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Texas Instruments SN74HCT240NSR
- Part No.:
- SN74HCT240NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HCT240NSR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,933
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Product details
Overview
SN74HCT240NSR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for memory address and bus driving in industrial control and embedded systems. It operates at 4.5–5.5 V, delivers ±6 mA output drive per channel, exhibits 12 ns typical propagation delay, and draws ≤80 μA supply current. Its dual 4-bit architecture with independent OE inputs enables selective bus isolation in high-density PCB layouts.
For engineers reviewing the SN74HCT240NSR datasheet, SN74HCT240NSR pinout, SN74HCT240NSR application, or SN74HCT240NSR equivalent, key selection criteria include TTL-compatible input thresholds, 3-state bus contention management, thermal performance in SOP-20 (12.6 mm × 7.8 mm), and compatibility with 5-V logic families in memory interface and clock distribution circuits.
Technical Context
The SN74HCT240NSR implements two independent 4-bit inverting buffers, each controlled by a dedicated output-enable (OE) input. When OE is low, inverted data passes from A inputs to Y outputs; when OE is high, all eight outputs enter high-impedance state-enabling bidirectional bus sharing without external logic.
Its HCT logic family ensures TTL-voltage compatibility (VIH = 2 V, VIL = 0.8 V at VCC = 4.5–5.5 V), while CMOS input structure limits input current to ≤1 μA. The device supports CL = 50 pF loads with tpd = 12 ns (VCC = 5.5 V, TA = 25°C) and maintains stable operation across –40°C to +85°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V logic rails and tolerant of ±5% regulation variation |
| Propagation Delay (tpd) | 12 ns typical at 5.5 V - enables reliable timing in 33-MHz bus cycles with margin |
| Output Drive | ±6 mA per channel at 5 V - drives up to 15 LSTTL loads without external buffering |
| Input Compatibility | TTL-voltage levels (VIH ≥ 2 V, VIL ≤ 0.8 V) - interoperable with legacy 74LS and microcontroller GPIOs |
| Quiescent Current (ICC) | ≤80 μA max - supports low-power standby modes in battery-backed or energy-sensitive systems |
| 3-State Leakage (IOZ) | ≤5 μA at VCC = 5.5 V - minimizes bus leakage during high-impedance hold, critical for multi-drop integrity |
| Operating Temperature | –40°C to +85°C - qualified for industrial environments including motor control and PLC I/O modules |
Pinout & Package
SOP-20 (NS) package: 12.6 mm × 7.8 mm body size, 1.27 mm pitch, surface-mount, RoHS-compliant, moisture sensitivity level 1 (260°C peak reflow).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1OE, 19 | Input (OE1) | Active-low enable for first 4-bit inverting buffer (Y1–Y4); asserts inversion when low |
| 2OE, 1 | Input (OE2) | Active-low enable for second 4-bit inverting buffer (Y5–Y8); independent control for bus partitioning |
| 1A1–1A4, 2–4,8 | Inputs | Inverting data inputs for first buffer group; TTL-compatible, ≤1 μA input current |
| 2A1–2A4, 11,13,15,17 | Inputs | Inverting data inputs for second buffer group; electrically isolated from first group |
| 1Y1–1Y4, 18,16,14,12 | Outputs | Inverted outputs of first buffer group; high-impedance when 1OE = high |
| 2Y1–2Y4, 9,5,3,7 | Outputs | Inverted outputs of second buffer group; high-impedance when 2OE = high |
| VCC, 20 | Power | 5-V supply pin; requires local 0.1 μF bypass capacitor per TI layout guidelines |
| GND, 10 | Ground | Reference return path; must be low-impedance connection to minimize switching noise |
Key Features
| Feature | Design Value |
|---|---|
| Inverting 3-state buffer architecture | Dual independent 4-bit sections allow selective bus isolation without external gating logic |
| TTL-compatible input thresholds | VIH = 2 V / VIL = 0.8 V ensures robust interfacing with 74LS, microcontrollers, and FPGA I/O banks |
| Low ICC quiescent current | ≤80 μA enables use in always-on subsystems (e.g., watchdog interfaces) without thermal penalty |
| High-output current drive | ±6 mA per Y output eliminates need for discrete pull-up/pull-down resistors on shared buses |
| Controlled switching characteristics | tpd = 12 ns (typ), ten/tdis = 19 ns (typ) at 5.5 V support deterministic timing in synchronous designs |
Applications
| Memory Address Buffering | Industrial Bus Transceiver |
|---|---|
|
Use Scenario: Driving 16-bit address lines from a microcontroller to multiple SRAM or flash devices on a shared bus. IC Role / Device Role / Timing Role: Inverting 3-state buffer isolating address latches during memory access arbitration. Use Value: Prevents bus contention during chip select transitions; ±6 mA drive ensures clean edges across 10-cm traces loaded with 3–4 memory ICs. |
Use Scenario: Bidirectional data routing between PLC CPU and field I/O modules over RS-485 or CAN physical layer transceivers. IC Role / Device Role / Timing Role: Direction-controlled bus driver enabling half-duplex communication with precise OE timing alignment. Use Value: Independent OE pins allow synchronized enable/disable of transmit/receive paths, eliminating glitches during protocol handshaking. |
| Legacy System Interface | Test Equipment Signal Conditioning |
|
Use Scenario: Interfacing modern ARM-based controllers with legacy 74LS-based peripheral cards requiring inverted address/data signals. IC Role / Device Role / Timing Role: Level-shifting and signal inversion bridge between 3.3-V MCU outputs and 5-V TTL bus loads. Use Value: TTL-compatible inputs accept 3.3-V logic highs directly; 12 ns tpd preserves setup/hold margins in 20-MHz backplane timing budgets. |
