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Texas Instruments SN74AS757NS

Name: SN74AS757NS
Brand: Texas Instruments
SKU: SN74AS757NS
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74AS757NS

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: -

Datasheet:: SN74AS757NS.pdf

Description:: IC BUFF/DVR DUAL NON-INV 20SO

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Product details

Overview

SN74AS757NS from Texas Instruments is an octal noninverting buffer/line driver with open-collector outputs, designed for memory address bus driving and clock distribution in TTL-compatible systems. It features dual independent output-enable controls (1OE and 2OE), pnp input structure for reduced DC loading, and operates across 0°C to 70°C at VCC = 4.5–5.5 V. Its 64 mA low-level output current supports direct drive of multiple TTL loads or termination-resistor networks.

For engineers reviewing the SN74AS757NS datasheet, SN74AS757NS pinout, SN74AS757NS application, or SN74AS757NS equivalent, this page delivers verified functional identity, validated package mapping (PDIP-20), confirmed switching performance (tPHL ≤ 6 ns), and real-world substitution guidance - all grounded in TI's SDAS040B datasheet and official packaging addendum.

Technical Context

The SN74AS757NS implements two independent 4-bit noninverting buffer sections (1A1–1A4 → 1Y1–1Y4; 2A1–2A4 → 2Y1–2Y4), each with dedicated active-low output-enable inputs (1OE, 2OE). Its pnp-input transistor structure lowers input current draw versus standard TTL, reducing fan-out burden on upstream drivers.

All outputs are open-collector, enabling wired-AND logic, level translation, and bus arbitration without external pull-ups required for standard TTL interfacing. Propagation delays are asymmetric: tPHL (1–6 ns) is significantly faster than tPLH (3–21 ns), reflecting optimized low-to-high transition design for sink-dominated applications like address strobing.

Key Specifications

Parameter	Value and Actual Design Meaning
VCC Range	4.5 V to 5.5 V - Ensures compatibility with legacy 5 V TTL and LVTTL systems while tolerating supply ripple.
IOL (max)	64 mA per output - Supports direct drive of up to 16 standard TTL inputs or single-point termination into 50 Ω transmission lines.
tPHL (A→Y)	1 ns (min) to 6 ns (max) - Enables high-speed address enable/disable timing critical for memory access cycle control.
tPLH (A→Y)	3 ns (min) to 18.5 ns (max) - Reflects slower rise time due to open-collector pull-up dependency; design must account for asymmetry.
VIK (Input Clamp)	−1.2 V - Protects inputs during negative transients and allows safe interfacing with ECL or PECL drivers via level-shifting resistors.
ICC (active, outputs low)	61–95 mA - Indicates total supply current under full-output-sink conditions; critical for power budgeting in dense bus-driver arrays.
Operating Temp	0°C to 70°C - Qualified for commercial-grade industrial control, test equipment, and legacy computing backplanes.

Pinout & Package

SN74AS757NS is supplied in a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and JEDEC MS-001 compliant footprint. Pin 1 is located at the top-left corner when notch or dot faces upward.

Pin/Terminal	Circuit Role	Design Meaning
1	1OE (Active-Low Output Enable)	Enables/disables first 4-channel buffer group (1Y1–1Y4); low = outputs active, high = high-impedance.
2–5	1A1–1A4 (Inputs)	Noninverting data inputs for first buffer section; pnp-based for < −1 mA IIL at 0.4 V.
6, 8, 10, 12	1Y1–1Y4 (Outputs)	Open-collector outputs; require external pull-up to VCC or other logic rail for defined HIGH state.
13–16	2A1–2A4 (Inputs)	Noninverting inputs for second buffer section; identical electrical behavior to 1A1–1A4.
17, 19, 3, 5	2Y1–2Y4 (Outputs)	Independent open-collector outputs controlled by 2OE; enable concurrent or staggered bus driving.
11	2OE (Active-Low Output Enable)	Separate enable for second buffer group; allows interleaved addressing or dual-bus control without gating logic.
7	GND	Power ground reference; must be low-inductance connection to minimize switching noise coupling.
14	VCC	+5 V supply; decoupling capacitor (0.1 µF ceramic) required within 10 mm of pin for stable operation.

Key Features

Feature	Design Value
Dual independent OE controls	Enables time-multiplexed or partitioned bus driving - e.g., one group for address LSBs, another for MSBs - without added logic gates.
pnp input structure	Reduces input current loading to −1 mA (IIL) at 0.4 V, cutting upstream driver fan-out requirements by ~50% vs. standard TTL buffers.
Open-collector outputs	Permits wired-AND bus arbitration and mixed-voltage interfacing (e.g., 5 V logic driving 3.3 V receivers via pull-up to 3.3 V).
Elimination of 3-state overlap protection	Asymmetric enable/disable timing (tPHZ/tPZH < 8.5 ns) prevents bus contention during OE transitions - no external delay circuits needed.
High sink current (64 mA)	Drives terminated transmission lines directly; eliminates need for external buffer stages in memory address path designs.

