Texas Instruments SN74LS641DWRE4

Overview

SN74LS641DWRE4 from Texas Instruments is an octal bus transceiver with open-collector outputs, designed for bidirectional data flow control in TTL-level parallel bus systems. It features 8-bit non-inverting data paths, active-low output-enable (OE\), and operates over 0°C to 70°C. Used in legacy industrial backplanes and microprocessor address/data bus isolation.

For engineers reviewing the SN74LS641DWRE4 datasheet, SN74LS641DWRE4 pinout, SN74LS641DWRE4 application, or SN74LS641DWRE4 equivalent, key selection criteria include open-collector drive capability, TTL-compatible input thresholds, 20-pin SOIC packaging, and compatibility with LS-family timing and voltage levels.

Technical Context

This device implements dual 4-bit bidirectional bus transceivers with separate transmit (T) and receive (R) controls per nibble, enabling independent direction management on A- and B-side buses. Each output supports wired-AND logic via open-collector configuration, requiring external pull-up resistors.

It uses standard TTL circuitry with guaranteed V_IH ≥ 2.0 V, V_IL ≤ 0.8 V, and I_OH = 0 mA (open-circuit), I_OL = 24 mA at V_CC = 5 V - matching LS-series drive strength and noise margin requirements.

Key Specifications

Pinout & Package

SN74LS641DWRE4 is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, with 1.27 mm pitch and 2.65 mm maximum height. Pin 1 marked by notch or bevel; pin 10 is GND, pin 20 is V_CC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS245N, SN74LS641DWRE4 offers native wired-AND capability critical for shared bus signaling; compared with SN74LS642DWRE4, it provides non-inverting data path essential for transparent address/data forwarding without polarity reversal.

Availability

SN74LS641DWRE4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor bus extensions, and LED multiplexing applications requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS641DWRE4 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 with broad industrial and automotive qualification.

SN74LS641DWRE4 belongs to TI's legacy 74LS logic family, engineered for robustness and interoperability in TTL-based digital systems deployed from the 1980s through modern retro-fit and maintenance programs.

FAQ

What is the function of the T/R\ pin on SN74LS641DWRE4?

The T/R\ (Transmit/Receive) pin is an active-low control that determines data direction: when low, data flows from A-side to B-side; when high, data flows from B-side to A-side. This enables bidirectional bus management without external direction logic. SN74LS641DWRE4 relies on this pin for real-time bus arbitration in systems like shared memory interfaces or multi-controller backplanes.

Does SN74LS641DWRE4 support 3.3 V logic levels?

No - SN74LS641DWRE4 is a TTL LS-family device requiring 4.75 V to 5.25 V V_CC and exhibits TTL input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V). It does not tolerate 3.3 V supply or guarantee correct operation with 3.3 V inputs. SN74LS641DWRE4 must be used in 5 V-only systems or with level-shifting circuitry for mixed-voltage designs.

Can SN74LS641DWRE4 replace SN74LS245 in an existing design?

Not directly - while both are octal transceivers, SN74LS641DWRE4 has open-collector outputs and T/R\ control, whereas SN74LS245 uses tri-state outputs and DIR control. Pinouts differ, and SN74LS641DWRE4 requires external pull-ups. SN74LS641DWRE4 substitution demands schematic and layout changes unless the design already accommodates open-collector behavior and wiring.

What is the maximum sink current per output on SN74LS641DWRE4?

Each output of SN74LS641DWRE4 can sink up to 24 mA at V_CC = 5 V while maintaining VO_L ≤ 0.5 V. This rating applies under steady-state DC conditions and supports driving multiple TTL loads, LEDs, or optocouplers. SN74LS641DWRE4 must use appropriate pull-up resistors (e.g., 1 kΩ for 5 V) to ensure proper logic levels and thermal limits.

Is SN74LS641DWRE4 RoHS compliant?

Yes - SN74LS641DWRE4 uses NiPdAu (NIPDAU) lead finish and is RoHS compliant per TI's packaging documentation. The "E4" suffix denotes TI's green packaging standard, confirming absence of lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE per EU Directive 2011/65/EU. SN74LS641DWRE4 meets JEDEC J-STD-609A Class 1 marking requirements.