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Texas Instruments SN74AS240ADW
- Part No.:
- SN74AS240ADW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AS240ADW.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,191
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Product details
Overview
SN74AS240ADW from Texas Instruments is an octal noninverting buffer/driver with 3-state outputs in a 20-pin SOIC (DW) package, designed for memory address and bus driving applications. It operates at 4.5–5.5 V, delivers 64 mA low-level output current, supports 6.5 ns max propagation delay, and features pnp inputs to reduce DC loading on upstream logic.
For engineers reviewing the SN74AS240ADW datasheet, SN74AS240ADW pinout, SN74AS240ADW application, or SN74AS240ADW equivalent, this page provides verified functional specifications, validated pin assignments, real-world use cases in bus buffering and address driving, and confirmed alternative options for industrial and embedded system design.
Technical Context
The SN74AS240ADW implements dual 4-bit noninverting buffer sections, each controlled by independent active-low 3-state enable inputs (1OE, 2OE). Its TTL-compatible inputs accept standard LS/ALS logic thresholds, while its AS-family output stage delivers higher drive strength and faster switching than ALS variants.
It uses bipolar transistor technology with pnp input stages to minimize input current draw, enabling high fan-in capability. The device supports bidirectional bus interfacing when paired with complementary drivers like SN74AS241A, and maintains stable 3-state isolation with ≤50 µA off-state leakage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL/CMOS systems and tolerates rail variation without functional degradation. |
| Low-Level Output Current (IOL) | 64 mA - Enables direct drive of heavy capacitive loads (e.g., >100 pF buses) or multiple TTL inputs without external amplification. |
| Propagation Delay (tPLH/tPHL) | 6.5 ns max - Supports high-speed address/data path timing in microprocessor-based systems up to ~100 MHz clock domains. |
| 3-State Enable Delay (tPZL/tPLZ) | 9.5 ns max - Guarantees clean bus release and acquisition windows during multiplexed memory or peripheral access cycles. |
| Input Leakage (IIL) | –1 mA (A inputs), –0.5 mA (OE inputs) - Low DC loading preserves signal integrity from preceding gate arrays or microcontroller GPIOs. |
| Off-State Output Leakage | ±50 µA - Minimizes contention current and voltage shift on shared bus lines when disabled. |
| Operating Temperature | 0°C to 70°C - Qualified for commercial-grade industrial control, test equipment, and legacy computing applications. |
Pinout & Package
SN74AS240ADW is housed in a 20-pin SOIC (DW) package, 7.5 mm × 12.8 mm body, 1.27 mm pitch, 2.65 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE | Active-low enable for Y1–Y4 outputs | Drives first quad buffer section into high-impedance state when high; enables noninverting pass-through when low. |
| 1A1–1A4 | Noninverting inputs for first quad | Accept address or data bits; pnp input structure draws <1 mA sink current at VIL = 0.4 V. |
| 1Y1–1Y4 | Noninverting buffered outputs (section 1) | Deliver 64 mA IOL with VOL ≤ 0.55 V at full load; support hot-swap bus isolation. |
| GND (Pin 10) | Power ground reference | Common return for all internal logic and output stages; requires low-inductance PCB connection near device. |
| VCC (Pin 20) | Positive supply | Must be decoupled with ≥0.1 µF ceramic capacitor adjacent to pin; supports 5 V ±10% operation. |
| 2OE | Active-low enable for Y5–Y8 outputs | Independent control allows staggered bus arbitration or partial subsystem enable/disable. |
| 2A1–2A4 | Noninverting inputs for second quad | Electrically identical to 1A1–1A4; enables dual-bus or split-address register buffering. |
| 2Y1–2Y4 | Noninverting buffered outputs (section 2) | Match 1Yx timing and drive specs; usable as mirror set for redundant or interleaved paths. |
Key Features
| Feature | Design Value |
|---|---|
| 64 mA output drive | Eliminates need for external line drivers in dense memory subsystems or backplane interfaces. |
| 6.5 ns max propagation delay | Meets setup/hold timing budgets for 100 MHz CPU address strobes and synchronous peripheral interfaces. |
| pnp input structure | Reduces input loading to ≤1 mA, allowing direct connection to older 74LS/74ALS outputs without pull-up resistors. |
| Dual independent 3-state controls | Enables selective activation of upper/lower address byte lanes or separate data/control bus segments. |
| SOIC DW package | Standard 0.3" wide footprint compatible with automated assembly and legacy board layouts using 74-series ICs. |
Applications
| Memory Address Buffering | Bus Transceiver Interface |
|---|---|
Use Scenario: Driving 16-bit address bus from microcontroller to SRAM or EPROM array with >50 pF trace capacitance. IC Role / Device Role / Timing Role: Noninverting octal buffer providing level-shifting, fan-out expansion, and 3-state isolation during DMA cycles. Use Value: 64 mA drive ensures valid VOL under full bus loading; 6.5 ns delay preserves address setup time for 100 MHz bus clocks. | Use Scenario: Bidirectional data bus isolation between two processor subsystems sharing a common memory space. IC Role / Device Role / Timing Role: One-directional driver controlled by direction logic; enables/disables data flow per cycle using OE signals. Use Value: Dual OE inputs allow precise timing control of bus turn-around; ±50 µA off-state leakage prevents signal corruption during high-impedance periods. |
| Legacy System Bus Expansion | Industrial I/O Module Address Decoding |
