My Inquiry
My Account
Texas Instruments SN74ALS642A-1DW
- Part No.:
- SN74ALS642A-1DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS642A-1DW.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,545
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS642A-1DW from Texas Instruments is an octal inverting bidirectional bus transceiver in a 20-pin SOIC (DW) package, designed for asynchronous two-way data communication between A and B buses. It features direction control (DIR), output enable (OE), 48 mA low-level output drive (IOL), 5 V supply operation, and operates from 0°C to 70°C - used in legacy industrial backplane and memory expansion interfaces.
For engineers reviewing the SN74ALS642A-1DW datasheet, SN74ALS642A-1DW pinout, SN74ALS642A-1DW application, or SN74ALS642A-1DW equivalent, key selection criteria include its inverting logic function, -1 version's enhanced 48 mA sink capability, SOIC-DW thermal and layout compatibility, and TTL-compatible input thresholds with 50 pF load timing performance.
Technical Context
The SN74ALS642A-1DW implements true 3-state bidirectional I/O with separate DIR and OE controls: DIR selects data flow direction (A→B or B→A), while OE disables all outputs into high-impedance state. Its inverting logic path ensures signal polarity reversal across the transceiver path.
It uses ALS (Advanced Low-Power Schottky) bipolar technology, delivering lower power than standard AS while maintaining speed - typical ICC is 8–15 mA (high-output) and 18–28 mA (low-output) at VCC = 5.5 V, with propagation delays of 10–30 ns under 50 pF load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting bidirectional bus transceiver - output complements input during active transfer, critical for polarity-sensitive bus arbitration |
| IOL (Max) | 48 mA at VCC = 4.75–5.25 V - supports driving heavy capacitive loads or multiple TTL inputs without external buffers |
| VCC Range | 4.5 V to 5.5 V - compatible with standard 5 V logic rails and tolerant of supply ripple in industrial systems |
| tPLH / tPHL | 10–30 ns (A↔B, DIR, OE) - meets timing budgets for 33 MHz synchronous bus handshaking when combined with proper PCB routing |
| Operating Temp | 0°C to 70°C - qualified for commercial/industrial ambient environments, not extended temperature grades |
| Package | SOIC-20 (DW), 7.5 mm × 12.8 mm, 1.27 mm pitch - surface-mount compatible with standard reflow profiles (MSL Level-1) |
Pinout & Package
SOIC-20 (DW) package: 7.5 mm × 12.8 mm body, 1.27 mm lead pitch, 2.65 mm max height, gull-wing leads, MSL Level-1 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | DIR (Direction Control) | Active-High control: DIR = H enables A→B transfer; DIR = L enables B→A transfer - determines real-time data path polarity |
| 2, 18 | OE (Output Enable) | Active-Low control: OE = L enables transceiver; OE = H places all A/B I/Os in high-Z - isolates buses during arbitration or standby |
| 3–10 | A1–A8 (A-side I/O) | Octal inverting bidirectional ports - each pin functions as input or output depending on DIR/OE state; internal inverters ensure complemented data transfer |
| 11–18 | B1–B8 (B-side I/O) | Octal inverting bidirectional ports - electrically identical to A-side but physically separated for bus isolation; same inversion behavior applies |
| 9 | GND | Ground reference for all logic and output stages - must be low-impedance connection to minimize ground bounce in high-speed switching |
| 20 | VCC | +5 V supply for ALS circuitry - requires local 0.1 µF ceramic decoupling adjacent to pin to suppress switching noise |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Data Path | Guarantees signal polarity inversion during A↔B transfer - essential for matching legacy system-level logic conventions where inverted bus signaling is required |
| 48 mA Sink Capability (-1 Version) | Enables direct interface to up to 12 standard TTL loads (IIL = −1.6 mA) without fanout buffers - reduces component count in dense backplane designs |
| Independent DIR and OE Controls | Allows full bus arbitration: DIR sets direction while OE independently gates data flow - supports time-multiplexed bidirectional protocols |
| ALS Process Technology | Delivers 30% lower power vs. AS family at comparable speed - ICC = 8–28 mA vs. AS641's 50–136 mA - extends thermal margin in compact enclosures |
Applications
| Memory Expansion Interface | Industrial Backplane Bus |
|---|---|
Use Scenario: Connecting microprocessor address/data bus to external SRAM or EPROM modules with separate read/write control paths. IC Role / Device Role / Timing Role: Bidirectional inverting transceiver managing data flow between CPU and memory banks; DIR synchronized with RD/WR strobes, OE gated by chip select. Use Value: Inversion matches memory device input polarity requirements; 48 mA drive ensures reliable setup/hold timing across 15 cm PCB traces loaded with 50 pF per stub. | Use Scenario: Interfacing multiple controller cards via shared parallel backplane in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Isolating and translating data between card-local buses and backplane; DIR set per card role (master/slave), OE controlled by slot arbitration logic. Use Value: High-Z isolation prevents bus contention during hot-swap; ALS speed supports 20 MB/s burst transfers under 50 pF loading per segment. |
| Legacy System Bus Bridge | Test Equipment Data Acquisition |
