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Texas Instruments SN74ALS639ADWRG4
- Part No.:
- SN74ALS639ADWRG4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS639ADWRG4.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,323
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Product details
Overview
SN74ALS639ADWRG4 from Texas Instruments is a true-logic octal bus transceiver with open-collector A-bus outputs and 3-state B-bus outputs, designed for asynchronous bidirectional communication between mixed-logic buses. It operates from 4.5 V to 5.5 V, supports 0°C to 70°C ambient temperature, delivers 24 mA low-level output current per port, and features propagation delays as low as 2 ns (A→B) - used in legacy industrial backplane interfaces and TTL-to-open-collector level translation.
For engineers reviewing the SN74ALS639ADWRG4 datasheet, SN74ALS639ADWRG4 pinout, SN74ALS639ADWRG4 application, or SN74ALS639ADWRG4 equivalent, key selection criteria include direction-control logic behavior, open-collector vs. 3-state drive capability, thermal operating range compliance, and SOIC-20 package compatibility with legacy PCB footprints.
Technical Context
This device implements dual-bus isolation using DIR and OE inputs: DIR selects data flow direction (A→B or B→A), while OE disables both buses into high-impedance or open-circuit states. The A-side ports tolerate up to 7 V, enabling safe interfacing with higher-voltage systems, whereas B-side outputs are rated for 5.5 V maximum and support –15 mA high-level sink current.
Switching performance is characterized under 50 pF load with defined pull-up/pull-down networks: tPLH/tPHL from A to B are 2–12 ns; from B to A they range 10–30 ns; and OE-controlled enable/disable times (tPZH, tPZL) fall within 2–25 ns. All timing specs apply across the full 0°C to 70°C operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | True-logic bidirectional transceiver - no inversion between A and B buses. |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with standard 5 V TTL/ALS systems without regulation overhead. |
| A-Bus Output Type | Open-collector - requires external pull-up; enables wired-AND and voltage-level flexibility up to 7 V. |
| B-Bus Output Type | 3-state (high-impedance off-state) - allows shared bus arbitration without contention. |
| Output Drive Current | 24 mA per port (IOL) - sufficient for driving multiple TTL loads or moderate-capacitance backplanes. |
| Propagation Delay (A→B) | 2 ns min / 12 ns max - ensures tight timing margins in high-speed synchronous bus handshaking. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade industrial control and instrumentation environments. |
Pinout & Package
SN74ALS639ADWRG4 is housed in a 20-pin SOIC (DW) package with 1.27 mm pitch, 7.6 mm body width, and 12.83 mm length - RoHS-compliant, moisture sensitivity level 1, and reflow-compatible up to 260°C peak.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data transfer; High = A→B data transfer - determines real-time bus flow polarity. |
| 2–9 (A1–A8) | A-Bus I/O Terminals | Open-collector outputs - require external pull-ups; tolerate up to 7 V; sink current only. |
| 10 (GND) | Ground Reference | Power return path for all internal logic and output stages; must be low-impedance for noise immunity. |
| 11–18 (B1–B8) | B-Bus I/O Terminals | 3-state outputs - driven high/low when enabled; high-Z when OE is high - prevents bus contention. |
| 19 (OE) | Output Enable Input | Low = outputs active; High = all outputs disabled (A open-circuit, B high-Z) - enables bus isolation. |
| 20 (VCC) | Positive Supply | 5 V nominal supply input - powers internal logic and output drivers; bypass capacitor required at pin. |
Key Features
| Feature | Design Value |
|---|---|
| True-logic data path | Preserves signal polarity across A↔B transfer - eliminates need for external inverters in non-inverting bus bridges. |
| Mixed-output architecture | Combines open-collector A-side (for wired-OR, level-shifting) and 3-state B-side (for clean bus sharing) in one IC. |
| Robust voltage tolerance | A-bus pins withstand 7 V - allows safe interface with +5 V, +12 V, or mixed-supply subsystems without clamping diodes. |
| Fast enable/disable control | tPZH/tPZL ≤ 10 ns - enables rapid bus arbitration and dynamic reconfiguration in time-critical applications. |
| Industrial temperature rating | 0°C to 70°C operation - validated for use in programmable logic controllers, test equipment, and factory automation hardware. |
Applications
| Industrial Backplane Interface | TTL-to-Open-Collector Translation |
|---|---|
|
Use Scenario: Interfacing a microcontroller-based master card with legacy peripheral cards on a 20-slot ISA-style backplane using shared address/data lines. IC Role / Device Role / Timing Role: SN74ALS639ADWRG4 acts as a direction-controlled bus buffer, isolating the microcontroller's 3-state data bus from the open-collector interrupt request (IRQ) lines of peripherals. Use Value: Enables reliable bidirectional handshake without bus contention; open-collector IRQ lines remain functional even when B-bus is tri-stated. |
Use Scenario: Converting 5 V TTL logic signals from an FPGA I/O bank to drive a 12 V relay driver array requiring wired-AND capability. IC Role / Device Role / Timing Role: SN74ALS639ADWRG4 serves as a level-translating transceiver where A-bus connects to 12 V pull-ups and B-bus interfaces the FPGA's 3-state outputs. Use Value: Eliminates discrete transistor arrays; A-side 7 V tolerance avoids overvoltage damage during relay coil flyback events. |
| Legacy System Bus Arbitration | Test Equipment Signal Routing |
|
Use Scenario: Managing shared memory bus access between two CPU modules in a redundant industrial controller, where arbitration signals must be OR'd and data routed selectively. IC Role / Device Role / Timing Role: SN74ALS639ADWRG4 provides isolated bidirectional data coupling with DIR-controlled flow and OE-gated bus release. Use Value: Supports sub-15 ns propagation delay for arbitration response; OE allows hot-swap-safe bus disconnection during module replacement. |