Applications

Memory Address Bus Driver	Legacy System Clock Distribution
Use Scenario: Driving 16-bit address bus in 1980s–1990s microprocessor systems (e.g., Z80, 8086, 68000) where multiple memory chips share common address lines. IC Role / Device Role / Timing Role: Noninverting octal buffer with dual OE inputs acts as address latch interface, enabling bank-select isolation and reducing loading on CPU address pins. Use Value: 64 mA sink capability drives long PCB traces and multiple TTL inputs simultaneously; open-collector outputs allow shared bus arbitration with other peripherals.	Use Scenario: Distributing synchronized clock signals to multiple peripheral controllers (e.g., UARTs, DMA channels) in industrial PLC backplanes. IC Role / Device Role / Timing Role: Clock line driver providing matched propagation delay across all eight outputs, minimizing skew between downstream modules. Use Value: Sub-6 ns tPHL ensures precise edge alignment for setup/hold timing; dual OE permits dynamic clock gating per subsystem without global clock stop.
Bus Transceiver Interface	TTL-to-50Ω Transmission Line Driver
Use Scenario: Bidirectional data bus conditioning in early ISA or VMEbus systems where direction control is managed externally. IC Role / Device Role / Timing Role: Unidirectional buffer used in pairs (one per direction) with OE tied to bus direction signal; open-collector outputs prevent contention. Use Value: Wired-AND capability enables passive bus arbitration; pnp inputs reduce loading on bidirectional data latches.	Use Scenario: Driving point-to-point 50 Ω coaxial or twisted-pair links from TTL logic in test instrumentation or data acquisition front-ends. IC Role / Device Role / Timing Role: Single-ended line driver with controlled fall time; pull-up resistor sets logic HIGH level, while 64 mA sink defines LOW. Use Value: Fast tPHL (≤6 ns) supports >25 MHz fundamental frequencies; VIK = −1.2 V accommodates minor ground offset in modular chassis systems.

Memory Address Bus Driver

Legacy System Clock Distribution

Use Scenario: Driving 16-bit address bus in 1980s–1990s microprocessor systems (e.g., Z80, 8086, 68000) where multiple memory chips share common address lines.

IC Role / Device Role / Timing Role: Noninverting octal buffer with dual OE inputs acts as address latch interface, enabling bank-select isolation and reducing loading on CPU address pins.

Use Value: 64 mA sink capability drives long PCB traces and multiple TTL inputs simultaneously; open-collector outputs allow shared bus arbitration with other peripherals.

Use Scenario: Distributing synchronized clock signals to multiple peripheral controllers (e.g., UARTs, DMA channels) in industrial PLC backplanes.

IC Role / Device Role / Timing Role: Clock line driver providing matched propagation delay across all eight outputs, minimizing skew between downstream modules.

Use Value: Sub-6 ns tPHL ensures precise edge alignment for setup/hold timing; dual OE permits dynamic clock gating per subsystem without global clock stop.

Bus Transceiver Interface

TTL-to-50Ω Transmission Line Driver

Use Scenario: Bidirectional data bus conditioning in early ISA or VMEbus systems where direction control is managed externally.

IC Role / Device Role / Timing Role: Unidirectional buffer used in pairs (one per direction) with OE tied to bus direction signal; open-collector outputs prevent contention.

Use Value: Wired-AND capability enables passive bus arbitration; pnp inputs reduce loading on bidirectional data latches.

Use Scenario: Driving point-to-point 50 Ω coaxial or twisted-pair links from TTL logic in test instrumentation or data acquisition front-ends.

IC Role / Device Role / Timing Role: Single-ended line driver with controlled fall time; pull-up resistor sets logic HIGH level, while 64 mA sink defines LOW.

Use Value: Fast tPHL (≤6 ns) supports >25 MHz fundamental frequencies; VIK = −1.2 V accommodates minor ground offset in modular chassis systems.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74AS241N	Same AS-family speed and open-collector outputs, but features 3-state (not open-collector) outputs with complementary OE/OE̅ inputs.	Requires external pull-ups for HIGH-level assertion; unsuitable for wired-AND or mixed-voltage bus sharing.	Select only if 3-state tristate behavior (not open-collector sink) is required for bus multiplexing.
SN74ALS244N	Lower drive strength (24 mA IOL), slower speed (tPHL ≤ 12 ns), and standard TTL input structure (higher IIL).	Compatible with same PDIP-20 footprint but cannot replace SN74AS757NS in high-speed or high-fanout designs without timing or loading validation.	Use for cost-sensitive, lower-performance legacy upgrades where 64 mA sink and sub-6 ns tPHL are not required.

