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Texas Instruments SN74AHCT540DW
- Part No.:
- SN74AHCT540DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74AHCT540DW.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,127
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Product details
Overview
SN74AHCT540DW from Texas Instruments is an octal noninverting buffer/driver with 3-state outputs, designed for bus line driving and memory address register buffering in 5-V TTL-compatible digital systems. It features dual output-enable inputs (OE1/OE2), ±8 mA drive strength, 5.5 V absolute max supply rating, and operates from –40°C to 125°C.
For engineers reviewing the SN74AHCT540DW datasheet, SN74AHCT540DW pinout, SN74AHCT540DW application, or SN74AHCT540DW equivalent, this page delivers verified electrical specs, SOIC-20 package details, functional mode behavior, real-world layout guidance, and validated alternative options for industrial control, data acquisition, and legacy system upgrades.
Technical Context
The SN74AHCT540DW implements two independent 4-bit groups (A1–A4/Y1–Y4 and A5–A8/Y5–Y8), each controlled by a dedicated active-low output-enable input (OE1, OE2). Its 3-state logic uses dual-input AND gates with active-low enables-asserting either OE high forces all eight outputs into high-impedance.
It supports TTL-voltage compatible inputs (VIH = 2 V min, VIL = 0.8 V max), delivers rail-to-rail CMOS-level outputs (VOH ≥ 3.8 V at IOH = –8 mA, VOL ≤ 0.44 V at IOL = 8 mA), and exhibits propagation delays of 4.0 ns (typ) at CL = 15 pF under 5-V operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5-V logic rails and tolerance to supply ripple |
| Output Drive | ±8 mA - sufficient to drive multiple TTL loads or short PCB traces without external buffering |
| Propagation Delay | 4.0 ns (typ) at CL = 15 pF - enables reliable operation in high-speed address/data bus applications up to ~100 MHz |
| Input Compatibility | TTL-level (VIH ≥ 2 V, VIL ≤ 0.8 V) - allows direct interfacing with legacy 74LS/74F families without level shifters |
| ESD Rating | ±2000 V HBM - meets industrial handling requirements and reduces risk of field failure during assembly |
| Operating Temp | –40°C to +125°C - supports deployment in extended-temperature industrial and automotive under-hood environments |
| Power Dissipation | 12 pF typical Cpd - enables low dynamic power consumption in clocked bus applications |
Pinout & Package
SN74AHCT540DW is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 10.3 mm (body: 12.80 mm × 7.50 mm), optimized for surface-mount assembly and thermal dissipation in dense PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | OE1, OE2 | Active-low output enable inputs - independently disable Y1–Y4 (OE1) or Y5–Y8 (OE2); tied high via pullup for power-up high-Z safety |
| 2–9 | A1–A8 | Buffer input terminals - accept TTL-compatible signals; must be tied to VCC or GND if unused to prevent floating states |
| 10 | GND | Ground reference - requires local 0.1 µF bypass capacitor adjacent to pin for noise suppression |
| 11–18 | Y1–Y8 | 3-state noninverting outputs - present inverted logic relative to inputs only when enabled; float high-Z otherwise |
| 20 | VCC | Positive supply - must be decoupled with 0.1 µF ceramic capacitor placed within 2 mm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Input voltage compatibility | Accepts 0–5.5 V inputs - eliminates need for external level translators when interfacing with mixed-voltage subsystems |
| Output isolation control | Dual independent OE pins - enables selective gating of upper/lower nibbles for partial bus arbitration or power-gated operation |
| Latch-up immunity | Exceeds 250 mA per JESD17 - ensures robustness against transient current surges in noisy industrial environments |
| Thermal performance | RθJA = 58 °C/W (SOIC) - supports continuous operation at full drive strength without heatsinking below 85°C ambient |
| Low quiescent current | ICC = 4 µA (typ) at 25°C - minimizes standby power in battery-backed or energy-sensitive applications |
Applications
| Industrial PLC Backplane Interface | Legacy Memory Address Buffering |
|---|---|
Use Scenario: Interfacing microcontroller GPIO banks to modular I/O expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus driver isolating CPU address/data lines from hot-swappable I/O modules. Use Value: Dual OE control allows per-slot enable/disable without affecting other modules; ±8 mA drive sustains signal integrity across 15-cm backplane traces. | Use Scenario: Buffering 16-bit address lines between Z80 or 8086 CPUs and SRAM/ROM chips in retro-computing or instrumentation systems. IC Role / Device Role / Timing Role: Noninverting address latch driver with 3-state outputs enabling shared memory bus access. Use Value: TTL-compatible inputs eliminate level-shifting components; 4.0 ns propagation delay preserves timing margins in sub-10 MHz CPU designs. |
| Automotive ECU Diagnostic Port | Test Equipment Signal Conditioning |
Use Scenario: Isolating diagnostic UART and CAN controller pins from external test connectors in engine control units. IC Role / Device Role / Timing Role: Level-translating and fault-isolating buffer for service port signals exposed to ESD-prone environments. Use Value: ±2000 V HBM rating protects against technician-handling ESD; 125°C rating ensures reliability near exhaust manifolds. | Use Scenario: Driving multiple DUT (device-under-test) inputs simultaneously from a single pattern generator channel in automated test fixtures. IC Role / Device Role / Timing Role: Fanout buffer distributing synchronized stimulus signals while maintaining edge fidelity. Use Value: Matched propagation delays (<1 ns skew) across all eight channels ensure simultaneous signal arrival at DUT pins. |
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 |
|---|---|---|---|
| SN74AHCT244DW | Noninverting octal buffer with identical pinout, same SOIC-20 package, and matching 4.5–5.5 V supply range | No functional difference - identical logic behavior, timing, and drive capability; fully interchangeable in existing designs | Select when sourcing new production lots, as SN74AHCT244DW remains active (non-obsolete) per TI's packaging addendum |
| 74LVC244APW | 3.3-V-only operation (1.65–3.6 V), lower drive (±24 mA), smaller TSSOP-20 package (6.5 × 4.4 mm) | Requires level translation for 5-V systems; unsuitable for direct replacement but preferred for new 3.3-V designs with space constraints | Choose for next-generation low-voltage, high-density boards where power efficiency and footprint reduction outweigh legacy voltage compatibility |
Compared with SN74AHCT540DW, SN74AHCT244DW offers identical functionality and drop-in compatibility for ongoing production, while 74LVC244APW provides higher drive and smaller size at the cost of 5-V interoperability - making it suitable only for greenfield 3.3-V designs.
