Texas Instruments SN74HCT540DW

Overview

SN74HCT540DW from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interface and load driving in 5-V TTL-compatible digital systems. It operates from 4.5 V to 5.5 V, delivers ±6-mA output drive per channel, exhibits typical propagation delay of 12 ns at 5.5 V, and draws ≤80 µA ICC in quiescent state. It is used in microcontroller peripheral interfacing and system bus buffering.

For engineers reviewing the SN74HCT540DW datasheet, SN74HCT540DW pinout, SN74HCT540DW application, or SN74HCT540DW equivalent, key selection criteria include its inverted data path, dual 3-state enable (OE1/OE2) logic, data flow-through SOIC-20 pinout, and compatibility with LSTTL loads up to 15 units.

Technical Context

The SN74HCT540DW implements eight independent inverting buffer channels, each with high-current 3-state outputs controlled by a 2-input NOR gate (OE1 and OE2). When either OE input is high, all outputs enter high-impedance mode-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, while outputs guarantee VOH ≥ 3.7 V and VOL ≤ 0.33 V at 6-mA load. The device uses silicon-gate CMOS technology for HCT-level speed-power trade-off and supports CL = 50 pF and CL = 150 pF load conditions with characterized tpd, ten, and tdis timing.

Key Specifications

Pinout & Package

SN74HCT540DW is housed in a 20-pin SOIC (DW) package with 7.5-mm body width, 2.65-mm max height, and 1.27-mm lead pitch. Its data flow-through layout places all eight inputs (A1–A8) on one side and all eight inverted outputs (Y1–Y8) on the opposite side, simplifying PCB trace routing and reducing crosstalk.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal inverting 3-state buffer applications.

Compared with SN74HCT240N and 74ACT540SCX, the SN74HCT540DW uniquely combines SOIC-20 surface-mount compatibility, proven 12 ns timing at 5.5 V, and ≤80 µA quiescent current-making it optimal for space-constrained, low-power industrial control designs requiring pinout continuity with legacy HCT layouts.

Availability

SN74HCT540DW is available at Aetrix Electronics and suitable for industrial control systems, test instrumentation, and embedded microcontroller peripheral interfacing requiring stable component supply and long-term manufacturability.

Supply support for SN74HCT540DW 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with global manufacturing and quality certification.

The SN74HCT540DW belongs to TI's 74HCT logic family, engineered for TTL-compatible operation in industrial and commercial applications where speed, power efficiency, and bus isolation are essential.

FAQ

What is the recommended power-up sequence for SN74HCT540DW to avoid bus contention?

TI recommends tying both OE1 and OE2 to VCC through a pullup resistor (minimum value determined by driver sink capability) to ensure all outputs remain in high-impedance state during power ramp-up. This prevents undefined logic states on shared buses before system initialization completes. The SN74HCT540DW datasheet specifies this practice to guarantee safe power sequencing behavior.

Does SN74HCT540DW support mixed-voltage operation between 3.3 V and 5 V systems?

No, SN74HCT540DW is specified only for 4.5 V to 5.5 V operation and does not support 3.3 V logic levels. Its inputs require TTL-compatible thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), and outputs swing rail-to-rail within the 5-V domain. For 3.3 V–5 V interfacing, a level translator or dual-supply buffer such as SN74LVC245A is required-not the SN74HCT540DW.

Can SN74HCT540DW drive a 50-pF capacitive load reliably at 20 MHz?

Yes, SN74HCT540DW is characterized for CL = 50 pF and delivers typical tpd = 12 ns at 5.5 V, supporting signal frequencies up to ~40 MHz under ideal conditions. At 20 MHz, its output rise/fall times (<15 ns) and ±6-mA drive ensure clean edges. However, layout parasitics and trace impedance must be controlled-the SN74HCT540DW performance assumes proper decoupling and short traces.

What is the maximum continuous output current rating for SN74HCT540DW per pin?

The absolute maximum continuous output current for SN74HCT540DW is ±35 mA per output pin, as specified in the Absolute Maximum Ratings table. However, functional operation at that level is not guaranteed-TI recommends limiting steady-state current to ±6 mA (per the Electrical Characteristics table) to maintain VOH ≥ 3.7 V and VOL ≤ 0.33 V. Exceeding ±6 mA may degrade switching performance or cause thermal stress in the SN74HCT540DW.

Is SN74HCT540DW RoHS compliant and what is its moisture sensitivity level?

Yes, SN74HCT540DW is RoHS compliant (lead-free NiPdAu finish) and rated MSL Level-1 at 260°C peak reflow temperature, meaning it has unlimited floor life and requires no baking prior to soldering. This information is confirmed in TI's Package Option Addendum for SN74HCT540DWRG4, the tape-and-reel variant of the SN74HCT540DW.