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Texas Instruments SN74ALS640BDW
- Part No.:
- SN74ALS640BDW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640BDW.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,597
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Product details
Overview
SN74ALS640BDW 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, operating temperature range of 0°C to 70°C, and supports 12 mA low-level output current at 5 V supply. It is used in legacy industrial control backplanes and board-to-board communication interfaces.
For engineers reviewing the SN74ALS640BDW datasheet, SN74ALS640BDW pinout, SN74ALS640BDW application, or SN74ALS640BDW equivalent, key selection considerations include its 3-state bidirectional control architecture, ALS logic family timing (tPLH/tPHL ≤ 11 ns), IOL = 12 mA drive capability, and compatibility with standard 5-V TTL signal levels and bus isolation requirements.
Technical Context
The SN74ALS640BDW implements dual 8-bit bidirectional data paths controlled by DIR (direction) and OE (output enable) inputs. Its inverting logic architecture means data propagates with polarity inversion across the transceiver path. The device operates exclusively in the commercial temperature range (0°C to 70°C) and is rated for 4.5 V to 5.5 V supply voltage.
It uses bipolar ALS (Advanced Low-Power Schottky) technology, delivering lower power than standard LS while maintaining TTL-compatible input thresholds (VIL = 0.8 V max, VIH = 2 V min) and output drive (VOH ≥ 2.4 V at IOH = –12 mA, VOL ≤ 0.4 V at IOL = 12 mA). Propagation delays are specified up to 11 ns (tPHL) under 50-pF load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - enables TTL-compatible operation with reduced power vs. LS, suitable for legacy 5-V bus systems. |
| Supply Voltage | 4.5 V to 5.5 V - requires stable 5-V rail; not compatible with 3.3-V or mixed-voltage domains without level shifting. |
| Output Drive | IOL = 12 mA / IOH = –12 mA - sufficient to drive standard TTL loads (up to 10 unit loads) on shared buses. |
| Propagation Delay | tPHL ≤ 10 ns, tPLH ≤ 11 ns (CL = 50 pF) - supports high-speed bus handshaking in backplane and motherboard applications. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems, not extended or industrial temperature environments. |
| 3-State Enable Time | tPZL ≤ 24 ns, tPHZ ≤ 10 ns - ensures fast bus release and acquisition during direction switching or arbitration. |
| Input Thresholds | VIH = 2 V min, VIL = 0.8 V max - matches standard TTL logic levels, enabling direct interface with 74LS/74ALS peripherals. |
Pinout & Package
SN74ALS640BDW 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 via notch or bevel on the package top edge.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Determines data flow direction: LOW enables B→A transfer; HIGH enables A→B transfer. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines connected to A-side bus; internally inverted during transfer. |
| 10 (GND) | Ground Reference | Primary power return for logic and output stages; must be low-impedance connection. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines connected to B-side bus; inverted relative to A-port signals. |
| 19 (OE) | Output Enable Input | Active-LOW control: LOW enables transceiver; HIGH places all A/B pins in high-impedance state. |
| 20 (VCC) | Positive Supply | 5-V power supply input; requires local 0.1 µF ceramic decoupling adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Bidirectional Data Path | Ensures signal polarity consistency across bus segments when cascading multiple transceivers in daisy-chained architectures. |
| 3-State Output Isolation | Enables true bus contention avoidance: OE HIGH disconnects both A and B ports electrically from their respective buses. |
| TTL-Compatible Input/Output Levels | Directly interfaces with legacy 74LS, 74ALS, and 74AS devices without level-shifting circuitry. |
| ALS Technology Power Efficiency | Typical ICC = 55 mA (outputs low) - ~30% lower supply current than equivalent 74LS transceivers at same speed. |
| 20-Pin High-Density SOIC Packaging | Reduces PCB footprint by >50% versus equivalent PDIP (N) packages while supporting automated SMT assembly. |
Applications
| Industrial Backplane Interface | Legacy Computer Memory Expansion |
|---|---|
Use Scenario: Interfacing CPU local bus to peripheral expansion slots in programmable logic controllers (PLCs) and CNC motion controllers. IC Role / Device Role / Timing Role: Bidirectional data bridge between microprocessor address/data bus and isolated I/O module backplane, synchronized via external clock and control strobes. Use Value: Enables hot-swap-safe bus isolation using OE control and provides robust 12-mA drive to overcome trace capacitance across 150-mm backplane runs. | Use Scenario: Adding RAM or EPROM modules to vintage 8-bit computer motherboards (e.g., Z80 or 8080-based systems). IC Role / Device Role / Timing Role: Transceiver managing data flow between CPU and memory banks during read/write cycles, with DIR tied to memory R/W signal and OE controlled by chip select decoding. Use Value: Inverting logic aligns with common memory controller signal polarity conventions, eliminating need for external inverters in data path. |
| Test Equipment Bus Arbitration | Modular Instrumentation Chassis |
