 interfacing capability. |
| Direction Control | Bidirectional with direction pin (DIR) and output enable (OE) | Unidirectional (inverter only) | Bidirectional capability is essential for bus transceiver applications, while an inverter only propagates signals one way. |
| 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 compatibility with driving logic levels. |
| Supply Voltage Range | 2.0 V to 5.5 V | 4.5 V to 5.5 V | A wider supply range allows the VHC device to operate in low-voltage systems where the VHCT device cannot. |
| Propagation Delay (typical) | ~3.5 ns at 5 V | ~5.0 ns at 5 V | Propagation delay influences maximum operating frequency and timing margins in synchronous designs. |
| Package | TSSOP-20 | TSSOP-14 | Different pin counts and footprints prevent direct drop-in replacement on the same PCB pad layout. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Both devices support industrial temperature ranges, so thermal conditions are not a differentiator. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC245FT | 74VHCT05ATTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74VHC | 74VHCT |
| Part Status | Active | Obsolete |
| Logic Type | Transceiver, 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 | 1 | - |
| Number of Bits per Element | 8 | - |
| Output Type | 3-State | - |
Frequently asked questions
What are the primary functional differences between the 74VHC245FT and the 74VHCT05ATTR?
The 74VHC245FT is an octal bidirectional transceiver with 3-state outputs, designed for bus-oriented applications. The 74VHCT05ATTR is a hex inverter with open-drain outputs. They differ in logic function, output type, and channel count.
Are the 74VHC245FT and 74VHCT05ATTR pin-to-pin compatible?
No. The 74VHC245FT is typically offered in a 20-pin TSSOP or similar package, while the 74VHCT05ATTR is typically offered in a 14-pin TSSOP. Pin counts and pin functions differ, so they are not drop-in replacements.
Can the 74VHC245FT and 74VHCT05ATTR operate from the same supply voltage?
Both devices are specified for a nominal 5 V supply, but the 74VHC245FT operates over 2.0 V to 5.5 V, while the 74VHCT05ATTR is characterized for 4.5 V to 5.5 V. The 74VHCT05ATTR includes TTL-compatible input thresholds, whereas the 74VHC245FT uses CMOS input thresholds.
What is the difference in output drive capability between the 74VHC245FT and the 74VHCT05ATTR?
The 74VHC245FT provides standard balanced CMOS outputs with symmetrical source/sink current. The 74VHCT05ATTR has open-drain outputs, meaning it can only sink current and requires an external pull-up resistor for a high logic level.
Which device is better suited for bidirectional bus interfacing?
The 74VHC245FT is specifically designed for bidirectional bus interfacing due to its direction control pin and 3-state outputs. The 74VHCT05ATTR is a unidirectional inverter and is not intended for bidirectional bus applications.
Do both devices support 3-state output functionality?
No. The 74VHC245FT has 3-state outputs that can be placed in a high-impedance state via the output enable pins. The 74VHCT05ATTR has open-drain outputs, which are either low or high-impedance, but it does not provide a separate 3-state control.
Are the 74VHC245FT and 74VHCT05ATTR interchangeable in level-shifting applications?
They are not directly interchangeable. The 74VHCT05ATTR can be used with a pull-up resistor to a different voltage for simple level shifting, while the 74VHC245FT is a non-inverting transceiver that does not provide open-drain level-shifting capability without additional circuitry.
What are the typical propagation delay characteristics of these two devices?
The 74VHC245FT typically has propagation delays in the range of a few nanoseconds at 5 V. The 74VHCT05ATTR also has nanosecond-range propagation delays, but its open-drain output rise time depends on the external pull-up resistor and load capacitance, which can significantly increase the effective delay.