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Texas Instruments SN74ALS746DWR
- Part No.:
- SN74ALS746DWR
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS746DWR.pdf
- Description:
- BUS DRIVER, ALS SERIES
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Inventory:7,000
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Product details
Overview
SN74ALS746DWR 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 2-input NOR output-enable logic (OE1/OE2), and a data-flow-through pinout with inputs on one side and outputs on the opposite side. Operating from 4.5 V to 5.5 V at 0°C to 70°C, it delivers 24 mA sink and −15 mA source drive capability.
For engineers reviewing the SN74ALS746DWR datasheet, SN74ALS746DWR pinout, SN74ALS746DWR application, or SN74ALS746DWR equivalent, key selection criteria include its inverted output logic, dual independent 3-state control, built-in bus-termination pullups, propagation delay under 12 ns, and SOIC-20 package compatibility with legacy 74ALS system designs.
Technical Context
The SN74ALS746DWR implements eight identical inverting buffer channels, each with open-collector–compatible totem-pole outputs capable of high-impedance disable via either OE1 or OE2. Its 2-input NOR enable structure ensures that asserting either enable input forces all eight Y outputs into high-Z - critical for shared-bus arbitration.
Input pullup resistors (20 kΩ) are internally connected between each A input and VCC, eliminating external termination components when interfacing with high-impedance data buses. The device adheres to standard 74ALS logic thresholds (VIL = 0.8 V, VIH = 2.0 V) and supports CL = 50 pF load conditions with tPLH ≤ 12 ns and tPHL ≤ 9 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with 3-state outputs - provides signal inversion and bus isolation simultaneously. |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with standard 5-V TTL systems and tolerant of rail variation in industrial backplanes. |
| Output Drive | 24 mA sink / −15 mA source - sufficient to drive multiple TTL loads or terminate unterminated buses without external drivers. |
| Propagation Delay | tPLH ≤ 12 ns, tPHL ≤ 9 ns (VCC = 4.5–5.5 V, CL = 50 pF) - enables reliable operation in sub-20-ns timing-critical address/data paths. |
| Input Pullup | 20 kΩ internal resistor per input - eliminates need for external pullups in tri-state bus applications where idle-high logic is required. |
| Enable Logic | 2-input NOR (OE1, OE2) - either enable asserted → all outputs high-Z; supports flexible bus arbitration using separate control signals. |
| Operating Temperature | 0°C to 70°C - specified for commercial-grade embedded and computing equipment environments. |
Pinout & Package
SN74ALS746DWR is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, 13.5 mm long, with 1.27 mm pitch and maximum height of 2.65 mm. Pin 1 is marked by a beveled corner or notch; the package is lead-free (RoHS exempt pending TI confirmation) and moisture sensitivity level not specified.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | OE1, OE2 | Independent 3-state enable inputs - NOR logic: high on either disables all outputs; allows dual-control bus gating. |
| 2–9 | A1–A8 | Inverting data inputs - each drives corresponding inverted output; internal 20-kΩ pullup to VCC aids bus idle-state integrity. |
| 10 | GND | Ground reference - common return for all logic and output current paths. |
| 11–18 | Y1–Y8 | Inverted 3-state outputs - active-low logic with totem-pole structure; high-Z when OE1 or OE2 is high. |
| 20 | VCC | Positive supply - powers internal logic and output stages; decoupling capacitor recommended near pin 20. |
Key Features
| Feature | Design Value |
|---|---|
| Data-flow-through pinout | Inputs (pins 2–9) and outputs (pins 11–18) on opposite sides - simplifies PCB routing and reduces crosstalk in dense bus layouts. |
| Integrated 20-kΩ input pullups | Eliminates external resistors for data-bus termination - reduces BOM count and board area in memory interface and address latch circuits. |
| Dual independent 3-state control | OE1 and OE2 provide redundant or partitioned bus enable - supports fault-tolerant or multi-master arbitration schemes. |
| ALS-family performance | Matches SN74ALS240A speed/power profile while adding pullups and optimized pinout - drop-in upgrade path for existing ALS designs. |
| TTL-compatible thresholds | VIL = 0.8 V, VIH = 2.0 V - ensures interoperability with legacy 74LS, 74S, and microprocessor bus interfaces without level-shifting. |
Applications
| Memory Address Buffering | Parallel Bus Isolation |
|---|---|
|
Use Scenario: Driving 16-bit address lines from a microprocessor to multiple memory chips on a shared bus. IC Role / Device Role / Timing Role: Inverting buffer with 3-state control acts as address latch driver and bus isolator during DMA cycles. Use Value: Built-in 20-kΩ pullups maintain valid high state on un-driven address lines; dual OE inputs allow synchronized disable across memory banks. |
Use Scenario: Isolating two processor subsystems sharing a common data bus in a modular industrial controller. IC Role / Device Role / Timing Role: Octal inverting buffer provides direction-controlled data path with fast enable/disable (tPZL ≤ 20 ns). Use Value: Data-flow-through pinout minimizes trace length; 24-mA sink strength drives 10+ TTL loads without fanout buffers. |
| Legacy System Bus Termination | EPROM Programming Interface |
|
