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Texas Instruments SN74ALS240ADW
- Part No.:
- SN74ALS240ADW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74ALS240ADW.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:417
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Product details
Overview
SN74ALS240ADW 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 from 4.5 V to 5.5 V, delivers 24 mA low-level output current (IOL), supports 9 ns typical propagation delay (tPHL), and features pnp input structure to reduce DC loading on upstream logic.
For engineers reviewing the SN74ALS240ADW datasheet, SN74ALS240ADW pinout, SN74ALS240ADW application, or SN74ALS240ADW equivalent, key selection considerations include its 3-state bus-driving capability, ALS family speed-power trade-off, SOIC-20 thermal performance (θJA = 58°C/W), and compatibility with legacy TTL/LS systems requiring symmetrical active-low OE control.
Technical Context
This device implements two independent 4-bit noninverting buffer sections, each with dedicated active-low output-enable (OE) inputs (1OE and 2OE). Its pnp input stage reduces input current draw versus standard TTL, enabling higher fan-in without excessive loading of preceding drivers.
The 3-state outputs support bidirectional bus interfacing with fast enable/disable timing: tPZL = 5–18 ns and tPHZ = 2–10 ns over temperature. Output drive strength is specified at 24 mA sink (IOL) and –15 mA source (IOH), with VOL ≤ 0.4 V and VOH ≥ 2.4 V under standard load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - balances speed and power vs. standard LS; 9 ns tPHL at 5 V. |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL systems; no operation below 4.5 V. |
| Output Drive | 24 mA sink (IOL), –15 mA source (IOH) - sufficient for driving 50-pF bus loads with defined VOL/VOH. |
| Propagation Delay | 2–9 ns (tPHL), 2–9 ns (tPLH) - enables high-speed address/data buffering in memory subsystems. |
| 3-State Enable Time | tPZL = 5–18 ns, tPHZ = 2–10 ns - ensures clean bus release and acquisition during multiplexed access. |
| Input Structure | pnp-based inputs - reduces VIH/VIL current draw, lowering loading on preceding gate outputs. |
| Thermal Resistance | θJA = 58°C/W (SOIC-DW) - defines maximum power dissipation limit under natural convection. |
Pinout & Package
SN74ALS240ADW uses a 20-pin SOIC (DW) package with 7.5 mm × 12.8 mm body, 1.27 mm lead pitch, and 2.65 mm max height per JEDEC MS-013.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE, 2OE | Active-low output enable | Disables both Y outputs per section when high; enables when low - enables time-multiplexed bus sharing. |
| 1A1–1A4, 2A1–2A4 | Noninverting data inputs | Passes logic state directly to corresponding Y outputs when OE is asserted - no inversion. |
| 1Y1–1Y4, 2Y1–2Y4 | 3-state buffered outputs | Drive external bus lines; high-impedance when OE is deasserted - prevents contention. |
| VCC (Pin 20) | Positive supply | Must be 4.5–5.5 V; powers all internal logic and output stages - decoupling required near pin. |
| GND (Pin 10) | Ground reference | Common return for all inputs, outputs, and supply - critical for noise immunity and timing stability. |
Key Features
| Feature | Design Value |
|---|---|
| Octal noninverting buffer architecture | Two independent 4-bit sections simplify memory address or data bus expansion without signal inversion. |
| Symmetrical active-low OE inputs | 1OE and 2OE allow independent control of each 4-bit group - supports interleaved or segmented bus access. |
| pnp input structure | Reduces input current (IIL ≤ –0.1 mA) - minimizes loading on upstream drivers and improves fan-in capability. |
| ALS speed-power optimization | 9 ns max tPHL at 5 V with 24 mA IOL - faster than LS, lower power than AS, ideal for legacy system upgrades. |
| 3-state bus interface compliance | IOZH ≤ 20 µA, IOZL ≥ –20 µA - ensures high-impedance state meets TTL bus leakage requirements. |
Applications
| Memory Address Buffering | System Bus Driver |
|---|---|
Use Scenario: Driving 16-bit address lines from a microprocessor to multiple memory ICs in a 1980s–1990s embedded controller. IC Role / Device Role / Timing Role: Noninverting buffer with 3-state outputs isolates CPU address bus during DMA cycles and enables shared address decoding. Use Value: 24 mA drive strength ensures reliable logic levels across 10+ TTL loads; 9 ns propagation supports 10 MHz bus timing. | Use Scenario: Interfacing a Z80 or 8086 CPU data bus to peripheral controllers with shared I/O space. IC Role / Device Role / Timing Role: Bidirectional bus driver controlled by RD/WR strobes via OE pins - enables read/write arbitration. Use Value: Fast 5–18 ns disable time prevents bus contention; pnp inputs reduce loading on CPU data pins. |
| Legacy Clock Distribution | Industrial Control Backplane |
Use Scenario: Distributing a master clock signal to multiple synchronous peripherals in a PLC rack with long trace runs. IC Role / Device Role / Timing Role: Low-skew buffer replicating clock to 8 destinations while maintaining edge integrity. Use Value: 2 ns min tPLH/tPHL ensures sub-10 ns skew across outputs; 50 pF load rating matches PCB trace capacitance. | Use Scenario: Isolating sensor input signals from a central controller in an industrial automation backplane. IC Role / Device Role / Timing Role: Input buffer conditioning analog-to-digital converter address/control lines before latching. Use Value: High noise immunity (VIK = –1.2 V) rejects EMI on noisy factory floors; 3-state allows hot-swap diagnostics. |
