STMicroelectronics 74LCX240MTR

Overview

74LCX240MTR from STMicroelectronics is a low-voltage CMOS octal 3-state inverting bus buffer with 5V-tolerant inputs and outputs, designed for 3.3V system interfacing to 5V buses. It delivers 6.5 ns max propagation delay at VCC = 3.0–3.6 V, ±24 mA symmetrical output drive, and operates across 2.0–3.6 V supply range - used in memory address driver circuits and PCI bus interface applications.

For engineers reviewing the 74LCX240MTR datasheet, 74LCX240MTR pinout, 74LCX240MTR application, or 74LCX240MTR equivalent, key selection criteria include 5V tolerance on all I/Os, guaranteed PCI bus levels at 24 mA, power-down protection, balanced tPLH/tPHL delays, and SO-20 package compatibility with standard 74-series 240 logic.

Technical Context

The 74LCX240 implements dual 4-bit inverting 3-state buffers (Group 1: pins 1Y1–1Y4 enabled by 1G; Group 2: 2Y1–2Y4 enabled by 2G), each with independent output enable control. All inputs and outputs feature integrated protection diodes enabling 2 kV HBM ESD immunity and safe operation under 5V signal stress while powered at 3.3V.

Its C2MOS sub-micron process ensures latch-up immunity >500 mA (JESD17), data retention down to 1.5 V, and symmetrical |IOH| = |IOL| ≥ 24 mA at VCC = 3.0–3.6 V - critical for driving terminated transmission lines in mixed-voltage backplanes.

Key Specifications

Pinout & Package

74LCX240MTR is housed in a 20-pin SOIC (Small Outline Integrated Circuit) package per JEDEC MS-013, with 1.27 mm pitch, body width 7.5 mm, and tape-and-reel packaging (T&R) compliant with EIA-481-D.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LVC240APW and SN74LVC240APWR, the 74LCX240MTR uniquely combines 5V I/O tolerance, −55°C to +125°C operation, and power-down protection - making it the only choice for ruggedized mixed-voltage backplane and hot-swap designs requiring full industrial temperature compliance.

Availability

74LCX240MTR is available at Aetrix Electronics and suitable for PCI bus interface, memory address buffering, hot-swappable backplane, and mixed-voltage industrial control applications requiring stable component supply and long-term lifecycle support.

Supply support for 74LCX240MTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in microcontrollers, power management, analog ICs, and discrete components for industrial, automotive, and consumer markets.

The 74LCX logic family was engineered specifically for low-voltage, high-speed 3.3V system interfacing with legacy 5V infrastructure - emphasizing robustness, mixed-voltage compatibility, and industrial temperature reliability.

FAQ

Is 74LCX240MTR compatible with standard 74-series 240 pinout and function?

Yes. The 74LCX240MTR is pin- and function-compatible with the industry-standard 74-series 240 octal inverting buffer, including identical pin numbering, truth table behavior, and active-low output enable control. This allows drop-in replacement in existing 74AC/74ACT designs upgraded to 3.3V operation.

Can 74LCX240MTR safely drive a 5V PCI bus while operating at 3.3V supply?

Yes. Its 5V-tolerant inputs and outputs guarantee PCI bus signaling levels at ±24 mA drive strength when VCC = 3.0–3.6 V. The device meets PCI specification requirements without external components, verified across −55°C to +125°C operating temperature.

What is the maximum recommended load capacitance for maintaining 6.5 ns propagation delay?

The 6.5 ns max tPD is specified with CL = 50 pF and RL = 500 Ω per AC test conditions. For loads exceeding 50 pF, propagation delay increases linearly with capacitance; design margin requires limiting total trace + load capacitance to ≤45 pF to maintain timing compliance at 150 MHz bus rates.

Does 74LCX240MTR require external pull-up or pull-down resistors on unused inputs?

No. Unused inputs may be left floating due to integrated input protection circuitry and low input leakage (±5 µA). However, for noise immunity in high-EMI environments, tying unused inputs to VCC or GND via 10 kΩ resistors is recommended - not required for functionality or DC stability.