onsemi 74LCX245SJX

Overview

74LCX245SJX from ON Semiconductor (formerly Fairchild) is a low-voltage bidirectional transceiver with 5V-tolerant inputs and outputs, designed for bus interface between 2.3V–3.6V logic domains and 5V systems. It features 8-bit non-inverting data flow, 3-STATE outputs controlled by OE and T/R pins, 7.0ns max propagation delay at VCC = 3.3V, ±24mA drive capability at VCC = 3.0V, and operates from –40°C to +85°C.

For engineers reviewing the 74LCX245SJX datasheet, pinout, applications, or equivalent options, key selection criteria include 5V tolerance in mixed-voltage buses, live-insertion support, power-down high-impedance behavior, and compatibility with SOP-20 (EIAJ TYPE II, 5.3mm wide) packaging for legacy board designs.

Technical Context

The 74LCX245SJX implements dual-directional bus buffering using CMOS technology optimized for low-voltage operation while maintaining robust 5V signal interoperability. Its T/R input selects data direction (A→B or B→A), and OE enables/disables both ports simultaneously into high-impedance states - critical for hot-swap and shared-bus arbitration.

It supports live insertion/withdrawal via controlled power-up sequencing: OE must be pulled up to VCC during power transitions to ensure defined high-Z state. The device exhibits latch-up immunity >500mA and ESD protection exceeding 2000V (HBM), making it suitable for industrial backplane and peripheral interface applications where voltage domain bridging and reliability are essential.

Key Specifications

Pinout & Package

74LCX245SJX is packaged in a 20-lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm wide (package code M20D), with gull-wing leads and standard JEDEC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LCX245SJX, SN74LVC245APWR extends low-voltage operation down to 1.65V and offers slightly faster timing, while 74ALVC245MTCX delivers significantly reduced propagation delay but mandates a different package footprint - neither is pin-compatible with the SOP-20 74LCX245SJX without layout changes.

Availability

74LCX245SJX is available at Aetrix Electronics and suitable for industrial backplane interfaces, embedded controller expansion buses, hot-swappable module interconnects, and legacy system upgrade bridges requiring stable component supply and long-term obsolescence management.

Supply support for 74LCX245SJX 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 leader in intelligent power and sensing solutions, delivering high-performance semiconductor components for automotive, industrial, cloud computing, and consumer applications.

The 74LCX family was developed to address mixed-voltage system interfacing needs in late-1990s industrial and telecom equipment, emphasizing robust 5V tolerance, low static power, and reliable hot-swap operation in mission-critical bus architectures.

FAQ

What is the maximum recommended operating voltage for 74LCX245SJX inputs and outputs?

The 74LCX245SJX supports DC input and output voltages from –0.5V to +5.5V regardless of VCC level, enabling safe connection to 5V signal sources and sinks. This 5V tolerance is maintained across the full operating temperature range (–40°C to +85°C) and does not require external clamping diodes or series resistors. Always observe absolute maximum ratings: VI and VO must not exceed –0.5V to +7.0V under any condition.

Can 74LCX245SJX operate with a 2.5V supply voltage?

Yes, 74LCX245SJX is fully specified for VCC = 2.5V ± 0.2V, with guaranteed AC performance including 8.4ns max propagation delay (tPHL/tPLH), 10.5ns max output enable time (tPZL/tPZH), and ±8mA output drive. DC parameters such as VIH (1.7V min), VIL (0.7V max), and ICC (10µA max) are also validated at this voltage, making it suitable for 2.5V system integration without derating.

What is the correct power-up sequence to avoid bus contention with 74LCX245SJX?

To prevent bus contention during power-up, OE must be held HIGH (i.e., tied to VCC via a pull-up resistor) until VCC reaches its final regulated value. The minimum pull-up resistance is determined by the current-sourcing capability of the driving circuit; typical values range from 4.7kΩ to 10kΩ. This ensures both A and B ports remain in high-impedance state until system initialization completes and OE is actively driven LOW.

Is 74LCX245SJX compatible with lead-free soldering processes?

Yes, 74LCX245SJX is lead-free and complies with JEDEC J-STD-020B reflow profile requirements. Its M20D SOP package is qualified for peak reflow temperatures up to 260°C (per JEDEC Level 3 moisture sensitivity), and the device undergoes rigorous qualification testing including thermal cycling, highly accelerated stress testing (HAST), and solder heat resistance verification to ensure reliability in RoHS-compliant manufacturing.

Does 74LCX245SJX support hot-swap functionality in backplane applications?

Yes, 74LCX245SJX explicitly supports live insertion/withdrawal when OE is properly biased to VCC during power transitions. Its power-down high-impedance feature ensures all I/Os enter a defined tri-state condition before VCC stabilizes, eliminating risk of backfeeding or bus contention. This behavior is verified per JEDEC standards and documented in Fairchild Application Note AN-4012 for backplane interface design.