Part A
74VHC244FT
Toshiba Semiconductor và lưu trữ
- Lifecycle
- Active
- Stock
- 2156 PCS
- Package
- TSSOP-20
- Series
- Logic - Buffers, Drivers, Receivers, Transceivers
Replacement verdict
Not a drop-in replacement
The 74VHC244FT and 74VHC74TTR are not functionally interchangeable. The 74VHC244FT is an octal non-inverting buffer/line driver with 3-state outputs, while the 74VHC74TTR is a dual D-type flip-flop with complementary outputs. They differ in logic function, channel count, output type, and pin configuration, making direct substitution impossible without circuit redesign.
Different logic function
Different channel count
Different output type
Different pin configuration
Parts at a glance
Part B
74VHC74TTR
STMicroelectronics
- Lifecycle
- Active
- Stock
- 9883 PCS
- Series
- Logic - Flip Flops
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 | 74VHC74TTR | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver (3-State) | Dual D-Type Flip-Flop (Positive Edge Triggered) | Defines the fundamental function; these devices are not functionally interchangeable. |
| Number of Channels | 8 | 2 | Determines how many independent signal lines can be handled by the device. |
| Output Type | 3-State | Push-Pull | 3-State outputs allow bus sharing; push-pull outputs cannot be tied together directly. |
| Propagation Delay (tpd) | ~5.5 ns at 5 V | ~6.5 ns at 5 V | Affects maximum operating frequency and timing margins in synchronous designs. |
| Trigger Type | Level-sensitive (enable) | Edge-triggered (positive edge) | Determines whether the device latches data on a clock edge or passes data continuously. |
| Supply Voltage Range | 2.0 V to 5.5 V | 2.0 V to 5.5 V | Both support the same VHC voltage range, allowing use in 3.3 V and 5 V systems. |
| Package | TSSOP-20 | TSSOP-14 | Different pin counts and footprints prevent direct PCB drop-in replacement. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Both meet industrial temperature requirements for reliable operation. |
| Output Drive Current | ±8 mA at 5 V | ±8 mA at 5 V | Determines fan-out capability and ability to drive capacitive or resistive loads. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC244FT | 74VHC74TTR |
|---|---|---|
| Supplier | - | STMicroelectronics |
| Series | 74VHC | 74VHC |
| Part Status | Active | Obsolete |
| Function | - | Set(Preset) and Reset |
| Type | - | D-Type |
| Output Type | 3-State | Complementary |
| Number of Elements | 2 | 2 |
| Number of Bits per Element | 4 | 1 |
| Clock Frequency | - | 115 MHz |
| Max Propagation Delay @ V Max CL | - | 9.3ns @ 5V, 50pF |
| Trigger Type | - | Positive Edge |
| Current - Output High Low | 8mA, 8mA | 8mA, 8mA |
| Voltage - Supply | 2V ~ 5.5V | 2V ~ 5.5V |
| Current - Quiescent (Iq) | - | 2 µA |
| Input Capacitance | - | 7 pF |
| Operating Temperature | -40°C ~ 125°C (TA) | -55°C ~ 125°C (TA) |
| Mounting Type | Surface Mount | Surface Mount |
| Logic Type | Buffer, Non-Inverting | - |
Frequently asked questions
What are the primary functional differences between the 74VHC244FT and the 74VHC74TTR?
The 74VHC244FT is an octal non-inverting buffer/line driver with 3-state outputs, while the 74VHC74TTR is a dual D-type positive-edge-triggered flip-flop with preset and clear. They serve fundamentally different logic functions and are not interchangeable.
Do the 74VHC244FT and 74VHC74TTR share the same package type?
No. The 74VHC244FT is typically supplied in a TSSOP-20 package, whereas the 74VHC74TTR is supplied in a TSSOP-14 package. Pin counts and PCB land patterns differ, preventing direct footprint compatibility.
Can the 74VHC244FT and 74VHC74TTR operate from the same supply voltage range?
Yes. Both devices are members of the VHC logic family and are specified for a nominal supply voltage range of 2.0 V to 5.5 V, with characterized operation at 3.3 V and 5.0 V.
Are the 74VHC244FT and 74VHC74TTR pin-compatible with each other?
No. The 74VHC244FT has 20 pins with eight buffer channels, two output-enable pins, and multiple VCC/GND pins. The 74VHC74TTR has 14 pins with two flip-flop channels, each with D, CLK, PRE, CLR, Q, and Q-bar pins. Pin functions and assignments are entirely different.
Which device is suitable for signal buffering and which for sequential logic?
The 74VHC244FT is intended for signal buffering, line driving, and bus isolation due to its 3-state outputs. The 74VHC74TTR is intended for sequential logic applications such as registers, counters, and toggle functions due to its edge-triggered D-type flip-flop architecture.
Do both devices support 3-state output operation?
No. Only the 74VHC244FT features 3-state outputs controlled by two active-low output-enable pins. The 74VHC74TTR provides complementary Q and Q-bar outputs without a high-impedance state.
Are the 74VHC244FT and 74VHC74TTR directly substitutable in a PCB design?
No. They differ in logic function, pin count, package size, and pinout. Direct substitution is not possible without redesigning the circuit and PCB layout.