Part A
74VHC245FT
東芝電晶體與存儲
- Lifecycle
- Active
- Stock
- 4188 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 74VHC245FT and 74VHC00TTR are not functionally interchangeable. The 74VHC245FT is an octal bus transceiver with 3-state outputs and bidirectional data flow, while the 74VHC00TTR is a quad 2-input NAND gate with unidirectional logic outputs. Their logic functions, pin configurations, and I/O structures are fundamentally different, making direct substitution impossible without circuit redesign.
Different logic function
Different output type
Different channel count
Different pinout
Parts at a glance
Part B
74VHC00TTR
意法半導體
- Lifecycle
- Active
- Stock
- 5852 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 | 74VHC245FT | 74VHC00TTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Bus Transceiver (3-state) | Quad 2-Input NAND Gate | Defines the core function; these devices are not functionally interchangeable as they perform entirely different logic operations. |
| Number of Channels / Gates | 8 channels (bidirectional) | 4 gates | Determines how many independent signal paths or logic operations the device can handle in a circuit. |
| Output Type | 3-State | Push-Pull | 3-state outputs allow bus sharing and high-impedance isolation, while push-pull outputs are for standard logic drive. |
| Direction Control | Yes (DIR pin, A-to-B or B-to-A) | No | Direction control enables bidirectional data flow on shared buses, a feature absent in fixed-direction logic gates. |
| Output Enable | Yes (active-low OE) | No | Output enable allows the device to be disconnected from the bus, essential for multiplexed bus architectures. |
| Supply Voltage Range | 2.0 V to 5.5 V | 2.0 V to 5.5 V | Both support the same VHC family voltage range, allowing operation in 3.3 V and 5 V mixed systems. |
| Logic Family | VHC (Very High Speed CMOS) | VHC (Very High Speed CMOS) | Same logic family ensures compatible input/output thresholds and similar propagation delays when interfacing. |
| Propagation Delay (typ.) | ~4.5 ns at 5 V | ~4.3 ns at 5 V | Affects maximum operating frequency and timing margins in synchronous designs. |
| Package | TSSOP-20 | TSSOP-14 | Different pin counts and footprints prevent direct PCB drop-in replacement without layout changes. |
| Pin Count | 20 | 14 | Pin count determines board footprint and available I/O; mismatched counts mean incompatible sockets. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC245FT | 74VHC00TTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74VHC | 74VHC |
| Part Status | Active | Obsolete |
| Logic Type | Transceiver, Non-Inverting | NAND Gate |
| Number of Circuits | - | 4 |
| Number of Inputs | - | 2 |
| Voltage - Supply | 2V ~ 5.5V | 2V ~ 5.5V |
| Current - Quiescent (Max) | - | 2 µA |
| Current - Output High Low | 8mA, 8mA | 8mA, 8mA |
| Logic Level - Low | - | 0.5V |
| Logic Level - High | - | 1.5V |
| Max Propagation Delay @ V Max CL | - | 7.5ns @ 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 functions of the 74VHC245FT and 74VHC00TTR?
The 74VHC245FT is an octal bidirectional transceiver with 3-state outputs, designed for asynchronous two-way data transfer between buses. The 74VHC00TTR is a quad 2-input NAND gate that performs the basic logic NAND function. They serve fundamentally different roles: one is a bus interface/transceiver, the other is a logic gate.
Can the 74VHC245FT and 74VHC00TTR be used interchangeably in a design?
No. The 74VHC245FT is an octal bus transceiver with direction and output-enable control, while the 74VHC00TTR is a quad 2-input NAND gate. Their pinouts, functions, and logic behavior are completely different, so they are not pin-to-pin or function-to-function replacements.
What are the key electrical specifications of the 74VHC245FT?
The 74VHC245FT operates from a 2.0 V to 5.5 V supply, features 3-state outputs, and provides bidirectional data flow with a direction control pin and an output-enable pin. It is typically specified with ±8 mA output drive at 5.0 V and is housed in a TSSOP-20 package. These parameters are consistent with the manufacturer datasheet.
What are the key electrical specifications of the 74VHC00TTR?
The 74VHC00TTR operates from a 2.0 V to 5.5 V supply and contains four independent 2-input NAND gates. It typically provides ±8 mA output drive at 5.0 V and is offered in a TSSOP-14 package. Propagation delay and input/output voltage thresholds follow the standard 74VHC family specifications.
Do both devices belong to the same logic family and have similar supply voltage ranges?
Yes. Both the 74VHC245FT and 74VHC00TTR are part of the 74VHC (Very High Speed CMOS) logic family and both support a supply voltage range of 2.0 V to 5.5 V. This means they share similar CMOS input/output characteristics and can operate in the same system voltage domain.
What package types are used for the 74VHC245FT and 74VHC00TTR?
The 74VHC245FT is supplied in a TSSOP-20 package, while the 74VHC00TTR is supplied in a TSSOP-14 package. Both are surface-mount thin-shrink small outline packages, but they differ in pin count and footprint, so PCB layout must be designed accordingly.
Are the 74VHC245FT and 74VHC00TTR compatible with 5 V TTL logic levels?
Yes. Both devices are 74VHC-family CMOS parts that are designed to be compatible with TTL voltage levels when operated at 5.0 V. Their input thresholds and output drive characteristics allow direct interfacing with many 5 V TTL systems, subject to the timing and loading conditions in the manufacturer datasheet.
Which device should be selected for bus interfacing versus logic gating?
For bus interfacing, data direction control, and 3-state isolation, the 74VHC245FT is the appropriate choice. For implementing NAND logic functions, signal gating, or simple combinational logic, the 74VHC00TTR is the correct device. Selection depends on the required function, not on interchangeability.