My Inquiry
My Account
Texas Instruments SN74ALS639ADW
- Part No.:
- SN74ALS639ADW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS639ADW.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,322
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS639ADW from Texas Instruments is an octal bus transceiver with true logic polarity, designed for asynchronous bidirectional communication between open-collector A-bus and 3-state B-bus interfaces. It features 20-pin SOIC (DW) packaging, operates from 0°C to 70°C, supports 5-V supply, and delivers 24 mA low-level output current on both buses. It is used in legacy industrial backplane and parallel bus isolation systems.
For engineers reviewing the SN74ALS639ADW datasheet, SN74ALS639ADW pinout, SN74ALS639ADW application, or SN74ALS639ADW equivalent, key selection criteria include direction-control (DIR) and output-enable (OE) timing behavior, A-bus open-collector drive capability, B-bus 3-state voltage compliance (VOH ≥ 2.4 V at –15 mA), and compatibility with TTL/ALS logic families in mixed-technology systems.
Technical Context
This device implements a dual-bus interface with asymmetric I/O architecture: A-bus terminals are open-collector with 7-V absolute max rating and –1.5 V input clamp voltage (VIK), while B-bus outputs are 3-state with 5.5-V max output voltage and VOH = 2.4 V min at –15 mA. Direction flow is controlled by DIR, and bus isolation is enabled via OE.
Propagation delays are asymmetric: A→B transitions exhibit tPLH/tPHL ≤ 12 ns, whereas B→A transitions reach up to 30 ns (tPHL). Enable/disable times for B-bus outputs range from 2 ns (tPHZ) to 25 ns (tPZL), confirming fast 3-state control suitable for dynamic bus arbitration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | True (non-inverting) octal bus transceiver with DIR/OE control |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V TTL/ALS systems |
| A-Bus Output Type | Open-collector - enables wired-AND, level-shifting, and pull-up flexibility |
| B-Bus Output Type | 3-state - allows direct connection to shared data buses without contention |
| Output Drive | 24 mA IOL (A or B ports) - sufficient for driving multiple TTL loads or 500-Ω termination |
| Propagation Delay | A→B: ≤12 ns; B→A: ≤30 ns - defines maximum synchronous bus toggle rate |
| Operating Temperature | 0°C to 70°C - rated for commercial/industrial ambient environments |
Pinout & Package
SN74ALS639ADW uses a 20-pin SOIC (DW) package with 0.300-inch body width, 1.27-mm lead pitch, and 2.65-mm max height per JEDEC MS-013. Pin 1 is marked by a beveled corner or notch; leads are gull-wing, NIPDAU-finished, and MSL Level-1 rated.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | DIR | Direction control: LOW enables B→A data flow; HIGH enables A→B data flow |
| 2–9 | A1–A8 | Open-collector A-bus inputs/outputs - require external pull-ups for logic HIGH |
| 10 | GND | Ground reference for all internal circuitry and I/O |
| 11–18 | B1–B8 | 3-state B-bus outputs - high-impedance when OE = HIGH |
| 19 | OE | Output enable: LOW activates transceiver; HIGH disables both A and B buses |
| 20 | VCC | Positive supply (4.5–5.5 V) for internal logic and output drivers |
Key Features
| Feature | Design Value |
|---|---|
| Asymmetric I/O architecture | Combines open-collector A-bus (wired-AND capable) with 3-state B-bus (bus-sharing compliant) |
| True logic polarity | Preserves signal phase across A↔B paths - essential for parity, address, or control bus integrity |
| Low propagation skew | A→B delay ≤12 ns ensures tight timing alignment in high-speed parallel transfers |
| Robust input clamping | VIK = –1.5 V prevents latch-up during negative transients on A-bus lines |
| Controlled 3-state disable | tPZH/tPLZ ≤10 ns guarantees rapid bus release during arbitration or power sequencing |
Applications
| Industrial Backplane Interface | Legacy Parallel Printer Port |
|---|---|
|
Use Scenario: Isolating microcontroller address/data buses from multi-drop industrial backplanes with mixed-voltage peripherals. IC Role / Device Role / Timing Role: Bidirectional level translator and bus driver enabling safe A-bus (open-collector) to B-bus (3-state) handshaking under DIR/OE control. Use Value: Prevents bus contention during hot-swap events and supports 24-mA sink capability for driving long traces or multiple TTL inputs. |
Use Scenario: Managing bi-directional data transfer between host controller and parallel printer port (IEEE 1284 compliant legacy designs). IC Role / Device Role / Timing Role: True-polarity transceiver synchronizing STROBE/ACK handshake signals with data lanes using DIR-driven direction switching. Use Value: Enables reliable 12-ns A→B propagation for strobe-to-data setup and meets 30-ns B→A timing for ACK response latency. |
| EPROM Programming Adapter | TTL-to-Open-Collector Bus Bridge |
|
Use Scenario: Interfacing 5-V microcontroller GPIOs to EPROM programming voltage (VPP) and data/address pins requiring open-collector drive. IC Role / Device Role / Timing Role: Direction-controlled buffer translating 3-state MCU outputs to open-collector EPROM inputs while isolating VPP domains. Use Value: Supports 7-V A-bus tolerance and –1.5-V VIK clamping to protect MCU during high-voltage programming cycles. |