Use Scenario: Dynamic sharing of GPIB or IEEE-488 bus resources among multiple instrument controllers in automated test systems. IC Role / Device Role / Timing Role: Direction-controlled gate between master controller bus and slave instrument bus, with OE coordinated by system arbitration logic. Use Value: Sub-12 ns propagation delay ensures minimal timing skew during bus handover, preserving IEEE-488 setup/hold margins. | Use Scenario: Data routing between main controller card and plug-in measurement modules in rack-mounted DAQ systems. IC Role / Device Role / Timing Role: Isolating and translating data between controller's local bus and module-specific sensor/actuator interfaces, with DIR set per module function (input vs. output). Use Value: 3-state disable capability prevents signal contention when modules are inserted or removed under power, enhancing system reliability. |
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 ALS logic, identical electrical specs, but in 20-pin PDIP (N) package - through-hole mount, larger footprint, higher thermal resistance. | Suitable for prototyping, repair, or legacy through-hole PCBs; lacks SOIC reflow compatibility and density advantage. | Select SN74ALS640BN only when manual assembly or socketing is required; SN74ALS640BDW preferred for volume SMT production. |
| SN74AS640N | AS-family variant: faster (tPHL ≤ 6 ns), higher drive (IOL = 64 mA), but higher ICC (123 mA) and stricter VIH/VIL thresholds (VIH = 2 V, VIL = 0.8 V). | Better for high-speed, low-latency bus interconnects where power budget allows; not drop-in due to increased supply current and noise sensitivity. | Choose SN74AS640N only when sub-8 ns propagation is mandatory and thermal/power design accommodates +100% ICC increase. |
Compared with SN74ALS640BN and SN74AS640N, the SN74ALS640BDW delivers optimal balance of speed (≤11 ns), power efficiency (ICC ≤ 55 mA), and SOIC manufacturability for commercial-grade 5-V bus bridging - making it the preferred choice for cost-sensitive, high-volume legacy system upgrades.
Availability
SN74ALS640BDW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy computer memory expansion, test equipment bus arbitration, and modular instrumentation chassis requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74ALS640BDW 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 logic families.
The SN74ALS640BDW belongs to TI's legacy 74ALS logic product line, engineered specifically for reliable, low-power bidirectional bus interfacing in commercial 5-V TTL systems deployed from the 1980s onward.
FAQ
What is the maximum operating temperature for SN74ALS640BDW?
The SN74ALS640BDW is characterized for operation from 0°C to 70°C, consistent with commercial-grade specifications. It is not rated for extended temperature ranges such as –40°C to 85°C or military –55°C to 125°C. Operation outside this range may result in undefined timing behavior or parametric failure. Always verify ambient and junction temperature limits in thermal design for the SN74ALS640BDW.
Does SN74ALS640BDW support 3.3-V logic levels?
No, the SN74ALS640BDW does not support 3.3-V logic levels. It requires a 4.5 V to 5.5 V supply and features TTL-compatible input thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V) and output voltages (VOH ≥ 2.4 V, VOL ≤ 0.4 V). Direct interface with 3.3-V systems requires level-shifting circuitry; the SN74ALS640BDW is intended for pure 5-V TTL environments.
Is SN74ALS640BDW pin-compatible with SN74ALS640BN?
Yes, the SN74ALS640BDW and SN74ALS640BN share identical pin functions and numbering, differing only in package type: DW (SOIC) versus N (PDIP). Both use the same 20-pin layout with DIR on pin 1, A1–A8 on pins 2–9, GND on pin 10, B1–B8 on pins 11–18, OE on pin 19, and VCC on pin 20. Mechanical mounting and PCB footprint differ, but logic-level connectivity is preserved.
What is the meaning of "inverting logic" in SN74ALS640BDW?
"Inverting logic" in the SN74ALS640BDW means that data appearing at the A port appears inverted at the B port (and vice versa) during active transfer. For example, if A1 = HIGH, then B1 = LOW when DIR and OE are asserted for A→B mode. This is inherent to the internal gate structure and must be accounted for in system-level signal definition - it is not a configurable feature.
Can SN74ALS640BDW replace SN74LS640?
The SN74ALS640BDW can functionally replace SN74LS640 in most 5-V TTL systems due to matching pinout, logic function, and voltage thresholds. However, the ALS version offers faster propagation (≤11 ns vs. ≤17 ns for LS), lower power (ICC ≤ 55 mA vs. ~70 mA), and improved noise immunity. No PCB changes are needed, but verify timing margins and loading in high-fanout configurations before substitution.
SN74ALS640BDW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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, 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
SN74ALS640BDW FAQ
1.How can I place an order for SN74ALS640BDW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BDW 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 SN74ALS640BDW reliable?
The price and inventory of SN74ALS640BDW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BDW is usually 5 days.
3.What payment methods are accepted for SN74ALS640BDW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640BDW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BDW?
SN74ALS640BDW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BDW 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 SN74ALS640BDW?
For technical support, including SN74ALS640BDW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BDW requirements.
6.How does Aetrix verify that SN74ALS640BDW is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BDW 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 SN74ALS640BDW meets industry standards.
7.What is the process for return or replacement of SN74ALS640BDW?
All SN74ALS640BDW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BDW, 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 SN74ALS640BDW part is unused and in its original packaging.
Return procedure for SN74ALS640BDW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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