Use Scenario: Terminating unused data bus lines in vintage minicomputer backplanes where floating inputs cause metastability. IC Role / Device Role / Timing Role: Input pullup network replaces discrete 20-kΩ resistors across eight bus lines; outputs left unconnected. Use Value: Reduces component count by eight resistors per IC; eliminates solder joints and layout space for termination networks. |
Use Scenario: Controlling write-enable and output-enable signals to an EPROM during in-system programming sequences. IC Role / Device Role / Timing Role: Inverting buffer translates microcontroller GPIO logic levels to EPROM-compatible active-low controls with precise timing. Use Value: Propagation delay ≤ 12 ns ensures setup/hold compliance with EPROM programming pulse specifications (e.g., Intel 27C256). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer with 3-state applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS240AN | No internal pullups; standard non-inverting/inverting dual-octal configuration with separate polarity controls. | Lacks built-in termination - requires external pullups for bus-idle integrity; pinout differs (inputs/outputs interleaved). | Select when design already uses external termination or requires mixed inverting/non-inverting channels. |
| SN74F240N | Fast TTL family: faster propagation (tPLH ≈ 6 ns) but higher ICC (22 mA typical), no internal pullups, wider VCC tolerance (4.5–5.5 V same). | Higher power consumption and noise sensitivity - less suitable for noise-prone industrial backplanes with long traces. | Select only when absolute speed >8 ns is mandatory and power budget allows ~2× increase over ALS. |
Compared with SN74ALS240AN and SN74F240N, the SN74ALS746DWR uniquely integrates bus-termination pullups and a flow-through pinout - reducing layout complexity and component count in memory-mapped and legacy bus systems without sacrificing ALS-speed timing margins.
Availability
SN74ALS746DWR is available at Aetrix Electronics and suitable for memory address buffering, parallel bus isolation, and legacy system bus termination requiring stable component supply and long-term obsolescence mitigation support.
Supply support for SN74ALS746DWR 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, logic, and power management ICs for industrial, automotive, and communications markets.
The SN74ALS746DWR belongs to TI's legacy 74ALS logic family, engineered for high-speed, low-power TTL-compatible digital interfacing in commercial-grade computing and control systems of the 1980s–1990s.
FAQ
What logic function does the SN74ALS746DWR implement?
The SN74ALS746DWR implements eight identical inverting buffer channels, each with 3-state totem-pole outputs controlled by a dual-input NOR gate (OE1/OE2). It inverts input signals A1–A8 to produce Y1–Y8 and enters high-impedance state when either OE input is high. This behavior is confirmed in the logic diagram and truth table of the SDAS052A datasheet.
Does the SN74ALS746DWR have internal pullup resistors, and what value are they?
Yes, the SN74ALS746DWR includes internal 20-kΩ pullup resistors connected between each input (A1–A8) and VCC. This feature is explicitly documented in the "description" section and logic diagram footnote of the SDAS052A datasheet, enabling direct bus termination without external components.
What is the operating temperature range for the SN74ALS746DWR?
The SN74ALS746DWR is characterized for operation from 0°C to 70°C, as stated in both the "description" paragraph and the "recommended operating conditions" table of the SDAS052A datasheet. It is rated for commercial-grade environments and is not specified for extended industrial (−40°C to 85°C) or automotive temperature ranges.
What package type is used for the SN74ALS746DWR, and how many pins does it have?
The SN74ALS746DWR uses a 20-pin SOIC (DW) package, as confirmed in TI's Packaging Information addendum and the DW0020A package outline drawing. It measures 13.5 mm × 7.5 mm with 1.27 mm lead pitch and maximum height of 2.65 mm - distinct from the PDIP (N) variant.
How does the 3-state enable logic work on the SN74ALS746DWR?
The SN74ALS746DWR uses a 2-input NOR gate for 3-state control: if either OE1 or OE2 is high, all eight outputs (Y1–Y8) enter high-impedance mode. This is verified in the logic diagram, truth table, and functional description of the SDAS052A datasheet - enabling flexible bus arbitration using either or both enable signals.
SN74ALS746DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
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- Supplier Device Package:
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SN74ALS746DWR FAQ
1.How can I place an order for SN74ALS746DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS746DWR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
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5.How can I obtain technical support or documentation for SN74ALS746DWR?
For technical support, including SN74ALS746DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS746DWR requirements.
6.How does Aetrix verify that SN74ALS746DWR is sourced from the original manufacturer or authorized distributors?
All SN74ALS746DWR 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 SN74ALS746DWR meets industry standards.
7.What is the process for return or replacement of SN74ALS746DWR?
All SN74ALS746DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS746DWR, 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 SN74ALS746DWR part is unused and in its original packaging.
Return procedure for SN74ALS746DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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