onsemi 74LCX245WMX

Overview

74LCX245WMX from ON Semiconductor (formerly Fairchild) is a low-voltage bidirectional transceiver IC designed for bus interface between 2.5V/3.3V logic domains and 5V systems. It features 5V-tolerant inputs/outputs, 2.3V–3.6V V_CC operation, 7.0 ns max propagation delay at 3.3V, ±24 mA output drive at 3.0V, and 3-STATE bidirectional control via OE and T/R pins. It is used in mixed-voltage motherboard data buses and peripheral interconnects.

For engineers reviewing the 74LCX245WMX datasheet, pinout, applications, or equivalent options, key selection criteria include 5V tolerance with sub-3.6V supply, bidirectional flow direction control, high-speed 3-STATE enable/disable timing, and SOIC-20 package compatibility for legacy board upgrades.

Technical Context

The 74LCX245WMX implements eight non-inverting bidirectional buffers with independent 3-STATE control per port. Direction is determined by the T/R input, while OE enables or disables both A and B ports simultaneously into high-impedance states. Its advanced CMOS process ensures high speed with low power dissipation.

It supports live insertion/withdrawal when OE is pulled up to V_CC, and meets stringent ESD requirements (>2000V HBM). Absolute maximum ratings include 7.0V on I/O pins and –0.5V to +7.0V V_CC, enabling robust interfacing across voltage domains without level-shifting circuitry.

Key Specifications

Pinout & Package

74LCX245WMX is housed in a 20-lead Small Outline Integrated Circuit (SOIC), JEDEC MS-013, 0.300" wide (M20B), with standard gull-wing leads and pin 1 indicator notch. The package is lead-free and RoHS-compliant per JEDEC J-STD-020B.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bidirectional transceiver applications.

Compared with SN74LVC245APWR and 74ALVC245MTCX, the 74LCX245WMX uniquely balances 5V I/O tolerance, 7 ns speed, and 10 µA quiescent current in a standard SOIC-20 footprint - making it optimal for cost-sensitive, mixed-voltage industrial upgrades where layout reuse is mandatory.

Availability

74LCX245WMX is available at Aetrix Electronics and suitable for industrial PLC backplanes, embedded memory expansion interfaces, and automotive infotainment subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for 74LCX245WMX 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor solutions for automotive, industrial, cloud computing, and IoT applications.

The 74LCX family was developed to enable seamless interoperability between emerging low-voltage logic and legacy 5V systems, targeting bus interface, memory expansion, and mixed-rail board-level integration.

FAQ

What is the maximum clock frequency supported by the 74LCX245WMX in a data bus application?

The 74LCX245WMX does not operate on a clock signal-it is an asynchronous transceiver. Its usable data rate depends on propagation delay and system timing margins. With a max t_PD of 7.0 ns at 3.3V, it supports reliable bidirectional bus toggling up to approximately 70 MHz in well-terminated, low-skew layouts. Actual achievable frequency must be verified per PCB stackup, trace length, and load capacitance using the device's AC electrical characteristics table.

Can the 74LCX245WMX be used to interface a 1.8V microcontroller to a 5V sensor?

No-the 74LCX245WMX requires V_CC between 2.3V and 3.6V and is not rated for 1.8V operation. Its inputs are 5V-tolerant, but the core logic and outputs are not functional below 2.3V. For 1.8V-to-5V translation, consider the 74LVC245 or similar LVC-family devices with 1.65V–3.6V V_CC range and 5V-tolerant inputs-though outputs would still require clamping for 5V bus driving.

Is the 74LCX245WMX pin-compatible with other 74-series transceivers in SOIC-20 packages?

Yes-the 74LCX245WMX uses the industry-standard 20-pin SOIC pinout defined for 74-series octal transceivers (e.g., 74LS245, 74HC245). Pin 1 (OE), pins 2–9 (A0–A7), pin 10 (GND), pins 11–18 (B0–B7), pin 19 (T/R), and pin 20 (V_CC) match the functional mapping. However, voltage ratings and timing differ significantly-direct substitution requires validation of V_CC, I/O tolerance, and timing margins in the target design.

Does the 74LCX245WMX require external pull-up resistors on OE or T/R inputs?

OE must be actively driven or pulled up to V_CC (not left floating) to ensure defined high-impedance behavior during power-up. A pull-up resistor is recommended if OE is not actively controlled-minimum value depends on driver strength but typically 4.7 kΩ suffices. T/R may be tied HIGH or LOW permanently or driven by logic; no pull-up is required unless open-drain control is used.

What is the thermal performance of the 74LCX245WMX in continuous operation at 3.3V and 24 mA per output?

At V_CC = 3.3V and full ±24 mA drive on all 8 outputs, total DC power dissipation is ~120 mW (calculated from V_CC × I_CC plus I²R losses). In a standard SOIC-20 package on a 2-layer PCB with 1 in² copper pour, junction temperature rise is typically <25°C above ambient-well within the 150°C max rating. Derating is advised above 70°C ambient or with limited airflow.