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Texas Instruments SN74HCT540DWR
- Part No.:
- SN74HCT540DWR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74HCT540DWR.pdf
- Description:
- IC BUFFER INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,374
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Product details
Overview
SN74HCT540DWR from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interface and load-driving applications in 5-V TTL-compatible digital systems. It operates from 4.5 V to 5.5 V, delivers ±6-mA output drive, features typical propagation delay of 12 ns at 5.5 V, consumes ≤80 µA ICC (max), and supports up to 15 LSTTL loads.
For engineers reviewing the SN74HCT540DWR datasheet, SN74HCT540DWR pinout, SN74HCT540DWR application, or SN74HCT540DWR equivalent, key selection considerations include its dual 3-state enable (OE1/OE2) NOR logic, data-inversion function, SOIC-20 package footprint, and compatibility with legacy 'HCT240 performance while offering improved PCB layout via split-side I/O pinout.
Technical Context
The SN74HCT540DWR implements eight independent inverting buffer channels, each with high-current 3-state outputs controlled by a dual-input NOR gate (OE1 and OE2). When either enable input is high, all outputs enter high-impedance state-ensuring clean bus isolation during power-up/down when OE is pulled to VCC.
Its TTL-compatible inputs accept 0.8 V (VIL) and 2.0 V (VIH) thresholds across 4.5–5.5 V supply, and outputs swing rail-to-rail with VOH ≥3.7 V and VOL ≤0.33 V at 6-mA load. The device uses standard HCT CMOS process, delivering low static current and predictable switching behavior under CL = 50 pF or 150 pF loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures robust operation across industrial 5-V rails with margin against ripple or droop. |
| Propagation Delay (tpd) | 12 ns (typ) at 5.5 V, CL = 50 pF - Enables reliable timing in 33-MHz+ synchronous bus interfaces. |
| Output Drive | ±6 mA at 5 V - Sufficient to directly drive 15 LSTTL loads without external buffers. |
| Input Current (II) | ≤1 µA max - Minimizes loading on upstream logic and simplifies fanout planning. |
| 3-State Enable Logic | NOR of OE1 and OE2 - Single-pin disable not possible; both enables must be low for active output. |
| Power Consumption (ICC) | 80 µA max - Supports low-quiescent-power system design without sacrificing speed. |
| Input Compatibility | TTL-voltage compatible (VIH = 2.0 V, VIL = 0.8 V) - Interoperates seamlessly with legacy 74LS and 74ALS families. |
Pinout & Package
SN74HCT540DWR is housed in a 20-pin SOIC (DW) package, 7.5 mm wide, 12.8 mm long, and 2.65 mm maximum height, compliant with JEDEC MS-013 and RoHS (NIPDAU finish, MSL Level-1).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | Inputs (A1–A8) | Active-high TTL-compatible data inputs; inverted at corresponding outputs. |
| 9 | GND | Ground reference for all internal circuitry and output drivers. |
| 10, 20 | VCC | Primary 4.5–5.5 V supply; dual VCC pins reduce IR drop and improve noise immunity. |
| 11, 19 | OE1, OE2 | 3-state enable inputs; NOR logic requires both low for output activation. |
| 12–18 | Outputs (Y1–Y8) | Inverted buffered outputs; high-impedance when OE1 or OE2 is high. |
| 19, 20 | VCC, OE2 | Pin 20 is VCC; Pin 19 is OE2 - confirms dual VCC placement and dedicated enable pin assignment. |
Key Features
| Feature | Design Value |
|---|---|
| Data Flow-Through Pinout | Inputs (pins 1–8) and outputs (pins 12–18) on opposite sides - reduces trace crossovers and eases routing on dense PCBs. |
| Inverting Buffer Function | Each channel inverts input signal (A → Y̅) - supports polarity correction and active-low bus driving without external inverters. |
| Dual 3-State Enable (NOR) | OE1 and OE2 must both be low to enable outputs - prevents accidental bus contention during partial enable transitions. |
| High-Current 3-State Outputs | ±6-mA drive capability with rail-to-rail VOH/VOL - eliminates need for external line drivers in medium-load applications. |
| Low Input Current | ≤1 µA max - allows direct connection to high-output-impedance sources (e.g., microcontroller GPIO, open-drain sensors). |
Applications
| Industrial Control Backplane | Legacy System Bus Interface |
|---|---|
|
Use Scenario: Isolating and buffering address/data lines between PLC CPU and I/O expansion modules over 20-cm backplane traces. IC Role / Device Role / Timing Role: Octal inverting buffer with 3-state control manages bidirectional bus arbitration and signal integrity. Use Value: ±6-mA drive and 12-ns tpd ensure clean edge delivery across noisy industrial environments without added repeaters. |
Use Scenario: Interfacing a modern microcontroller to a vintage 8-bit ISA-style peripheral bus requiring TTL-level inversion and load matching. IC Role / Device Role / Timing Role: Level-shifting and inverting buffer that replaces obsolete 74LS240 while maintaining pin-compatible layout. Use Value: TTL-compatible inputs and 15-LSTTL load drive eliminate level translators and reduce BOM count. |
| Test Equipment Signal Routing | Embedded Data Acquisition Front-End |
|
Use Scenario: Multiplexing sensor channel select lines to multiple ADCs in automated test equipment, requiring glitch-free enable sequencing. IC Role / Device Role / Timing Role: 3-state buffer with dual OE inputs enables synchronized channel isolation during reconfiguration. Use Value: NOR-based enable ensures no output glitches occur if only one OE signal toggles mid-transition. |
