Part A
74VHC245FT
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 4188 PCS
- Package
- TSSOP-20
- Series
- Logic - Buffers, Drivers, Receivers, Transceivers
Replacement verdict
Not a drop-in replacement
The 74VHC245FT and 74VHC08FT are not functionally interchangeable. The 74VHC245FT is an octal bidirectional bus transceiver with 3-state outputs, while the 74VHC08FT is a quad 2-input AND gate. They differ in logic function, channel count, output type, and pinout, so substituting one for the other is not feasible in existing designs.
Different logic function
Different channel count
Different output type
Different pinout
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 | 74VHC08FT | Why it matters |
|---|---|---|---|
| Logic Function | Octal Bus Transceiver (3-state, bidirectional) | Quad 2-input AND gate | Defines the core function; these devices are not functionally interchangeable as they perform entirely different logic operations. |
| Number of Channels | 8 | 4 | Determines how many independent signal paths can be handled simultaneously. |
| Output Type | 3-state (tri-state) | Push-pull (totem-pole) | 3-state outputs allow bus sharing and high-impedance disconnection, while push-pull outputs cannot be tied together. |
| Direction Control | Yes (DIR pin, A-to-B or B-to-A) | No | Bidirectional control enables the transceiver to route signals in either direction, which the AND gate cannot do. |
| Output Enable | Yes (active-low OE) | No | Output enable allows the device to be placed in high-impedance state for bus arbitration, absent in the AND gate. |
| 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 systems. |
| Logic Family | VHC (Very High-speed CMOS) | VHC (Very High-speed CMOS) | Same family ensures compatible input/output thresholds and similar propagation delays. |
| Package | TSSOP-20 (FT suffix) | TSSOP-14 (FT suffix) | Different pin counts and footprints prevent direct drop-in replacement on the same PCB pad layout. |
| Propagation Delay (typ.) | ~4.5 ns at 5 V | ~5.5 ns at 5 V | Timing differences affect signal integrity and maximum operating frequency in synchronous designs. |
| Input/Output Drive Current | ±8 mA at 5 V | ±8 mA at 5 V | Drive strength affects fan-out and ability to drive capacitive or resistive loads. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC245FT | 74VHC08FT |
|---|---|---|
| Series | 74VHC | TC74VHC |
| Part Status | Active | Active |
| Logic Type | Transceiver, Non-Inverting | AND 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 |
| Input Logic Level - Low | - | 0.5V |
| Input Logic Level - High | - | 1.5V |
| Max Propagation Delay @ V, Max CL | - | 7.9ns @ 5V, 50pF |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
| Base Product Number | - | 74VHC08 |
| Number of Elements | 1 | - |
| Number of Bits per Element | 8 | - |
| Output Type | 3-State | - |
| Current - Output High Low | 8mA, 8mA | - |
Frequently asked questions
What are the primary functions of the 74VHC245FT and 74VHC08FT?
The 74VHC245FT is an octal bidirectional transceiver with 3-state outputs, designed for asynchronous two-way data bus communication. The 74VHC08FT is a quad 2-input AND gate that performs basic logic AND operations. They serve fundamentally different roles: the 74VHC245FT handles bus interfacing and signal buffering, while the 74VHC08FT implements combinational logic.
Can the 74VHC245FT and 74VHC08FT be used interchangeably in a design?
No. The 74VHC245FT is a bidirectional bus transceiver with direction control and 3-state outputs, whereas the 74VHC08FT is a quad 2-input AND gate. Their pin functions, logic behavior, and internal circuitry are entirely different, so they are not pin-compatible or functionally interchangeable.
Do the 74VHC245FT and 74VHC08FT share the same package and pinout?
Both devices are commonly offered in TSSOP-20 packages by manufacturers such as Toshiba, but their pinouts differ. The 74VHC245FT uses pins for data inputs/outputs, direction control (DIR), and output enable (OE), while the 74VHC08FT uses pins for four independent 2-input AND gates with shared power and ground. Always verify the specific manufacturer datasheet for exact pin assignments.
What are the operating voltage and logic level specifications for these devices?
Both the 74VHC245FT and 74VHC08FT are members of the VHC family and typically operate over a supply voltage range of 2.0 V to 5.5 V. They provide CMOS-compatible input thresholds and are characterized for balanced propagation delays and low power consumption. For precise VIL, VIH, VOL, VOH, and timing parameters, consult the respective manufacturer datasheet.
Which device is suitable for bus-oriented applications?
The 74VHC245FT is specifically designed for bus-oriented applications. Its octal bidirectional transceiver with 3-state outputs allows it to drive and receive data on a shared bus, with direction and output-enable controls to manage bus contention. The 74VHC08FT is not intended for bus interfacing and lacks 3-state or bidirectional capabilities.
Are the 74VHC245FT and 74VHC08FT available in the same package options?
Package availability depends on the manufacturer. Toshiba offers both the 74VHC245FT and 74VHC08FT in TSSOP-20 (thin shrink small outline package) under the "FT" suffix. However, other package options may differ between the two part numbers. Always confirm package availability from the manufacturer or authorized distributor.
What are the typical propagation delay characteristics of these devices?
Both devices are fabricated with advanced CMOS technology and feature typical propagation delays in the low nanosecond range at 5 V supply. The 74VHC245FT propagation delay is specified for both low-to-high and high-to-low transitions, while the 74VHC08FT specifies propagation delay for AND gate inputs to output. Exact values vary with supply voltage, load capacitance, and temperature; refer to the manufacturer datasheet for guaranteed limits.
Can the 74VHC245FT and 74VHC08FT be used in mixed-voltage systems?
Both devices support a supply voltage range of 2.0 V to 5.5 V, which allows operation in mixed-voltage systems when the supply is set appropriately. However, input voltage levels must not exceed the supply voltage or the absolute maximum ratings. For level-shifting between different voltage domains, additional circuitry or level translators may be required. Verify input/output voltage compatibility with the target system.