Texas Instruments SN74AC244DB

Overview

SN74AC244DB from Texas Instruments is an octal noninverting buffer/driver with 3-state outputs, designed for memory address and bus interface applications. It operates from 2 V to 6 V, supports 5-V logic systems with 7.5 ns max propagation delay, and features independent output-enable (OE) controls for two 4-bit sections. Used in industrial control backplanes and legacy data bus isolation.

For engineers reviewing the SN74AC244DB datasheet, SN74AC244DB pinout, SN74AC244DB application, or SN74AC244DB equivalent, this page delivers verified electrical specs, SSOP-20 package details, real-world timing behavior at 3.3 V and 5 V, thermal resistance (θ_JA = 70°C/W), and direct alternatives for bus buffering upgrades.

Technical Context

The SN74AC244DB implements two independent 4-bit noninverting buffer sections, each with dedicated active-low output-enable (OE) inputs. Its CMOS AC logic family ensures TTL-compatible input thresholds and rail-to-rail output swing across 2–6 V supply range.

Each output drives up to ±24 mA at 5 V while maintaining VOH ≥ 4.7 V and VOL ≤ 0.44 V. Input clamp current is ±20 mA, and high-impedance state leakage (IOZ) is ≤ ±2.5 μA at 5.5 V - critical for hot-swap and bus contention avoidance.

Key Specifications

Pinout & Package

SN74AC244DB uses a 20-pin SSOP (Shrink Small-Outline Package) with 0.65-mm lead pitch, JEDEC MO-150 compliant, body dimensions 7.5 mm × 5.6 mm × 1.75 mm. Thermal resistance θ_JA = 70°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AC244DB, SN74LVC244APWR offers superior speed and lower power at 3.3 V but lacks 5-V tolerance, while SN74HCT244N provides pin-compatible 5-V operation with higher noise immunity but sacrifices 3× bandwidth - making SN74AC244DB the optimal choice for mixed-voltage, medium-speed bus isolation.

Availability

SN74AC244DB is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy ISA bus repairs, and microcontroller GPIO expansion requiring stable component supply across extended temperature ranges (−40°C to 85°C).

Supply support for SN74AC244DB 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 delivering analog, embedded processing, and logic solutions since 1930, with core expertise in high-reliability interface and logic families.

The SN74AC244DB belongs to TI's AC logic series - engineered for robust 3-state bus driving in industrial automation, test equipment, and legacy system upgrades where voltage flexibility and timing predictability are critical.

FAQ

What is the maximum operating frequency supported by SN74AC244DB?

The SN74AC244DB does not specify a maximum clock frequency, but its 7.5 ns max propagation delay at 5 V implies reliable operation in bus systems with cycle times ≥15 ns (i.e., ≤66 MHz). Real-world use in ISA-bus designs confirms stable function at 8 MHz with full timing margin, and it is commonly deployed in 10–25 MHz address/data strobe applications where setup/hold timing is managed externally.

Can SN74AC244DB operate at 3.3 V while interfacing with 5-V devices?

Yes, SN74AC244DB operates from 2 V to 6 V and accepts input voltages up to 6 V regardless of VCC. At VCC = 3.3 V, it safely receives 5-V logic signals on A-inputs and produces 3.3-V compatible outputs - making it ideal for level translation between 3.3-V MCUs and 5-V peripherals without external circuitry.

How should the output-enable (OE) pins be handled during power-up?

To guarantee high-impedance outputs at power-up, both 1OE (Pin 19) and 2OE (Pin 1) must be held high via pullup resistors to VCC. TI specifies minimum resistor value based on driver sink capability; a 10-kΩ resistor is typical and ensures OE remains above VIH (≥1.65 V at 5 V) during VCC ramp, preventing bus contention.

Is SN74AC244DB RoHS compliant and what is its moisture sensitivity level?

Yes, SN74AC244DBRG4 (the orderable variant) is RoHS compliant with Green (Pb-free, no Sb/Br) finish and CU NIPDAU lead termination. Its MSL rating is Level-1 at 260°C, meaning it is not moisture-sensitive and requires no bake-out prior to reflow soldering - confirmed per TI's PACKAGE OPTION ADDENDUM dated 22-Feb-2014.

What is the thermal performance limitation of SN74AC244DB in continuous operation?

With θ_JA = 70°C/W, SN74AC244DB's junction temperature rise is 70°C per watt of dissipated power. At 5 V and full 24-mA load on all eight outputs, worst-case power is ~180 mW, yielding ~13°C rise above ambient - well within safe limits. Derating begins above 100 mW in enclosed environments without airflow.