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Texas Instruments SN74ALS746N
- Part No.:
- SN74ALS746N
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS746N.pdf
- Description:
- OCTAL BUFFER/LINE DRIVER
- Quantity:
- Payment:
- Shipping:
Inventory:2,724
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Product details
Overview
SN74ALS746N from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus driving and memory address register buffering in TTL-compatible systems. It features integrated 20-kΩ input pullup resistors, dual output-enable (OE1/OE2) NOR logic control, and data-flow-through pinout for simplified PCB layout. Operating at 4.5 V to 5.5 V over 0°C to 70°C, it delivers 24 mA sink and −15 mA source drive capability.
For engineers reviewing the SN74ALS746N datasheet, SN74ALS746N pinout, SN74ALS746N application, or SN74ALS746N equivalent, key selection considerations include its inverted output polarity, dual independent 3-state enable architecture, bus-termination resistor integration, and compatibility with legacy ALS logic families in industrial control and retro-computing systems.
Technical Context
The SN74ALS746N implements a dual-gated 3-state control using a 2-input NOR structure: either OE1 or OE2 high forces all eight outputs into high-impedance. Its internal 20-kΩ pullup resistors eliminate external termination components when interfacing with tri-stated data buses.
It provides true inversion (A → Y̅) across all eight channels, with propagation delays as low as 2 ns (tPHL) and 3 ns (tPLH) at VCC = 4.5–5.5 V and CL = 50 pF. Output switching is characterized for both enabled and transition states (tPZH, tPZL, tPHZ, tPLZ), supporting precise timing analysis in synchronous bus architectures.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures stable operation within standard 5 V TTL/ALS rail tolerances |
| Output Drive | 24 mA sink / −15 mA source - sufficient to drive multiple TTL loads or terminated transmission lines |
| Input Pullup | 20 kΩ to VCC - eliminates need for external bus-termination resistors in high-Z bus idle conditions |
| Propagation Delay | 2–12 ns (A→Y) - supports high-speed bus buffering up to ~50 MHz clock domains |
| 3-State Enable Logic | NOR gate (OE1 + OE2) - enables flexible bus arbitration with either enable line asserting high-Z |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded and computing applications |
| Output Polarity | Inverting (Y = A̅) - matches system-level signal inversion requirements in address/data path buffering |
Pinout & Package
SN74ALS746N is housed in a 20-pin plastic DIP (300-mil) package (N suffix), with 3.94 mm lead pitch and 24.2 mm × 6.35 mm body dimensions. Pin numbering follows standard DIP convention with Pin 1 marked by notch or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | OE1, OE2 | Dual 3-state enable inputs - NOR logic: high on either disables all outputs |
| 2–9 | A1–A8 | Data inputs - inverted and buffered to corresponding Y outputs |
| 11–18 | Y1–Y8 | Inverted 3-state outputs - high-Z when OE1 or OE2 = high |
| 10 | GND | Ground reference - common return for logic and output current paths |
| 20 | VCC | Positive supply - powers internal logic and output drivers at 4.5–5.5 V |
Key Features
| Feature | Design Value |
|---|---|
| Data-flow-through pinout | Inputs (Pins 2–9) on left side, outputs (Pins 11–18) on right - reduces PCB trace crossovers and improves signal integrity |
| Integrated 20-kΩ input pullups | Eliminates external termination components on data/address buses during high-impedance idle states |
| Dual independent 3-state control | OE1 and OE2 allow selective bus partitioning or redundant enable signaling without additional logic |
| ALS family compatibility | Matches SN74ALS240A performance while offering optimized pinout - drop-in replacement where inversion is acceptable |
Applications
| Memory Address Buffering | Parallel Bus Isolation |
|---|---|
Use Scenario: Driving 16-bit address bus between CPU and memory controller in vintage microcomputer systems. IC Role / Device Role / Timing Role: Inverting octal buffer providing level-shifting, fanout expansion, and bus isolation with controlled enable timing. Use Value: Integrated pullups maintain valid high state on address lines during CPU reset or DMA cycles when other devices are tri-stated. | Use Scenario: Isolating two 8-bit peripheral data buses sharing a common backplane in industrial PLC I/O modules. IC Role / Device Role / Timing Role: Bidirectional bus driver with independent OE1/OE2 control enabling time-multiplexed bus access. Use Value: NOR-based enable logic allows either bus master to force high-Z on the driver, preventing contention during arbitration. |
| Retrocomputing System Expansion | TTL-Based Test Equipment Interface |
