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Texas Instruments SN74AS756N
- Part No.:
- SN74AS756N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74AS756N.pdf
- Description:
- IC BUFFER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,093
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Product details
Overview
SN74AS756N 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 4-bit channels, symmetrical active-low output-enable (1OE and 2OE), pnp input structure for reduced DC loading, and operates over 0°C to 70°C with VCC = 4.5–5.5 V.
For engineers reviewing the SN74AS756N datasheet, SN74AS756N pinout, SN74AS756N application, or SN74AS756N equivalent, key selection criteria include open-collector drive capability (64 mA sink), propagation delay (1–19 ns), dual independent enable control, and PDIP-20 packaging for through-hole prototyping and industrial control backplanes.
Technical Context
The SN74AS756N implements two independent 4-bit noninverting buffer sections, each with dedicated active-low output-enable inputs (1OE and 2OE), enabling selective channel gating without 3-state overlap concerns. Its pnp input stage minimizes input current draw, while open-collector outputs support wired-AND logic and direct interface to higher-voltage buses.
It belongs to the 74AS family, delivering advanced Schottky TTL performance: high-speed switching (tPHL as low as 1 ns), high fan-out (≥20 74LS loads), and robust noise immunity (VIL = 0.8 V, VIH = 2 V). The device eliminates need for external overlap protection circuitry in memory address driver applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL and mixed-voltage system rails. |
| IOL (Max) | 64 mA - Supports direct driving of multiple TTL inputs or termination resistors on shared buses. |
| tPHL / tPLH | 1 ns / 19 ns - Enables sub-20 ns address or clock path timing in high-density memory subsystems. |
| VIL / VIH | 0.8 V / 2.0 V - Provides 0.4 V noise margin against TTL logic thresholds for reliable signal reception. |
| Operating Temp | 0°C to 70°C - Qualified for commercial and industrial control equipment operating in ambient environments. |
| ICC (Outputs Low) | 80 mA - Indicates total supply current under worst-case active-drive conditions for power budgeting. |
| Input Structure | pnp-based - Reduces DC input loading to ≤0.5 mA per A-input, minimizing bus contention current. |
Pinout & Package
SN74AS756N is supplied in a 20-pin plastic dual in-line package (PDIP-N), 300-mil width, with standard through-hole mounting and 0.1-inch pin pitch. Pin 1 is marked by a notch or dot at the top-left corner of the package body.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1OE | Active-low enable for first 4-bit buffer channel (1Y1–1Y4); disables outputs to high-impedance state when high. |
| 2–5, 8 | 1A1–1A4 | Noninverting inputs for first channel; drive corresponding open-collector outputs 1Y1–1Y4. |
| 9, 12, 14, 16, 18 | 1Y1, 1Y2, 1Y3, 1Y4, GND | Open-collector outputs (pins 9,12,14,16) and ground reference (pin 18); require external pull-up for logic HIGH. |
| 11, 13, 15, 17 | 2A1–2A4 | Noninverting inputs for second 4-bit channel; drive outputs 2Y1–2Y4 (pins 3,5,7,9). |
| 19 | 2OE | Active-low enable for second channel; independent control allows staggered bus access or channel isolation. |
| 3, 5, 7, 9 | 2Y1–2Y4 | Open-collector outputs for second channel; share pin 9 with 1Y4 - requires careful PCB routing. |
| 20 | VCC | +5 V supply rail; decoupling capacitor placement near this pin is critical for noise suppression. |
Key Features
| Feature | Design Value |
|---|---|
| Open-collector outputs | Enable wired-AND bus arbitration and level translation up to 15 V with external pull-up resistors. |
| Dual independent OE controls | Allow interleaved or isolated activation of two 4-bit data paths without timing overlap risk. |
| pnp input structure | Reduces input current to ≤0.5 mA per pin, lowering cumulative bus loading in multi-driver configurations. |
| High-speed AS-family logic | Delivers 1 ns minimum tPHL for critical clock/address paths where setup/hold margins are constrained. |
| No 3-state overlap protection needed | Eliminates external diodes or timing delays previously required to prevent bus contention during enable transitions. |
Applications
| Memory Address Buffering | Industrial Bus Interface |
|---|---|
|
Use Scenario: Driving 16-bit address lines from a microprocessor to multiple SRAM or EPROM chips on a shared bus. IC Role / Device Role / Timing Role: Noninverting octal buffer providing current gain and isolation between CPU address pins and memory device inputs. Use Value: Open-collector outputs allow safe wired-OR expansion across multiple memory banks; dual OE enables bank-select gating without timing hazards. |
Use Scenario: Interfacing a PLC CPU to legacy 24 V DC field I/O modules via a discrete-level bus. IC Role / Device Role / Timing Role: Level-shifting line driver translating 5 V TTL logic to 24 V open-collector bus signals using external pull-ups. Use Value: 64 mA sink capability supports direct connection to 24 V optocoupler inputs or relay drivers without intermediate transistors. |
| Clock Distribution Network | Backplane Signal Conditioning |
|
Use Scenario: Distributing a master system clock to multiple synchronous peripherals with matched trace lengths. IC Role / Device Role / Timing Role: Low-skew buffer replicating clock signal to eight destinations with minimal added jitter. Use Value: 1 ns tPHL and symmetrical propagation ensures <2 ns skew across all eight outputs, preserving setup/hold timing. |