Use Scenario: Converting 3-state system bus signals to open-collector format for wired-AND interrupt aggregation or status monitoring. IC Role / Device Role / Timing Role: One-way or bidirectional bridge where B-bus receives 3-state data and A-bus outputs open-collector logic for shared-line signaling. Use Value: Delivers 24-mA sink per A-port to drive 500-Ω pull-ups typical in interrupt bus designs, with <10-ns enable/disable for glitch-free state transitions. |
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 with 300-mil width and no MSL rating | Preferred for through-hole prototyping or legacy PCBs with DIP footprints; lacks SOIC thermal and density advantages | Select SN74ALS639AN only when board layout requires DIP mounting or manual soldering is needed. |
| SN74AS639 | Faster switching (B→A tPHL ≤9 ns vs. 22 ns), higher IOL (64 mA), but increased ICC (up to 154 mA) and tighter VIH/VIL thresholds | Suitable for high-speed backplanes demanding sub-10-ns B→A latency; not drop-in due to higher power and noise sensitivity | Choose SN74AS639 only when timing budget requires <10 ns B→A delay and system can accommodate 2× power draw. |
Compared with SN74ALS639AN and SN74AS639, the SN74ALS639ADW offers optimal balance of SOIC footprint, 24-mA drive, 0–70°C operation, and ALS-family noise immunity-making it the preferred choice for space-constrained industrial control boards where reliability and legacy compatibility outweigh peak speed needs.
Availability
SN74ALS639ADW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy parallel port adapters, EPROM programming fixtures, and TTL-to-open-collector bus bridging requiring stable component supply across extended production lifecycles.
Supply support for SN74ALS639ADW 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.
The SN74ALS639ADW belongs to TI's legacy 74ALS logic family, engineered for robustness in mixed-technology digital systems requiring noise margin, open-collector flexibility, and 3-state bus sharing in commercial-temperature environments.
FAQ
What is the logic polarity of SN74ALS639ADW?
The SN74ALS639ADW implements true (non-inverting) logic polarity: data transmitted from A-bus to B-bus or B-bus to A-bus retains its original logic state without inversion. This distinguishes it from the SN74ALS638A, which provides inverting functionality. The truth table confirms identical logic levels appear on corresponding A and B terminals when enabled and directionally aligned.
Can SN74ALS639ADW drive standard TTL loads directly?
Yes, SN74ALS639ADW can drive standard TTL loads directly: its B-bus 3-state outputs deliver VOH ≥ 2.4 V at –15 mA and VOL ≤ 0.5 V at 24 mA, meeting TTL VIH/VIL thresholds. A-bus open-collector outputs require external pull-up resistors (typically 1–4.7 kΩ to 5 V) to establish HIGH logic levels compatible with TTL inputs.
What is the maximum clock/data rate supported by SN74ALS639ADW?
SN74ALS639ADW does not operate on a clock; it is asynchronous. Its usable data rate depends on propagation delay and system timing margins. With A→B tPLH/tPHL ≤12 ns and B→A tPHL ≤22 ns, it supports reliable bidirectional handshaking up to ~40 MHz in well-terminated, low-capacitance bus configurations (CL = 50 pF, RL = 500–680 Ω).
Is SN74ALS639ADW RoHS compliant?
Yes, SN74ALS639ADW is RoHS compliant per TI's Package Option Addendum: it carries "Yes" in the RoHS column, uses NIPDAU lead finish, and meets EU Directive 2011/65/EU requirements. The SOIC (DW) package contains no lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE above threshold limits.
How does the DIR pin control data flow direction in SN74ALS639ADW?
In SN74ALS639ADW, the DIR pin determines bidirectional path direction: when DIR = LOW, data flows from B-bus (3-state) to A-bus (open-collector); when DIR = HIGH, data flows from A-bus to B-bus. This is independent of OE - if OE = HIGH, both buses are isolated regardless of DIR state. The function table in the SDAS123A datasheet confirms this behavior.
SN74ALS639ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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
SN74ALS639ADW FAQ
1.How can I place an order for SN74ALS639ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS639ADW 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 SN74ALS639ADW reliable?
The price and inventory of SN74ALS639ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS639ADW is usually 5 days.
3.What payment methods are accepted for SN74ALS639ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS639ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS639ADW?
SN74ALS639ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS639ADW 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 SN74ALS639ADW?
For technical support, including SN74ALS639ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS639ADW requirements.
6.How does Aetrix verify that SN74ALS639ADW is sourced from the original manufacturer or authorized distributors?
All SN74ALS639ADW 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 SN74ALS639ADW meets industry standards.
7.What is the process for return or replacement of SN74ALS639ADW?
All SN74ALS639ADW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS639ADW, 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 SN74ALS639ADW part is unused and in its original packaging.
Return procedure for SN74ALS639ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS639ADW 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…
