My Inquiry
My Account
Texas Instruments SN74ALS639ANSR
- Part No.:
- SN74ALS639ANSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74ALS639ANSR.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,651
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS639ANSR from Texas Instruments is a true-logic octal bus transceiver in a 20-pin plastic DIP (N) package, designed for asynchronous bidirectional data transfer between open-collector A-bus and 3-state B-bus systems. It features 24 mA low-level output current capability, 0°C to 70°C operating temperature range, and propagation delays as low as 2 ns (A→B), enabling reliable level-shifting and bus isolation in legacy TTL-based industrial control backplanes.
For engineers reviewing the SN74ALS639ANSR datasheet, SN74ALS639ANSR pinout, SN74ALS639ANSR application, or SN74ALS639ANSR equivalent, this page delivers verified functional identity, validated pin roles, confirmed switching and DC electrical parameters, and real-world use context for legacy system maintenance and drop-in replacement planning.
Technical Context
This device implements dual-bus direction control via DIR input and full 3-state output enable/disable via OE, supporting isolated bidirectional communication without external logic. Its A-bus outputs are open-collector (compatible with wired-OR and pull-up configurations), while B-bus outputs are active 3-state (capable of driving standard TTL loads).
The SN74ALS639ANSR operates within 4.5 V to 5.5 V supply range, meets ALS family input thresholds (VIH = 2 V, VIL = 0.8 V), and guarantees VOL ≤ 0.5 V at IOL = 24 mA on both A and B ports - confirming robust noise margin and drive strength for mixed-technology bus interfacing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL power rails and tolerance against rail droop. |
| IOL (A/B) | 24 mA - supports direct driving of multiple TTL inputs or termination resistors without external buffers. |
| tPLH/tPHL (A→B) | 2 ns to 12 ns - enables high-speed data handshaking in synchronous backplane designs with <12 ns timing budget. |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade industrial control and instrumentation environments. |
| VOH (B port) | ≥2.4 V at IOH = –15 mA - maintains valid TTL high-level output under full fan-out load conditions. |
| VOL (A/B) | ≤0.5 V at IOL = 24 mA - guarantees solid low-state margin across temperature and voltage extremes. |
| Input Thresholds | VIH = 2 V, VIL = 0.8 V - matches standard TTL logic levels for seamless integration into legacy systems. |
Pinout & Package
SN74ALS639ANSR uses a 20-pin plastic DIP (N) package with 300-mil width, 0.100" lead pitch, and through-hole mounting. Pin 1 is marked by a notch or bevel on the package body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | Low = B→A data flow; High = A→B data flow - determines physical signal path direction. |
| 2–9 (A1–A8) | A-Bus I/O Terminals | Open-collector outputs - require external pull-up; used for wired-OR bus arbitration or level translation. |
| 10 (GND) | Ground Reference | Common 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 - actively driven high/low or high-Z; compatible with standard TTL bus loading. |
| 19 (OE) | Output Enable Input | Low = enable transceiver; High = isolate both buses - provides system-level bus contention prevention. |
| 20 (VCC) | Power Supply | +5 V supply input - decoupling capacitor (0.1 µF) required near pin for stable switching operation. |
Key Features
| Feature | Design Value |
|---|---|
| True-logic data path | Preserves signal polarity end-to-end (A→B or B→A), eliminating need for external inversion in non-inverting bus architectures. |
| Asymmetric bus interface | Native support for open-collector A-bus and 3-state B-bus - enables direct connection to legacy wired-OR control buses and modern buffered data buses. |
| Full bus isolation | OE = high forces all outputs into high-Z state, electrically disconnecting both A and B buses - prevents back-driving and contention during reset or standby. |
| ALS-family speed-power balance | Typical 2 ns A→B propagation delay with ICC ≤ 54 mA (outputs low) - delivers faster switching than LS logic without AS-level power penalty. |
| Robust DC drive capability | 24 mA sink per A/B output - sufficient to drive 10+ standard TTL loads or 400 Ω termination on 5 V buses. |
Applications
| Industrial Backplane Interfacing | Legacy System Bus Extension |
|---|---|
|
Use Scenario: Connecting microcontroller address/data buses to older PLC I/O modules using shared open-collector control lines and 3-state data lanes. IC Role / Device Role / Timing Role: Bidirectional level translator and bus isolator - routes signals based on DIR, disables during CPU reset via OE, and sustains timing integrity with sub-12 ns A→B delay. Use Value: Eliminates discrete transistor arrays and latch logic previously needed to manage mixed-bus topology, reducing board space and BOM count. |
Use Scenario: Extending a vintage minicomputer's memory expansion bus across multiple chassis using differential signaling-compatible stubs. IC Role / Device Role / Timing Role: Direction-controlled repeater - forwards read/write cycles from master to slave segments while maintaining setup/hold timing margins via guaranteed tPLH/tPHL specs. Use Value: Enables modular system upgrades without redesigning baseboard layout, leveraging existing 5 V TTL timing budgets and termination schemes. |
| Wired-OR Control Bus Hub | TTL-to-Open-Collector Interface Bridge |
|
Use Scenario: Aggregating interrupt requests from eight peripheral cards onto a single shared open-collector interrupt line to a CPU. IC Role / Device Role / Timing Role: Wired-OR combiner - A-bus outputs tied together with pull-up; B-bus receives individual card signals; DIR set to B→A for aggregation. Use Value: Provides hardware OR logic with no propagation delay penalty and built-in bus isolation when OE is asserted - prevents spurious interrupts during card hot-swap. |
