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Texas Instruments SN74ALS642A-1DWRG4
- Part No.:
- SN74ALS642A-1DWRG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS642A-1DWRG4.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,838
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Product details
Overview
SN74ALS642A-1DWRG4 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 current (IOL), 0°C to 70°C operating temperature, and 5 V nominal supply voltage - used in legacy industrial backplane and board-to-board interconnect systems.
For engineers reviewing the SN74ALS642A-1DWRG4 datasheet, SN74ALS642A-1DWRG4 pinout, SN74ALS642A-1DWRG4 application, or SN74ALS642A-1DWRG4 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/output thresholds for mixed-logic system interfacing.
Technical Context
The SN74ALS642A-1DWRG4 implements true inverting bidirectional data flow controlled by DIR: when DIR = L, B-bus data propagates to A-bus; when DIR = H, A-bus data propagates to B-bus. Its 3-state outputs are disabled via OE = H, providing high-impedance isolation between buses.
It belongs to the ALS (Advanced Low-Power Schottky) logic family, delivering lower power than AS while maintaining higher speed than standard LS. The -1 suffix denotes increased IOL rating (48 mA vs. 24 mA), validated only at VCC = 4.75–5.25 V, with propagation delays ranging 5–38 ns under 50 pF load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting bidirectional bus transceiver with DIR and OE controls |
| Supply Voltage (VCC) | 4.5 V to 5.5 V - compatible with standard 5 V TTL/ALS systems |
| Low-Level Output Current (IOL) | 48 mA - enables direct driving of multiple TTL inputs or moderate-current loads |
| Propagation Delay (tPLH/tPHL) | 5–38 ns - supports up to ~20 MHz bus switching in typical 50 pF loading |
| Operating Temperature | 0°C to 70°C - rated for commercial/industrial ambient environments |
| Input Thresholds (VIH/VIL) | VIH = 2 V, VIL = 0.8 V - ensures robust noise margin against TTL logic levels |
| Output Voltage (VOL) | ≤0.5 V at IOL = 48 mA - guarantees valid LOW level under full sink load |
Pinout & Package
SN74ALS642A-1DWRG4 is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, 12.83 mm long, 2.65 mm max height, with 1.27 mm pitch and gull-wing leads. RoHS-compliant NIPDAU finish, MSL Level-1, and tape-and-reel packaging (25 per tube) support automated assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | DIR (Direction Control) | Active-HIGH signal selecting A→B (DIR=H) or B→A (DIR=L) data path |
| 2, 18 | OE (Output Enable) | Active-LOW enable; OE=H forces all I/O pins into high-impedance state |
| 3–10 | A1–A8 (A-Bus I/O) | Octal inverting bidirectional port connected to A-side data bus |
| 11–18 | B1–B8 (B-Bus I/O) | Octal inverting bidirectional port connected to B-side data bus |
| 9 | GND | Ground reference for logic and power return |
| 20 | VCC | +5 V supply pin - must be decoupled locally with 0.1 µF ceramic capacitor |
Key Features
| Feature | Design Value |
|---|---|
| Inverting data path | Ensures polarity-consistent bus translation without external inverters in A↔B link design |
| 48 mA output sink (IOL) | Supports fan-out of ≥20 standard TTL loads, reducing need for buffer stages |
| 3-state isolation via OE | Enables multi-drop bus arbitration and prevents contention during bus sharing |
| ALS logic family | Delivers 2× speed vs. LS with ~50% lower power - optimal for legacy 5 V backplanes |
| SOIC-DW package | Provides compact footprint (12.83 × 7.5 mm), thermal reliability, and surface-mount compatibility |
Applications
| Industrial Backplane Interconnect | Legacy System Bus Expansion |
|---|---|
Use Scenario: Isolating and translating data between CPU and peripheral modules across a 20-slot ISA-style backplane. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A-bus (CPU side) ↔ B-bus (peripheral side) with DIR-controlled flow direction and OE-gated arbitration. Use Value: Enables hot-swap-safe bus isolation and inverting logic alignment without additional gate logic, supporting deterministic timing under 38 ns delay budget. | Use Scenario: Extending memory-mapped I/O space between two PCBs in a modular test instrument rack. IC Role / Device Role / Timing Role: Octal inverting transceiver synchronizing parallel address/data lines between master and slave boards using shared DIR/OE control lines. Use Value: Delivers 48 mA drive strength to overcome trace capacitance across 15 cm inter-board runs, maintaining signal integrity at 12 MHz burst rates. |
| Embedded Controller Data Bridge | TTL-Level Protocol Converter |
Use Scenario: Bridging an 8-bit microcontroller data bus to an external ADC/DAC interface operating on inverted control signaling. IC Role / Device Role / Timing Role: Direction-controlled inverting transceiver aligning MCU data phase with external device expectations while enabling tri-state isolation during conversion cycles. Use Value: Eliminates discrete inverters and bus buffers, reducing BOM count and PCB area in space-constrained embedded designs. | Use Scenario: Converting between non-inverting and inverting data streams in a legacy RS-232 peripheral controller using TTL-level handshaking. IC Role / Device Role / Timing Role: Logic-level translator performing simultaneous inversion and bidirectional buffering between UART TX/RX and modem control lines. Use Value: Maintains <25 ns skew across all 8 bits, ensuring setup/hold compliance for synchronous protocol handshakes at 9600–38.4 kbaud. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS642ADWR | Standard version with 24 mA IOL; identical pinout, timing, and logic function | Lower drive strength limits fan-out in high-capacitance or long-trace scenarios | Select when 24 mA suffices and cost optimization is prioritized over margin |
| SN74AS641DW | True (non-inverting) logic; higher speed (1–10 ns delays) but 64 mA IOL and 84–136 mA ICC | Requires external inversion for inverting-path use; consumes >5× more supply current | Choose for maximum speed in non-inverting paths where power budget allows |
Compared with SN74ALS642ADWR, the SN74ALS642A-1DWRG4 provides double the output sink current for improved noise immunity and load drive, while SN74AS641DW trades inversion capability for raw speed and higher power - making the -1 version optimal for legacy 5 V systems requiring robust, inverting, medium-speed bus bridging.