Use Scenario: Bridging ISA-style peripheral bus to custom FPGA-based I/O subsystem in retro-computing or instrumentation upgrades. IC Role / Device Role / Timing Role: Level-shifting and inverting transceiver enabling protocol translation between legacy bus timing and modern logic; DIR tied to bus grant, OE to DMA acknowledge. Use Value: Matches TTL voltage thresholds (VIH = 2 V, VIL = 0.8 V) for robust noise immunity; SOIC-DW footprint allows drop-in replacement on aging PCBs. | Use Scenario: Routing sensor data from analog front-end ADCs to digital processing unit in automated test equipment (ATE) racks. IC Role / Device Role / Timing Role: Buffering and direction-controlling parallel 8-bit data streams from multi-channel ADCs; DIR toggled per channel scan cycle, OE synchronized to sample clock edge. Use Value: 10–30 ns propagation delay ensures sub-33 MHz sampling synchronization; 48 mA drive maintains signal integrity across 200 mm ribbon cable runs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS642ADW | Standard version: IOL = 24 mA (not 48 mA); otherwise identical pinout, timing, and logic function | Suitable only for lighter loads (<6 TTL inputs); insufficient for high-fanout backplane segments | Select SN74ALS642ADW only if existing design already meets fanout requirements and cost optimization is prioritized over margin. |
| SN74AS641DW | True (non-inverting) logic; higher speed (tPHL down to 1 ns), higher power (ICC up to 136 mA), 64 mA IOL | Requires logic inversion elsewhere in system; better for speed-critical paths but increases thermal load and layout complexity | Choose SN74AS641DW only when absolute minimum propagation delay is mandatory and system-level inversion can be accommodated. |
Compared with SN74ALS642ADW, the SN74ALS642A-1DW provides double the output sink current for robust bus driving; compared with SN74AS641DW, it trades raw speed for lower power and built-in inversion - making it optimal for cost- and thermally constrained industrial interfaces where polarity alignment matters.
Availability
SN74ALS642A-1DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, memory expansion subsystems, and legacy system bus bridging requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS642A-1DW 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 company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS642A-1DW belongs to TI's legacy 74ALS logic family, engineered for reliable 5 V TTL-compatible operation in commercial-temperature industrial control and computing infrastructure.
FAQ
What logic function does the SN74ALS642A-1DW implement?
The SN74ALS642A-1DW implements an inverting bidirectional bus transceiver function: data transferred from A to B or B to A is logically complemented. This distinguishes it from the true-logic SN74ALS641A-1DW and is explicitly confirmed in the function table and logic diagrams of the SDAS300 datasheet. The inversion occurs regardless of direction, and the SN74ALS642A-1DW part number itself denotes the inverting variant within the ALS64x family.
What is the maximum output sink current for SN74ALS642A-1DW, and under what conditions is it guaranteed?
The SN74ALS642A-1DW guarantees a maximum low-level output current (IOL) of 48 mA, but only when VCC is maintained between 4.75 V and 5.25 V - a condition explicitly stated in the "recommended operating conditions" table of the SDAS300 datasheet. This rating applies exclusively to the "-1" version; the standard SN74ALS642ADW is rated for 24 mA. Exceeding this voltage window invalidates the 48 mA specification.
Does SN74ALS642A-1DW support operation outside the 0°C to 70°C range?
No, the SN74ALS642A-1DW is characterized and specified only for operation from 0°C to 70°C, as confirmed in both the "recommended operating conditions" and "absolute maximum ratings" sections of the SDAS300 datasheet. It is not rated for extended temperature ranges (e.g., −40°C to 85°C or −55°C to 125°C), and no industrial or military grade variants of this specific part number exist in TI's packaging addendum.
What package type and dimensions does SN74ALS642A-1DW use?
The SN74ALS642A-1DW uses the SOIC-20 (DW) package: 7.5 mm × 12.8 mm body size, 1.27 mm lead pitch, 2.65 mm maximum height, gull-wing leads, and JEDEC MS-013 compliant outline. This is verified in TI's Package Option Addendum and the DW0020A package drawing referenced in the datasheet, with tube quantity of 25 units per reel-compatible tube.
How does the direction control (DIR) and output enable (OE) interact in SN74ALS642A-1DW?
In the SN74ALS642A-1DW, DIR and OE operate independently: DIR selects data direction (H = A→B, L = B→A), while OE (active-low) enables or disables all I/Os (L = active, H = high-Z isolation). When OE = H, both A and B ports enter high-impedance regardless of DIR state - ensuring complete bus isolation during arbitration or reset. This dual-control architecture is defined in the function table and logic diagram of the SDAS300 datasheet.
SN74ALS642A-1DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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-SOIC
SN74ALS642A-1DW FAQ
1.How can I place an order for SN74ALS642A-1DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS642A-1DW 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-1DW reliable?
The price and inventory of SN74ALS642A-1DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS642A-1DW is usually 5 days.
3.What payment methods are accepted for SN74ALS642A-1DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS642A-1DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS642A-1DW?
SN74ALS642A-1DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS642A-1DW 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-1DW?
For technical support, including SN74ALS642A-1DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS642A-1DW requirements.
6.How does Aetrix verify that SN74ALS642A-1DW is sourced from the original manufacturer or authorized distributors?
All SN74ALS642A-1DW 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-1DW meets industry standards.
7.What is the process for return or replacement of SN74ALS642A-1DW?
All SN74ALS642A-1DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS642A-1DW, 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-1DW part is unused and in its original packaging.
Return procedure for SN74ALS642A-1DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS642A-1DW 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…
