onsemi 74VCX2245BQX

Overview

74VCX2245BQX from Fairchild Semiconductor is a low-voltage bidirectional transceiver IC with 3.6V-tolerant I/O, 1.4V–3.6V V_CC operation, 26Ω series resistors on B-port outputs, and 3-STATE bidirectional bus interface capability. It serves as a voltage-level translating bus transceiver in memory address drivers, clock distribution networks, and low-noise data buses.

For engineers reviewing the 74VCX2245BQX datasheet, pinout, applications, or equivalent options, this device supports live insertion, offers sub-5 ns propagation delay at 3.3V, delivers ±12 mA drive on B outputs, and integrates patented Quiet Series™ EMI reduction circuitry for high-integrity signal routing in compact PCB layouts.

Technical Context

The 74VCX2245BQX implements an octal non-inverting bidirectional buffer with independent T/R direction control and active-low OE enable. Its dual-bus architecture allows data flow from A-to-B or B-to-A depending on T/R state, while OE forces both ports into high-impedance mode.

It features integrated 26Ω series termination on all B-port outputs to suppress ringing and reduce EMI without external components. The device uses advanced CMOS process technology to achieve high-speed performance (t_PHL/t_PLH ≤ 4.4 ns max at V_CC = 3.3V) with ultra-low static current (I_CC ≤ 20 µA).

Key Specifications

Pinout & Package

Pb-Free 20-terminal DQFN package (JEDEC MO-241), 2.5 mm × 4.5 mm footprint, 0.5 mm pitch, no leads, thermal pad exposed on bottom.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC2245APWR and 74ALVC2245MTCX, the 74VCX2245BQX uniquely integrates 26Ω B-port series termination and Quiet Series™ noise suppression - delivering lower EMI and simplified layout at the cost of slightly reduced drive strength and speed.

Availability

74VCX2245BQX is available at Aetrix Electronics and suitable for memory subsystems, clock distribution networks, hot-swappable modules, and industrial control buses requiring stable component supply and long-term obsolescence management.

Supply support for 74VCX2245BQX 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 communications infrastructure.

The VCX logic family was designed specifically for low-voltage, mixed-signal bus interfacing with emphasis on noise immunity, voltage tolerance, and hot-swap readiness - targeting embedded control, telecom backplanes, and memory subsystems.

FAQ

What is the function of the T/R pin on the 74VCX2245BQX?

The T/R (Transmit/Receive) pin controls data direction: when T/R is LOW, data flows from B-port to A-port; when HIGH, data flows from A-port to B-port. This bidirectional control enables flexible bus arbitration without external logic, making the 74VCX2245BQX ideal for shared-memory and peripheral interface applications where direction changes dynamically during operation.

Does the 74VCX2245BQX require external pull-up resistors on OE or T/R?

Yes - to ensure high-impedance state during power-up and power-down, OE must be tied to V_CC through a pull-up resistor (minimum value determined by driver sourcing capability). T/R may be driven directly but should not float; unused T/R inputs must be held HIGH or LOW per datasheet Note 6 to prevent metastability and excessive current draw in the 74VCX2245BQX.

Can the 74VCX2245BQX operate with V_CC = 1.5V?

Yes - the 74VCX2245BQX is fully specified down to 1.4V V_CC, including AC timing (t_PHL/t_PLH ≤ 19.6 ns at 1.5V, CL = 15 pF) and DC drive (±1 mA on B outputs). This makes it suitable for ultra-low-power applications such as battery-operated sensor nodes where the 74VCX2245BQX maintains functional I/O translation even at minimum supply.

What does "26 series resistors in B outputs" mean for the 74VCX2245BQX?

Each B-port output (B0–B7) integrates a 26Ω series resistor inside the die, placed between the internal driver and the bond pad. This provides inherent source termination to dampen reflections and reduce EMI without requiring external components - a key differentiator of the 74VCX2245BQX versus standard LVC or ALVC transceivers, especially in high-speed or high-density PCB layouts.

Is the 74VCX2245BQX pin-compatible with other 20-pin transceivers like the 74LVC2245?

No - the 74VCX2245BQX uses a DQFN (MLP020B) package with 2.5 mm × 4.5 mm footprint and 0.5 mm pitch, whereas standard 74LVC2245 variants use SOIC or TSSOP packages. While logic function and pin numbering align across the family, physical pinout and soldering requirements differ; the 74VCX2245BQX is not a drop-in replacement without PCB redesign.