My Inquiry
My Account
Texas Instruments SN74ALS640BDWE4
- Part No.:
- SN74ALS640BDWE4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS640BDWE4.pdf
- Description:
- IC TXRX INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,788
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS640BDWE4 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) at VCC = 4.5 V. It is used in legacy industrial control backplanes and board-to-board communication interfaces.
For engineers reviewing the SN74ALS640BDWE4 datasheet, SN74ALS640BDWE4 pinout, SN74ALS640BDWE4 application, or SN74ALS640BDWE4 equivalent, key selection considerations include its 3-state bidirectional control architecture, DIR/OE dual-input logic interface, ALS family propagation delay (≤11 ns), and compatibility with 5-V TTL bus loading requirements.
Technical Context
This device implements a dual-control 8-bit bidirectional bus interface using separate direction (DIR) and output-enable (OE) inputs. Its inverting logic ensures signal polarity consistency across both data paths, and the 3-state outputs provide high-impedance isolation when OE is high.
The SN74ALS640BDWE4 belongs to the ALS (Advanced Low-Power Schottky) logic family, delivering lower power consumption than standard LS while maintaining compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V) and drive strength. It operates strictly within 4.5–5.5 V supply range and is not rated for mixed-voltage or 3.3-V operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Must be supplied with regulated 5-V rail; no brown-out tolerance below 4.5 V. |
| Propagation Delay (tPLH/tPHL) | ≤11 ns max - Enables reliable operation in 20-MHz bus systems with 50-pF load. |
| IOL (Low-Level Output) | 12 mA @ VCC = 4.5 V - Sufficient to drive 10 LS-TTL loads or 20 ALS loads on shared bus. |
| IOH (High-Level Output) | –12 mA @ VCC = 4.5 V - Supports fan-out to standard TTL inputs without level-shifting. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade embedded systems, not extended or industrial temp. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - Matches standard TTL logic levels; no CMOS-level compatibility. |
| 3-State Enable Time (tPZH) | ≤21 ns - Critical for synchronous bus arbitration where OE is dynamically controlled. |
Pinout & Package
SN74ALS640BDWE4 uses a 20-pin SOIC (DW) package with 0.300-inch body width, 1.27-mm lead pitch, and maximum height of 2.65 mm. Pin 1 is marked by a beveled corner or notch; leads are gull-wing, RoHS-compliant NiPdAu finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Determines data flow: LOW = B→A, HIGH = A→B; active-high logic polarity. |
| 2–9 (A1–A8) | Port A I/O Terminals | Bidirectional data lines tied to A-side bus; high-impedance when OE = HIGH. |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output currents; must be low-inductance connection. |
| 11–18 (B1–B8) | Port B I/O Terminals | Bidirectional data lines tied to B-side bus; electrically isolated from A ports when OE = HIGH. |
| 19 (OE) | Output Enable Input | Active-LOW enable: LOW enables transceiver, HIGH forces all A/B pins into 3-state (Hi-Z). |
| 20 (VCC) | Power Supply | 5-V nominal supply; requires local 0.1-µF ceramic decoupling capacitor placed ≤5 mm from pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting bidirectional logic | Maintains consistent signal inversion across both A→B and B→A paths, simplifying timing analysis in symmetric bus architectures. |
| Dual independent controls (DIR + OE) | Enables precise bus arbitration: DIR selects direction while OE globally disables outputs-no contention during state transitions. |
| ALS-family speed-power balance | Delivers 11-ns max propagation delay with ICC ≤55 mA (outputs low), reducing dynamic power vs. AS-series at comparable speed. |
| TTL-compatible input thresholds | VIH = 2.0 V / VIL = 0.8 V ensures interoperability with legacy 74LS, 74F, and microcontroller GPIOs without level shifters. |
| 20-pin SOIC (DW) footprint | Standardized land pattern per IPC-7351; supports automated placement and reflow with 0.125-mm stencil thickness. |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Bus Extension |
|---|---|
Use Scenario: Isolating CPU address/data bus from peripheral expansion slots in programmable logic controllers (PLCs). IC Role / Device Role / Timing Role: Bidirectional buffer enabling read/write cycles between MPU and add-on I/O modules via shared 8-bit data bus. Use Value: Prevents bus contention during slot insertion/removal; 3-state isolation ensures safe hot-swap capability under firmware control. |
Use Scenario: Extending Z80 or 8085 system bus to external memory or peripheral ICs on daughterboards. IC Role / Device Role / Timing Role: Direction-controlled transceiver synchronizing data transfers between mainboard and expansion card with minimal added latency. Use Value: Meets strict 20-ns setup/hold timing budgets for 4-MHz Z80 systems; inverting logic preserves bus protocol integrity. |
| Test Equipment Signal Routing | Automated Test Fixture Interfacing |
Use Scenario: Configurable signal path switching inside benchtop DMMs or logic analyzers with modular front-end boards. IC Role / Device Role / Timing Role: Reconfigurable bus coupler routing test signals between measurement ASICs and FPGA-based control logic. Use Value: DIR/OE separation allows deterministic path selection and glitch-free bus release during mode changes. |
Use Scenario: Interfacing production test handlers with DUT boards requiring bidirectional stimulus/response on shared test pins. IC Role / Device Role / Timing Role: Level-shifting and bus-isolation element between handler controller (TTL) and DUT (ALS-compatible). Use Value: 12-mA drive strength ensures robust signal integrity across 15-cm ribbon cables; 0°C–70°C rating matches factory ambient conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bidirectional 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 instead of SOIC (DW). | Used where through-hole assembly, manual prototyping, or socket-based field repair is required. | Select SN74ALS640BN for breadboarding, legacy rework, or systems with mixed-technology PCBs. |
| SN74AS640N | Faster AS-family variant: tPHL/tPLH ≤7 ns, IOL = 48 mA, but higher ICC (up to 123 mA) and tighter VIH/VIL (2.0 V / 0.8 V still met). | Suitable for high-speed bus extensions where propagation delay dominates over power budget. | Choose SN74AS640N only if sub-10-ns timing is mandatory and thermal/power margins allow increased dissipation. |
Compared with SN74ALS640BN and SN74AS640N, SN74ALS640BDWE4 offers optimal balance of SOIC manufacturability, moderate speed (11 ns), and low static/dynamic power-making it preferred for cost-sensitive, volume-produced commercial equipment where layout density and reflow compatibility matter most.
