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Texas Instruments SN74AS640DWG4
- Part No.:
- SN74AS640DWG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AS640DWG4.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,949
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Product details
Overview
SN74AS640DWG4 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in TTL-compatible systems. It features inverting logic, 20-pin SOIC (DW) package, 0°C to 70°C operating temperature, 48 mA low-level output drive, and direction-control (DIR) and output-enable (OE) inputs for precise bus isolation.
For engineers reviewing the SN74AS640DWG4 datasheet, SN74AS640DWG4 pinout, SN74AS640DWG4 application, or SN74AS640DWG4 equivalent, key selection criteria include its 48 mA IOL capability, 7 ns max tPHL/tPLH propagation delay at 5 V, 3-state control timing (tPZH/tPLZ), and compatibility with legacy 5-V TTL bus architectures requiring robust drive strength and bidirectional flow control.
Technical Context
This device implements a dual-rail, inverting octal transceiver architecture with separate DIR and OE inputs enabling independent control of data direction and output state. Its internal circuitry supports true 3-state operation-high-impedance output when OE is high-and guarantees rail-to-rail logic thresholds (VIL = 0.8 V, VIH = 2 V) for reliable interfacing with standard TTL and LS families.
Designed for 5-V operation only, it delivers 48 mA sink current per output under recommended conditions (VCC = 4.75–5.25 V), with ICC up to 123 mA during active low-drive states. Switching performance is characterized across full temperature range with CL = 50 pF and R1/R2 = 500 Ω load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Supply Voltage | 4.5 V to 5.5 V - operates strictly within 5-V TTL domain; no 3.3-V support. |
| IOL Low-Level Output Current | 48 mA - enables direct driving of multiple TTL loads or termination-resistor networks without external buffers. |
| tPHL / tPLH Propagation Delay | Max 7 ns - ensures sub-10 ns bidirectional bus turnaround critical for high-speed backplane or memory bus applications. |
| VOH / VOL Output Voltage | VOH ≥ 2.4 V @ IOH = –12 mA; VOL ≤ 0.55 V @ IOL = 48 mA - meets TTL VOH/VOL margins for noise-immune interconnect. |
| Operating Temperature Range | 0°C to 70°C - commercial-grade rating suitable for industrial control panels and embedded computing chassis. |
| Package Type | SOIC-20 (DW) - 7.5 mm × 12.8 mm body, 1.27 mm pitch, RoHS-compliant NIPDAU lead finish. |
| Logic Function | Inverting bidirectional transceiver - A→B or B→A data flow controlled by DIR; outputs disabled to high-Z when OE = HIGH. |
Pinout & Package
SN74AS640DWG4 uses a 20-pin SOIC (DW) package with standard 1.27 mm pitch and 2.65 mm maximum height. Pin 1 is located at the top-left corner (quadrant Q1) with beveled edge marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Determines data flow direction: LOW = B→A, HIGH = A→B; referenced to GND, TTL-compatible threshold. |
| 2–9 (A1–A8) | Input/Output Port A | Bidirectional I/O pins for A-side bus; internally connected to transceiver core with 3-state output drivers. |
| 10 (GND) | Ground Reference | Primary power return path; must be low-inductance connection to minimize switching noise coupling. |
| 11–18 (B1–B8) | Input/Output Port B | Bidirectional I/O pins for B-side bus; electrically symmetrical to A-port with identical drive/sink specs. |
| 19 (OE) | Output Enable Input | Active-LOW enable: LOW = outputs enabled, HIGH = all A/B pins enter high-impedance state for bus isolation. |
| 20 (VCC) | Power Supply | +5 V DC supply input; requires local 0.1 µF ceramic decoupling capacitor placed within 5 mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional data path | Eliminates need for external inverters in systems requiring complemented bus signals, reducing component count and layout area. |
| 48 mA output sink capability | Supports direct interface to unterminated 50-Ω transmission lines or fan-out to ≥10 standard TTL loads without signal degradation. |
| Independent DIR and OE controls | Enables concurrent direction arbitration and selective bus segment isolation-critical for multi-master or hot-swap-capable backplanes. |
| Sub-10 ns propagation delay | Meets timing budgets for 100+ MHz bus clock domains when used with 50 pF trace capacitance and 500 Ω source/load impedance. |
| SOIC-20 RoHS-compliant packaging | Enables automated SMT assembly with standard reflow profiles (MSL Level-1, peak 260°C), compatible with IPC-7351 land patterns. |
Applications
| Industrial Backplane Interface | Legacy System Bus Extension |
|---|---|
Use Scenario: Interfacing a microcontroller-based I/O module to a 20-bit parallel backplane in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional data bridge between CPU address/data bus and peripheral expansion slots, managing direction via FPGA-controlled DIR signal. Use Value: 48 mA drive strength ensures clean signal integrity across 15 cm backplane traces; 7 ns delay enables synchronous handshaking at 12.5 MHz burst rates. | Use Scenario: Extending the data bus of a vintage 1980s minicomputer system using modern PCBs while preserving original timing. IC Role / Device Role / Timing Role: Replacing obsolete 74LS640 in bus repeater cards to restore full 8-bit bidirectional throughput without redesigning control logic. Use Value: Pin-compatible drop-in replacement with identical function table and tighter VOL spec (≤0.55 V), improving noise margin over aging LS parts. |
| Test Equipment Data Acquisition | Automated Test Fixture Control |
Use Scenario: Routing sensor data from multiple analog front-end boards to a central digitizer in benchtop test systems. IC Role / Device Role / Timing Role: Isolating and steering time-multiplexed ADC output streams onto shared data lanes using synchronized OE gating. Use Value: Precise 3-state disable timing (tPLZ ≤ 13 ns) prevents bus contention during channel switching, eliminating sampling glitches. | Use Scenario: Controlling relay matrices and DUT power sequencing in production-line functional testers. IC Role / Device Role / Timing Role: Translating low-voltage control signals from FPGA I/O banks to 5-V relay driver inputs while providing bidirectional status feedback. Use Value: Dual-bus capability allows simultaneous command issuance and hardware-ready acknowledgment on same physical lines, cutting fixture wiring by 40%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BDWR | ALS family: lower IOL (24 mA), slower speed (11 ns max tPHL), higher noise immunity (VIK = –1.5 V). | Suitable for low-power, noise-sensitive environments where 48 mA drive is unnecessary. | Select SN74ALS640BDWR only if system load is light (<5 TTL units) and EMI rejection is prioritized over speed/drive. |
| SN74AS864N | Same AS family but non-inverting logic, PDIP-20 package, 64 mA IOL, 6 ns max tPHL. | Requires logic inversion in external circuitry; incompatible pinout due to different DIR/OE placement. | Choose SN74AS864N only when non-inverting behavior is required and board layout allows PDIP footprint and revised routing. |
Compared with SN74ALS640BDWR and SN74AS864N, SN74AS640DWG4 uniquely balances high drive (48 mA), fast propagation (7 ns), inverting logic, and SOIC-20 packaging-making it optimal for space-constrained, high-fanout 5-V bus interfaces where timing and signal integrity are co-critical.
