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onsemi 74AC540SC
- Part No.:
- 74AC540SC
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
74AC540SC.pdf
- Description:
- IC BUFF INVERT 6V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,760
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Product details
Overview
74AC540SC from onsemi is an octal inverting buffer/line driver with 3-state outputs, designed for memory addressing, bus interfacing, and microprocessor output port applications. It operates from 2.0 V to 6.0 V, delivers ±24 mA output drive, features flow-through pinout (inputs and outputs on opposite sides), and supports −40 °C to +85 °C industrial temperature range.
For engineers reviewing the 74AC540SC datasheet, pinout, applications, or equivalent options, key selection criteria include 3-state control logic (dual OE inputs), high-speed propagation (≤8.0 ns at 5 V), low ICC/IOZ leakage, Pb-free SOIC-20W packaging, and compatibility with TTL/CMOS logic families.
Technical Context
The 74AC540SC implements eight independent inverting buffers, each with separate 3-state enable control via two active-low OE inputs (OE1 and OE2). Its flow-through architecture places all eight inputs on one side and all eight outputs on the opposite side of the SOIC-20W package, optimizing PCB routing for microprocessor I/O expansion.
It uses advanced CMOS AC technology to achieve rail-to-rail output swing, guaranteed VOH ≥ 4.4 V and VOL ≤ 0.44 V at VCC = 4.5 V with 24 mA load, and meets JEDEC MS-013 mechanical standards for SOIC-20W (case 751BJ).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2.0 V to 6.0 V - supports mixed-voltage system interfacing (3.3 V and 5 V logic domains) |
| Output Drive | ±24 mA - sufficient to directly drive terminated transmission lines or multiple TTL loads |
| Propagation Delay | ≤6.5 ns (tPLH/tPHL at VCC = 5.0 V, CL = 50 pF) - enables high-speed address/data buffering in 20–25 MHz bus systems |
| 3-State Leakage | ±2.5 µA max (IOZ at VCC = 5.5 V) - ensures minimal bus contention current during high-impedance state |
| Input Thresholds | VIH = 3.15 V, VIL = 1.35 V at VCC = 4.5 V - provides robust noise margin (>1.3 V) against ground bounce and crosstalk |
| Operating Temperature | −40 °C to +85 °C - qualified for industrial-grade embedded control and instrumentation environments |
Pinout & Package
74AC540SC is housed in a Pb-free SOIC-20W package (case 751BJ), 7.5 mm wide, 12.8 mm long, 2.36 mm height, with 1.27 mm pitch and JEDEC MS-013 compliance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | Inputs (D1–D8) | Inverting data inputs; accept standard CMOS/TTL logic levels; flow-through layout simplifies microprocessor bus connection |
| 9, 10 | Output Enables (OE1, OE2) | Active-low dual enables - both must be LOW to activate all eight outputs; allows grouped or split bus control |
| 11–18 | Outputs (Y1–Y8) | Inverting 3-state outputs; sink/source up to 24 mA; high-impedance when either OE is HIGH |
| 19 | GND | Ground reference for all logic and output stages; requires low-inductance connection to minimize switching noise |
| 20 | VCC | Positive supply input; bypassing with 0.1 µF ceramic capacitor near pin is mandatory for stable AC performance |
Key Features
| Feature | Design Value |
|---|---|
| Flow-through pinout | Inputs on pins 1–8, outputs on pins 11–18 - eliminates layer jumps and reduces trace length in dense microprocessor I/O layouts |
| Dual 3-state enable | Separate OE1 and OE2 inputs - enables flexible bus partitioning (e.g., upper/lower byte control) without external logic |
| Low ICC and IOZ | ICC ≤ 80 µA, IOZ ≤ ±2.5 µA - minimizes standby power and prevents false bus activation in multi-driver systems |
| Pb-free SOIC-20W | RoHS-compliant case 751BJ package - meets IPC/JEDEC moisture sensitivity level 1 (MSL-1) and reflow profile requirements |
Applications
| Memory Address Buffering | Microprocessor I/O Port Expansion |
|---|---|
Use Scenario: Driving 16-bit address bus from an 8-bit microcontroller using two 74AC540SC devices in parallel. IC Role / Device Role / Timing Role: Inverting octal buffer with 3-state control - provides level translation, fanout amplification, and bus isolation during DMA cycles. Use Value: Guaranteed tPLH ≤ 6.5 ns at 5 V ensures setup/hold timing margins for SRAM access at ≤20 MHz clock rates. | Use Scenario: Expanding GPIO capability of an ARM Cortex-M0+ MCU by adding eight programmable output lines with tri-state capability. IC Role / Device Role / Timing Role: Bidirectional bus driver - configured as output port with OE tied to chip select, enabling clean peripheral interface without contention. Use Value: ±24 mA drive strength allows direct LED or relay coil driving without external transistors, reducing BOM count. |
| Industrial Bus Transceiver Interface | Legacy System Logic Level Translation |
Use Scenario: Isolating and buffering RS-485 transceiver control signals (DE/RE) in a noisy factory-floor PLC backplane. IC Role / Device Role / Timing Role: Noise-immune 3-state line driver - decouples microcontroller GPIO from high-noise bus sections using controlled enable timing. Use Value: VIH/VIL thresholds provide >1.3 V noise margin at 5 V supply, preventing spurious enable/disable transitions in EMI-prone environments. | Use Scenario: Interfacing 3.3 V FPGA I/O banks to legacy 5 V TTL peripherals (e.g., EPROMs, latch chips) in system upgrades. IC Role / Device Role / Timing Role: Voltage-tolerant CMOS buffer - accepts 3.3 V inputs while sourcing 5 V-compatible outputs, eliminating level-shifter ICs. Use Value: Operates down to 2.0 V VCC but maintains full 5 V output swing - enables seamless mixed-supply domain bridging without external bias networks. |
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 |
|---|---|---|---|
| 74ACT540PW,118 | TTL-compatible input thresholds (VIH = 2.0 V min), slightly higher ICC (100 µA max), TSSOP-20 package | Better suited for 3.3 V systems interfacing to legacy 5 V TTL, less ideal for pure CMOS designs requiring tighter threshold symmetry | Select when interfacing with older TTL logic families where lower VIH is required; verify PCB footprint compatibility |
| SN74AC540N | DIP-20 package, identical AC/DC specs, same SOIC marking prefix but through-hole mounting | Used in prototyping, educational labs, or legacy through-hole production where SOIC reflow is unavailable | Select for hand-soldered development boards or repair scenarios requiring DIP form factor; no electrical or functional change |
Compared with 74AC540SC, the 74ACT540PW offers enhanced TTL input compatibility at the cost of higher quiescent current, while SN74AC540N provides identical functionality in through-hole format-both serve distinct mechanical or interface-level needs without altering core buffering behavior.
