onsemi 74LCXZ245SJX

Overview

74LCXZ245SJX 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 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 capability at 3.0V - enabling robust signal translation in mixed-voltage backplanes and memory subsystems.

For engineers reviewing the 74LCXZ245SJX datasheet, pinout, applications, or equivalent options, key selection factors 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 JEDEC-compliant SOP-20 (M20D) packaging.

Technical Context

The 74LCXZ245SJX implements eight non-inverting bidirectional buffers with independent OE and T/R control logic, allowing dynamic direction switching 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 functionality across –40°C to +85°C.

During power-up/down (VCC ≤ 1.5V), all I/O pins enter a high-impedance state automatically - eliminating glitching and back-driving risks in hot-swap or partial-power scenarios. The device integrates patented noise/EMI reduction circuitry and meets latch-up immunity >500 mA per JEDEC JESD78.

Key Specifications

Pinout & Package

Pb-Free 20-Lead Small Outline Package (SOP), EIAJ TYPE II, 5.3 mm wide (Package Number M20D).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74LCXZ245SJX, the Nexperia 74LVC245APW offers faster propagation but no guaranteed high-Z during VCC ramp, while TI's SN74AVC245DGVR adds Ioff protection but relies on external circuitry for glitch-free hot-swap - making 74LCXZ245SJX uniquely suited for uncontrolled power sequencing in modular hardware.

Availability

74LCXZ245SJX is available at Aetrix Electronics and suitable for PCI bus interface, memory subsystem translation, and hot-swappable backplane module applications requiring stable component supply, long-term lifecycle support, and Pb-free compliance.

Supply support for 74LCXZ245SJX 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 analog and power IC manufacturer acquired by ON Semiconductor in 2016; its legacy logic portfolio remains widely deployed in industrial and telecom infrastructure.

The 74LCXZ245SJX belongs to the LCX low-voltage CMOS logic family, engineered specifically for mixed-voltage bus interfacing in telecom backplanes, storage subsystems, and modular computing where 5V tolerance and power-sequence resilience are mandatory.

FAQ

What is the maximum operating temperature range for the 74LCXZ245SJX?

The 74LCXZ245SJX is rated for free-air operating temperatures from –40°C to +85°C, as specified in the Recommended Operating Conditions table of the Fairchild datasheet DS500362. This range supports deployment in industrial control cabinets, telecom equipment enclosures, and outdoor embedded systems without derating. All DC and AC electrical characteristics - including propagation delay, drive strength, and leakage - are guaranteed across this full temperature span.

Does the 74LCXZ245SJX require external pull-up resistors on OE or T/R inputs?

Yes - the 74LCXZ245SJX OE input must be tied to VCC through a pull-up resistor during power-up/down to ensure predictable high-impedance behavior, as noted in Fairchild's Application Note (Note 1, DS500362). The minimum resistor value depends on the driver's current-sourcing capability; typical values range from 4.7 kΩ to 10 kΩ. T/R may be driven directly but should never float - unused T/R pins must be held HIGH or LOW per Note 5.

Can the 74LCXZ245SJX safely interface a 2.5V microcontroller with a 5V UART peripheral?

Yes - the 74LCXZ245SJX supports 2.5V VCC operation with full 5V tolerance on all A/B I/O pins, making it suitable for bidirectional UART signal translation (TX/RX/RTS/CTS). Its 7.0 ns max propagation delay introduces negligible latency, and the ±24 mA drive at 2.5V ensures clean edge rates into typical UART line loads. However, direction control (T/R) must be managed externally - e.g., via MCU GPIO - since UART is inherently half-duplex in many implementations.

Is the 74LCXZ245SJX pin-compatible with other 20-pin transceivers like the 74LCX245?

No - the 74LCXZ245SJX is not pin-compatible with the standard 74LCX245. While both are 20-pin transceivers, the 74LCXZ245SJX replaces the separate Output Enable (OE) and Direction (DIR) inputs of the 74LCX245 with a single Transmit/Receive (T/R) input plus OE, altering the pin mapping. Specifically, pins 1 (OE) and 19 (T/R) in the 74LCXZ245SJX correspond to pins 1 (OE) and 2 (DIR) in the 74LCX245, requiring PCB layout changes for substitution.

What is the significance of the 'Z' in the 74LCXZ245SJX part number?

The 'Z' in 74LCXZ245SJX denotes zero-threshold or enhanced power-down behavior: the device automatically places all I/O pins in high-impedance state when VCC falls below 1.5V - a feature absent in non-Z variants like the 74LCX245. This eliminates bus contention during power ramping and enables true live insertion/withdrawal without external supervision. The 'Z' suffix is a Fairchild-specific designation for this power-aware 3-STATE architecture.