Texas Instruments SN74AS757N

Overview

SN74AS757N from Texas Instruments is a dual 4-bit noninverting open-collector buffer/line driver IC designed for memory address bus driving and clock distribution in TTL-compatible systems. It features two independent 4-bit channels (1A–1Y and 2A–2Y), active-low output-enable inputs (1OE and 2OE), 64 mA low-level output sink current, propagation delays as low as 1 ns (tPHL), and operates from 0°C to 70°C on 4.5 V–5.5 V supply.

For engineers reviewing the SN74AS757N datasheet, SN74AS757N pinout, SN74AS757N application, or SN74AS757N equivalent, this page delivers verified functional identity, validated pin roles, confirmed timing and drive specs, and real-world use context for bus interface and address buffering design.

Technical Context

The SN74AS757N implements two independent 4-bit noninverting buffer sections with open-collector outputs, enabling wired-OR bus configurations and direct interfacing with TTL/CMOS loads. Each channel has dedicated active-low output-enable control (1OE, 2OE), supporting independent gating of 1Y and 2Y groups without 3-state overlap concerns.

Its pnp-input structure reduces DC loading on preceding logic stages, while its high-current open-collector outputs (64 mA sink) support direct driving of memory address registers, bus lines, and LED indicators. The device belongs to the advanced Schottky (AS) family, delivering faster switching (tPHL = 1 ns) and lower power-delay product than standard TTL or ALS variants.

Key Specifications

Pinout & Package

SN74AS757N is supplied in a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is located at the top-left corner (notch-down orientation).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal noninverting open-collector buffer applications.

Compared with SN74AS240N and SN74AS244N, the SN74AS757N provides superior current drive (64 mA), independent dual-OE control for flexible bus partitioning, and the lowest tPHL (1 ns), making it optimal for high-density, high-speed address and clock distribution where timing integrity and load flexibility are critical.

Availability

SN74AS757N is available at Aetrix Electronics and suitable for memory address buffering, bus line driving, LED interface, and TTL-to-discrete load interfacing requiring stable component supply and long-term industrial availability.

Supply support for SN74AS757N 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 SN74AS757N belongs to TI's Advanced Schottky TTL logic family, engineered to deliver high-speed, low-power bus interface and memory addressing performance for legacy and hybrid digital systems.

FAQ

What is the function of SN74AS757N in a digital system?

The SN74AS757N functions as a dual 4-bit noninverting open-collector buffer used primarily for memory address bus driving, clock distribution, and high-current logic interfacing. Its two independent output-enable inputs (1OE and 2OE) allow selective activation of each 4-bit group, and its 64 mA sink capability supports direct connection to TTL loads, LEDs, or discrete switches without intermediate amplification. This makes SN74AS757N especially valuable in systems where timing precision, bus contention avoidance, and load flexibility are essential.

Does SN74AS757N support 3.3 V logic inputs?

No, SN74AS757N is an AS-TTL device designed for 5 V operation and does not guarantee reliable recognition of 3.3 V logic-high levels. Its VIH (high-level input voltage) minimum is 2.0 V under recommended conditions, but due to TTL input thresholds and noise margin constraints, interfacing with 3.3 V CMOS outputs requires a level-shifter or pull-up resistor network to ensure robust high-level detection. The SN74AS757N datasheet specifies operation only within 4.5 V–5.5 V VCC and does not characterize 3.3 V input compatibility.

Can SN74AS757N replace SN74AS244N in an existing design?

SN74AS757N can replace SN74AS244N only if the design leverages its dual independent output-enable (1OE/2OE) functionality and requires 64 mA sink current. While both are octal noninverting buffers in PDIP-20 packages, SN74AS244N uses a single shared OE input, whereas SN74AS757N provides separate enables for each 4-bit group. If the original design relies on global enable control and does not need per-group gating, SN74AS244N remains functionally adequate - but SN74AS757N offers enhanced timing (1 ns tPHL vs. 2 ns) and drive strength.

What is the maximum allowable output voltage on SN74AS757N open-collector pins?

The absolute maximum off-state output voltage for SN74AS757N is 7 V, as specified in the datasheet. This means the external pull-up voltage applied to any 1Y or 2Y pin must not exceed 7 V to avoid permanent damage. In practice, 5 V pull-ups are standard for TTL compatibility, but the device safely supports higher-voltage loads (e.g., 12 V relays) when used with appropriate series current-limiting and flyback protection - provided the output voltage never exceeds 7 V during switching transients or fault conditions.

Is SN74AS757N RoHS compliant?

Yes, SN74AS757N is RoHS compliant. According to Texas Instruments' packaging addendum, the SN74AS757N orderable part number carries "Yes" for RoHS status, uses NiPdAu (NIPDAU) lead finish, and meets JEDEC standards for lead-free assembly. It is rated for peak reflow temperatures up to 260°C (Level-1 moisture sensitivity) and is approved for use in environmentally regulated commercial electronics manufacturing.