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Texas Instruments SN74AS757DW
- Part No.:
- SN74AS757DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AS757DW.pdf
- Description:
- IC BUF NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,086
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Product details
Overview
SN74AS757DW from Texas Instruments is an octal noninverting buffer/line driver with open-collector outputs, designed for memory address bus driving and clock distribution in TTL-compatible systems. It features dual independent output-enable controls (1OE, 2OE), 0°C to 70°C operating range, 64 mA low-level output current capability, and 1.8 ns typical propagation delay (tPHL) at VCC = 5 V.
For engineers reviewing the SN74AS757DW datasheet, SN74AS757DW pinout, SN74AS757DW application, or SN74AS757DW equivalent, this page delivers verified electrical specs, package mapping, functional role in bus interface design, and validated alternative options for legacy system maintenance and industrial control upgrades.
Technical Context
The SN74AS757DW implements two independent 4-bit noninverting buffer sections, each with dedicated active-low output-enable inputs (1OE and 2OE). Its open-collector outputs support wired-AND logic and direct connection to 5-V bus lines without external pull-ups when used with compatible loads.
It uses pnp input stages to reduce DC loading on preceding drivers and eliminates 3-state overlap timing constraints. The device operates strictly within 4.5 V–5.5 V supply range and exhibits asymmetrical switching performance: tPHL (1–6 ns) is significantly faster than tPLH (3–21 ns), reflecting its optimized low-to-high transition behavior under open-collector sink conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures compatibility with standard 5-V TTL and AS-family logic rails. |
| Output Type | Open-collector - Enables wired-AND bus arbitration and direct interfacing with higher-voltage peripherals up to 7 V. |
| IOL (Max) | 64 mA - Supports driving heavy capacitive bus loads or multiple TTL inputs without external buffers. |
| tPHL (A→Y) | 1 ns (min) to 6 ns (max) - Critical for setup-time-critical address strobes in fast memory subsystems. |
| VIL / VIH | 0.8 V / 2.0 V - Matches standard TTL input thresholds, ensuring reliable interfacing with legacy 74LS/AS sources. |
| ICC (Outputs Low) | 61–95 mA - Indicates power consumption during active bus-driving state; impacts thermal design in dense layouts. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded systems, not extended industrial or automotive use. |
Pinout & Package
SN74AS757DW is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, 12.8 mm long, 2.65 mm max height, RoHS-compliant with NiPdAu lead finish and Level-1 moisture sensitivity rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1OE | Active-low enable for first 4-bit buffer section (1Y1–1Y4); disables outputs to high-impedance when high. |
| 2–5 | 1A1–1A4 | Noninverting inputs for first buffer section; drive corresponding open-collector outputs 1Y1–1Y4. |
| 9–12 | 1Y1–1Y4 | Open-collector outputs of first section; require external pull-up for logic HIGH assertion. |
| 13–16 | 2A1–2A4 | Noninverting inputs for second 4-bit buffer section; drive outputs 2Y1–2Y4 when enabled. |
| 18–19, 3 | 2Y1–2Y4 | Open-collector outputs of second section; pin 18 = 2Y1, 19 = 2Y2, 3 = 2Y3, 5 = 2Y4 (see top-view diagram). |
| 11 | 2OE | Active-low enable for second buffer section; independent control enables staggered bus access. |
| 10, 20 | GND, VCC | Power pins - Pin 10 is GND, Pin 20 is VCC; decoupling required within 1 cm for stable high-speed operation. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent OE controls | Enables time-multiplexed bus access between two 4-bit data paths without external gating logic. |
| pnp input structure | Reduces input current loading to ≤ −1 mA (IIL), minimizing fan-out burden on upstream TTL drivers. |
| Open-collector outputs | Supports mixed-voltage interfacing (e.g., 5-V logic driving 12-V peripheral enable lines via pull-up). |
| No 3-state overlap requirement | Eliminates need for precise OE timing margins, simplifying control logic in memory address latching. |
| High sink current (64 mA) | Drives up to 20 standard TTL loads per output, reducing need for external bus transceivers. |
Applications
| Memory Address Buffering | Industrial Bus Interface |
|---|---|
|
Use Scenario: Driving 20-bit address bus in vintage minicomputer backplane with TTL-compatible memory modules. IC Role / Device Role / Timing Role: Noninverting octal buffer providing low-latency, high-current sinking for address line stabilization during CPU read/write cycles. Use Value: Eliminates 3-state timing conflicts between CPU and DMA controllers, enabling deterministic bus arbitration without added glue logic. |
Use Scenario: Interfacing PLC I/O expansion cards with legacy 5-V parallel control buses. IC Role / Device Role / Timing Role: Open-collector line driver translating microcontroller GPIO signals to robust, noise-immune bus segments. Use Value: 64 mA sink capacity ensures reliable logic LOW assertion across 1-meter ribbon cable runs with distributed capacitance. |
| Legacy Clock Distribution | EPROM Programming Adapter |
|
Use Scenario: Distributing synchronized clock signals to multiple EPROM sockets on a development programmer board. IC Role / Device Role / Timing Role: Low-skew buffer replicating master clock to eight address latch ICs with matched propagation delay. Use Value: Sub-6 ns tPHL consistency minimizes clock skew across parallel programming channels, improving write reliability. |
Use Scenario: Enabling high-voltage programming pulses (VPP = 12.5 V) to EPROM address pins while isolating 5-V MCU logic. IC Role / Device Role / Timing Role: Open-collector level translator using external 12-V pull-up to generate VPP-gated address strobes. Use Value: Withstands 7 V off-state output voltage, allowing safe 12-V pull-up without clamping diode protection. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal open-collector buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AS240N | Octal inverting buffer with 3-state (not open-collector) outputs; identical pinout but different logic polarity and output architecture. | Requires redesign of OE timing and external pull-ups; unsuitable where wired-AND or mixed-voltage drive is needed. | Select only if existing layout supports 3-state bus sharing and inversion is acceptable in signal path. |
| SN74ALS244N | Lower drive strength (24 mA IOL), slower speed (tPHL up to 12 ns), and ALS-family power profile (lower ICC). | Better suited for low-power, cost-sensitive legacy upgrades where 64 mA sink is unnecessary. | Choose when thermal budget or BOM cost outweighs need for maximum bus drive capability. |
Compared with SN74AS757DW, SN74AS240N offers pin-compatible 3-state control but lacks open-collector flexibility, while SN74ALS244N trades performance for reduced power and cost-making SN74AS757DW optimal for high-fanout, noise-resilient bus interfaces requiring TTL-AS speed and drive.
