When your MCU cannot drive a full address bus alone, you reach for a bus buffer. The 74HC244 and 74HCT244 are the industry-standard answer — but choosing the wrong variant can break your interface. This guide covers specs, pinouts, application scenarios, and the key differences between both 74HCT244 Logic ICs so you can select the right part the first time.
Key Takeaways
- 74HCT244 Logic ICs are 20-pin octal bus buffers with two independent 4-bit enable groups.
- The HCT variant accepts TTL-level inputs and requires a 4.5–5.5 V supply.
- The HC variant operates from 2.0–6.0 V and suits modern 3.3 V CMOS designs.
- Both variants source and sink up to 7.8 mA per output.
- Propagation delay is approximately 7–8 ns at 5 V supply.
- Operating temperature covers −40 °C to +125 °C for industrial and automotive use.
- Packages include DIP-20, SOIC-20, and TSSOP-20 for through-hole and SMT designs.
What Are 74HCT244 Logic ICs?
The 74HC244 and 74HCT244 are high-speed CMOS octal buffer/line driver ICs. Engineers also call them octal bus buffers or octal tri-state drivers. Each device contains eight non-inverting buffer stages with tri-state outputs. Two active-low output enable pins (OE) control the outputs in two independent 4-bit groups.
When OE is LOW, outputs follow their respective inputs. When OE is HIGH, all outputs enter a high-impedance state. This tri-state capability allows multiple devices to share a common bus safely. Furthermore, the 74HC244 and 74HCT244 are pin-compatible replacements for older TTL and LSTTL bus drivers.
Key Features of 74HCT244 Logic ICs
High-Speed CMOS Technology in 74HCT244 Logic ICs
Both devices use advanced CMOS silicon processes. This delivers propagation delays of 7–8 ns at 5 V supply. As a result, they suit clock rates far beyond typical bus applications. In addition, quiescent current stays below 80 µA, reducing power consumption significantly.
Tri-State Output Control
Two independent active-low enable pins control the outputs. Pin 1OE controls outputs 1Y1–1Y4. Pin 2OE controls outputs 2Y1–2Y4. Therefore, designers can manage two separate 4-bit data paths independently. This is essential for bus multiplexing and data direction control.
High Output Drive Current
Each output sources or sinks 7.8 mA. This exceeds older CMOS families by a factor of three or more. For example, one 74HC244 drives four standard CMOS inputs simultaneously. As a result, bus fanout increases without the need for additional buffers.
TTL-Compatible Input Thresholds in 74HCT244 Logic ICs
The HCT variant uses input thresholds matching the TTL logic family. A logic HIGH is any voltage above 2.0 V. A logic LOW is any voltage below 0.8 V. Therefore, 74HCT244 Logic ICs interface directly with 74LS, 74AS, and similar TTL families. No external level-shifting circuits are required.
Wide Voltage Range in 74HC244
The HC variant operates across a supply range of 2.0–6.0 V. This makes it suitable for 3.3 V microcontrollers and 5 V peripherals in the same system. Also, it works in battery-powered applications where supply voltage varies over time.
Technical Specifications for 74HCT244 Logic ICs
The table below lists key electrical parameters for both variants. Always consult the manufacturer datasheet for final design verification.
| Parameter | Symbol | 74HC244 | 74HCT244 | Unit |
| Supply Voltage | VCC | 2.0 – 6.0 | 4.5 – 5.5 | V |
| Input High Voltage | VIH | 3.5 V (@ 5 V) | 2.0 V | V |
| Input Low Voltage | VIL | 1.5 V (@ 5 V) | 0.8 V | V |
| Output High Current | IOH | −7.8 mA | −7.8 mA | mA |
| Output Low Current | IOL | 7.8 mA | 7.8 mA | mA |
| Propagation Delay | tpd | ≈ 7 ns (@ 5 V) | ≈ 8 ns (@ 5 V) | ns |
| Output Enable Time | ten | ≈ 5 ns | ≈ 6 ns | ns |
| Quiescent Current | ICC | 80 µA (max) | 80 µA (max) | µA |
| Operating Temperature | TA | −40 to +125 | −40 to +125 | °C |
| Package Options | — | DIP-20, SOIC-20, TSSOP-20 | DIP-20, SOIC-20, TSSOP-20 | — |
Propagation delay (tpd) measures input to output with a 50 pF load. Output enable time (ten) measures the delay from OE assertion to valid output. Both devices meet JEDEC standard JESD8C for CMOS logic interfacing. However, the HCT variant is not specified below 4.5 V — do not operate it at 3.3 V.
