Texas Instruments SN74HCT245N

Overview

SN74HCT245N from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between two 8-bit buses. It operates at 4.5–5.5 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 14 ns (CL = 50 pF), and supports TTL-compatible inputs - enabling robust signal integrity in industrial backplane and ribbon-cable interconnects.

For engineers reviewing the SN74HCT245N datasheet, SN74HCT245N pinout, SN74HCT245N application, or SN74HCT245N equivalent, this device serves as a high-current, low-power logic-level translator for isolated bus communication where direction control and output enable are required to prevent contention and manage timing-critical data flow.

Technical Context

The SN74HCT245N implements a dual-bus bidirectional buffer architecture with active-low output enable (OE) and unidirectional direction control (DIR). Its CMOS HCT logic family ensures TTL-voltage compatibility while maintaining low static current (≤80 µA) and balanced rise/fall times (typ. 8–11 ns at 5.5 V).

It features center-aligned VCC and GND pins to minimize switching noise, supports up to 15 LSTTL loads per output, and operates across –40°C to +85°C - making it suitable for factory automation and telecom infrastructure where thermal stability and noise immunity are critical.

Key Specifications

Pinout & Package

SN74HCT245N uses a 20-pin Plastic Dual In-line Package (PDIP) with nominal body size 24.33 mm × 6.35 mm. Pin 10 is GND and pin 20 is VCC, providing symmetrical power/ground placement to reduce ground bounce.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT245DW and SN74LS245N, the SN74HCT245N offers through-hole manufacturability with modern CMOS efficiency - delivering 8× lower static current than LS variants and matching SOIC performance without requiring PCB redesign.

Availability

SN74HCT245N is available at Aetrix Electronics and suitable for factory automation, telecom infrastructure, and motor drive applications requiring stable component supply, long-term industrial lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for SN74HCT245N 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 logic solutions with over 50 years of industrial-grade product development.

The SN74HCT245N belongs to TI's 74HCT logic family, engineered for TTL-compatible operation in industrial control, instrumentation, and communications systems where reliability, noise immunity, and 5-V interoperability are essential.

FAQ

What is the maximum operating temperature range for the SN74HCT245N?

The SN74HCT245N is rated for operation from –40°C to +85°C. This industrial temperature range ensures reliable functionality in demanding environments such as motor drives, factory automation equipment, and outdoor telecom enclosures where ambient temperatures fluctuate significantly. The PDIP package provides adequate thermal dissipation within this range without forced cooling.

Does the SN74HCT245N require external pull-up or pull-down resistors on DIR or OE pins?

No, the SN74HCT245N does not require external biasing on DIR or OE - its CMOS inputs draw ≤1 µA, so direct connection to VCC or GND is sufficient. However, unused A/B pins must be terminated to avoid floating states; TI recommends tying them to VCC or GND via 10-kΩ resistors if not actively driven, as specified in application note SCBA004.

Can the SN74HCT245N drive a 50-pF load at 25 MHz reliably?

Yes, the SN74HCT245N achieves typical propagation delay of 14 ns (CL = 50 pF, VCC = 5.5 V), supporting clean signal edges up to ~35 MHz. At 25 MHz, setup/hold margins remain robust, especially when combined with proper 0.1 µF local bypassing and controlled-impedance routing - verified in TI's typical application curves for ribbon cable interfaces.

Is the SN74HCT245N pin-compatible with older 74LS245 devices?

The SN74HCT245N shares identical 20-pin PDIP pinout and logic function with 74LS245, enabling mechanical drop-in replacement. However, electrical differences exist: HCT offers TTL-compatible inputs with CMOS power efficiency (80 µA vs. 40 mA ICC), faster tpd (14 ns vs. 25 ns), and improved noise margin - requiring no layout changes but validating timing in high-speed designs.

How does the SN74HCT245N handle bus contention during direction switching?

The SN74HCT245N prevents bus contention through strict functional mode control: OE must be high before changing DIR state, ensuring both A and B ports enter high-impedance simultaneously. TI's function table confirms that OE = high forces isolation regardless of DIR value - a design requirement enforced in all valid state transitions to avoid shoot-through currents.