Availability
74AC540SC is available at Aetrix Electronics and suitable for industrial control systems, microprocessor-based instrumentation, and legacy bus interface designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for 74AC540SC 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
onsemi (formerly ON Semiconductor) is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.
The 74AC540SC belongs to onsemi's legacy AC logic family - engineered for high-speed, low-power, pin-compatible replacement of 74LS and 74F series devices in industrial and computing infrastructure.
FAQ
What is the maximum output current per pin for the 74AC540SC?
The 74AC540SC guarantees ±24 mA output sink/source capability per output pin under recommended operating conditions (VCC = 4.5 V, TA = −40 °C to +85 °C). This is verified in the DC Electrical Characteristics table for IOL and IOH at 24 mA load, with VOL ≤ 0.44 V and VOH ≥ 3.76 V respectively. The 74AC540SC also supports peak transient currents up to ±50 mA per pin, though sustained operation above ±24 mA is not recommended for thermal and reliability reasons.
Does the 74AC540SC support 3.3 V operation?
Yes, the 74AC540SC fully supports 3.3 V operation across its entire industrial temperature range (−40 °C to +85 °C). At VCC = 3.3 V, it guarantees VIH = 2.1 V, VIL = 0.9 V, VOH ≥ 2.9 V, and VOL ≤ 0.1 V, providing >1.2 V noise margin. Propagation delay remains ≤8.0 ns (tPLH/tPHL), making the 74AC540SC suitable for mixed-voltage systems interfacing 3.3 V FPGAs or microcontrollers to 5 V peripherals.
How are the two output enable inputs (OE1 and OE2) used in the 74AC540SC?
The 74AC540SC requires both OE1 and OE2 to be LOW for all eight outputs to be active (inverted); if either OE is HIGH, all outputs enter high-impedance state. This dual-enable architecture allows grouped bus control - for example, tying OE1 to a system address decoder and OE2 to a write strobe enables precise timing of output activation only during valid write cycles. The 74AC540SC truth table confirms that outputs go to Z-state whenever OE1 or OE2 is HIGH, regardless of data inputs.
Is the 74AC540SC pin-compatible with the 74LS540?
No, the 74AC540SC is not pin-compatible with the 74LS540. Although both are octal inverting 3-state buffers in 20-pin packages, the 74AC540SC uses a flow-through pinout (inputs on pins 1–8, outputs on 11–18), whereas the 74LS540 uses a folded pinout (inputs and outputs interleaved). The 74AC540SC's SOIC-20W (case 751BJ) footprint differs mechanically from the 74LS540's standard SOIC-20. Direct replacement requires PCB redesign; the 74AC540SC is functionally compatible but not physically interchangeable.
What is the thermal performance rating of the 74AC540SC in SOIC-20W package?
While the 74AC540SC datasheet does not specify junction-to-ambient thermal resistance (θJA) explicitly, its SOIC-20W package (case 751BJ) has a typical θJA of 100 °C/W under standard JEDEC test conditions (1-layer 1-in² copper pad). With maximum ICC ≤ 80 µA and output loading limited to ±24 mA, power dissipation stays below 100 mW under normal operation - resulting in negligible junction temperature rise (<10 °C above ambient). The 74AC540SC is rated for continuous operation up to +85 °C ambient, confirmed by its Recommended Operating Conditions table.
74AC540SC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74AC
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 24mA, 24mA
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
74AC540SC FAQ
1.How can I place an order for 74AC540SC through Aetrix?
Please submit a Request for Quotation (RFQ) for 74AC540SC 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 74AC540SC reliable?
The price and inventory of 74AC540SC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74AC540SC is usually 5 days.
3.What payment methods are accepted for 74AC540SC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74AC540SC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74AC540SC?
74AC540SC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74AC540SC 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 74AC540SC?
For technical support, including 74AC540SC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74AC540SC requirements.
6.How does Aetrix verify that 74AC540SC is sourced from the original manufacturer or authorized distributors?
All 74AC540SC 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 74AC540SC meets industry standards.
7.What is the process for return or replacement of 74AC540SC?
All 74AC540SC units undergo pre-shipment inspection (PSI). If there is an issue with 74AC540SC, 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 74AC540SC part is unused and in its original packaging.
Return procedure for 74AC540SC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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