74HCT244 Logic ICs Pinout and Package Details
Both HC244 and HCT244 share an identical 20-pin dual in-line layout. This guarantees drop-in pin compatibility between the two variants. The pinout follows the standard established by original TTL bus buffer ICs.
| Pin(s) | Name | Type | Function |
| 1 | 1OE | Input | Output Enable Group 1 — active LOW |
| 2, 4, 6, 8 | 1A1–1A4 | Input | Data inputs, Group 1 |
| 3, 5, 7, 9 | 1Y1–1Y4 | Output | Buffered tri-state outputs, Group 1 |
| 10 | GND | Power | Ground |
| 11, 13, 15, 17 | 2Y4–2Y1 | Output | Buffered tri-state outputs, Group 2 |
| 12, 14, 16, 18 | 2A4–2A1 | Input | Data inputs, Group 2 |
| 19 | 2OE | Input | Output Enable Group 2 — active LOW |
| 20 | VCC | Power | Supply voltage |
DIP-20 suits through-hole prototyping and hand assembly. SOIC-20 is the most common SMT package for production PCBs. TSSOP-20 reduces board area in space-constrained designs. Finally, all three packages deliver identical electrical performance.
Configuration Options for 74HCT244 Logic ICs
Output Enable Configurations
Tying both OE pins to GND enables all eight outputs permanently. This suits unidirectional buffer applications with no bus-sharing requirements. Alternatively, connecting OE pins to a logic controller enables dynamic tri-state switching. For example, an MCU GPIO can control each enable group independently.
Cascading 74HCT244 Logic ICs for Wider Buses
Two 74HC244 devices can cascade to buffer a 16-bit bus. Connect data inputs in parallel and control each device with separate OE signals. As a result, each 8-bit segment activates independently. This is common in memory controller and FPGA interface designs.
Package and Tape-and-Reel Options
SOIC-20 and TSSOP-20 are available in tape-and-reel format for automated SMT assembly. DIP-20 is available in tube packaging. LCSC Electronics stocks multiple variants from leading manufacturers. In addition, cut-tape options are available for low-volume procurement.
Common Application Scenarios for 74HCT244 Logic ICs
Microcontroller Address Bus Buffering
Microcontrollers have limited output drive current per pin. A 74HC244 buffers the address bus between the MCU and multiple peripherals. For example, it drives four SRAM chips simultaneously from a single MCU port. First, the MCU asserts the address; next, the buffer drives the downstream bus with sufficient current.
FPGA I/O Expansion and Level Shifting with 74HCT244 Logic ICs
FPGAs commonly use 3.3 V I/O standards. Legacy memory or peripheral devices may require 5 V TTL signals. The 74HCT244 bridges these two domains safely at a 5 V supply. In addition, it absorbs bus contention during arbitration between multiple masters.
Bus Isolation in Test and Debug Systems
Tri-state outputs allow safe isolation between bus segments. For instance, a debug probe can share a data bus using OE control. Therefore, system engineers can isolate subsections during hardware bring-up. Also, this prevents bus conflicts during boundary-scan testing.
Industrial PLC and Panel I/O Interfaces
Industrial programmable logic controllers mix TTL and CMOS signals. The 74HCT244 handles direct interfacing at a 5 V supply. It also tolerates temperature extremes common in factory automation environments. As a result, it is a reliable choice for robust industrial I/O designs.
Manufacturing and Procurement of 74HCT244 Logic ICs
Key Manufacturers
Multiple manufacturers second-source the 74HC244 and 74HCT244. Leading suppliers include Texas Instruments, NXP Semiconductors, ON Semiconductor, and Nexperia. All produce devices meeting the same JEDEC electrical and pinout standard. Therefore, cross-manufacturer substitution is straightforward in most designs.
Testing and Quality Standards for 74HCT244 Logic ICs
Manufacturers test devices to JEDEC JESD8C for CMOS logic compliance. Industrial-grade parts meet AEC-Q100 for automotive temperature and reliability. First, the manufacturer performs wafer-level testing. Second, package-level testing verifies propagation delay, drive current, and leakage. Finally, tape-and-reel parts go through automated optical inspection before shipping.
Procurement at LCSC Electronics
LCSC Electronics stocks 74HC244 and 74HCT244 Logic ICs from multiple brands. DIP-20, SOIC-20, and TSSOP-20 packages are all available. Cut-tape, tape-and-reel, and tube formats suit different order volumes. In addition, LCSC provides datasheets, reference designs, and LCSC part numbers for BOM integration.
