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Texas Instruments SN74ALS640BDWR
- Part No.:
- SN74ALS640BDWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640BDWR.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,507
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Product details
Overview
SN74ALS640BDWR 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, and supports 12 mA low-level output current (IOL) under standard conditions.
For engineers reviewing the SN74ALS640BDWR datasheet, SN74ALS640BDWR pinout, SN74ALS640BDWR application, or SN74ALS640BDWR equivalent, key selection criteria include direction-control (DIR) and output-enable (OE) timing behavior, 3-state isolation performance, bus loading compatibility with ALS logic families, and SOIC-20 thermal and layout constraints.
Technical Context
This device implements a dual-rail bidirectional bus interface using complementary control inputs: DIR selects data flow direction (A→B or B→A), while OE enables/disables all outputs into high-impedance state. Its internal architecture uses bipolar ALS (Advanced Low-power Schottky) technology, delivering faster propagation delays than standard LS logic while maintaining TTL voltage thresholds.
Switching characteristics are specified under 50 pF load and 500 Ω source impedance, with tPLH/tPHL ≤ 11 ns and tPZH/tPLZ ≤ 24 ns at VCC = 4.5–5.5 V. The device operates only within its recommended supply range (4.5–5.5 V) and does not support mixed-voltage I/O or level-shifting.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Must be regulated within this window; operation outside risks functional failure or damage. |
| Operating Temperature | 0°C to 70°C - Validated only for commercial-grade environments; not rated for extended industrial or automotive use. |
| IOL (Standard) | 12 mA - Sustains 12 mA sink per output at VOL ≤ 0.4 V, sufficient for driving 2–3 standard TTL loads. |
| tPLH / tPHL | ≤11 ns - Propagation delay from input transition to valid output, critical for synchronous bus timing budgets. |
| tPZH / tPLZ | ≤24 ns - Time from OE assertion to output entering/exiting high-impedance state, determines bus contention window. |
| VIH / VIL | 2.0 V / 0.8 V - TTL-compatible input thresholds; ensures interoperability with 74LS, 74ALS, and 74AS families. |
| ICC (Outputs Disabled) | 28 mA max - Quiescent supply current when OE = high, defining static power in isolated-bus states. |
Pinout & Package
SN74ALS640BDWR is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, 12.8 mm long, with 1.27 mm pitch and maximum height of 2.65 mm. Pin 1 is marked by a beveled corner or notch on the top surface.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data transfer; High = A→B transfer; must be stable before data launch. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines tied to A bus; driven or received depending on DIR state. |
| 10 (GND) | Ground Reference | Primary signal and power return; requires low-inductance connection to minimize noise coupling. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines tied to B bus; functionally mirrored to A port under DIR control. |
| 19 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter 3-state; controls bus isolation timing. |
| 20 (VCC) | Supply Voltage | +5 V nominal supply; decoupling capacitor (0.1 µF ceramic) required adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Logic Architecture | Input-to-output polarity inversion simplifies bus arbitration logic in legacy backplane designs. |
| 3-State Output Isolation | OE-controlled high-impedance mode prevents bus contention during multi-master or hot-swap operations. |
| TTL-Compatible Voltage Thresholds | VIH = 2.0 V and VIL = 0.8 V ensure reliable interfacing with 74LS/ALS/AS logic without level shifters. |
| ALS Process Technology | Delivers 2× speed improvement over standard LS while reducing power consumption by ~30% at same frequency. |
| SOIC-20 Surface-Mount Package | Enables automated assembly and higher board density versus through-hole DIP alternatives. |
Applications
| Industrial Backplane Data Routing | Legacy Test Equipment Bus Interface |
|---|---|
Use Scenario: Bidirectional data exchange between CPU module and I/O expansion cards in modular PLC chassis. IC Role / Device Role / Timing Role: SN74ALS640BDWR acts as a direction-controlled bus buffer, isolating address/data lines during DMA cycles and enabling shared bus arbitration. Use Value: Enables deterministic 3-state control timing (tPZH ≤ 21 ns) to prevent glitches during bus handoff between masters. | Use Scenario: Interfacing microcontroller-based test sequencer with legacy GPIB or IEEE-488 peripheral controllers. IC Role / Device Role / Timing Role: SN74ALS640BDWR serves as a level-consistent bus translator, preserving TTL logic levels across subsystem boundaries. Use Value: Maintains VIH/VIL compatibility with vintage instruments while supporting modern controller clock rates up to 20 MHz. |
| Embedded Instrumentation Data Mux | Repair-Serviceable Digital Logic Trainer |
Use Scenario: Multiplexing sensor data streams from multiple analog front-ends into a single ADC interface in portable diagnostic gear. IC Role / Device Role / Timing Role: SN74ALS640BDWR functions as a controlled bidirectional data switch, routing samples under firmware DIR/OE coordination. Use Value: Provides guaranteed VOL ≤ 0.4 V at 12 mA load, ensuring clean digital sampling even with long PCB traces. | Use Scenario: Replacing failed transceivers in educational lab trainers where original SN74ALS640BN parts are obsolete. IC Role / Device Role / Timing Role: SN74ALS640BDWR substitutes for through-hole variants using adapter footprints or rework pads. Use Value: Matches pinout and electrical specs exactly, allowing drop-in replacement without schematic or layout modification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS640BN | Same electrical specs and pinout; PDIP-20 package instead of SOIC-20. | Through-hole mounting; higher thermal resistance and larger footprint. | Select for prototyping, repair, or legacy through-hole production where reflow capability is unavailable. |
| SN74AS640N | Faster switching (tPLH ≤ 7 ns), higher drive (IOL = 64 mA), but increased ICC (78 mA max). | Higher power consumption and stricter noise control requirements; not a direct drop-in due to different AC characteristics. | Choose only when timing budget demands sub-8 ns propagation or >20 mA per line drive capability. |
Compared with SN74ALS640BN and SN74AS640N, SN74ALS640BDWR offers optimal balance of speed, power, and SOIC manufacturability for commercial-grade embedded bus interfaces-without requiring PCB redesign or thermal derating.
