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Home > Products > Integrated Circuits (ICs) > Logic > Buffers, Drivers, Receivers, Transceivers

Texas Instruments SN74ALS641A-1NSR

Name: SN74ALS641A-1NSR
Brand: Texas Instruments
SKU: SN74ALS641A-1NSR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74ALS641A-1NSR

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 20-SOIC (0.209", 5.30mm Width)

Datasheet:: SN74ALS641A-1NSR.pdf

Description:: IC TRANSCEIVER INVERT 5.5V 20SO

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Product details

Overview

SN74ALS641A-1NSR from Texas Instruments is an octal bidirectional bus transceiver in a 20-pin SOP (NS) package, designed for asynchronous two-way data transfer between A and B buses. It features true logic polarity, direction control (DIR), output enable (OE), and supports 48 mA low-level output current (I_OL) in the -1 version. Used in legacy industrial backplane and board-to-board communication systems requiring TTL-compatible level shifting and bus isolation.

For engineers reviewing the SN74ALS641A-1NSR datasheet, SN74ALS641A-1NSR pinout, SN74ALS641A-1NSR application, or SN74ALS641A-1NSR equivalent, key selection criteria include its 48 mA I_OL drive capability, 0°C to 70°C operating range, 3-state bidirectional control architecture, and SOP-20 footprint compatibility with legacy 74ALS logic designs.

Technical Context

The SN74ALS641A-1NSR implements a dual-rail 3-state bus interface with independent DIR and OE inputs enabling precise control of data flow direction and bus isolation. Its internal structure supports simultaneous high-impedance states on all A and B I/O ports when OE is high, and directional pass-through (A→B or B→A) when OE is low and DIR is asserted.

It operates strictly within 4.5 V–5.5 V V_CC, meets ALS family propagation delays (t_PLH/t_PHL ≤ 32 ns at 50 pF), and maintains input thresholds compatible with standard TTL (V_IL = 0.8 V, V_VIH = 2.0 V). The -1 suffix denotes enhanced 48 mA I_OL rating under 4.75–5.25 V V_CC, distinguishing it from the standard SN74ALS641A.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.5 V to 5.5 V - Ensures stable operation across standard 5 V supply tolerances in industrial environments.
I_OL (max)	48 mA - Enables direct driving of multiple TTL loads or moderate-capacitance buses without external buffers.
t_PLH/t_PHL	≤32 ns - Supports reliable 30+ MHz bus switching in synchronous backplane applications.
V_IL/V_IH	0.8 V / 2.0 V - Guarantees interoperability with legacy 74LS/74ALS logic families and microcontroller GPIOs.
Operating Temp	0°C to 70°C - Qualified for commercial and industrial ambient conditions in non-extended-temperature equipment.
Package	SOP-20 (NS) - Surface-mount 0.3-inch body width, 12.6 mm × 7.5 mm footprint, compatible with standard reflow profiles.
Logic Type	True (non-inverting) - Preserves signal polarity during bidirectional transfer, simplifying timing analysis.

Pinout & Package

SOP-20 (NS) package: 12.6 mm × 7.5 mm body, 1.27 mm lead pitch, 2.65 mm max height, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.

Pin/Terminal	Circuit Role	Design Meaning
1, 19	DIR	Direction control input: Low = B→A transfer; High = A→B transfer.
2, 18	OE	Output enable input: Low = active transceiver; High = all A/B ports in high-impedance state.
3–10	A1–A8	Octal A-side bidirectional I/O ports - connect to local bus or controller side.
11–18	B1–B8	Octal B-side bidirectional I/O ports - connect to remote bus or peripheral side.
9	GND	Ground reference for logic and output drivers.
20	V_CC	+5 V power supply - must be decoupled locally per ALS design guidelines.

Key Features

Feature	Design Value
48 mA I_OL drive	Supports fan-out to ≥10 standard TTL loads or direct connection to 50 Ω transmission lines with minimal overshoot.
True logic polarity	Eliminates need for external inversion logic in A↔B data mirroring applications like memory-mapped I/O bridges.
Independent DIR/OE control	Enables dynamic bus arbitration: OE disables all ports while DIR selects direction-no contention risk during state transitions.
ALS family compatibility	Matches voltage thresholds, noise margins, and timing behavior of SN74ALS00, SN74ALS244, and other 74ALS-series components.
300-mil SOP footprint	Direct drop-in replacement for PDIP-20 in space-constrained PCB layouts without redesigning land patterns.