74HC244 vs 74HCT244: Which 74HCT244 Logic IC Should You Choose?
Choosing between the HC and HCT variants depends on your supply voltage and logic family. The table below summarises the key engineering decision points.
| Feature | 74HC244 | 74HCT244 | Best Choice |
| Supply Voltage Range | 2.0 – 6.0 V | 4.5 – 5.5 V | HC for wide range |
| TTL Input Compatibility | No | Yes (VIH = 2 V) | HCT for legacy TTL |
| 3.3 V System Support | Yes | No | HC for modern CMOS |
| Propagation Delay @ 5 V | ~7 ns | ~8 ns | HC for speed-critical use |
| Mixed TTL / CMOS Interface | Limited | Full | HCT for 5 V bus bridging |
| Low-Power Battery Systems | Yes | No | HC for low-voltage apps |
| Drop-in Pin Compatibility | Yes | Yes | Either — same pinout |
In summary, choose 74HCT244 Logic ICs when your system uses 5 V TTL signals. Choose 74HC244 for modern 3.3 V CMOS or wide-voltage systems. Both variants are pin-compatible, so switching between them requires no PCB changes.
Frequently Asked Questions About 74HCT244 Logic ICs
What Is the Difference Between 74HC244 and 74HCT244 Logic ICs?
The HC and HCT variants serve different logic families. The HC variant accepts CMOS-level inputs with a HIGH threshold of 3.5 V at 5 V supply. It also operates from 2.0–6.0 V, making it ideal for modern 3.3 V designs. The HCT variant, by contrast, accepts TTL-level inputs with a HIGH threshold of just 2.0 V. This makes it a direct drop-in for legacy 5 V TTL systems using 74LS, 74AS, or similar families. However, the HCT variant only operates between 4.5–5.5 V — it is not suitable for 3.3 V supplies. Both variants are pin-compatible and share identical drive current and package options.
Can I Use a 74HCT244 at 3.3 V?
No. The 74HCT244 requires a supply voltage of at least 4.5 V. Operating it below this threshold causes unreliable output behaviour and undefined logic levels. For 3.3 V designs, use the 74HC244 instead. The HC variant operates reliably from 2.0–6.0 V and delivers the same drive current and propagation delay performance. If you are migrating from a 5 V TTL system to a 3.3 V CMOS design, switching from 74HCT244 to 74HC244 requires no PCB changes, only the part number changes.
How Much Current Can 74HCT244 Logic ICs Drive?
Both variants source up to 7.8 mA (IOH) and sink up to 7.8 mA (IOL) per output. This exceeds older CMOS families by a factor of three or more. In practice, one device drives four standard CMOS inputs simultaneously without additional buffering. For heavier bus loads, cascading two devices across a 16-bit bus is a common solution. The drive current specification holds across the full operating temperature range of −40 °C to +125 °C. Always verify fan-out calculations against the target device’s input current in the manufacturer datasheet.
What Package Should I Choose for 74HCT244 Logic ICs in SMT Assembly?
SOIC-20 is the standard SMT choice and the most practical for most production designs. Its wider pin pitch is easy to hand-solder and inspect visually. TSSOP-20 saves significant board area in dense PCB layouts and suits high-density designs. DIP-20 suits prototyping and through-hole designs only. All three packages deliver identical electrical performance — the choice is purely mechanical. SOIC-20 and TSSOP-20 are available in tape-and-reel format for automated pick-and-place assembly. DIP-20 is available in tube packaging for low-volume or through-hole builds.
Are 74HCT244 Logic ICs from Different Manufacturers Interchangeable?
Yes. Both are standard logic devices with full cross-manufacturer compatibility. Texas Instruments, NXP Semiconductors, ON Semiconductor, and Nexperia all produce 74HC244 and 74HCT244 parts. All manufacturers follow the same JEDEC pinout and electrical standard. As a result, substituting one brand for another requires no schematic or PCB changes. However, always review the target manufacturer’s datasheet before finalising your BOM. Minor differences in propagation delay, output slew rate, or ESD ratings can exist between manufacturers, even within the same logic family.
Find What You Need on LCSC
Finding the right 74HCT244 Logic ICs for your design is straightforward on LCSC. LCSC stocks 74HC244 and 74HCT244 parts from Texas Instruments, NXP, Nexperia, and more. You can filter by package, manufacturer, and order format to match your BOM exactly. Browse the full 74HCT244 Logic ICs catalogue on LCSC today.
