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Texas Instruments SN74S240NE4
- Part No.:
- SN74S240NE4
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74S240NE4.pdf
- Description:
- 8-CH, 4.75-V TO 5.25-V BIPOLAR I
- Quantity:
- Payment:
- Shipping:
Inventory:2,613
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Product details
Overview
SN74S240NE4 from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving applications in TTL-compatible systems. It features dual 4-bit independent channels, 7 ns typical propagation delay at 5 V, ±64 mA output drive capability, and operates across 0°C to 70°C. It is commonly used to isolate and strengthen address/data signals in industrial control backplanes.
For engineers reviewing the SN74S240NE4 datasheet, SN74S240NE4 pinout, SN74S240NE4 application, or SN74S240NE4 equivalent, key selection considerations include its Schottky TTL logic family speed-power trade-off, 3-state enable timing (tPZH/tPZL), input hysteresis for noise immunity, and compatibility with terminated 133-Ω transmission lines.
Technical Context
The SN74S240NE4 implements two independent 4-bit inverting buffer sections, each with active-low output-enable (G) control. Its Schottky-clamped bipolar architecture delivers faster switching than LS variants while maintaining TTL voltage thresholds and fan-out compatibility.
Each channel supports high-current sinking (64 mA) and sourcing (15 mA) in active state, and transitions fully to high-impedance when G is high. Input hysteresis (0.2–0.4 V) and PNP input structure reduce DC loading and improve noise margins on shared buses.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | SN74S240NE4 uses Schottky TTL (S-series), enabling 7 ns typical tPLH/tPHL - 2× faster than LS equivalents for time-critical bus buffering. |
| Supply Voltage | Operates at 4.75–5.25 V; deviation beyond this range risks functional failure or accelerated degradation. |
| Output Drive | Sinks up to 64 mA per output (IOL), supporting direct drive of multiple TTL loads or terminated transmission lines down to 133 Ω. |
| Propagation Delay | tPLH/tPHL = 4.5–7 ns (typ) at RL = 90 Ω, CL = 50 pF - optimized for high-speed memory address or data bus extension. |
| Input Hysteresis | 0.2–0.4 V (VT+ − VT−) improves noise immunity on noisy industrial bus environments without external filtering. |
| 3-State Enable Timing | tPZH = 6.5–10 ns, tPZL = 10–15 ns - critical for glitch-free bus arbitration in multi-master systems. |
| Operating Temperature | 0°C to +70°C ambient range - validated for commercial-grade embedded systems, not extended or military temperature grades. |
Pinout & Package
SN74S240NE4 is supplied in a 20-pin plastic DIP (PDIP-N) package measuring 24.33 mm × 6.35 mm, with through-hole mounting and standard 0.3-inch row spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | 1G / 2G | Active-low output-enable inputs - both must be low to activate respective 4-bit inverting buffer channels; tie high via pullup for power-up high-Z safety. |
| 2, 4, 6, 8 | 1A1–1A4 | Inverting input pins for Channel 1 - drive corresponding Y outputs with logical inversion (e.g., 1A1 → 1Y1). |
| 11, 13, 15, 17 | 2A1–2A4 | Inverting input pins for Channel 2 - electrically isolated from Channel 1; enables bidirectional bus partitioning. |
| 12, 14, 16, 18 | 1Y1–1Y4 | Inverting 3-state outputs for Channel 1 - high-impedance when 1G = high; sinks 64 mA when low. |
| 3, 5, 7, 9 | 2Y1–2Y4 | Inverting 3-state outputs for Channel 2 - identical drive strength and timing to Channel 1 outputs. |
| 10 | GND | Power ground reference - must be low-impedance connection to minimize switching noise coupling into logic thresholds. |
| 20 | VCC | +5 V supply - requires local 0.1 µF ceramic decoupling adjacent to pin to suppress SSO noise during simultaneous output transitions. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent 4-bit inverting buffers | Enables separate control of two bus segments (e.g., upper/lower address bytes) using discrete 1G/2G enables - no inter-channel timing skew. |
| 3-state outputs with fast enable/disable | tPZH ≤ 10 ns and tPZL ≤ 15 ns ensure minimal bus contention windows during multi-device arbitration in shared-memory systems. |
| Input hysteresis (0.2–0.4 V) | Rejects <400 mV of common-mode noise on address/data lines - eliminates need for external Schmitt triggers in noisy PLC or motor-drive environments. |
| PNP input structure | Reduces input DC loading to ≤400 µA (IIL), preventing excessive current draw on upstream TTL or CMOS drivers sharing the same bus. |
| High-current sink capability (64 mA) | Drives terminated 133-Ω transmission lines directly - avoids external line drivers in backplane or rack-mounted I/O modules. |
Applications
| Memory Address Buffering | Industrial Backplane Bus Driver |
|---|---|
|
Use Scenario: Driving 16-bit memory address lines from a microcontroller to multiple SRAM/ROM chips across a 150-mm PCB trace. IC Role / Device Role / Timing Role: SN74S240NE4 acts as a high-drive inverting repeater, compensating for trace capacitance-induced signal degradation and ensuring clean setup/hold timing at downstream devices. Use Value: 7 ns propagation delay and 64 mA sink current maintain TTL logic margins over 150-mm FR-4 traces, eliminating timing violations at 8 MHz bus rates. |
Use Scenario: Isolating and strengthening I/O expansion bus signals between a main controller card and peripheral I/O modules in an industrial PLC rack. IC Role / Device Role / Timing Role: SN74S240NE4 provides bidirectional 3-state control per 4-bit nibble, enabling hot-swap-safe bus arbitration and noise-immune signal regeneration. Use Value: Input hysteresis and PNP inputs reject EMI from nearby motor drives, while dual-channel independence allows staggered enable sequencing to prevent simultaneous switching noise. |
| LED Display Row Driver | Legacy System Bus Repeater |
|