Availability
SN74ALS640BDWE4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor bus extensions, test equipment signal routing, and automated test fixture interfacing requiring stable component supply across multi-year production cycles.
Supply support for SN74ALS640BDWE4 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and communications reach.
SN74ALS640BDWE4 belongs to TI's legacy ALS logic product line, engineered specifically for reliable, low-power bidirectional bus interfacing in commercial-grade digital systems operating at 5 V.
FAQ
What is the maximum clock rate supported by SN74ALS640BDWE4 in a synchronous bus application?
The SN74ALS640BDWE4 does not include an internal clock; it is an asynchronous transceiver. Its usable data rate depends on propagation delay (≤11 ns) and system setup/hold timing. In practice, it reliably supports bidirectional bus cycles up to 20 MHz when driving 50-pF loads with proper termination and layout-verified in TI's SDAS122A characterization at CL = 50 pF.
Can SN74ALS640BDWE4 interface directly with 3.3-V logic devices?
No. SN74ALS640BDWE4 is a 5-V-only device with TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V) and no 3.3-V tolerant I/O. Driving its inputs from 3.3-V sources risks marginal VIH margin, and connecting its 5-V outputs to 3.3-V inputs violates absolute maximum ratings. Level-shifting circuitry is required for mixed-voltage interoperation.
Is SN74ALS640BDWE4 pin-compatible with SN74ALS640BDWR?
Yes. SN74ALS640BDWE4 and SN74ALS640BDWR share identical SOIC (DW)-20 packaging, pinout, and electrical specifications. The "E4" suffix denotes TI's green, RoHS-compliant packaging standard (NiPdAu lead finish, Pb-free die attach), while "DWR" indicates tape-and-reel packaging-both are functionally and mechanically interchangeable.
What is the recommended decoupling strategy for SN74ALS640BDWE4?
Place one 0.1-µF X7R ceramic capacitor between VCC (pin 20) and GND (pin 10), located ≤5 mm from the device with short, wide traces. For systems with multiple SN74ALS640BDWE4 units or high di/dt noise, add a bulk 4.7-µF tantalum or aluminum electrolytic capacitor near the board's 5-V entry point. Avoid shared vias between decoupling and signal return paths.
Does SN74ALS640BDWE4 support hot-swap or live-insertion on a powered bus?
SN74ALS640BDWE4 supports controlled hot-swap only when OE is held HIGH (3-state disabled) during insertion. Its absolute maximum I/O voltage is 5.5 V, and applying bus signals before VCC stabilization may cause latch-up or damage. TI does not specify or guarantee live-insertion behavior; use external series resistors and power-sequencing controllers for robust hot-swap implementations.
SN74ALS640BDWE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- 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, 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
SN74ALS640BDWE4 FAQ
1.How can I place an order for SN74ALS640BDWE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS640BDWE4 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 SN74ALS640BDWE4 reliable?
The price and inventory of SN74ALS640BDWE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS640BDWE4 is usually 5 days.
3.What payment methods are accepted for SN74ALS640BDWE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS640BDWE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS640BDWE4?
SN74ALS640BDWE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS640BDWE4 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 SN74ALS640BDWE4?
For technical support, including SN74ALS640BDWE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS640BDWE4 requirements.
6.How does Aetrix verify that SN74ALS640BDWE4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS640BDWE4 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 SN74ALS640BDWE4 meets industry standards.
7.What is the process for return or replacement of SN74ALS640BDWE4?
All SN74ALS640BDWE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS640BDWE4, 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 SN74ALS640BDWE4 part is unused and in its original packaging.
Return procedure for SN74ALS640BDWE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS640BDWE4 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…
