Texas Instruments SN74F245NSR

Overview

SN74F245NSR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between two 8-bit buses. It features direction control (DIR), output enable (OE), ±48 mA A-side and ±128 mA B-side output drive capability, and operates over 0°C to 70°C. It is used in legacy industrial backplane interfaces and board-level bus isolation.

For engineers reviewing the SN74F245NSR datasheet, SN74F245NSR pinout, SN74F245NSR application, or SN74F245NSR equivalent, key selection considerations include 3-state bus contention prevention, asymmetric current drive (B-side higher), SOIC-20 package compatibility, and TTL-compatible input thresholds at 5 V supply.

Technical Context

The SN74F245NSR implements a dual-bus bidirectional transceiver architecture with independent DIR and OE logic inputs. Its operation is defined by a three-state function table: OE low enables data flow (A→B when DIR high; B→A when DIR low); OE high forces all outputs into high-impedance state regardless of DIR.

It uses standard TTL circuitry with Schottky-clamped bipolar transistors, delivering propagation delays of 1.7–7 ns (tPLH/tPHL) and enable/disable transition times of 1.2–9 ns (tPZL/tPHZ) under 5 V/50 pF conditions. Input thresholds are VIH = 2 V min and VIL = 0.8 V max, ensuring robust noise margin in mixed-logic systems.

Key Specifications

Pinout & Package

SN74F245NSR is housed in a 20-pin SOP (Small Outline Package) with 0.635 mm pitch, 7.5 mm body width, and 2.65 mm maximum height per JEDEC MS-013. The package is RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F245NSR, SN74LS245N trades speed and drive for lower power and cost, while SN74HC245N offers voltage flexibility and CMOS efficiency at the expense of peak current capability - selection depends on bus loading, timing budget, and supply architecture.

Availability

SN74F245NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus isolation, memory expansion bridges, and test equipment data path control requiring stable component supply and long-term obsolescence management.

Supply support for SN74F245NSR 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74F245NSR belongs to TI's 74F family of fast TTL logic devices, engineered for high-speed digital interconnect in legacy computing, instrumentation, and control systems where 5 V TTL compatibility and robust bus driving are essential.

FAQ

What is the maximum clock frequency supported by the SN74F245NSR?

The SN74F245NSR does not operate on a clock signal-it is an asynchronous transceiver. Its usable data rate is determined by propagation delay (1.7–7 ns) and bus capacitance. In practice, it reliably supports burst data transfers up to ~100 MHz on properly terminated 50 pF buses, as confirmed by switching characteristics in the official TI datasheet SDFS010A.

Can SN74F245NSR be used with 3.3 V logic systems?

No-SN74F245NSR is a 5 V-only TTL device. Its VIH minimum is 2.0 V and VIL maximum is 0.8 V, but it requires VCC = 4.5–5.5 V to function correctly. Driving its inputs from 3.3 V logic may result in marginal or non-functional high-level recognition. For 3.3 V systems, consider SN74LVC245A or similar CMOS alternatives.

What is the pin 1 marking and orientation for SN74F245NSR?

SN74F245NSR uses standard SOIC-20 packaging with pin 1 located at the top-left corner, identified by a small beveled edge or dot in the upper-left corner of the package body. The marking "74F245" appears on the top surface, aligned left-to-right starting from pin 1 side, per TI's package drawing DW0020A and tape-and-reel documentation.

Does SN74F245NSR support hot-swap or live insertion?

SN74F245NSR is not hot-swap rated. While its 3-state outputs provide isolation when OE is high, the device lacks built-in power sequencing protection, bus-fault current limiting, or ESD hardening beyond standard HBM ratings. Use external current-limiting resistors and controlled power ramping if live insertion is required in the target system.

How does the DIR input interact with OE in SN74F245NSR operation?

In SN74F245NSR, OE is dominant: when OE is high (disabled), all outputs go high-impedance regardless of DIR state. Only when OE is low does DIR determine direction-DIR high enables A→B transfer; DIR low enables B→A transfer. This priority ensures safe bus isolation during configuration or fault states.