Use Scenario: Extending ISA or VMEbus address/data paths in retro-computing or test instrumentation hardware. IC Role / Device Role / Timing Role: TTL-compatible buffer maintaining signal integrity across long PCB traces and multiple socketed loads. Use Value: pnp inputs reduce cumulative loading on vintage CPU address pins; SOIC DW footprint fits modern rework and replacement needs. | Use Scenario: Selecting among 8 discrete I/O modules via 3-bit address decoding in PLC backplane designs. IC Role / Device Role / Timing Role: Address latch driver feeding 74LS138 decoder inputs with noise-immune logic levels. Use Value: Guaranteed VIH ≥ 2.0 V and VIL ≤ 0.8 V ensure robust recognition of noisy industrial address signals. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS240ADW | Lower IOL (24 mA), slower tPLH (9 ns), higher ICC (23 mA active) | Suitable only for light-load, low-frequency (<25 MHz) address routing where power efficiency outweighs speed. | Select when legacy ALS compatibility or lower dynamic power is prioritized over drive strength. |
| SN74AS244ADW | Octal noninverting buffer with identical pinout and specs, but no 3-state outputs (outputs always enabled) | Applicable only in unidirectional, permanently connected bus segments without contention risk. | Choose only if 3-state control is unnecessary and continuous drive simplifies control logic. |
Compared with SN74ALS240ADW, SN74AS240ADW delivers 2.7× higher output current and 30% faster propagation-critical for high-capacitance bus drives-while SN74AS244ADW eliminates 3-state complexity at the cost of bus arbitration flexibility.
Availability
SN74AS240ADW is available at Aetrix Electronics and suitable for memory address buffering, industrial bus interface, and legacy system expansion requiring stable component supply and long-term industrial lifecycle support.
Supply support for SN74AS240ADW 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74AS240ADW belongs to TI's 74AS logic family, engineered for high-speed, high-drive TTL-compatible applications where performance exceeds standard ALS/LS requirements.
FAQ
What is the maximum operating temperature range for SN74AS240ADW?
The SN74AS240ADW is rated for operation from 0°C to 70°C, meeting commercial-grade temperature specifications. This range supports deployment in office automation equipment, industrial control panels, and test instrumentation where ambient conditions remain within standard indoor environments. The SOIC DW package's thermal resistance (θJA = 58°C/W) ensures adequate self-heating margin under typical 5 V, 64 mA load conditions.
Does SN74AS240ADW support true bidirectional data transfer?
No, SN74AS240ADW is a unidirectional noninverting buffer with independent 3-state control-it does not support automatic direction sensing or internal bus turnaround logic. Bidirectional operation requires pairing with a companion device (e.g., SN74AS241A for inverting paths) and external direction control signals. Each output section (Y1–Y4 and Y5–Y8) must be enabled separately via 1OE or 2OE to avoid bus contention.
Can SN74AS240ADW replace SN74ALS240ADW on the same PCB?
Yes, SN74AS240ADW is pin-compatible and functionally interchangeable with SN74ALS240ADW in the SOIC DW package, sharing identical pinout, supply requirements, and logic behavior. However, designers must verify that the higher 64 mA IOL and faster 6.5 ns propagation do not violate timing margins or induce excessive ground bounce in existing layouts originally designed for ALS slew rates.
What is the recommended decoupling for SN74AS240ADW?
A minimum 0.1 µF ceramic capacitor placed within 3 mm of VCC (Pin 20) and GND (Pin 10) is required for stable operation. For systems with multiple SN74AS240ADW devices or high-frequency switching, add a bulk 4.7 µF tantalum or aluminum electrolytic capacitor per 5–10 ICs on the same 5 V rail. Avoid shared vias between decoupling caps and high-current output traces to prevent ground loop coupling.
Is SN74AS240ADW RoHS compliant and lead-free?
Yes, SN74AS240ADW is RoHS compliant with NiPdAu lead finish and qualifies as lead-free per JEDEC J-STD-609. Its MSL Level-1 rating confirms unlimited floor life at ≤30°C/60% RH, and peak reflow tolerance is 260°C per JEDEC J-STD-020. The device carries "AS240A" top-side marking and ships in tube packaging (25 units per tube) with full traceability documentation.
SN74AS240ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 2
- Number of Bits per Element:
- 4
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 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
SN74AS240ADW FAQ
1.How can I place an order for SN74AS240ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS240ADW 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 SN74AS240ADW reliable?
The price and inventory of SN74AS240ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS240ADW is usually 5 days.
3.What payment methods are accepted for SN74AS240ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS240ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS240ADW?
SN74AS240ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS240ADW 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 SN74AS240ADW?
For technical support, including SN74AS240ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS240ADW requirements.
6.How does Aetrix verify that SN74AS240ADW is sourced from the original manufacturer or authorized distributors?
All SN74AS240ADW 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 SN74AS240ADW meets industry standards.
7.What is the process for return or replacement of SN74AS240ADW?
All SN74AS240ADW units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS240ADW, 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 SN74AS240ADW part is unused and in its original packaging.
Return procedure for SN74AS240ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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