Part A
74VHC244FT
Toshiba Halbleiter und Speicher
- Lifecycle
- Active
- Stock
- 2156 Stückzahl
- Package
- TSSOP-20
- Series
- Logic c Puffer, Treiber, Empfänger, Transceiver
Replacement verdict
Not a drop-in replacement
The 74VHC244FT and 74VHCT574AMTC are not functionally interchangeable. The 74VHC244FT is a quad non-inverting buffer with 3-state outputs, while the 74VHCT574AMTC is an octal D-type flip-flop with 3-state outputs. They differ in logic function, channel count, package type, and input threshold technology, making direct substitution impossible without circuit redesign.
Different logic function
Different channel count
Different package type
Different input threshold technology
Parts at a glance
Part B
74VHCT574AMTC
Fairchild Halbleiter
- Lifecycle
- Active
- Stock
- 105 Stückzahl
- Series
- Logik für 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 | 74VHCT574AMTC | Why it matters |
|---|---|---|---|
| Logic Function | Octal Buffer/Line Driver with 3-State Outputs | Octal D-Type Flip-Flop with 3-State Outputs | These are fundamentally different logic functions; a buffer passes signals combinationally while a flip-flop latches data on a clock edge, so they are not functionally interchangeable. |
| Logic Family | VHC (Very High-Speed CMOS) | VHCT (Very High-Speed CMOS with TTL-Compatible Inputs) | VHCT inputs are TTL-voltage compatible while VHC inputs are CMOS-level, affecting direct interfacing with 5 V TTL logic. |
| Number of Flip-Flops / Channels | 8 buffers (2 groups of 4) | 8 D-type flip-flops | Channel count and internal organization determine how many signals can be handled and how they are grouped. |
| Clock Input | None | Yes (common clock, positive-edge triggered) | A clocked device stores data synchronously, whereas a buffer has no clock and cannot hold state. |
| Output Type | 3-State | 3-State | Both offer high-impedance output states for bus sharing, but the control mechanism differs (enable vs. output enable plus clock). |
| Propagation Delay (typical) | ~3.5 ns at 5 V | ~5.6 ns at 5 V | Timing differences affect maximum operating frequency and signal integrity in synchronous designs. |
| Supply Voltage Range | 2.0 V to 5.5 V | 4.5 V to 5.5 V | The narrower supply range of the VHCT device limits low-voltage operation compared to the VHC part. |
| Input Compatibility | CMOS-level inputs | TTL-level compatible inputs | TTL-compatible inputs allow direct connection to 5 V TTL logic without additional level shifting. |
| Package | TSSOP-20 | TSSOP-20 | Matching package and pin count can simplify PCB layout, but pin functions differ between the two devices. |
| Operating Temperature Range | -40 °C to +85 °C | -40 °C to +85 °C | Identical temperature ratings mean both are suitable for the same industrial environments. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | 74VHC244FT | 74VHCT574AMTC |
|---|---|---|
| Supplier | - | Rochester Electronics, LLC |
| Series | 74VHC | 74VHCT |
| Part Status | Active | Active |
| Function | - | Standard |
| Type | - | D-Type |
| Output Type | 3-State | Tri-State, Non-Inverted |
| Number of Elements | 2 | 1 |
| Number of Bits per Element | 4 | 8 |
| Clock Frequency | - | 130 MHz |
| Max Propagation Delay @ V Max CL | - | 10.4ns @ 5V, 50pF |
| Trigger Type | - | Positive Edge |
| Current - Output High Low | 8mA, 8mA | 8mA, 8mA |
| Voltage - Supply | 2V ~ 5.5V | 4.5V ~ 5.5V |
| Current - Quiescent (Iq) | - | 4 µA |
| Input Capacitance | - | 4 pF |
| Operating Temperature | -40°C ~ 125°C (TA) | -40°C ~ 85°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 74VHCT574AMTC?
The 74VHC244FT is an octal non-inverting buffer/line driver with 3-state outputs, while the 74VHCT574AMTC is an octal D-type flip-flop with 3-state outputs. The 74VHC244FT provides combinational buffering, whereas the 74VHCT574AMTC provides edge-triggered storage of data.
Are the 74VHC244FT and 74VHCT574AMTC pin-to-pin compatible?
No. The 74VHC244FT is typically supplied in a TSSOP-20 package, and the 74VHCT574AMTC is supplied in a TSSOP-20 package as well, but their pin functions differ. The 74VHC244FT has two active-low output enable pins (1OE and 2OE) and no clock pin, while the 74VHCT574AMTC has a clock input, an output enable, and no separate per-nibble enable pins. They are not direct drop-in replacements.
Can the 74VHC244FT and 74VHCT574AMTC operate from the same power supply voltage?
Yes. Both devices are specified for a nominal 5 V supply, with recommended operating ranges typically from 4.5 V to 5.5 V. However, the 74VHCT574AMTC includes TTL-compatible input thresholds, while the 74VHC244FT uses CMOS-compatible input thresholds.
What is the difference in input threshold compatibility between the 74VHC244FT and the 74VHCT574AMTC?
The 74VHC244FT has CMOS-level inputs, meaning its switching thresholds are proportional to VCC. The 74VHCT574AMTC has TTL-level inputs, allowing it to accept 5 V TTL logic levels directly while operating at 5 V. This makes the 74VHCT574AMTC more suitable for interfacing with legacy TTL logic without additional level shifting.
Do both devices feature 3-state outputs?
Yes. Both the 74VHC244FT and the 74VHCT574AMTC provide 3-state outputs, allowing their outputs to be placed in a high-impedance state for bus sharing. On the 74VHC244FT, the outputs are controlled by two active-low output enable pins. On the 74VHCT574AMTC, the outputs are controlled by a single active-low output enable pin.
Which device is better suited for capturing and holding data?
The 74VHCT574AMTC is better suited for capturing and holding data because it contains octal D-type flip-flops that latch data on the rising edge of the clock signal. The 74VHC244FT does not have storage elements and only buffers signals continuously while enabled.
Are the drive strengths of the 74VHC244FT and 74VHCT574AMTC the same?
Both devices are specified with standard CMOS output drive typically capable of sourcing and sinking 8 mA at 5 V, based on published datasheet parameters for the VHC and VHCT families. Exact drive current should always be verified against the specific manufacturer datasheet for the exact part number and package.
Can the 74VHC244FT be used to replace the 74VHCT574AMTC in an existing design?
No, not directly. The 74VHC244FT lacks the clocked D-type flip-flop function of the 74VHCT574AMTC. Replacing the 74VHCT574AMTC with the 74VHC244FT would remove the data storage capability and change the timing behavior of the circuit. A functional redesign would be required.