Texas Instruments SN74HC245NSRE4

Overview

SN74HC245NSRE4 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5 V or 3.3 V digital systems. It features ±6 mA output drive at 5 V, 12 ns typical propagation delay (VCC = 5 V, CL = 50 pF), wide 2–6 V supply range, and low 80 µA max ICC - enabling robust bus isolation in PC motherboard I/O expansion and industrial control backplanes.

For engineers reviewing the SN74HC245NSRE4 datasheet, SN74HC245NSRE4 pinout, SN74HC245NSRE4 application, or SN74HC245NSRE4 equivalent, key selection criteria include direction-control logic behavior, 3-state enable timing (ten/tdis), thermal resistance (RθJA = 74.1 °C/W for NS package), and compatibility with LSTTL loads (up to 15 units).

Technical Context

The SN74HC245NSRE4 implements dual-bus bidirectional communication via a single DIR input that selects A→B or B→A data flow, while OE independently enables or disables all outputs into high-impedance state. Its CMOS design ensures balanced rise/fall times and reduced output ringing compared to higher-drive families.

It operates across –40°C to +85°C with guaranteed switching performance at 2 V, 4.5 V, and 6 V supply levels. Input thresholds scale with VCC (VIH = 0.7×VCC min, VIL = 0.3×VCC max), and output drive remains stable up to ±7.8 mA at 6 V - supporting mixed-voltage interface bridging without level shifters.

Key Specifications

Pinout & Package

SN74HC245NSRE4 uses the NS (SOIC-20) package: 12.60 mm × 5.30 mm body, 1.27 mm lead pitch, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC245NSRE4, SN74LVC245A offers superior speed and drive in 3.3 V domains but sacrifices 5 V interoperability, while 74ACT245 delivers legacy TTL compatibility at the cost of quiescent power and supply flexibility - making SN74HC245NSRE4 optimal for mixed-voltage, low-power, and thermally constrained applications.

Availability

SN74HC245NSRE4 is available at Aetrix Electronics and suitable for PC motherboards, industrial PLC backplanes, and network switch management interfaces requiring stable component supply across extended production lifecycles.

Supply support for SN74HC245NSRE4 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in logic and interface ICs.

The SN74HC245NSRE4 belongs to TI's HC (High-Speed CMOS) logic family, engineered for low-power, wide-supply-voltage bidirectional bus interfacing in commercial-grade computing and industrial control systems.

FAQ

What is the maximum operating temperature for SN74HC245NSRE4?

The SN74HC245NSRE4 is rated for operation from –40°C to +85°C ambient temperature. This industrial-grade temperature range ensures reliable performance in PC chassis, network equipment enclosures, and factory-floor control panels where airflow and thermal management may be limited. The NS package's RθJA of 74.1 °C/W supports sustained operation at full load within this envelope when proper PCB copper area and decoupling are applied.

Does SN74HC245NSRE4 support 5 V logic levels when powered from 3.3 V?

No - SN74HC245NSRE4 does not support 5 V-tolerant inputs when VCC = 3.3 V. Its absolute maximum input voltage is VCC + 0.5 V, so applying 5 V signals risks damage. For mixed-voltage operation, SN74HC245NSRE4 must be powered at 5 V to safely accept 5 V inputs, or used with external level-shifting circuitry when VCC = 3.3 V. This limitation is inherent to its HC-family architecture and is documented in Section 6.1 Absolute Maximum Ratings.

How does the DIR pin affect data flow direction in SN74HC245NSRE4?

In SN74HC245NSRE4, the DIR pin controls real-time bidirectional data routing: when DIR = Low, data flows from Port B to Port A; when DIR = High, data flows from Port A to Port B. This control is asynchronous and independent of OE - meaning direction can be changed while outputs remain disabled, eliminating bus contention during mode transitions. The function table in Section 8.4 confirms this behavior applies across the full 2–6 V supply range.

Can SN74HC245NSRE4 drive 15 LSTTL loads directly?

Yes - SN74HC245NSRE4 is explicitly specified to drive up to 15 LSTTL loads directly, as stated in its Features list and verified by its ±6 mA output drive capability at 5 V. This rating assumes standard LSTTL input characteristics (IIH = 20 µA, IIL = –0.4 mA) and accounts for worst-case voltage margins. Designers should verify trace capacitance and ensure total capacitive load per line stays below 50 pF for guaranteed timing compliance per Section 6.6.

What is the recommended bypass capacitor for SN74HC245NSRE4?

Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC pin (Pin 20) of SN74HC245NSRE4, with low-inductance connection to GND (Pin 10). This value is validated for noise suppression across the 2–6 V operating range and aligns with layout guidelines in Section 10. For systems with multiple logic devices sharing the same rail, paralleling a 1 µF tantalum or aluminum electrolytic capacitor nearby further stabilizes bulk supply impedance.