Applications

Industrial Backplane Interface	Legacy System Bus Extension
Use Scenario: Connecting CPU bus to expansion slot in programmable logic controllers (PLCs) with hot-swap isolation requirements. IC Role / Device Role / Timing Role: Bidirectional bus buffer providing direction-controlled data path between master and slave modules, with OE-gated isolation during slot insertion/removal. Use Value: Prevents bus contention during live module replacement by enabling high-Z state via OE before DIR changes, meeting IEC 61000-4-2 ESD immunity requirements.	Use Scenario: Extending 8-bit ISA-style data bus between two PCBs in test instrumentation rack systems. IC Role / Device Role / Timing Role: Level-shifting and impedance-matching transceiver ensuring signal integrity across 15 cm inter-board ribbon cable runs. Use Value: 48 mA drive strength maintains <1 V_OL under 300 pF total load, eliminating need for additional line drivers in multi-drop configurations.
Microcontroller Peripheral Bridge	Memory-Mapped I/O Isolation
Use Scenario: Interfacing 8-bit microcontroller GPIO port to external SRAM or EPROM in embedded control firmware. IC Role / Device Role / Timing Role: Direction-controlled data path synchronized to microcontroller address strobes, isolating memory bus during instruction fetch cycles. Use Value: Propagation delay ≤32 ns ensures setup/hold timing compliance with 12 MHz Z80 or 8051 derivatives using standard wait-state generators.	Use Scenario: Isolating shared I/O address space between two microcontrollers in redundant safety-critical subsystems. IC Role / Device Role / Timing Role: Bidirectional gate enforcing mutual exclusion: only one MCU accesses peripherals at a time, controlled via dedicated DIR/OE handshake lines. Use Value: True logic polarity preserves register read/write semantics across both sides, avoiding software-level bit-flipping compensation.

Industrial Backplane Interface

Legacy System Bus Extension

Use Scenario: Connecting CPU bus to expansion slot in programmable logic controllers (PLCs) with hot-swap isolation requirements.

IC Role / Device Role / Timing Role: Bidirectional bus buffer providing direction-controlled data path between master and slave modules, with OE-gated isolation during slot insertion/removal.

Use Value: Prevents bus contention during live module replacement by enabling high-Z state via OE before DIR changes, meeting IEC 61000-4-2 ESD immunity requirements.

Use Scenario: Extending 8-bit ISA-style data bus between two PCBs in test instrumentation rack systems.

IC Role / Device Role / Timing Role: Level-shifting and impedance-matching transceiver ensuring signal integrity across 15 cm inter-board ribbon cable runs.

Use Value: 48 mA drive strength maintains <1 V_OL under 300 pF total load, eliminating need for additional line drivers in multi-drop configurations.

Microcontroller Peripheral Bridge

Memory-Mapped I/O Isolation

Use Scenario: Interfacing 8-bit microcontroller GPIO port to external SRAM or EPROM in embedded control firmware.

IC Role / Device Role / Timing Role: Direction-controlled data path synchronized to microcontroller address strobes, isolating memory bus during instruction fetch cycles.

Use Value: Propagation delay ≤32 ns ensures setup/hold timing compliance with 12 MHz Z80 or 8051 derivatives using standard wait-state generators.

Use Scenario: Isolating shared I/O address space between two microcontrollers in redundant safety-critical subsystems.

IC Role / Device Role / Timing Role: Bidirectional gate enforcing mutual exclusion: only one MCU accesses peripherals at a time, controlled via dedicated DIR/OE handshake lines.

Use Value: True logic polarity preserves register read/write semantics across both sides, avoiding software-level bit-flipping compensation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74ALS641A-1N	Same electrical specs and logic function, but in 20-pin PDIP (N) package with 300-mil width and through-hole mounting.	Used in prototyping, legacy repair, or systems requiring manual assembly or socket-based field upgrades.	Select when mechanical compatibility with existing DIP sockets or hand-soldered serviceability is required over surface-mount density.
SN74ALS642A-1NSR	Identical package and -1 performance, but inverting logic polarity (B→A outputs inverted relative to inputs).	Required where system-level signal inversion is needed for timing alignment or noise cancellation in differential-like bus topologies.	Select only if the application specifically requires inverted data path behavior; not a functional drop-in replacement due to polarity mismatch.