Use Scenario: Strengthening weak control signals (e.g., chip select, write enable) across a 6-layer industrial backplane. IC Role / Device Role / Timing Role: Fan-out amplifier restoring signal integrity degraded by trace capacitance and connector losses. Use Value: High fan-out (>20 74LS loads) and fast edge rates compensate for >100 pF net capacitance on long backplane traces. |
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 | Inverting outputs; dual 4-bit with 3-state (not open-collector); different pinout and enable polarity. | Suitable for bus transceivers requiring bidirectional flow but not wired-AND logic. | Select when inversion is acceptable and 3-state (not open-collector) operation is preferred for multiplexed buses. |
| SN74ALS244N | Lower speed (tPLH ≈ 12 ns), lower drive (IOL = 24 mA), ALS family; compatible pinout but not drop-in. | Better suited for cost-sensitive, lower-frequency systems where power efficiency outweighs speed. | Choose for legacy ALS-based designs needing footprint compatibility but tolerating 3× slower propagation and half the drive strength. |
Compared with SN74AS756N, SN74AS240N provides inversion and 3-state control at the expense of wired-AND capability, while SN74ALS244N trades speed and drive for lower power and broader legacy support - neither is pin-compatible, requiring layout revision for substitution.
Availability
SN74AS756N is available at Aetrix Electronics and suitable for memory address buffering, industrial bus interfacing, clock distribution, and backplane signal conditioning requiring stable component supply across extended production lifecycles.
Supply support for SN74AS756N 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 ICs for industrial, automotive, and communications markets.
The SN74AS756N belongs to TI's 74AS advanced Schottky TTL logic family, engineered for high-speed, high-drive digital interfacing in memory, bus, and clock subsystems where reliability and timing precision are critical.
FAQ
What is the maximum sink current per output of the SN74AS756N?
The SN74AS756N guarantees a minimum sink current (IOL) of 48 mA at VOL = 0.55 V and can deliver up to 64 mA under typical conditions. This rating allows direct driving of multiple TTL inputs or termination networks without external amplification, making it suitable for dense bus architectures where load sharing is required.
Does the SN74AS756N support 3-state operation?
No, the SN74AS756N does not provide 3-state outputs. It features open-collector outputs only, which go to high-impedance when disabled via OE inputs - but require external pull-up resistors to assert HIGH logic levels. Unlike 3-state buffers, it cannot actively drive HIGH; this architecture enables wired-AND functionality essential for priority encoding and bus arbitration.
Can the SN74AS756N be used with a 3.3 V supply?
No, the SN74AS756N is specified only for VCC = 4.5 V to 5.5 V and is not rated for 3.3 V operation. Its input thresholds (VIH = 2.0 V, VIL = 0.8 V) and internal pnp transistor biasing depend on nominal 5 V rail compliance. Using 3.3 V may result in marginal or non-functional switching behavior and is outside guaranteed operating conditions.
How are the two output-enable inputs (1OE and 2OE) used in practice?
In the SN74AS756N, 1OE controls the first four outputs (1Y1–1Y4) and 2OE controls the second four (2Y1–2Y4), both active-low. This allows independent gating - for example, enabling one channel for address bits A0–A3 while holding A4–A7 inactive, or sequencing enable asserts to avoid simultaneous bus loading. No internal logic ties the two enables together.
Is the SN74AS756N RoHS compliant?
Yes, the SN74AS756N is RoHS compliant, with lead finish specified as NiPdAu (NIPDAU) and no exemption required. It meets EU Directive 2011/65/EU requirements and is suitable for environmentally regulated commercial and industrial applications where lead-free assembly is mandated.
SN74AS756N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Buffer, 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:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74AS756N FAQ
1.How can I place an order for SN74AS756N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS756N 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 SN74AS756N reliable?
The price and inventory of SN74AS756N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS756N is usually 5 days.
3.What payment methods are accepted for SN74AS756N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS756N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS756N?
SN74AS756N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS756N 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 SN74AS756N?
For technical support, including SN74AS756N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS756N requirements.
6.How does Aetrix verify that SN74AS756N is sourced from the original manufacturer or authorized distributors?
All SN74AS756N 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 SN74AS756N meets industry standards.
7.What is the process for return or replacement of SN74AS756N?
All SN74AS756N units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS756N, 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 SN74AS756N part is unused and in its original packaging.
Return procedure for SN74AS756N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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