Texas Instruments SN74ACT245NG4

Overview

SN74ACT245NG4 from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data bus communication between 5-V logic domains. It operates at 4.5 V to 5.5 V, supports TTL-compatible inputs up to 5.5 V, delivers ≤8 ns propagation delay at 5 V, and features independent direction (DIR) and output-enable (OE) control - used in industrial I/O expansion and legacy bus bridging.

For engineers reviewing the SN74ACT245NG4 datasheet, SN74ACT245NG4 pinout, SN74ACT245NG4 application, or SN74ACT245NG4 equivalent, key selection criteria include its 20-pin PDIP package, 3-state bidirectional bus isolation capability, ±24 mA drive strength, overvoltage-tolerant inputs, and compatibility with 5-V TTL/CMOS systems requiring robust level-shifting and contention-free bus control.

Technical Context

The SN74ACT245NG4 implements a dual-bus architecture with DIR-controlled signal flow direction and OE-gated 3-state output drivers. Its CMOS design ensures balanced rise/fall times and low output ringing, while input tolerance to 5.5 V enables safe interfacing with mixed-voltage sources without external clamping.

Functional modes are defined by DIR and OE: OE = L enables bidirectional transfer (A→B if DIR = H; B→A if DIR = L); OE = H forces all A/B ports into high-impedance isolation. No internal pull-ups exist - external biasing of OE is required for power-up safety.

Key Specifications

Pinout & Package

The SN74ACT245NG4 is housed in a 20-pin plastic dual in-line package (PDIP-N), with 0.300-inch body width, 0.100-inch lead pitch, and through-hole mounting compatible with standard PCB layouts and wave soldering processes.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus transceiver applications.

Compared with SN74ACT245N, the SN74ACT245NG4 provides identical functionality with RoHS-compliant packaging; versus SN74LS245N, it delivers 33% faster timing, 60% higher drive current, and essential overvoltage protection - making it the preferred choice for new 5-V industrial bus designs.

Availability

SN74ACT245NG4 is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, factory automation backplanes, and legacy bus bridging requiring stable component supply across extended product lifecycles.

Supply support for SN74ACT245NG4 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 specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74ACT245NG4 belongs to TI's ACT (Advanced CMOS Technology) logic family, engineered for high-speed, low-noise 5-V bus interfacing in noise-sensitive industrial control and instrumentation systems.

FAQ

What is the maximum operating voltage for SN74ACT245NG4?

The SN74ACT245NG4 has an absolute maximum VCC rating of 7 V, but its recommended operating range is strictly 4.5 V to 5.5 V per TI's SCAS452H datasheet. Operation outside this window risks parametric degradation or latch-up. Inputs tolerate up to 5.5 V regardless of VCC level - a key robustness feature confirmed in Section 5.1 and 5.3.

Does SN74ACT245NG4 support bidirectional data flow without external logic?

Yes. The SN74ACT245NG4 natively supports bidirectional data transfer using its dedicated DIR (pin 1) and OE (pin 19) inputs. When OE is low, DIR determines direction: HIGH enables A→B transfer; LOW enables B→A. This dual-control scheme eliminates need for external multiplexers or glue logic in bus arbitration applications.

What is the pin 1 marking and orientation for SN74ACT245NG4?

The SN74ACT245NG4 uses standard PDIP-20 packaging with pin 1 located at the left end of the top row (identified by a small circular depression or notch at the top-left corner of the package). Pin numbering proceeds counterclockwise: pins 1–10 along the top edge, pins 11–20 along the bottom edge - matching TI's DB/DW/N package diagrams in Figure 4-1.

Can SN74ACT245NG4 interface with 3.3-V microcontrollers?

Yes - but only as a receiver from 3.3-V outputs. Its VIH = 2.0 V and VIL = 0.8 V are compatible with 3.3-V CMOS logic levels. However, SN74ACT245NG4 outputs swing rail-to-rail (0 V to VCC), so driving a 3.3-V input requires external voltage limiting (e.g., series resistor + clamp diode) unless the 3.3-V device explicitly tolerates 5-V inputs.

Is SN74ACT245NG4 pin-compatible with SN74LS245N?

Yes - SN74ACT245NG4 and SN74LS245N share identical 20-pin PDIP mechanical footprint and pin functions (DIR, A1–A8, GND, B8–B1, OE, VCC). However, they are not functionally interchangeable without system-level validation due to differences in drive strength, propagation delay, input thresholds, and overvoltage tolerance - confirmed in TI's logic family comparison guides.