Texas Instruments SN74AC245NS

Overview

SN74AC245NS from Renesas is an octal non-inverting bi-directional transceiver with 3-state inputs/outputs, designed for bus interface isolation and level translation between two 8-bit data buses. It supports 2.0–6.0 V supply operation, sinks/sourses ±24 mA per I/O, features 7.0 ns typical propagation delay at 5 V, and operates across –40°C to +85°C. It is used in industrial control backplanes and legacy microprocessor system data bus expansion.

For engineers reviewing the SN74AC245NS datasheet, SN74AC245NS pinout, SN74AC245NS application, or SN74AC245NS equivalent, key selection criteria include bidirectional flow control via T/R input, independent 3-state enable (OE), ±24 mA drive strength, 50 pF load AC timing, and compatibility with both AC- and ACT-series logic families.

Technical Context

The SN74AC245NS implements eight independent bidirectional buffer channels, each controlled by a shared Transmit/Receive (T/R) signal that determines data direction (A→B on high, B→A on low) and a global Output Enable (OE) that places all A and B ports into high-impedance state when asserted high. Its CMOS AC logic family ensures TTL-compatible voltage thresholds only at 5 V - unlike the HD74ACT245 variant which guarantees TTL compatibility across full VCC range.

It operates with rail-to-rail input/output voltage swing (0 to VCC), supports dynamic output currents up to ±75 mA (pulse-tested), and maintains guaranteed VOL ≤ 0.37 V and VOH ≥ 4.4 V at 5 V/24 mA sink/source - critical for noise margin preservation in multi-drop bus environments.

Key Specifications

Pinout & Package

SN74AC245NS is supplied in a 20-pin plastic DIP package (JEDEC MS-001, package code DP-20N), 0.300" wide body, 2.54 mm lead pitch, with through-hole mounting and Pb-free plating option (DP-20NEV).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bi-directional transceiver applications.

Compared with SN74AC245NS, SN74LVC245A lacks 5 V operation and industrial temperature support, while 74ABT245 trades thermal reliability and low ICC for raw speed - making SN74AC245NS the optimal choice for cost-sensitive, wide-temperature, dual-voltage bus isolation.

Availability

SN74AC245NS is available at Aetrix Electronics and suitable for industrial PLC backplanes, retro-computing hardware restoration, and test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for SN74AC245NS 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

Renesas Technology Corp. is a Japanese semiconductor manufacturer specializing in microcontrollers, analog, and logic ICs for industrial, automotive, and infrastructure applications.

The HD74AC245 product line delivers robust, temperature-qualified bus interface solutions targeting legacy system upgrades and industrial control equipment where reliability and voltage flexibility outweigh ultra-high-speed requirements.

FAQ

What is the maximum recommended supply voltage for SN74AC245NS?

The absolute maximum supply voltage for SN74AC245NS is 7.0 V, but the recommended operating range is 2.0 V to 6.0 V. Operation above 6.0 V risks exceeding internal oxide breakdown limits and invalidates parametric guarantees. For reliable long-term use, maintain VCC ≤ 6.0 V with ±5% regulation, especially under transient load conditions where ringing may cause overshoot beyond nominal rails.

Can SN74AC245NS operate with a 3.3 V supply while interfacing with 5 V logic?

No - SN74AC245NS is not 5 V tolerant when operated at 3.3 V. Its inputs require VIH ≥ 2.0 V (min) at VCC = 3.3 V, but 5 V signals exceed the absolute maximum input voltage of VCC + 0.5 V (i.e., 3.8 V). Direct connection risks latch-up or permanent damage. Use a level-shifting solution such as dedicated translators or resistor-divider networks with current limiting for mixed-voltage interconnects involving SN74AC245NS.

What is the function of the T/R and OE pins on SN74AC245NS?

T/R (pin 1) controls data direction: high enables A→B transfer, low enables B→A transfer. OE (pin 11) is active-high and overrides T/R - when OE = high, all A0–A7 and B0–B7 pins enter high-impedance state regardless of T/R state. This dual-control architecture allows independent bus isolation (via OE) and directional data flow (via T/R), essential for arbitration in multi-master bus topologies using SN74AC245NS.

Does SN74AC245NS support hot-swapping on a live bus?

SN74AC245NS is not hot-swap rated. Its absolute maximum ratings do not cover powered insertion events, and the absence of bus-hold or Ioff partial-power-down features means uncontrolled current surges may occur during plug-in. To implement safe hot-swap behavior with SN74AC245NS, external series resistors (≥100 Ω), slew-rate limiting, and sequenced OE assertion prior to physical connection are mandatory design practices.

How does SN74AC245NS differ from HD74ACT245 in practical design use?

SN74AC245NS (HD74AC245) has CMOS input thresholds - VIH scales with VCC (e.g., 3.85 V at 5.5 V), while HD74ACT245 uses TTL-compatible fixed thresholds (VIH = 2.0 V min across all VCC). This makes HD74ACT245 more robust driving older TTL loads directly, whereas SN74AC245NS offers better noise immunity in clean 5 V CMOS systems. Both share identical pinout, drive strength, and timing - so substitution requires verifying input threshold compatibility in the target circuit.