onsemi MC74VHCT244AMELG

Overview

MC74VHCT244AMELG from onsemi is a dual 4-bit non-inverting 3-state buffer/line driver optimized for 5 V TTL-compatible operation with CMOS power efficiency. It features 8-channel bidirectional buffering, ±8 mA output drive at V_CC = 5 V, propagation delay of 6.5 ns (typ) at 50 pF load, and operates from −40 °C to +85 °C. It is used in address/data bus isolation and driving high-capacitance transmission lines in industrial control systems.

For engineers reviewing the MC74VHCT244AMELG datasheet, pinout, applications, or equivalent options, key selection criteria include 3-state enable timing, input hysteresis for noise immunity, rail-to-rail output swing, and compatibility with legacy 5 V TTL logic families in mixed-voltage board designs.

Technical Context

The MC74VHCT244AMELG implements two independent 4-bit buffers, each with separate active-low output-enable (OE) controls. Each channel uses CMOS input structure with TTL-level thresholds (V_IL = 0.8 V max, V_IH = 2.0 V min) and push-pull CMOS outputs capable of sourcing/sinking ±8 mA.

It supports hot insertion via I^OFF protection (input/output isolation when powered down), meets JEDEC JESD78 Class II latch-up immunity (>250 mA), and exhibits 1.5 V typical input hysteresis-critical for reliable operation in noisy industrial environments.

Key Specifications

Pinout & Package

MC74VHCT244AMELG is housed in a 20-pin SOIC (Small Outline Integrated Circuit) package with 0.300-inch body width and 1.27 mm lead pitch. The package complies with JEDEC MS-013 and is RoHS-compliant with matte tin lead finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar non-inverting 3-state buffer applications.

Compared with SN74HCT244N and 74VHC244M, the MC74VHCT244AMELG delivers superior timing performance, guaranteed hot-swap capability via I^OFF, and full industrial temperature qualification-making it the preferred choice for mission-critical embedded control interfaces.

Availability

MC74VHCT244AMELG is available at Aetrix Electronics and suitable for industrial PLC backplanes, automotive body control modules, and factory automation I/O expansion requiring stable component supply, long-term lifecycle support, and guaranteed RoHS compliance.

Supply support for MC74VHCT244AMELG includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

onsemi is a global semiconductor leader delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MC74VHCT244AMELG belongs to onsemi's VHCT logic family, engineered specifically for seamless interoperability between 5 V TTL systems and modern low-power CMOS designs in harsh-environment industrial control.

FAQ

What is the maximum clock frequency supported by MC74VHCT244AMELG in bus applications?

The MC74VHCT244AMELG is not a clocked device-it has no internal clock and functions as a combinational buffer. Its 6.5 ns typical propagation delay supports reliable operation in asynchronous 100 MHz bus systems with adequate setup/hold margins. For synchronous timing analysis, designers must account for worst-case t_PLH/t_PHL (8.5 ns max) and load capacitance. The MC74VHCT244AMELG does not impose a fundamental frequency limit but constrains maximum data rate based on trace length and fanout.

Does MC74VHCT244AMELG support mixed-voltage operation between 3.3 V and 5 V domains?

Yes-the MC74VHCT244AMELG accepts 3.3 V logic inputs reliably due to its TTL-compatible input thresholds (V_IH = 2.0 V min, V_IL = 0.8 V max), while its outputs swing rail-to-rail at 5 V when V_CC = 5 V. This allows safe interfacing between 3.3 V microcontrollers and 5 V peripherals without external level shifters, provided the 3.3 V device can tolerate 5 V inputs (or is 5 V tolerant). The MC74VHCT244AMELG itself is not 5 V-tolerant on inputs when V_CC < 5 V.

Is MC74VHCT244AMELG pin-compatible with standard 74HCT244 devices?

Yes-the MC74VHCT244AMELG uses the industry-standard 20-pin SOIC footprint and identical pin assignment as the 74HCT244 family, including matching input/output and OE pin locations. Electrical behavior-including propagation delay, drive strength, and input thresholds-is closely aligned, making it a drop-in replacement in most 5 V TTL-interfaced designs. Always verify timing margins and thermal derating in high-density layouts before substitution.

What is the purpose of the I^OFF feature in MC74VHCT244AMELG?

The I^OFF feature in MC74VHCT244AMELG disables all input and output circuits when V_CC = 0 V, preventing current backflow from live system buses into unpowered sections. This protects downstream components during hot-swap events, partial power-down, or firmware recovery sequences. It is especially valuable in modular I/O systems where card insertion/removal occurs under power. The MC74VHCT244AMELG guarantees I^OFF behavior per JEDEC JESD8-7A, distinguishing it from non-I^OFF variants like 74VHC244.

How does MC74VHCT244AMELG handle noise in industrial environments?

The MC74VHCT244AMELG incorporates 1.5 V typical input hysteresis, significantly exceeding standard CMOS thresholds, to reject EMI-induced glitches on long cables or near motor drives. Combined with dedicated GND/V_CC pins and low-output-impedance drive (±8 mA), it maintains clean signal edges even under 50 pF capacitive loading. Its −40 °C to +85 °C qualification and JESD78 Class II latch-up immunity further ensure robustness in factory-floor deployments. The MC74VHCT244AMELG is explicitly designed for such demanding settings.