Availability
SN74ALS640BDWR is available at Aetrix Electronics and suitable for industrial backplane routing, legacy test equipment interfacing, and embedded instrumentation data multiplexing requiring stable component supply across long-lifecycle programs.
Supply support for SN74ALS640BDWR 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 industrial and automotive electronics.
The SN74ALS640BDWR belongs to TI's legacy 74ALS logic family, engineered specifically for high-reliability, medium-speed bidirectional bus communication in commercial-grade systems where power efficiency and TTL compatibility are essential.
FAQ
What is the maximum allowable supply voltage for SN74ALS640BDWR?
The absolute maximum supply voltage (VCC) for SN74ALS640BDWR is 7 V, but operation above 5.5 V violates recommended conditions and risks permanent damage. Functional operation is guaranteed only between 4.5 V and 5.5 V per the datasheet's recommended operating conditions table. Exceeding 5.5 V may cause latch-up or accelerated aging, even if no immediate failure occurs. Always use a tightly regulated 5 V ±5% supply with local 0.1 µF ceramic decoupling at the VCC pin of SN74ALS640BDWR.
Does SN74ALS640BDWR support non-inverting data transfer?
No, SN74ALS640BDWR implements fixed inverting logic: data appearing at A1–A8 is inverted before appearing at B1–B8 (and vice versa) during active transfer. This is inherent to its ALS-series design and cannot be disabled or bypassed. If non-inverting behavior is required, external inverters or alternative devices such as SN74ALS245 (non-inverting octal transceiver) must be used. The SN74ALS640BDWR datasheet explicitly states "Inverting Logic" as a core feature.
Can SN74ALS640BDWR be used in place of SN74ALS640B-1DWR?
No-SN74ALS640BDWR and SN74ALS640B-1DWR are electrically distinct. The "-1" suffix denotes enhanced output drive: SN74ALS640B-1DWR supports 48 mA IOL (at VCC = 4.75–5.25 V), whereas SN74ALS640BDWR is rated for 12 mA (or 24 mA under specific test conditions). Substituting SN74ALS640BDWR in a -1 design may cause VOL violations or bus timing failures under heavy load. Always verify IOL requirements before interchange.
What is the thermal resistance (θJA) of SN74ALS640BDWR in SOIC-20 package?
Texas Instruments does not publish θJA for SN74ALS640BDWR in the SDAS122A datasheet or official package addendum. Thermal performance depends heavily on PCB layout: a 2-layer board with minimal copper pour yields θJA ≈ 120°C/W, while a 4-layer board with 1-in² 2-oz copper thermal pad reduces it to ~65°C/W. For reliability, limit power dissipation to ≤350 mW (calculated from ICC × VCC) and maintain junction temperature below 125°C. Refer to TI's application report SPRA087 for SOIC thermal modeling guidelines applicable to SN74ALS640BDWR.
Is SN74ALS640BDWR RoHS compliant and lead-free?
Yes, SN74ALS640BDWR is RoHS compliant and features NiPdAu (NIPDAU) lead finish, as confirmed in TI's Package Option Addendum. It meets JEDEC J-STD-020 moisture sensitivity Level-1 (unlimited floor life at ≤30°C/60% RH) and supports peak reflow temperatures up to 260°C. The part marking "ALS640B" appears on the top surface, and full compliance documentation-including substance declarations and test reports-is available via TI's Quality & Environmental Information portal for SN74ALS640BDWR.
SN74ALS640BDWR 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:
- Active
- 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, 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
SN74ALS640BDWR FAQ
1.How can I place an order for SN74ALS640BDWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BDWR 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 SN74ALS640BDWR reliable?
The price and inventory of SN74ALS640BDWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BDWR is usually 5 days.
3.What payment methods are accepted for SN74ALS640BDWR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640BDWR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BDWR?
SN74ALS640BDWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BDWR 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 SN74ALS640BDWR?
For technical support, including SN74ALS640BDWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BDWR requirements.
6.How does Aetrix verify that SN74ALS640BDWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BDWR 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 SN74ALS640BDWR meets industry standards.
7.What is the process for return or replacement of SN74ALS640BDWR?
All SN74ALS640BDWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BDWR, 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 SN74ALS640BDWR part is unused and in its original packaging.
Return procedure for SN74ALS640BDWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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