My Inquiry
My Account
Texas Instruments SN74ALS642A-1NSR
- Part No.:
- SN74ALS642A-1NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS642A-1NSR.pdf
- Description:
- IC TRANSCEIVER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,015
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS642A-1NSR from Texas Instruments is an inverting octal bus transceiver in a 20-pin SOP (NS) package, designed for asynchronous bidirectional data transfer between A and B buses. It features direction control (DIR), output enable (OE), 48 mA low-level output drive (IOL), 0°C to 70°C operating range, and 5 V nominal supply voltage - used in legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74ALS642A-1NSR datasheet, SN74ALS642A-1NSR pinout, SN74ALS642A-1NSR application, or SN74ALS642A-1NSR equivalent, key selection criteria include its inverting logic behavior, -1 version's enhanced 48 mA sink capability, SOP-20 thermal and layout compatibility, and TTL-compatible input thresholds with ALS family propagation delays.
Technical Context
The SN74ALS642A-1NSR implements true 3-state bidirectional bus interface logic with separate DIR and OE controls: DIR selects data flow direction (A→B or B→A), while OE disables all outputs to isolate buses. Its inverting function means A inputs are inverted at B outputs and vice versa during active transmission.
It operates strictly within 4.5 V–5.5 V VCC, supports 50 pF load capacitance, and delivers guaranteed tPHL/tPLH ≤ 38 ns under worst-case conditions. The -1 suffix denotes increased IOL rating (48 mA vs. standard 24 mA), valid only when VCC is 4.75–5.25 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL/ALS systems without regulation overhead |
| IOL (max) | 48 mA - enables direct driving of multiple TTL loads or termination-resistor networks without external buffers |
| Propagation Delay | tPHL/tPLH ≤ 38 ns - meets timing budgets for 20–25 MHz bus handshaking in legacy control systems |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade industrial equipment, not extended or automotive temperature ranges |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - matches standard TTL logic levels, ensuring interoperability with 74LS/74ALS families |
| Output Drive | VOL ≤ 0.5 V @ IOL = 48 mA - maintains noise margin below 0.5 V under full sink load, critical for reliable low-level recognition |
| ICC (active) | 8–28 mA - low static power vs. AS variants, suitable for power-constrained backplane slots |
Pinout & Package
SOP-20 (NS) package: 12.8 mm × 7.5 mm body, 1.27 mm pitch, 2.65 mm max height, gull-wing leads, RoHS-compliant NiPdAu finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow - determines real-time bus arbitration path |
| 2 (A1) | Bus A I/O Port | Inverting bidirectional terminal: driven by A bus when DIR/OE enable A→B; receives B bus when DIR/OE enable B→A |
| 3–9 (A2–A8) | Bus A I/O Ports | Octal set identical to A1 - supports full 8-bit parallel bus coupling with consistent inversion |
| 10 (GND) | Ground Reference | Primary signal return for all I/O and internal logic - must be low-impedance for noise immunity |
| 11–18 (B1–B8) | Bus B I/O Ports | Inverting counterparts to A1–A8 - data appears inverted relative to A-side during active transfer |
| 19 (VCC) | Power Supply | +5 V supply input - requires local 0.1 µF ceramic decoupling adjacent to pin |
| 20 (OE) | Output Enable Input | Low = transceiver active; High = all A/B ports in high-impedance state - enables bus sharing across multiple devices |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Function | Guarantees signal polarity inversion across A↔B paths - required for specific legacy bus protocols like certain ISA expansion designs |
| 48 mA Sink Capability (-1 version) | Supports direct connection to 10+ standard TTL inputs or 50 Ω terminated lines without external drivers |
| Independent DIR and OE Controls | Enables precise timing separation: DIR sets direction before OE enables, preventing bus contention during state transitions |
| ALS Family Speed-Power Tradeoff | Delivers 38 ns max delay with ~15 mA typical ICC - optimized for lower power than AS variants while retaining speed for mid-frequency buses |
| TTL-Compatible Thresholds | VIH = 2.0 V / VIL = 0.8 V ensures plug-and-play integration with 74LS, 74ALS, and microcontroller GPIOs without level shifters |
Applications
| Industrial Backplane Interface | Legacy Memory Expansion |
|---|---|
Use Scenario: Isolating and translating data between CPU address/data bus and peripheral card slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B (CPU→card) and B→A (card→CPU) transfers with direction arbitration via DIR and isolation via OE. Use Value: Inverting logic matches legacy ISA-style bus timing maps; 48 mA drive handles multi-drop TTL loading across 12-inch backplane traces. | Use Scenario: Extending 8-bit data bus width between microcontroller and external SRAM/ROM modules on retro-computing or test equipment PCBs. IC Role / Device Role / Timing Role: Octal transceiver enabling synchronous read/write handshaking between MCU data port and memory chip data pins. Use Value: SOP-20 footprint saves board space vs. DIP; ALS speed ensures <40 ns propagation aligns with 12 MHz MCU wait-state timing. |
| Test Equipment Bus Coupling | Automated Test Fixture Interface |
Use Scenario: Interfacing digital pattern generator and analyzer channels through shared test head cabling in ATE systems. IC Role / Device Role / Timing Role: Direction-controlled buffer isolating stimulus and response paths on common 8-bit ribbon cable harnesses. Use Value: OE-controlled 3-state operation prevents signal corruption during channel reconfiguration; SOP package eases routing in dense fixture PCBs. | Use Scenario: Connecting microcontroller-based control logic to DUT (device under test) I/O headers in production burn-in fixtures. IC Role / Device Role / Timing Role: Level-shifting and bus-driving interface between 3.3 V MCU GPIOs (via level translator) and 5 V DUT logic inputs/outputs. Use Value: Guaranteed VOL ≤ 0.5 V at 48 mA ensures robust low-level recognition despite contact resistance in spring-clip test sockets. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS642AN | Same logic function and specs, but in 20-pin PDIP (N) package - 300-mil width, through-hole mounting | Used where manual prototyping, socket-based testing, or legacy through-hole assembly is required | Select SN74ALS642AN for breadboarding or field-replaceable modules; SN74ALS642A-1NSR for surface-mount production. |
| SN74AS641DW | True (non-inverting) logic, higher speed (7.5 ns typ), higher power (84 mA ICC), 64 mA IOL - AS family, SOIC-20 | Suitable for high-speed non-inverting bus links where ALS timing margins are insufficient | Choose SN74AS641DW only if inversion is unnecessary and sub-10 ns propagation is mandatory; otherwise, SN74ALS642A-1NSR offers better power efficiency. |
Compared with SN74ALS642AN, SN74ALS642A-1NSR reduces board area and enables automated assembly, while SN74AS641DW trades ALS's power advantage for AS's speed - making SN74ALS642A-1NSR optimal for cost-sensitive, medium-speed industrial bus isolation where inversion is specified.