Use Scenario: Sourcing current to 8-row common-anode LED matrix displays in point-of-sale terminals or instrumentation panels. IC Role / Device Role / Timing Role: SN74S240NE4 serves as a low-side row sink driver, with 1G/2G enabling dynamic row scanning at >1 kHz refresh rates. Use Value: 64 mA per output supports bright LED operation without external transistors; 3-state disable prevents ghosting during row transitions. |
Use Scenario: Extending signal integrity of aging TTL-based computer backplanes (e.g., S-100, Multibus I) where original drivers have degraded. IC Role / Device Role / Timing Role: SN74S240NE4 functions as a drop-in replacement repeater, restoring edge rate and noise margin on long, unterminated bus runs. Use Value: Matches original SN74LS240 pinout and logic function while delivering 2× faster edges and 2.7× higher sink current - extends usable life of legacy hardware. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS240N | Slower tPLH/tPHL (9–14 ns), lower IOL (24 mA), no input hysteresis - LS-family baseline. | Better suited for low-noise, low-speed systems where power consumption (<27 mA ICC) is prioritized over speed. | Select SN74LS240N only if existing design uses LS timing margins and thermal budget is constrained. |
| SN74F240N | Fast TTL variant: 3.5 ns tPLH/tPHL, 20 mA IOL, no hysteresis, higher ICC (135 mA). | Optimized for ultra-high-speed clock distribution, not bus driving - insufficient sink current for terminated lines. | Choose SN74F240N only for sub-5 ns timing-critical paths with light capacitive loads; avoid for bus termination. |
Compared with SN74LS240N and SN74F240N, SN74S240NE4 uniquely balances speed (7 ns), drive strength (64 mA), and noise immunity (hysteresis) - making it the optimal choice for robust bus interfacing in electrically harsh industrial environments.
Availability
SN74S240NE4 is available at Aetrix Electronics and suitable for industrial backplane bus drivers, memory address buffering, LED display row control, and legacy system bus repeaters requiring stable component supply and long-term obsolescence management.
Supply support for SN74S240NE4 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 U.S.-based semiconductor company founded in 1930, specializing in analog ICs, embedded processors, and logic devices for industrial, automotive, and communications markets.
SN74S240NE4 belongs to TI's legacy TTL logic portfolio, engineered specifically for high-reliability bus interface and memory addressing in industrial control, test equipment, and retro-computing systems.
FAQ
What logic family does SN74S240NE4 belong to, and how does it differ from LS or F variants?
SN74S240NE4 is a Schottky TTL (S-series) device, distinguished by Schottky diode clamping that prevents transistor saturation - yielding faster switching (7 ns typical tPLH) than LS (14 ns) and higher output current (64 mA IOL) than F (20 mA). Unlike LS, it includes input hysteresis for noise immunity; unlike F, it maintains TTL-compatible input thresholds and lower power than F-family.
Can SN74S240NE4 interface directly with 3.3-V logic inputs?
SN74S240NE4 inputs tolerate down to 2 V and are compatible with 3.3-V logic high levels (VIH ≥ 2 V), but its outputs swing rail-to-rail (0 V to 5 V) and are not 3.3-V tolerant. Direct connection to 3.3-V inputs requires series resistors or level-shifting circuitry to avoid overstressing downstream receivers.
What is the recommended power supply decoupling for SN74S240NE4?
TI specifies a minimum 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 20) and GND (pin 10) pins of SN74S240NE4. For systems with multiple devices or high-frequency switching, add a 4.7 µF tantalum capacitor per 5–10 ICs on the same supply rail to suppress low-frequency ripple and SSO noise.
How does the input hysteresis of SN74S240NE4 improve system reliability?
The 0.2–0.4 V hysteresis (VT+ − VT−) in SN74S240NE4 raises the input threshold for rising signals and lowers it for falling signals. This prevents oscillation or metastability on slow-rising/noisy bus lines - such as those near motor drives or relay coils - ensuring clean, single-transition recognition without external filtering components.
Is SN74S240NE4 pin-compatible with SN74LS240N, and can it be used as a drop-in replacement?
Yes, SN74S240NE4 shares identical pinout, pin functions, and package (20-pin PDIP) with SN74LS240N. However, due to higher ICC (135 mA vs. 44 mA) and faster edge rates, verify PCB layout for adequate power delivery and potential signal integrity effects like ringing - especially on long traces without termination.
SN74S240NE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74S
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74S240NE4 FAQ
1.How can I place an order for SN74S240NE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74S240NE4 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 SN74S240NE4 reliable?
The price and inventory of SN74S240NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74S240NE4 is usually 5 days.
3.What payment methods are accepted for SN74S240NE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74S240NE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74S240NE4?
SN74S240NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74S240NE4 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 SN74S240NE4?
For technical support, including SN74S240NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74S240NE4 requirements.
6.How does Aetrix verify that SN74S240NE4 is sourced from the original manufacturer or authorized distributors?
All SN74S240NE4 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 SN74S240NE4 meets industry standards.
7.What is the process for return or replacement of SN74S240NE4?
All SN74S240NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74S240NE4, 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 SN74S240NE4 part is unused and in its original packaging.
Return procedure for SN74S240NE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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