Availability
SN74ALS642A-1DWRG4 is available at Aetrix Electronics and suitable for industrial backplane interconnect, legacy system bus expansion, embedded controller data bridging, and TTL-level protocol conversion requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS642A-1DWRG4 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 specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications electronics.
The SN74ALS642A-1DWRG4 belongs to TI's legacy ALS logic product line, engineered specifically for reliable, low-power, medium-speed bidirectional data transfer in 5 V TTL-compatible systems deployed in industrial control and instrumentation.
FAQ
What is the logic function of SN74ALS642A-1DWRG4?
The SN74ALS642A-1DWRG4 is an octal inverting bidirectional bus transceiver. When DIR = L, data flows from B-bus to A-bus with inversion; when DIR = H, data flows from A-bus to B-bus with inversion. OE = L enables transmission; OE = H places all I/O pins in high-impedance state. This behavior is confirmed in the FUNCTION TABLE on page 1 of the SDAS300 datasheet.
Does SN74ALS642A-1DWRG4 support 3.3 V operation?
No. SN74ALS642A-1DWRG4 is specified only for 4.5 V to 5.5 V supply operation, with recommended VCC = 5 V. Its input thresholds (VIH = 2 V, VIL = 0.8 V) and output characteristics are optimized for 5 V TTL/ALS systems. Operation below 4.5 V is not characterized and may result in undefined logic states or degraded timing.
What is the maximum capacitive load SN74ALS642A-1DWRG4 can drive reliably?
SN74ALS642A-1DWRG4 is characterized for CL = 50 pF in its switching specifications, with tPLH/tPHL values up to 38 ns under those conditions. Driving loads significantly above 50 pF will increase propagation delay and may violate setup/hold timing in synchronous systems. For >50 pF traces, verify signal integrity with oscilloscope measurements and consider local termination or reduced edge rates.
Is SN74ALS642A-1DWRG4 pin-compatible with SN74ALS641A-1DWRG4?
Yes - SN74ALS642A-1DWRG4 and SN74ALS641A-1DWRG4 share identical 20-pin SOIC (DW) packages and pin assignments. The only functional difference is logic polarity: SN74ALS641A is true (non-inverting), while SN74ALS642A is inverting. Swapping them requires verifying downstream logic compatibility with the inversion change.
What does the "-1" suffix indicate in SN74ALS642A-1DWRG4?
The "-1" suffix denotes an enhanced output drive specification: SN74ALS642A-1DWRG4 supports IOL = 48 mA (vs. 24 mA for standard SN74ALS642A), but only when VCC is maintained between 4.75 V and 5.25 V. This is explicitly stated in the "recommended operating conditions" table on page 3 of the SDAS300 datasheet.
SN74ALS642A-1DWRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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-1DWRG4 FAQ
1.How can I place an order for SN74ALS642A-1DWRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS642A-1DWRG4 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-1DWRG4 reliable?
The price and inventory of SN74ALS642A-1DWRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS642A-1DWRG4 is usually 5 days.
3.What payment methods are accepted for SN74ALS642A-1DWRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS642A-1DWRG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS642A-1DWRG4?
SN74ALS642A-1DWRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS642A-1DWRG4 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-1DWRG4?
For technical support, including SN74ALS642A-1DWRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS642A-1DWRG4 requirements.
6.How does Aetrix verify that SN74ALS642A-1DWRG4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS642A-1DWRG4 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-1DWRG4 meets industry standards.
7.What is the process for return or replacement of SN74ALS642A-1DWRG4?
All SN74ALS642A-1DWRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS642A-1DWRG4, 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-1DWRG4 part is unused and in its original packaging.
Return procedure for SN74ALS642A-1DWRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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