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 |
|---|---|---|---|
| SN74ALS240AN | Same ALS logic, but in 20-pin PDIP (N) package; θJA = 70°C/W vs. 58°C/W for DW. | Preferred for through-hole prototyping or legacy board rework; less suitable for high-density SMT layouts. | Select SN74ALS240AN only if PDIP footprint and manual assembly are required; otherwise SN74ALS240ADW offers better thermal performance. |
| SN74AS240ADW | AS family variant: faster (6.5 ns tPHL), higher drive (64 mA IOL), but higher ICC (51–75 mA vs. 13–23 mA). | Better for high-speed timing-critical paths; unsuitable where power budget or heat dissipation is constrained. | Choose SN74AS240ADW only when speed >9 ns is mandatory and extra 30–50 mA supply current is acceptable. |
Compared with SN74ALS240AN and SN74AS240ADW, SN74ALS240ADW provides optimal balance of speed (9 ns), power (23 mA max ICC), and thermal efficiency (58°C/W) in surface-mount form - making it the preferred choice for volume production of industrial and computing legacy systems.
Availability
SN74ALS240ADW is available at Aetrix Electronics and suitable for memory address buffering, system bus driving, legacy clock distribution, and industrial control backplane applications requiring stable component supply across extended product lifecycles.
Supply support for SN74ALS240ADW 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.
SN74ALS240ADW belongs to TI's legacy TTL-compatible logic portfolio, engineered specifically for high-density, low-power memory address and bus driver applications in 1980s–1990s computing and control systems.
FAQ
What is the maximum operating temperature range for SN74ALS240ADW?
The SN74ALS240ADW is rated for operation from 0°C to +70°C ambient temperature, consistent with commercial-grade TI logic devices. This range is validated per the recommended operating conditions table in the SDAS214E datasheet, and applies specifically to the SOIC-DW package variant. Operation outside this range may result in undefined timing or output behavior.
Does SN74ALS240ADW support true bidirectional data flow?
No, SN74ALS240ADW is a unidirectional noninverting buffer - inputs (A) drive outputs (Y) only. While its 3-state outputs allow connection to shared buses, it lacks internal direction control or data path reversal. For bidirectional operation, a transceiver like SN74ALS245 must be used instead of SN74ALS240ADW.
What is the purpose of the pnp input structure in SN74ALS240ADW?
The pnp input structure in SN74ALS240ADW reduces input current draw (IIL ≤ –0.1 mA) compared to standard TTL inputs, lowering DC loading on upstream drivers. This enables higher fan-in - more inputs driven by a single gate - without compromising noise margins or switching thresholds, a key advantage in dense memory address decoding networks using SN74ALS240ADW.
Can SN74ALS240ADW be used with 3.3 V logic systems?
No, SN74ALS240ADW requires a 4.5 V to 5.5 V supply and is not 3.3 V tolerant. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and output voltage specs (VOH ≥ 2.4 V, VOL ≤ 0.4 V) are defined only for 5 V operation. Interfacing with 3.3 V systems requires level-shifting circuitry or a 3.3 V–compatible buffer such as SN74LVC240A instead of SN74ALS240ADW.
Is SN74ALS240ADW pin-compatible with SN74ALS240ADWR?
Yes, SN74ALS240ADW and SN74ALS240ADWR share identical SOIC-20 (DW) pinout, electrical characteristics, and functional behavior. The only difference is packaging: SN74ALS240ADW ships in tubes (25 pcs), while SN74ALS240ADWR is supplied in tape-and-reel format (2000 pcs) - both use the same ALS240A top-side marking and are drop-in replacements in layout.
SN74ALS240ADW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- 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, 24mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74ALS240ADW FAQ
1.How can I place an order for SN74ALS240ADW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS240ADW 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 SN74ALS240ADW reliable?
The price and inventory of SN74ALS240ADW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS240ADW is usually 5 days.
3.What payment methods are accepted for SN74ALS240ADW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS240ADW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS240ADW?
SN74ALS240ADW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS240ADW 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 SN74ALS240ADW?
For technical support, including SN74ALS240ADW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS240ADW requirements.
6.How does Aetrix verify that SN74ALS240ADW is sourced from the original manufacturer or authorized distributors?
All SN74ALS240ADW 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 SN74ALS240ADW meets industry standards.
7.What is the process for return or replacement of SN74ALS240ADW?
All SN74ALS240ADW units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS240ADW, 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 SN74ALS240ADW part is unused and in its original packaging.
Return procedure for SN74ALS240ADW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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