Availability
SN74AHCT540DW is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy memory subsystems, and automotive diagnostic interfaces requiring stable component supply and long-term obsolescence management.
Supply support for SN74AHCT540DW 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 90 years of innovation in industrial, automotive, and communications markets.
The SN74AHCT540DW belongs to TI's 74AHCT logic family, engineered for seamless 5-V TTL-to-CMOS interfacing in industrial control, test equipment, and legacy system modernization where reliability and voltage compatibility are critical.
FAQ
What is the function of OE1 and OE2 on the SN74AHCT540DW?
OE1 and OE2 are active-low output-enable inputs controlling two independent 4-bit groups: OE1 enables Y1–Y4, OE2 enables Y5–Y8. When either is high, its associated outputs enter high-impedance state. This allows selective bus segmentation. The SN74AHCT540DW datasheet specifies that tying OE to VCC via a pullup resistor ensures safe high-Z during power-up.
Does SN74AHCT540DW support 3.3-V input levels?
No. The SN74AHCT540DW requires TTL-compatible inputs: VIH ≥ 2.0 V and VIL ≤ 0.8 V under 4.5–5.5 V supply. While 3.3-V logic may occasionally meet these thresholds, it is not guaranteed across temperature and process variation. For reliable 3.3-V interfacing, use SN74LVC244APW instead. The SN74AHCT540DW specification explicitly defines its input thresholds for 5-V operation only.
What is the maximum capacitive load the SN74AHCT540DW can drive reliably?
The SN74AHCT540DW is characterized up to 50 pF load capacitance, with tPLH/tPHL specified at 6.0–8.5 ns (max) and enable/disable times up to 12 ns. Driving >50 pF risks timing violations and increased rise/fall times. For heavier loads, add series termination or use a buffer with higher drive strength. The SN74AHCT540DW datasheet's switching characteristics table confirms CL = 50 pF as the upper validated limit.
Is SN74AHCT540DW still in active production?
No - according to TI's official Packaging Addendum (August 2024), SN74AHCT540DW is marked "Obsolete". However, SN74AHCT540DWR and SN74AHCT540DWRE4 (same SOIC-20 package, tape-and-reel) remain active and fully compatible. Aetrix Electronics stocks both active variants as direct replacements for SN74AHCT540DW in legacy BOMs.
How should unused inputs be handled on SN74AHCT540DW?
All unused A1–A8 inputs on SN74AHCT540DW must be tied to VCC or GND - floating inputs cause undefined output states and increased ICC. TI's application note SCBA004 mandates this practice. The SN74AHCT540DW layout guidelines explicitly prohibit leaving inputs unconnected, even if corresponding outputs are disabled. This prevents shoot-through current and ensures predictable 3-state behavior.
SN74AHCT540DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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:
- 8mA, 8mA
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
SN74AHCT540DW FAQ
1.How can I place an order for SN74AHCT540DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT540DW 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 SN74AHCT540DW reliable?
The price and inventory of SN74AHCT540DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT540DW is usually 5 days.
3.What payment methods are accepted for SN74AHCT540DW?
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4.How is shipping managed for SN74AHCT540DW?
SN74AHCT540DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHCT540DW 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 SN74AHCT540DW?
For technical support, including SN74AHCT540DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT540DW requirements.
6.How does Aetrix verify that SN74AHCT540DW is sourced from the original manufacturer or authorized distributors?
All SN74AHCT540DW 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 SN74AHCT540DW meets industry standards.
7.What is the process for return or replacement of SN74AHCT540DW?
All SN74AHCT540DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT540DW, 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 SN74AHCT540DW part is unused and in its original packaging.
Return procedure for SN74AHCT540DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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