Availability
SN74ALS642A-1NSR is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy memory expansion subsystems, and automated test fixture interconnects requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS642A-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 SN74ALS642A-1NSR belongs to TI's legacy 74ALS logic family, engineered for reliable 5 V TTL-compatible bus interfacing in cost-sensitive, medium-speed industrial control and instrumentation systems.
FAQ
What logic function does the SN74ALS642A-1NSR implement?
The SN74ALS642A-1NSR implements an inverting octal bus transceiver function: data transferred from A to B or B to A is inverted at the output. This behavior is fixed per device design and differs from the true-logic SN74ALS641A. The inversion applies to all eight channels simultaneously and is inherent to the SN74ALS642A-1NSR silicon implementation.
What does the "-1" suffix indicate in SN74ALS642A-1NSR?
The "-1" suffix in SN74ALS642A-1NSR specifies the enhanced output drive version, raising the maximum low-level output current (IOL) from 24 mA (standard) to 48 mA - but only when VCC is maintained between 4.75 V and 5.25 V. This allows the SN74ALS642A-1NSR to drive heavier capacitive or resistive loads without external buffering.
Is SN74ALS642A-1NSR pin-compatible with SN74ALS641A-1NSR?
No, SN74ALS642A-1NSR is not functionally pin-compatible with SN74ALS641A-1NSR. Although both are 20-pin SOP devices with identical pinouts (DIR, A1–A8, GND, VCC, OE, B1–B8), their logic functions differ: SN74ALS642A-1NSR is inverting, while SN74ALS641A-1NSR is true. Swapping them without circuit redesign will invert all data paths, causing system failure.
What is the maximum recommended operating temperature for SN74ALS642A-1NSR?
The SN74ALS642A-1NSR is characterized for operation from 0°C to 70°C ambient temperature - this is its absolute maximum rated operating free-air temperature range. Operation outside this range may result in parametric failure or reduced reliability. It is not rated for extended temperature (–40°C to 85°C) or automotive (–40°C to 125°C) use.
Does SN74ALS642A-1NSR support hot-swap or live-insertion?
No, SN74ALS642A-1NSR does not support hot-swap or live-insertion. It lacks bus-hold, power-up 3-state, or Ioff protection features. Applying VCC or signals while OE is inactive may cause undefined states or excessive current draw. System-level hot-swap capability requires external circuitry such as current-limiting resistors and controlled power sequencing - not provided by the SN74ALS642A-1NSR itself.
SN74ALS642A-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, 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
SN74ALS642A-1NSR FAQ
1.How can I place an order for SN74ALS642A-1NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS642A-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 SN74ALS642A-1NSR reliable?
The price and inventory of SN74ALS642A-1NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS642A-1NSR is usually 5 days.
3.What payment methods are accepted for SN74ALS642A-1NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS642A-1NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS642A-1NSR?
SN74ALS642A-1NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS642A-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 SN74ALS642A-1NSR?
For technical support, including SN74ALS642A-1NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS642A-1NSR requirements.
6.How does Aetrix verify that SN74ALS642A-1NSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS642A-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 SN74ALS642A-1NSR meets industry standards.
7.What is the process for return or replacement of SN74ALS642A-1NSR?
All SN74ALS642A-1NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS642A-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 SN74ALS642A-1NSR part is unused and in its original packaging.
Return procedure for SN74ALS642A-1NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS642A-1NSR Tags
-
SN74LVC1G17DBVR
Texas Instruments
-
SN74LVC1G07DCKR
Texas Instruments
-
SN74LVC1G17DCKR
Texas Instruments
-
SN74LVC1G07DBVR
Texas Instruments
-
SN74LVC1G125DCKR
Texas Instruments
-
SN74AHCT1G126DBVR
Texas Instruments
-
SN74LVC1G125DBVR
Texas Instruments
-
SN74AHCT1G125DBVR
Texas Instruments
-
SN74LVC2G17DBVR
Texas Instruments
-
SN74LVC2G07DCKR
Texas Instruments
-
SN74LVC1G34DCKR
Texas Instruments
-
SN74LVC2G17DCKR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