Use Scenario: Adding parallel I/O expansion to 1980s-era Z80 or 6502-based development boards requiring clean address latching. IC Role / Device Role / Timing Role: Inverting address latch buffer with fast tPHL/tPLH ensuring setup/hold compliance for 4 MHz–6 MHz CPU clocks. Use Value: 2 ns minimum propagation delay guarantees reliable address sampling before memory read/write strobes. | Use Scenario: Interfacing digital pattern generators or logic analyzers to legacy TTL test fixtures with unterminated signal lines. IC Role / Device Role / Timing Role: Signal conditioner and bus driver providing noise immunity via internal pullups and robust drive strength. Use Value: 24 mA sink capability drives long traces and multiple TTL inputs without signal degradation or ringing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS240N | Non-inverting outputs; identical pinout, drive strength, and temperature range | Used where signal polarity must be preserved (e.g., direct address bus mirroring) | Select SN74ALS240N when inversion is not required; SN74ALS746N is preferred when system-level inversion simplifies logic design |
| SN74F240N | F-family: faster tPLH/tPHL (1.5 ns typ), higher ICC (25 mA active), no internal pullups | Suitable for speed-critical designs but requires external termination resistors | Choose SN74F240N only if sub-2 ns delay is mandatory and board space allows discrete pullups |
Compared with SN74ALS240N and SN74F240N, the SN74ALS746N uniquely combines inversion, integrated pullups, and ALS power-efficiency-making it optimal for bus-termination-sensitive, polarity-flexible legacy system upgrades where layout simplicity is prioritized over raw speed.
Availability
SN74ALS746N is available at Aetrix Electronics and suitable for memory subsystem design, retrocomputing restoration, industrial bus isolation, and TTL logic modernization projects requiring stable component supply and long-term obsolescence support.
Supply support for SN74ALS746N 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and computing markets.
The SN74ALS746N belongs to TI's 74ALS advanced low-power Schottky logic family, engineered for high-speed, low-power TTL-compatible digital interfacing in commercial-grade systems from the 1980s onward.
FAQ
What is the logic function of the SN74ALS746N?
The SN74ALS746N is an octal inverting buffer with 3-state outputs. Each input (A1–A8) drives a corresponding inverted output (Y1–Y8 = A1̅–A8̅). Outputs enter high-impedance when either OE1 or OE2 is high, per NOR logic. This function is confirmed in the logic diagram and truth table of the SDAS052A datasheet.
Does the SN74ALS746N have internal pullup resistors, and what value are they?
Yes, the SN74ALS746N integrates 20-kΩ pullup resistors from each input (A1–A8, OE1, OE2) to VCC. This is explicitly stated in the datasheet description and verified in the "absolute maximum ratings" and "electrical characteristics" sections. These resistors eliminate the need for external termination on data or address buses during high-impedance states.
What is the operating temperature range for the SN74ALS746N?
The SN74ALS746N is characterized for operation from 0°C to 70°C, as specified under "recommended operating conditions" and "absolute maximum ratings" in the SDAS052A datasheet. This defines its commercial-grade qualification and excludes extended or industrial temperature variants.
Can the SN74ALS746N be used as a direct replacement for SN74ALS240N?
No - the SN74ALS746N is not a direct replacement for SN74ALS240N due to inverted output polarity. While both share identical pinout, drive strength, and 3-state control, SN74ALS240N provides non-inverting outputs. Substitution requires verifying system-level signal polarity tolerance; otherwise, logic errors will occur in address or data paths.
What package type does the SN74ALS746N use, and is it RoHS compliant?
The SN74ALS746N uses a 20-pin plastic DIP (PDIP) package with 300-mil width (N suffix), as confirmed in TI's packaging addendum. Per TI's 2013 status report, this part is obsolete and carries no defined RoHS or green status ("TBD"); it was manufactured prior to mandatory Pb-free conversion and contains leaded solder finish.
SN74ALS746N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Logic Type:
- Buffer, Line Driver
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74ALS746N FAQ
1.How can I place an order for SN74ALS746N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS746N 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 SN74ALS746N reliable?
The price and inventory of SN74ALS746N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS746N is usually 5 days.
3.What payment methods are accepted for SN74ALS746N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS746N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS746N?
SN74ALS746N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS746N 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 SN74ALS746N?
For technical support, including SN74ALS746N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS746N requirements.
6.How does Aetrix verify that SN74ALS746N is sourced from the original manufacturer or authorized distributors?
All SN74ALS746N 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 SN74ALS746N meets industry standards.
7.What is the process for return or replacement of SN74ALS746N?
All SN74ALS746N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS746N, 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 SN74ALS746N part is unused and in its original packaging.
Return procedure for SN74ALS746N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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