Use Scenario: Isolating and conditioning digital stimulus signals in automated test equipment (ATE) channel drivers. IC Role / Device Role / Timing Role: Output-enable gated buffer providing glitch-free signal injection into DUT under test. Use Value: High-impedance state prevents back-driving during test sequence pauses; ≤5 μA IOZ ensures minimal leakage into sensitive analog measurement nodes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT240DWR | SOP-20 (DW) package: larger 12.8 mm × 10.3 mm body, higher RθJA (109.1°C/W), same electrical specs | Better thermal mass for sustained 6-mA drive; less space-constrained layouts | Select SN74HCT240DWR when board area allows larger SOIC footprint and higher thermal inertia is beneficial |
| SN74LV240APWR | LV-family: 2–5.5 V supply, lower drive (±4 mA), faster tpd = 7.5 ns, non-TTL input thresholds | Compatible with mixed-voltage 3.3-V/5-V systems but requires level translation for pure TTL interfaces | Choose SN74LV240APWR only when operating below 3.3 V or when sub-10 ns timing dominates over TTL compatibility |
Compared with SN74HCT240DWR and SN74LV240APWR, the SN74HCT240NSR offers optimal balance of compact SOP-20 size, guaranteed TTL compatibility, and industrial temperature range-making it preferred for space-constrained 5-V bus interfaces where legacy interoperability is mandatory.
Availability
SN74HCT240NSR is available at Aetrix Electronics and suitable for industrial control, memory interface, and legacy system integration requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for SN74HCT240NSR 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 specializing in analog, embedded processing, and logic solutions with over 50 years of innovation in industrial and automotive electronics.
The SN74HCT240NSR belongs to TI's 74HCT logic family, engineered for robust 5-V TTL-to-CMOS interfacing in memory addressing, bus driving, and industrial control applications where noise immunity and voltage compatibility are critical.
FAQ
What is the function of the two OE pins on the SN74HCT240NSR?
The SN74HCT240NSR has two independent output-enable inputs: 1OE (pin 1) controls the first four inverting buffers (1Y1–1Y4), and 2OE (pin 19) controls the second four (2Y1–2Y4). When either OE is low, its associated Y outputs pass inverted data from corresponding A inputs; when high, those outputs go high-impedance. This enables granular bus partitioning without external logic gates.
Does the SN74HCT240NSR support 3.3-V input signals?
Yes-the SN74HCT240NSR accepts 3.3-V logic-high inputs reliably because its VIH threshold is 2.0 V minimum (at VCC = 4.5–5.5 V). A 3.3-V signal exceeds this requirement, ensuring valid high-level recognition. However, it does not operate from a 3.3-V supply; VCC must be 4.5–5.5 V.
What is the maximum capacitive load the SN74HCT240NSR can drive while maintaining specified tpd?
The SN74HCT240NSR's switching characteristics are characterized at CL = 50 pF (tpd = 12 ns typ at 5.5 V) and CL = 150 pF (tpd = 19 ns typ at 5.5 V). While it can drive heavier loads, timing margins degrade beyond 150 pF; for >150 pF, derating or buffer staging is recommended to maintain setup/hold compliance.
Is a bypass capacitor required for stable operation of the SN74HCT240NSR?
Yes-TI specifies a 0.1 μF ceramic bypass capacitor placed as close as possible to the VCC (pin 20) and GND (pin 10) pins. This suppresses supply noise induced by simultaneous output switching, preventing false triggering or increased ICC. Parallel 1 μF capacitance may be added for broadband noise suppression.
How does the SN74HCT240NSR differ from the non-inverting SN74HCT244NSR?
The SN74HCT240NSR provides inverting logic (A → Y̅), while the SN74HCT244NSR is non-inverting (A → Y). Both share identical supply range, drive strength, and 3-state behavior-but functional equivalence depends on system-level polarity requirements. Substituting one for the other requires logic inversion elsewhere in the signal path.
SN74HCT240NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 6mA, 6mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74HCT240NSR FAQ
1.How can I place an order for SN74HCT240NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HCT240NSR 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 SN74HCT240NSR reliable?
The price and inventory of SN74HCT240NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT240NSR is usually 5 days.
3.What payment methods are accepted for SN74HCT240NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HCT240NSR transactions.
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4.How is shipping managed for SN74HCT240NSR?
SN74HCT240NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HCT240NSR 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 SN74HCT240NSR?
For technical support, including SN74HCT240NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT240NSR requirements.
6.How does Aetrix verify that SN74HCT240NSR is sourced from the original manufacturer or authorized distributors?
All SN74HCT240NSR 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 SN74HCT240NSR meets industry standards.
7.What is the process for return or replacement of SN74HCT240NSR?
All SN74HCT240NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT240NSR, 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 SN74HCT240NSR part is unused and in its original packaging.
Return procedure for SN74HCT240NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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