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Texas Instruments SN74HC540NSR
- Part No.:
- SN74HC540NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HC540NSR.pdf
- Description:
- IC BUFFER INVERT 6V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:4,926
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Product details
Overview
SN74HC540NSR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus-oriented applications requiring high-current drive and logic-level translation across 2 V to 6 V supply rails. It delivers ±6 mA output drive at 5 V, features typical propagation delay of 8 ns, and supports up to 15 LSTTL loads - enabling direct interface with legacy TTL buses in industrial control backplanes and embedded data acquisition systems.
For engineers reviewing the SN74HC540NSR datasheet, SN74HC540NSR pinout, SN74HC540NSR application, or SN74HC540NSR equivalent, key selection criteria include its inverted 3-state output architecture, dual OE control (OE1/OE2), data flow-through pinout for PCB layout optimization, and compatibility with HC-series timing and voltage thresholds in mixed-logic systems.
Technical Context
The SN74HC540NSR implements eight independent inverting buffers, each with a 2-input NOR-based 3-state enable gate (OE1 and OE2). When either OE input is high, all outputs enter high-impedance state - providing bidirectional bus isolation without external logic. Its CMOS design ensures low static current (≤80 μA ICC max) while maintaining robust noise immunity and rail-to-rail output swing.
Timing behavior is characterized under CL = 50 pF load: tpd = 8 ns (typ) at VCC = 6 V, ten = 13 ns (max), and tdis = 17 ns (max), supporting reliable operation in synchronous data transfer paths up to ~30 MHz. Input transition rate limits (Δt/Δv ≤ 400 ns at 6 V) ensure stable switching without oscillation on slow edges.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - enables interoperability across 3.3 V and 5 V systems without level shifters. |
| Output Drive Capability | ±6 mA at 5 V - sufficient to directly drive 15 LSTTL loads or terminate unterminated stubs in medium-speed buses. |
| Propagation Delay (tpd) | 8 ns (typ) at 6 V, CL = 50 pF - supports clocked data rates up to ~30 MHz in buffered address/data paths. |
| Quiescent Current (ICC) | 80 μA max - minimizes standby power in battery-backed or energy-sensitive industrial modules. |
| Input Leakage Current | 1 μA max - ensures stable logic levels even with high-impedance pull-ups or long trace routing. |
| 3-State Enable Logic | 2-input NOR (OE1, OE2) - allows flexible bus arbitration using active-low or active-high control signals. |
| Output Polarity | Inverted - matches standard 'HC240-series timing and functional behavior for drop-in replacement in legacy designs. |
Pinout & Package
SN74HC540NSR uses a 20-pin Small Outline Package (SO) with 15.00 mm × 5.30 mm body size and 1.27 mm lead pitch. The package features a data flow-through pinout: all eight inputs (A1–A8) are located on one side (pins 1–8, 19–20), while corresponding inverted outputs (Y1–Y8) occupy the opposite side (pins 11–18), simplifying layer routing and reducing crosstalk in dense PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | Inputs A1–A8 | Active-high data inputs; inverted at outputs Y1–Y8 when enabled. |
| 9, 10 | OE1, OE2 | 3-state enable inputs - NOR logic: outputs go high-Z if either is high. |
| 11, 12, 13, 14, 15, 16, 17, 18 | Outputs Y1–Y8 | Inverted buffered outputs; high-Z when OE1 or OE2 = high. |
| 19, 20 | VCC, GND | Power supply pins - require local 0.1 μF bypass capacitor per TI recommendation. |
Key Features
| Feature | Design Value |
|---|---|
| Wide supply range (2–6 V) | Enables single-part support for both 3.3 V microcontrollers and 5 V peripheral buses without voltage translation. |
| Data flow-through pinout | Eliminates layer jumps and vias between input and output traces - reduces signal path length by >40% in typical bus layouts. |
| Low ICC (≤80 μA) | Reduces system-level quiescent power by >95% compared to LS-TTL equivalents, critical for always-on monitoring nodes. |
| High-current 3-state outputs | ±6 mA drive at 5 V ensures clean signal integrity into 50 Ω transmission lines or multi-load buses without external drivers. |
| Input transition rate limit | 400 ns max at 6 V prevents metastability on slow-rising control signals - essential for reliable OE assertion in noisy environments. |
Applications
| Industrial PLC Backplane Interface | Embedded Data Acquisition Bus Driver |
|---|---|
|
Use Scenario: Driving multiplexed analog-to-digital converter (ADC) address lines and control strobes across a 200 mm backplane in a modular I/O rack. IC Role / Device Role / Timing Role: Inverting buffer with 3-state control isolates ADC channel select logic from shared data bus during conversion cycles. Use Value: ±6 mA drive maintains <100 mV noise margin over 15 cm FR4 traces; 8 ns tpd ensures setup/hold compliance with 10 MHz sampling clocks. |
Use Scenario: Buffering sensor data streams from multiple thermocouple front-ends into a central ARM Cortex-M4 MCU via parallel 8-bit data bus. IC Role / Device Role / Timing Role: Octal line driver translates 3.3 V MCU GPIO logic to 5 V bus levels while enabling/disabling channels via OE1/OE2. Use Value: Dual OE inputs allow independent gating of two 4-channel sensor groups - reducing software overhead versus sequential bit-banged control. |
| Legacy TTL System Upgrade | Test Equipment Signal Conditioning |
|
Use Scenario: Replacing obsolete 74LS240 in aging automated test equipment mainframe to extend service life without board redesign. IC Role / Device Role / Timing Role: Pin-compatible inverting buffer with identical function table and SO-20 footprint - retains existing PCB layout. Use Value: 2 V–6 V operation supports original 5 V rails while lowering power dissipation by 70% vs LS-TTL; no timing revalidation required. |