Use Scenario: Routing stimulus and response signals between DUT interface connectors and measurement ASICs in automated test equipment (ATE) racks. IC Role / Device Role / Timing Role: SN74ALS639ADWRG4 functions as a configurable signal path switch - DIR selects source, OE enables/disables path to prevent crosstalk during calibration. Use Value: 24 mA drive strength ensures clean edges into 50 Ω coaxial paths; SOIC-20 footprint simplifies layout reuse across ATE board revisions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS639AN | Same logic function and electrical specs, but in 20-pin PDIP (N) package instead of SOIC (DW). | Used where through-hole assembly or socket-based prototyping is required; lacks surface-mount thermal and density advantages. | Select SN74ALS639AN only for hand-soldered evaluation or legacy DIP-based systems; SN74ALS639ADWRG4 preferred for volume SMT production. |
| SN74AS639 | Faster propagation (B→A min 5 ns vs. 10 ns), higher IOL (64 mA vs. 24 mA), but identical pinout and logic behavior. | Suitable for higher-speed backplanes or heavier capacitive loads; consumes more supply current (up to 154 mA vs. 50 mA). | Choose SN74AS639 when timing budget is critical and power/thermal headroom exists; SN74ALS639ADWRG4 remains optimal for cost- and power-sensitive industrial designs. |
Compared with SN74ALS639AN and SN74AS639, SN74ALS639ADWRG4 offers the best balance of SOIC-20 manufacturability, 24 mA drive capability, and 0°C–70°C qualification - making it the default choice for new industrial PCB designs requiring proven ALS-family reliability without speed or power penalties.
Availability
SN74ALS639ADWRG4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system upgrades, and test equipment signal routing requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS639ADWRG4 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 with over 90 years of analog and logic IC innovation, serving industrial, automotive, and communications markets.
SN74ALS639ADWRG4 belongs to the 74ALS family of advanced low-power Schottky logic devices, engineered specifically for robust, noise-immune digital interfacing in commercial and industrial control systems.
FAQ
What logic family does SN74ALS639ADWRG4 belong to, and how does it differ from standard TTL?
SN74ALS639ADWRG4 is part of the 74ALS (Advanced Low-Power Schottky) family, offering lower power consumption (ICC ≈ 16–54 mA) and improved noise immunity versus standard 74LS TTL. It retains TTL-compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V) but achieves faster switching via Schottky-clamped transistors - verified in the SDAS123A datasheet with 2–12 ns A→B propagation delays at 5 V.
Can SN74ALS639ADWRG4 interface a 5 V microcontroller with a 12 V peripheral bus?
Yes - the A-bus I/O ports of SN74ALS639ADWRG4 tolerate up to 7 V, and with appropriate external 12 V pull-up resistors on A1–A8, it safely translates 5 V logic levels to 12 V open-collector signaling. The B-bus side remains 5 V-compatible, matching the microcontroller's 3-state outputs - confirmed by absolute maximum ratings and recommended operating conditions in the TI datasheet.
Is SN74ALS639ADWRG4 pin-compatible with SN74ALS638A?
No - while both share the same SOIC-20 package and pin count, SN74ALS638A implements inverting logic (A↔B data is complemented), whereas SN74ALS639ADWRG4 is true-logic. Their function tables and truth behavior differ fundamentally; substituting one for the other without logic inversion elsewhere will cause functional failure.
What is the maximum capacitive load SN74ALS639ADWRG4 can drive on the B-bus outputs?
SN74ALS639ADWRG4 is characterized for CL = 50 pF on B-bus outputs in its switching specifications - tPLH/tPHL values (10–30 ns) assume this load with R1 = R2 = 500 Ω. Driving >50 pF may increase propagation delay and degrade edge rate; for heavier loads, verify timing margins using the VOL/IOL curve (0.35–0.5 V at 24 mA) and consider adding series termination.
Does SN74ALS639ADWRG4 support hot-swap or live-insertion into a powered backplane?
SN74ALS639ADWRG4 has no built-in hot-swap protection - applying VCC after signal voltages may violate absolute maximum ratings (e.g., VI > VCC + 0.5 V). For live insertion, ensure power sequencing (VCC applied before signals) or add external series resistors and clamping diodes. The device's 7 V A-bus tolerance helps mitigate transient overstress but does not guarantee hot-swap robustness.
SN74ALS639ADWRG4 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, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- Open Collector, Push-Pull
- Current - Output High, Low:
- -, 24mA; 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
SN74ALS639ADWRG4 FAQ
1.How can I place an order for SN74ALS639ADWRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS639ADWRG4 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 SN74ALS639ADWRG4 reliable?
The price and inventory of SN74ALS639ADWRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS639ADWRG4 is usually 5 days.
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SN74ALS639ADWRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS639ADWRG4 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 SN74ALS639ADWRG4?
For technical support, including SN74ALS639ADWRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS639ADWRG4 requirements.
6.How does Aetrix verify that SN74ALS639ADWRG4 is sourced from the original manufacturer or authorized distributors?
All SN74ALS639ADWRG4 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 SN74ALS639ADWRG4 meets industry standards.
7.What is the process for return or replacement of SN74ALS639ADWRG4?
All SN74ALS639ADWRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS639ADWRG4, 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 SN74ALS639ADWRG4 part is unused and in its original packaging.
Return procedure for SN74ALS639ADWRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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