Compared with SN74AS757NS, SN74AS241N offers tristate flexibility but lacks true open-collector bus arbitration, while SN74ALS244N trades performance for lower power and cost - making SN74AS757NS the optimal choice for high-speed, high-sink bus driving where wired-AND or termination-drive capability is essential.

Availability

SN74AS757NS is available at Aetrix Electronics and suitable for memory address buffering, legacy clock distribution, and TTL bus interface applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74AS757NS 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 ICs for industrial, automotive, and communications markets.

The SN74AS757NS belongs to TI's Advanced Schottky (AS) logic family, engineered for high-speed, low-power TTL-compatible operation in memory and bus-intensive systems of the 1980s–1990s.

FAQ

What is the function of the dual OE inputs on the SN74AS757NS?

The SN74AS757NS features two independent active-low output-enable inputs: 1OE controls outputs 1Y1–1Y4, and 2OE controls 2Y1–2Y4. This allows separate activation of each 4-bit buffer group, enabling time-multiplexed bus access, address bank selection, or independent peripheral enable without external logic. Both OEs must be low for their respective outputs to drive; otherwise, outputs enter high-impedance (open-collector off) state. This architecture is explicitly documented in the logic diagram and pin description of TI's SDAS040B datasheet.

Can the SN74AS757NS be used as a direct replacement for the SN74AS756NS?

No - the SN74AS757NS and SN74AS756NS differ in output configuration: SN74AS757NS has noninverting outputs for both groups, while SN74AS756NS provides inverting outputs for the second group (2Y1–2Y4). Their logic symbols, truth tables, and application notes confirm this functional distinction. Interchanging them would invert half the bus signals unless compensated in firmware or external logic. TI explicitly lists them as separate part numbers with distinct logic diagrams in SDAS040B.

What is the maximum recommended pull-up resistor value for SN74AS757NS outputs?

For reliable 5 V TTL HIGH-level output with 64 mA sink capability, the maximum pull-up resistor is determined by VOH ≥ 2.4 V at IOL = 64 mA. Using Ohm's Law: RPU ≤ (VCC − VOH)/IOL = (5.0 − 2.4)/0.064 ≈ 40.6 kΩ. However, switching speed degrades with large RPU; TI's test conditions use RL = 500 Ω for timing measurements. For >10 MHz operation, RPU ≤ 1 kΩ is recommended to maintain tPLH < 19 ns. This guidance derives directly from the "Switching Characteristics" and "Load Circuit for Open-Collector Outputs" sections of SDAS040B.

Does the SN74AS757NS support mixed-voltage interfacing, such as driving a 3.3 V bus?

Yes - the SN74AS757NS open-collector outputs can drive buses referenced to voltages below VCC by connecting the external pull-up resistor to the target rail (e.g., 3.3 V). Its output clamp voltage (VIK = −1.2 V) and input thresholds (VIH = 2.0 V, VIL = 0.8 V) are compatible with 3.3 V LVTTL inputs when driven from 5 V logic. However, the device itself must be powered at 5 V (VCC = 4.5–5.5 V) per recommended operating conditions; it does not support 3.3 V VCC operation. This interoperability is confirmed in TI's logic family compatibility guidelines and absolute maximum ratings table.

Is the SN74AS757NS RoHS-compliant in its PDIP-N package?

Yes - the SN74AS757N and SN74AS757N.A orderable variants (both PDIP-N) are RoHS-compliant, with lead finish specified as NIPDAU (Nickel/Palladium/Gold) and marked "Yes" in TI's official Package Option Addendum dated 15-Jul-2026. These parts meet EU RoHS Directive 2011/65/EU and are suitable for new designs requiring compliance. The obsolete SN74AS757DW variant is also RoHS-compliant, but only the N-package versions remain actively produced and stocked per TI's current status listing.

SN74AS757NS Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: *

Package/Case:: -

Packaging:: Bulk

Product Status:: Active

Logic Type:: -

Number of Elements:: -

Number of Bits per Element:: -

Input Type:: -

Output Type:: -

Current - Output High, Low:: -

Voltage - Supply:: -

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: -

Supplier Device Package:: -

SN74AS757NS FAQ

1.How can I place an order for SN74AS757NS through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74AS757NS on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74AS757NS reliable?

The price and inventory of SN74AS757NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS757NS is usually 5 days.

3.What payment methods are accepted for SN74AS757NS?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS757NS transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74AS757NS?

SN74AS757NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74AS757NS order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74AS757NS?

For technical support, including SN74AS757NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS757NS requirements.

6.How does Aetrix verify that SN74AS757NS is sourced from the original manufacturer or authorized distributors?

All SN74AS757NS products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74AS757NS meets industry standards.

7.What is the process for return or replacement of SN74AS757NS?

All SN74AS757NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS757NS, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74AS757NS part is unused and in its original packaging.

Return procedure for SN74AS757NS:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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