Compared with SN74ALS641A-1N, the SN74ALS641A-1NSR offers superior board-area efficiency and automated assembly compatibility; compared with SN74ALS642A-1NSR, it provides native true-logic signaling essential for transparent bus mirroring without downstream logic correction.

Availability

SN74ALS641A-1NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus extensions, and microcontroller peripheral bridges requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74ALS641A-1NSR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ALS641A-1NSR belongs to TI's legacy 74ALS logic family, engineered for high-speed, low-power bipolar TTL-compatible interfacing in mission-critical industrial control and instrumentation systems.

FAQ

What is the maximum output current specification for SN74ALS641A-1NSR?

The SN74ALS641A-1NSR supports a maximum low-level output current (I_OL) of 48 mA when V_CC is between 4.75 V and 5.25 V. This is the defining feature of the "-1" suffix variant and exceeds the 24 mA rating of the standard SN74ALS641A. The 48 mA rating enables direct driving of heavier capacitive or resistive bus loads without external buffering, and is validated per TI's SDAS300 datasheet Section "Recommended Operating Conditions".

Does SN74ALS641A-1NSR support hot-plug bus isolation?

Yes, SN74ALS641A-1NSR supports hot-plug isolation via its OE (output enable) input: asserting OE high places all A and B I/O ports into high-impedance state, electrically disconnecting both buses. This prevents signal contention during live module insertion or removal in backplane systems. The device's 0°C to 70°C rating and robust 48 mA I_OL ensure reliability during repeated hot-swap cycles in industrial PLC and test equipment applications.

What is the pin 1 location and orientation for SN74ALS641A-1NSR in SOP-20 package?

For SN74ALS641A-1NSR in SOP-20 (NS) package, pin 1 is located at the bottom-left corner of the component body when viewed from the top with the marking side up and the notch or dot oriented leftward. The pin numbering proceeds counterclockwise: pins 1–10 along the bottom edge, pin 11–20 along the top edge. This matches JEDEC MS-013 and TI DW0020A outline drawings, confirmed in TI's Package Materials Information document dated 10-Aug-2026.

Can SN74ALS641A-1NSR replace SN74ALS641ADWR in an existing design?

Yes, SN74ALS641A-1NSR can replace SN74ALS641ADWR in most cases, as both share identical logic function, pinout, and SOP-20 footprint. However, SN74ALS641A-1NSR offers enhanced 48 mA I_OL versus 24 mA for SN74ALS641ADWR, improving drive capability. Verify that V_CC remains within 4.75–5.25 V to fully utilize the -1 rating, and confirm thermal margin given higher ICC under full-load conditions per SDAS300 Table 4.

Is SN74ALS641A-1NSR RoHS compliant and what is its moisture sensitivity level?

Yes, SN74ALS641A-1NSR is RoHS compliant (lead-free NiPdAu finish) and rated MSL Level-1 (unlimited floor life at ≤30°C/60% RH), per TI's Package Option Addendum dated 15-Jul-2026. This eliminates bake requirements prior to reflow soldering and supports standard SMT assembly processes without special handling, making it suitable for high-reliability industrial manufacturing environments.

SN74ALS641A-1NSR Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74ALS

Package/Case:: 20-SOIC (0.209", 5.30mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

Logic Type:: Transceiver, Non-Inverting

Number of Elements:: 1

Number of Bits per Element:: 8

Input Type:: -

Output Type:: Open Collector

Current - Output High, Low:: -, 24mA

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-SO

SN74ALS641A-1NSR FAQ

1.How can I place an order for SN74ALS641A-1NSR through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74ALS641A-1NSR 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 SN74ALS641A-1NSR reliable?

The price and inventory of SN74ALS641A-1NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS641A-1NSR is usually 5 days.

3.What payment methods are accepted for SN74ALS641A-1NSR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS641A-1NSR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74ALS641A-1NSR?

SN74ALS641A-1NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74ALS641A-1NSR 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 SN74ALS641A-1NSR?

For technical support, including SN74ALS641A-1NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS641A-1NSR requirements.

6.How does Aetrix verify that SN74ALS641A-1NSR is sourced from the original manufacturer or authorized distributors?

All SN74ALS641A-1NSR 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 SN74ALS641A-1NSR meets industry standards.

7.What is the process for return or replacement of SN74ALS641A-1NSR?

All SN74ALS641A-1NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS641A-1NSR, 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 SN74ALS641A-1NSR part is unused and in its original packaging.

Return procedure for SN74ALS641A-1NSR:

1.Submit a request within 90 days.

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

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