onsemi 74LCXZ245MSAX

Overview

74LCXZ245MSAX from Fairchild Semiconductor is a low-voltage, 20-pin bidirectional transceiver with 5V-tolerant I/O, designed for bus interfacing between 2.5V/3.3V logic domains and 5V systems. It features 3-STATE outputs, direction control via T/R input, output enable (OE), 7.0 ns max propagation delay at 3.3V, and ±24 mA drive strength at 3.0V - enabling robust signal translation in mixed-voltage memory and peripheral buses.

For engineers reviewing the 74LCXZ245MSAX datasheet, pinout, applications, or equivalent options, key selection criteria include 5V tolerance on all I/O pins, power-down high-impedance behavior below 1.5V VCC, live insertion support, ESD ratings (2000V HBM), and compatibility with SSOP-20 (JEDEC MO-150) footprint.

Technical Context

The 74LCXZ245MSAX implements eight non-inverting bidirectional buffers with independent OE and T/R control logic, allowing dynamic direction reversal without bus contention. Its CMOS design ensures rail-to-rail 5V-tolerant inputs and outputs while operating from 2.3V to 3.6V VCC, with guaranteed high-impedance state during power-up/down when VCC ≤ 1.5V.

It supports live insertion via inherent power-down high-Z behavior and patented noise/EMI reduction circuitry. Input edge rate tolerance (0–10 ns/V) and low dynamic switching skew (≤1.0 ns) ensure timing integrity in high-speed parallel bus environments such as ISA, PCI-X stubs, and legacy microcontroller expansion interfaces.

Key Specifications

Pinout & Package

74LCXZ245MSAX is packaged in a 20-lead Shrink Small Outline Package (SSOP), JEDEC MO-150 compliant, 5.3 mm wide, with 0.65 mm lead pitch and exposed pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LCXZ245MSAX, the 74LVC245APW lacks native 5V-tolerant outputs and demands external protection, while SN74AVC245DBR offers faster timing but restricts 5V tolerance to inputs only - making 74LCXZ245MSAX uniquely suitable for full bidirectional 5V bus interfacing without added components.

Availability

74LCXZ245MSAX is available at Aetrix Electronics and suitable for memory expansion interfaces, legacy peripheral bridges, hot-swappable module backplanes, and industrial control bus isolation requiring stable component supply and long-term obsolescence management.

Supply support for 74LCXZ245MSAX 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

Fairchild Semiconductor was a U.S.-based designer and manufacturer of analog and mixed-signal ICs, acquired by ON Semiconductor in 2016; its legacy logic portfolio remains widely deployed in industrial and automotive systems.

The 74LCXZ245MSAX belongs to the LCX low-voltage CMOS logic family, engineered specifically for mixed-voltage system interconnect - balancing speed, power efficiency, and robust 5V-tolerant I/O in space-constrained SSOP packaging.

FAQ

What is the maximum operating frequency supported by the 74LCXZ245MSAX?

The 74LCXZ245MSAX does not specify a maximum clock frequency, but its 7.0 ns maximum propagation delay at 3.3V VCC supports reliable operation in bus systems with toggle rates up to approximately 70 MHz under typical load conditions (CL = 50 pF). Actual usable frequency depends on board layout, termination, and capacitive loading - verified via timing analysis using tPHL/tPLH and setup/hold margins from the datasheet.

Does the 74LCXZ245MSAX require external pull-up resistors on the OE pin?

Yes - to ensure predictable high-impedance behavior during power-up or power-down, the OE pin of the 74LCXZ245MSAX must be tied to VCC through a pull-up resistor. The minimum resistance value depends on the driver's current-sourcing capability; Fairchild recommends calculating based on VIH threshold (≥2.0V at VCC = 3.6V) and leakage current limits (±5 µA), typically resulting in 4.7 kΩ–10 kΩ values for most 3.3V systems.

Can the 74LCXZ245MSAX safely interface a 2.5V microcontroller with a 5V EEPROM?

Yes - the 74LCXZ245MSAX supports 2.3V–3.6V VCC operation and has fully 5V-tolerant inputs and outputs. When powered at 2.5V, it correctly translates logic levels between the 2.5V MCU and 5V EEPROM, maintaining VOL ≤ 0.55V and VOH ≥ VCC − 0.2V while driving ±24 mA, satisfying standard TTL and CMOS input thresholds on both sides without external components.

Is the 74LCXZ245MSAX RoHS-compliant and lead-free?

Yes - the 74LCXZ245MSAX is manufactured in a Pb-Free package per JEDEC J-STD-020B, with lead-free terminations and compatible with standard reflow soldering profiles. The "X" suffix in the part number confirms tape-and-reel packaging and RoHS compliance, and the MSA20 package variant uses matte tin plating on leads to meet EU Directive 2011/65/EU requirements.

How does the 74LCXZ245MSAX handle bus contention during direction switching?

The 74LCXZ245MSAX avoids bus contention through strict control of the T/R and OE inputs: when OE is asserted (low), direction changes via T/R occur only after both ports are already enabled, and the device guarantees monotonic output transitions. No internal arbitration or delay is needed - proper external sequencing (OE active before T/R change) ensures glitch-free handover, validated by truth table behavior and skew specification (≤1.0 ns).