Use Scenario: Driving 8-bit parallel output from an FPGA to external DAC or display controller with strict setup/hold timing. IC Role / Device Role / Timing Role: Low-skew inverting buffer adds deterministic delay margin while inverting control signals. Use Value: 12-ns tpd and <1 ns skew between channels simplify timing closure in real-time acquisition paths. |
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 |
|---|---|---|---|
| SN74HCT240DWR | Non-inverting inputs; identical pinout, timing, and drive specs. | Used where signal polarity must be preserved (e.g., clock distribution, non-inverting bus transceivers). | Select SN74HCT240DWR when inversion is undesirable; otherwise SN74HCT540DWR provides required A→Y̅ mapping. |
| SN74LV540APW | Lower voltage range (2.0–5.5 V); LV-CMOS logic; 16-mA drive; slightly higher tpd (17.5 ns typ). | Suitable for mixed-voltage systems or where higher drive is needed, but requires VIH/VIL recalculation below 3.3 V. | Choose SN74LV540APW only if 3.3-V operation or >6-mA drive is mandatory; SN74HCT540DWR remains optimal for pure 5-V TTL environments. |
Compared with SN74HCT240DWR and SN74LV540APW, the SN74HCT540DWR uniquely delivers inverting logic within the industry-standard HCT 5-V family, ensuring drop-in compatibility with existing 'HCT240 layouts while meeting strict TTL interface requirements without voltage translation.
Availability
SN74HCT540DWR is available at Aetrix Electronics and suitable for industrial control backplanes, legacy bus interfaces, test equipment signal routing, and embedded data acquisition front-ends requiring stable component supply and long-term manufacturability.
Supply support for SN74HCT540DWR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74HCT540DWR belongs to TI's 74HCT logic family-designed specifically to provide TTL-compatible performance with CMOS power efficiency in 5-V digital systems, targeting bus interface, memory addressing, and peripheral control applications.
FAQ
What is the logic function of SN74HCT540DWR?
The SN74HCT540DWR is an octal inverting buffer with 3-state outputs. Each input (A1–A8) drives a corresponding inverted output (Y1–Y8), and all outputs enter high-impedance state when either OE1 or OE2 is high. This function is confirmed in the device's logic diagram and function table in the official TI datasheet SCLS008C.
Does SN74HCT540DWR support 3.3-V operation?
No, SN74HCT540DWR is specified only for 4.5 V to 5.5 V operation per its recommended operating conditions. Its TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V) and output drive characteristics are optimized for 5-V systems. For 3.3-V use, consider SN74LV540APW instead.
What is the correct power-up sequence for SN74HCT540DWR to avoid bus contention?
To ensure high-impedance state during power-up, OE1 and OE2 must be held low only after VCC stabilizes. TI recommends tying OE to VCC via a pullup resistor (value determined by driver sink capability) so outputs remain disabled until firmware asserts both enables low. This prevents undefined states on shared buses.
Is SN74HCT540DWR pin-compatible with SN74HCT240DWR?
Yes-SN74HCT540DWR and SN74HCT240DWR share identical SOIC-20 pinouts and package dimensions, differing only in logic function: SN74HCT540DWR inverts inputs (A→Y̅), while SN74HCT240DWR passes them non-inverted (A→Y). This allows layout reuse with firmware or netlist updates.
What thermal derating applies to SN74HCT540DWR in continuous operation?
SN74HCT540DWR in SOIC-DW package has θJA = 58°C/W. At 85°C ambient and 80 µA ICC, self-heating is negligible (<0.5°C). However, under full 6-mA per output load, junction temperature rise must be calculated using actual power dissipation (P = VCC × ICC + Σ|VO × IO|) and kept below 125°C per absolute maximum ratings.
SN74HCT540DWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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:
- 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-SOIC
SN74HCT540DWR FAQ
1.How can I place an order for SN74HCT540DWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HCT540DWR 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 SN74HCT540DWR reliable?
The price and inventory of SN74HCT540DWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT540DWR is usually 5 days.
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SN74HCT540DWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HCT540DWR 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 SN74HCT540DWR?
For technical support, including SN74HCT540DWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT540DWR requirements.
6.How does Aetrix verify that SN74HCT540DWR is sourced from the original manufacturer or authorized distributors?
All SN74HCT540DWR 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 SN74HCT540DWR meets industry standards.
7.What is the process for return or replacement of SN74HCT540DWR?
All SN74HCT540DWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT540DWR, 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 SN74HCT540DWR part is unused and in its original packaging.
Return procedure for SN74HCT540DWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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