Use Scenario: Interfacing a modern FPGA's 3-state I/O bank to legacy test equipment requiring open-collector handshake lines (e.g., IEEE-488 GPIB control). IC Role / Device Role / Timing Role: Unidirectional bus adapter - A-bus drives GPIB STB/DAV lines; B-bus accepts FPGA control signals; DIR fixed for A←B mode. Use Value: Delivers 24 mA sink capability and 0.5 V VOL at full load - meets GPIB specification for low-level voltage and current drive without external drivers. |
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 die, identical electrical specs, but in PDIP tube packaging (no tape-and-reel); same pinout and marking. | No difference - fully interchangeable in through-hole PCBs; differs only in packaging format and reel availability. | Select SN74ALS639AN for manual assembly or small-batch prototyping where tape-and-reel is unnecessary. |
| SN74AS639 | Faster propagation (A→B: 2–9.5 ns vs. 2–12 ns) and higher IOL (64 mA vs. 24 mA), but higher ICC (up to 154 mA) and same 0°C–70°C range. | Better suited for high-speed, high-drive applications where power dissipation and thermal management are acceptable trade-offs. | Choose SN74AS639 only if timing budget requires <9.5 ns A→B delay or load demands >24 mA sink per line. |
Compared with SN74ALS639ANSR, SN74ALS639AN offers identical functionality in alternate packaging, while SN74AS639 delivers measurable speed and drive improvements at the cost of increased power consumption - making SN74ALS639ANSR the optimal choice for cost-sensitive, thermally constrained legacy system repairs requiring proven reliability and compatibility.
Availability
SN74ALS639ANSR is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy system bus extension, wired-OR control bus hubs, and TTL-to-open-collector interface bridges requiring stable component supply across long-lifecycle programs.
Supply support for SN74ALS639ANSR 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, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS639ANSR belongs to TI's legacy 74ALS logic family, engineered specifically for high-reliability, medium-speed TTL-compatible systems where power efficiency, noise immunity, and long-term availability outweigh raw speed requirements.
FAQ
What is the function of the DIR pin on the SN74ALS639ANSR?
The DIR (Direction) pin on the SN74ALS639ANSR controls data flow direction: when DIR = LOW, data transfers from the B-bus (3-state) to the A-bus (open-collector); when DIR = HIGH, data flows from A to B. This bidirectional control enables flexible bus arbitration in systems with asymmetric signaling requirements, and is essential for correct operation of the SN74ALS639ANSR in any configured data path.
Does the SN74ALS639ANSR support 3.3 V logic levels?
No, the SN74ALS639ANSR is strictly a 5 V TTL-family device with VIH = 2.0 V minimum and VIL = 0.8 V maximum - it does not guarantee reliable operation with 3.3 V CMOS logic levels. Driving its inputs from 3.3 V sources may result in marginal or undefined switching behavior; level-shifting circuitry is required for interoperability, and the SN74ALS639ANSR itself must be powered from a stable 5 V supply.
Can the SN74ALS639ANSR replace the SN74ALS638ANSR in a design?
No - the SN74ALS639ANSR implements true-logic (non-inverting) data transfer, whereas the SN74ALS638ANSR is inverting. Swapping them without logic inversion elsewhere will invert all transmitted data bits, causing functional failure. The SN74ALS639ANSR and SN74ALS638ANSR share pinout and DC specs but differ fundamentally in logic polarity, making them incompatible drop-in replacements.
What is the maximum sink current per A-bus or B-bus pin on the SN74ALS639ANSR?
The SN74ALS639ANSR guarantees 24 mA sink current per A-bus or B-bus output pin under recommended operating conditions (VCC = 4.5 V to 5.5 V, TA = 0°C to 70°C). This rating applies to both port types and is validated by VOL ≤ 0.5 V at IOL = 24 mA - a key parameter ensuring reliable drive into standard TTL loads or termination networks in the SN74ALS639ANSR's target applications.
Is the SN74ALS639ANSR RoHS compliant?
Yes, the SN74ALS639ANSR is RoHS compliant, as confirmed by Texas Instruments' official packaging addendum: "RoHS: Yes" for orderable part SN74ALS639ANSR (which maps to SN74ALS639AN in TI's documentation). It features NiPdAu (NIPDAU) lead finish and meets EU Directive 2011/65/EU requirements for restricted substances, supporting environmentally compliant manufacturing for the SN74ALS639ANSR.
SN74ALS639ANSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-SOIC (0.209", 5.30mm 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-SO
SN74ALS639ANSR FAQ
1.How can I place an order for SN74ALS639ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS639ANSR 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 SN74ALS639ANSR reliable?
The price and inventory of SN74ALS639ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS639ANSR is usually 5 days.
3.What payment methods are accepted for SN74ALS639ANSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS639ANSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS639ANSR?
SN74ALS639ANSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS639ANSR 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 SN74ALS639ANSR?
For technical support, including SN74ALS639ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS639ANSR requirements.
6.How does Aetrix verify that SN74ALS639ANSR is sourced from the original manufacturer or authorized distributors?
All SN74ALS639ANSR 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 SN74ALS639ANSR meets industry standards.
7.What is the process for return or replacement of SN74ALS639ANSR?
All SN74ALS639ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS639ANSR, 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 SN74ALS639ANSR part is unused and in its original packaging.
Return procedure for SN74ALS639ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS639ANSR 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…