Availability
SN74AS757DW is available at Aetrix Electronics and suitable for memory subsystem upgrades, industrial control backplanes, legacy instrumentation repair, and EPROM programming hardware requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74AS757DW 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 for industrial, automotive, and communications markets.
The SN74AS757DW belongs to TI's 74AS advanced Schottky logic family, engineered for high-speed, high-drive bus interface applications in commercial-temperature environments where TTL compatibility and robust sink capability are essential.
FAQ
What is the function of the 1OE and 2OE pins on the SN74AS757DW?
The 1OE and 2OE pins are independent active-low output-enable controls for the two 4-bit buffer sections of the SN74AS757DW. When pulled HIGH, they disable their respective outputs (1Y1–1Y4 or 2Y1–2Y4) into high-impedance state; when LOW, they enable noninverting buffering from corresponding A-inputs to Y-outputs. This allows time-multiplexed or isolated bus access without external logic.
Can SN74AS757DW drive a 12-V bus line?
Yes - the SN74AS757DW open-collector outputs tolerate up to 7 V off-state voltage, and with an external 12-V pull-up resistor, they can safely assert logic HIGH on a 12-V bus. The device itself remains powered at 5 V; the output transistor sinks current only, so no internal voltage violation occurs during 12-V pull-up operation.
Is SN74AS757DW pin-compatible with SN74AS756DW?
No - although both are 20-pin SOIC octal buffers, SN74AS756DW has inverting outputs and shared OE control, while SN74AS757DW has noninverting outputs and dual independent OE inputs. Their pinouts differ: SN74AS757DW assigns 1OE to Pin 1 and 2OE to Pin 11, whereas SN74AS756DW uses Pin 1 for 1OE and Pin 19 for 2OE/2OE, making them functionally and physically incompatible replacements.
What is the maximum capacitive load the SN74AS757DW can drive reliably?
The SN74AS757DW is characterized with CL = 50 pF in its switching specifications, and its 64 mA sink current supports heavier loads. In practice, it reliably drives ≤ 100 pF with maintained timing (tPHL < 8 ns), assuming proper PCB layout, 0.1 µF local decoupling, and ≤ 500 Ω pull-up resistance - exceeding typical backplane or ribbon cable capacitance in legacy systems.
Why does SN74AS757DW have asymmetric propagation delays (tPHL vs tPLH)?
The SN74AS757DW exhibits faster tPHL (1–6 ns) than tPLH (3–21 ns) because its open-collector output stage is optimized for sinking current (LOW assertion), not sourcing. Since it cannot actively drive HIGH (relying on external pull-up), tPLH depends on RC time constant of the external network - a deliberate architectural choice to maximize sink performance while maintaining TTL compatibility.
SN74AS757DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Logic Type:
- Buffer, Non-Inverting
- Number of Elements:
- 2
- Number of Bits per Element:
- 4
- Input Type:
- -
- Output Type:
- Open Collector
- Current - Output High, Low:
- -, 64mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74AS757DW FAQ
1.How can I place an order for SN74AS757DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS757DW 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 SN74AS757DW reliable?
The price and inventory of SN74AS757DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS757DW is usually 5 days.
3.What payment methods are accepted for SN74AS757DW?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS757DW?
SN74AS757DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS757DW 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 SN74AS757DW?
For technical support, including SN74AS757DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS757DW requirements.
6.How does Aetrix verify that SN74AS757DW is sourced from the original manufacturer or authorized distributors?
All SN74AS757DW 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 SN74AS757DW meets industry standards.
7.What is the process for return or replacement of SN74AS757DW?
All SN74AS757DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS757DW, 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 SN74AS757DW part is unused and in its original packaging.
Return procedure for SN74AS757DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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