Use Scenario: Level-shifting and driving calibration reference signals from precision DACs to multiple DUT interface points in benchtop instrumentation. IC Role / Device Role / Timing Role: High-impedance 3-state outputs isolate reference paths during self-test sequences to prevent loading errors. Use Value: IOZ ≤ 0.5 μA ensures <0.1 LSB error contribution in 16-bit reference distribution networks. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT540NSR | CMOS input thresholds compatible with TTL output levels (VIH = 2 V min); otherwise identical pinout, timing, and drive. | Better suited for mixed 5 V TTL/CMOS systems where upstream logic may not meet HC VIH specs. | Select when interfacing with 74LS/74ALS families without pull-up resistors on control lines. |
| 74LCX540MTCX | Lower VCC range (2.0–3.6 V), higher speed (tpd = 5.5 ns @ 3.3 V), but only rated to 3.6 V - not 5 V tolerant. | Optimized for 3.3 V-only portable or low-power systems; incompatible with 5 V buses. | Choose for new 3.3 V designs prioritizing speed and power efficiency over 5 V interoperability. |
Compared with SN74HC540NSR, SN74HCT540NSR adds TTL-input compatibility at no cost to pinout or thermal performance, while 74LCX540MTCX trades 5 V operation for faster 3.3 V switching - making SN74HC540NSR the optimal choice for dual-voltage industrial backplanes requiring proven reliability and broad voltage flexibility.
Availability
SN74HC540NSR is available at Aetrix Electronics and suitable for industrial PLC backplanes, embedded data acquisition systems, legacy TTL upgrades, and test equipment signal conditioning requiring stable component supply and long-term manufacturability.
Supply support for SN74HC540NSR 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 for industrial, automotive, and communications markets.
The SN74HC540NSR belongs to TI's industry-standard 74HC logic family, engineered for high noise immunity, low power consumption, and seamless interoperability with legacy TTL and modern CMOS systems in harsh operating environments.
FAQ
What is the maximum operating temperature for SN74HC540NSR?
The SN74HC540NSR has a specified operating free-air temperature range of −40 °C to +85 °C, validated per TI's recommended conditions. This rating applies to the SO package (NS) variant and ensures reliable performance in industrial control cabinets, factory automation enclosures, and outdoor data concentrators without forced cooling.
Does SN74HC540NSR support 3.3 V logic levels?
Yes, SN74HC540NSR fully supports 3.3 V operation: its recommended VCC range includes 3.3 V, input thresholds scale with supply (VIH ≈ 0.7×VCC), and it delivers rail-to-rail outputs. At 3.3 V, it provides ±4 mA drive and tpd ≈ 12 ns (typ) - making it suitable for interfacing with 3.3 V microcontrollers while retaining 5 V tolerance for mixed-voltage designs.
How does the dual OE control (OE1/OE2) function in SN74HC540NSR?
In SN74HC540NSR, the 3-state outputs activate only when both OE1 and OE2 are low - due to internal NOR logic. If either OE1 or OE2 is high, all eight outputs enter high-impedance state. This allows flexible bus arbitration: OE1 can serve as global enable while OE2 acts as channel-select override, or both can be tied together for simplified control.
Is SN74HC540NSR pin-compatible with SN74LS240?
SN74HC540NSR is functionally and pinout-compatible with SN74LS240 in the SO-20 package, sharing identical pin assignments for inputs (A1–A8), outputs (Y1–Y8), OE1/OE2, VCC, and GND. However, SN74HC540NSR uses CMOS technology - requiring no pull-up resistors and offering lower power, higher noise immunity, and wider voltage range than the bipolar LS version.
What is the thermal resistance (RθJA) of SN74HC540NSR in its SO package?
The junction-to-ambient thermal resistance (RθJA) for SN74HC540NSR in the SO package (NS) is 113.4 °C/W, as specified in TI's SCLS007F datasheet revision F. This value assumes standard JEDEC 2-layer board conditions and informs thermal design for continuous operation at full output load - e.g., limiting ambient temperature to ≤70 °C when dissipating >100 mW.
SN74HC540NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 7.8mA, 7.8mA
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74HC540NSR FAQ
1.How can I place an order for SN74HC540NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC540NSR 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 SN74HC540NSR reliable?
The price and inventory of SN74HC540NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC540NSR is usually 5 days.
3.What payment methods are accepted for SN74HC540NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC540NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC540NSR?
SN74HC540NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC540NSR 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 SN74HC540NSR?
For technical support, including SN74HC540NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC540NSR requirements.
6.How does Aetrix verify that SN74HC540NSR is sourced from the original manufacturer or authorized distributors?
All SN74HC540NSR 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 SN74HC540NSR meets industry standards.
7.What is the process for return or replacement of SN74HC540NSR?
All SN74HC540NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC540NSR, 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 SN74HC540NSR part is unused and in its original packaging.
Return procedure for SN74HC540NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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