Texas Instruments SN74LS365AD

Overview

SN74LS365AD from Texas Instruments is a hex buffer/driver with 3-state outputs, designed for bus-oriented bidirectional data transmission in TTL-compatible digital systems. It features six independent non-inverting buffers, each with separate output-enable control (1OE, 2OE), operates from 4.75 V to 5.25 V, supports 0°C to 70°C ambient temperature, and uses a 16-pin SOIC (D) package - commonly deployed in legacy industrial control backplanes and test equipment I/O expansion.

For engineers reviewing the SN74LS365AD datasheet, SN74LS365AD pinout, SN74LS365AD application, or SN74LS365AD equivalent, key selection considerations include its dual 3-state enable architecture, guaranteed TTL input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V), output drive capability (I_OH/I_OL = –15 mA / 24 mA), and compatibility with standard 5-V logic families in noise-immune bus-hold environments.

Technical Context

The SN74LS365AD implements six identical non-inverting buffer stages, each with individual 3-state output control via two shared active-low enables (1OE controls Y1–Y3; 2OE controls Y4–Y6). Its bipolar TTL design ensures deterministic propagation delay (t_PLH/t_PHL = 15 ns max at V_CC = 5 V, C_L = 15 pF) and robust noise margin (V_NH = 0.4 V, V_NL = 0.4 V).

It lacks internal bus-hold or Schmitt-trigger inputs, requiring external pull-ups for floating-bus stability. The device is not designed for hot-swap operation, and its output clamping diodes are rated for ±20 mA DC current - limiting use in high-impedance or capacitive-load scenarios beyond 50 pF without series termination.

Key Specifications

Pinout & Package

SN74LS365AD uses a 16-pin Small Outline Integrated Circuit (SOIC-D) package measuring 10.4 mm × 5.3 mm × 1.75 mm (max height), with 1.27-mm lead pitch and gull-wing terminations. Pin 1 is marked by a beveled corner or laser dot.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar hex buffer with 3-state output applications.

Compared with SN74LS365ADR, the SN74LS365AD offers identical functionality in tube packaging - ideal for low-volume repair. Against SN74LS244N, it trades channel count for direct pin compatibility and smaller footprint, making it preferable for space-constrained legacy upgrades.

Availability

SN74LS365AD is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy test equipment I/O expansion, and embedded system address latching requiring stable component supply and long-term obsolescence support.

Supply support for SN74LS365AD 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 broad industrial, automotive, and aerospace qualification coverage.

The SN74LS365AD belongs to TI's legacy 74LS logic family, engineered for reliable 5-V TTL system interfacing in cost-sensitive, medium-speed digital control applications where compatibility and predictability outweigh power efficiency.

FAQ

What is the function of the two output-enable pins on the SN74LS365AD?

The SN74LS365AD has two active-low output-enable pins: 1OE controls outputs Y1–Y3, and 2OE controls Y4–Y6. When either enable is high, its associated three outputs enter high-impedance state. This allows independent gating of two logical bus segments - for example, separating address and data paths or managing read/write direction in legacy parallel interfaces. Both enables must be low to activate all six buffers simultaneously.

Can SN74LS365AD drive LEDs directly?

Yes, SN74LS365AD can drive LEDs directly in sink configuration: each output delivers up to 24 mA when low, sufficient for standard 2-mA to 10-mA indicator LEDs with appropriate series resistors (e.g., 220 Ω for 5-V supply and 10-mA LED current). Do not source current - the high-side drive capability is only –15 mA, and sustained sourcing may exceed safe operating area limits.

Is SN74LS365AD compatible with 3.3-V logic inputs?

No, SN74LS365AD is not reliably compatible with 3.3-V logic inputs. Its TTL input high threshold (V_IH ≥ 2.0 V) is met by 3.3-V CMOS outputs, but its input structure draws significant DC current (I_IH ≈ 20 µA typical, up to 40 µA max) that may overload weak 3.3-V drivers. Use a level-shifting buffer or resistor divider if interfacing with 3.3-V systems - never connect directly without verifying driver strength per the 3.3-V device's datasheet.

What is the maximum capacitive load SN74LS365AD can drive while meeting timing specs?

The SN74LS365AD's published propagation delay (15 ns max) and output transition times are specified with C_L = 15 pF. Driving loads >50 pF increases delay nonlinearly and may cause ringing or undershoot. For reliable timing compliance, keep total load (including trace capacitance and input capacitance of downstream devices) ≤30 pF. Add series 33-Ω resistors near outputs for loads >20 pF to dampen reflections.

Does SN74LS365AD have built-in ESD protection diodes?

Yes, SN74LS365AD includes internal clamp diodes from each input and output to V_CC and GND, rated per MIL-STD-883 Class 3B (±2 kV HBM). These diodes protect against electrostatic discharge during handling but are not intended for continuous overvoltage clamping. Do not apply voltages exceeding V_CC + 0.5 V or GND – 0.5 V to any pin - sustained overvoltage will forward-bias and degrade the clamps.