Availability
SN74AS640DWG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system upgrades, test equipment data acquisition, and automated test fixture control requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74AS640DWG4 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 50 years of innovation in digital interface ICs.
The SN74AS640DWG4 belongs to TI's 74AS logic family-engineered for high-speed, high-drive 5-V TTL systems where propagation delay, output current, and noise immunity are critical in industrial and instrumentation applications.
FAQ
What is the maximum operating temperature for SN74AS640DWG4?
The SN74AS640DWG4 is characterized for operation from 0°C to 70°C, consistent with commercial-grade 74AS logic. It is not rated for extended temperature ranges like the military-grade SN54AS640 (–55°C to 125°C). Thermal derating is not specified, so operation outside this range may result in parametric failure or reduced reliability. Always verify ambient and junction temperatures in final PCB layout using TI's thermal resistance data for DW package.
Does SN74AS640DWG4 support 3.3-V logic levels?
No, SN74AS640DWG4 does not support 3.3-V logic levels. It is strictly a 5-V device with VCC specification of 4.5 V to 5.5 V and TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V). Applying 3.3-V signals to inputs may result in marginal or incorrect logic recognition, and VCC < 4.5 V violates recommended operating conditions. For mixed-voltage systems, level-shifting circuitry or a 3.3-V-compatible transceiver such as SN74LVC8T245 is required.
What is the meaning of "G4" in SN74AS640DWG4?
The "G4" suffix in SN74AS640DWG4 denotes Texas Instruments' green packaging standard: lead-free (Pb-free), RoHS-compliant construction with NiPdAu (NIPDAU) lead finish and halogen-free molding compound. It corresponds to TI's standard green part numbering convention and confirms compliance with JEDEC J-STD-020 moisture sensitivity Level-1 (unlimited floor life at ≤30°C/85% RH). The base part SN74AS640DW is functionally identical but may carry older finish specifications.
Can SN74AS640DWG4 replace SN74LS640 in existing designs?
Yes, SN74AS640DWG4 can directly replace SN74LS640 in most cases due to identical pinout, function table, and 5-V supply compatibility. However, SN74AS640DWG4 offers significantly faster propagation (7 ns vs. ~25 ns for LS), higher output drive (48 mA vs. 8 mA), and lower input current (IIL = –0.75 mA vs. –0.4 mA). Verify that downstream loads can tolerate faster edge rates and that power delivery supports higher ICC (up to 123 mA vs. ~60 mA for LS). No PCB changes are required.
What is the recommended decoupling for SN74AS640DWG4?
Texas Instruments recommends a minimum 0.1 µF ceramic capacitor placed as close as possible (≤5 mm) to the VCC (pin 20) and GND (pin 10) pins of SN74AS640DWG4. For systems with heavy simultaneous switching or long power traces, add a bulk 4.7 µF–10 µF tantalum or aluminum electrolytic capacitor near the power entry point. Avoid shared vias between decoupling caps and high-speed signal paths; use dedicated ground planes and short, wide traces for VCC/GND routing to suppress switching noise-induced jitter.
SN74AS640DWG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74AS640DWG4 FAQ
1.How can I place an order for SN74AS640DWG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS640DWG4 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 SN74AS640DWG4 reliable?
The price and inventory of SN74AS640DWG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS640DWG4 is usually 5 days.
3.What payment methods are accepted for SN74AS640DWG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS640DWG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS640DWG4?
SN74AS640DWG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS640DWG4 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 SN74AS640DWG4?
For technical support, including SN74AS640DWG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS640DWG4 requirements.
6.How does Aetrix verify that SN74AS640DWG4 is sourced from the original manufacturer or authorized distributors?
All SN74AS640DWG4 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 SN74AS640DWG4 meets industry standards.
7.What is the process for return or replacement of SN74AS640DWG4?
All SN74AS640DWG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS640DWG4, 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 SN74AS640DWG4 part is unused and in its original packaging.
Return procedure for SN74AS640DWG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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