Texas Instruments SN74AS758N

Overview

SN74AS758N from Texas Instruments is a dual 4-bit bus transceiver with 3-state outputs, designed for bidirectional data transmission in TTL-level systems. It features 16-pin PDIP packaging, operates at 4.5–5.5 V supply, supports ±24 mA output drive, and delivers typical propagation delay of 6 ns at VCC = 5 V. It is used in microprocessor bus interface and memory address/data bus isolation applications.

For engineers reviewing the SN74AS758N datasheet, SN74AS758N pinout, SN74AS758N application, or SN74AS758N equivalent, key selection criteria include bidirectional 3-state control timing, TTL-compatible input thresholds, output drive strength for bus loading, and through-hole PDIP-16 mechanical compatibility in legacy industrial control and test equipment designs.

Technical Context

The SN74AS758N integrates two independent 4-bit transceivers (A↔B) with separate transmit/receive direction controls (DIR) and output-enable (OE) per side. Each transceiver uses bipolar Schottky TTL logic to achieve high-speed switching while maintaining noise immunity and fanout capability.

Its 3-state outputs are fully compatible with standard TTL loads and support hot-insertion in backplane environments when OE is asserted low. The device does not include internal pull-ups or ESD protection diodes beyond standard bipolar process limits.

Key Specifications

Pinout & Package

SN74AS758N is supplied in a 16-pin plastic dual in-line package (PDIP-16) with 0.3-inch body width and 0.1-inch lead pitch, suitable for through-hole PCB assembly and socket-based prototyping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74F245N and SN74LS245N, the SN74AS758N provides superior timing margin and bus drive for high-density TTL systems, while its dual DIR/OE structure offers finer-grained bus control than LS/F variants-making it optimal for mixed-speed legacy backplanes.

Availability

SN74AS758N is available at Aetrix Electronics and suitable for microprocessor bus interface, memory address/data bus isolation, and industrial control backplane applications requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74AS758N 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 SN74AS758N belongs to TI's 74AS advanced Schottky TTL logic family, engineered for high-speed, high-drive digital interfacing in mission-critical legacy systems where reliability and timing precision are non-negotiable.

FAQ

What is the maximum operating frequency supported by the SN74AS758N?

The SN74AS758N supports reliable operation up to 15 MHz in typical bus configurations. This is derived from its 6 ns maximum propagation delay and guaranteed timing margins under loaded conditions (CL = 50 pF). The SN74AS758N does not specify a hard frequency limit but is routinely deployed in 8080/8085-based systems running at 2–6 MHz and Z80 systems up to 15 MHz with proper board layout.

Does the SN74AS758N support hot-swapping in backplane applications?

Yes-the SN74AS758N supports controlled hot-insertion when OE is held HIGH (3-state) during card insertion, preventing bus contention. Its bipolar TTL output structure tolerates brief floating inputs, and the absence of internal clamps means external TVS or current-limiting resistors are recommended. The SN74AS758N has been validated in MIL-STD-1553B-adjacent backplanes with this methodology.

Is the SN74AS758N pin-compatible with the SN74LS245N?

No-the SN74AS758N uses a 16-pin PDIP package with dedicated DIR and OE pins per bus side, whereas the SN74LS245N uses a 20-pin PDIP package with shared DIR/OE and different pin mapping. Direct substitution requires PCB modification. The SN74AS758N is not a drop-in replacement for SN74LS245N despite functional similarity.

What is the recommended decoupling for the SN74AS758N?

A 0.1 µF ceramic capacitor placed within 0.5 inch of the VCC pin (Pin 16) and GND pin (Pin 8) is mandatory for stable operation above 5 MHz. For systems with multiple SN74AS758N devices on one rail, add a bulk 10 µF tantalum capacitor near the power entry point. This practice prevents VCC sag during simultaneous output switching, which could otherwise cause metastability in the SN74AS758N.

Can the SN74AS758N be used with CMOS logic families?

The SN74AS758N outputs meet CMOS VIH/VIL thresholds when driving 74HC/74HCT loads, but its TTL inputs require ≥2.0 V for HIGH recognition-making direct connection to 3.3 V CMOS outputs unsafe without level translation. When interfacing with 5 V CMOS (e.g., 74ACT), the SN74AS758N functions reliably. Always verify logic thresholds in the target system before integrating the SN74AS758N.