Texas Instruments SN74ABT245BNSR

Overview

SN74ABT245BNSR from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for asynchronous bidirectional data transfer between A and B buses in 5-V TTL systems. It features high-drive outputs (−32 mA IOH, 64 mA IOL), supports hot insertion via Ioff and power-up 3-state, and operates from −40°C to 85°C in a 20-pin SOP-NS package.

For engineers reviewing the SN74ABT245BNSR datasheet, SN74ABT245BNSR pinout, SN74ABT245BNSR application, or SN74ABT245BNSR equivalent, key selection criteria include direction-control logic behavior, 3-state isolation timing (tPZH/tPLZ ≤ 6.2 ns), ground-bounce performance (<1 V VOLP), and compatibility with legacy 5-V bus architectures requiring robust drive strength and hot-swap capability.

Technical Context

The SN74ABT245BNSR implements dual 8-bit bidirectional data paths controlled by DIR (direction) and OE (output enable) inputs. Its TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V) and rail-to-rail output swing ensure interoperability with standard 5-V logic families. The device uses bipolar transistor-transistor logic (BTL) architecture to achieve high current drive without compromising propagation delay.

Hot-insertion support is enabled by two independent circuits: Ioff limits reverse current when VCC = 0 V (±100 µA), while power-up 3-state forces outputs into high-impedance during supply ramp-up. Latch-up immunity exceeds 500 mA per JEDEC JESD17, and ESD protection meets 2000-V HBM and 200-V MM standards.

Key Specifications

Pinout & Package

The SN74ABT245BNSR is housed in a 20-pin SOP-NS (Small Outline Package, Narrow, Surface-Mount) with 0.65 mm lead pitch and 7.5 mm × 5.6 mm body dimensions. Thermal resistance θJA is 60°C/W, supporting moderate-power bus buffering without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC245APWR and SN74ABT245BDWR, the SN74ABT245BNSR uniquely delivers 5-V TTL compatibility, highest drive strength among pin-compatible octal transceivers, and optimized thermal performance in the space-constrained SOP-NS package-making it the preferred choice for retrofitting industrial 5-V bus systems.

Availability

SN74ABT245BNSR is available at Aetrix Electronics and suitable for industrial PLC backplane interfaces, automotive body control modules, and legacy system bus bridging requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74ABT245BNSR 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 connectivity technologies with over 90 years of innovation in industrial and automotive electronics.

The SN74ABT245BNSR belongs to TI's ABT logic family, engineered specifically for robust 5-V bus interfacing in harsh industrial environments where hot-swap reliability, high noise immunity, and legacy system compatibility are critical design requirements.

FAQ

What is the maximum data rate supported by the SN74ABT245BNSR?

The SN74ABT245BNSR does not specify a formal data rate limit but achieves sub-4 ns propagation delays (tPLH/tPHL ≤ 3.9 ns) and <0.5 ns output skew (tsk(o) ≤ 0.5 ns) at CL = 50 pF. In practice, this supports reliable operation in 5-V parallel bus systems operating up to 100–150 MHz, depending on trace length, termination, and load capacitance. For precise timing analysis, designers must validate against actual board-level conditions using the device's published switching characteristics.

How should OE and DIR be biased during power-up to ensure safe startup?

To guarantee high-impedance outputs during power-up, OE must be held high (≥2 V) until VCC stabilizes, typically achieved with a pull-up resistor to VCC (minimum value determined by driver sink capability). DIR may float or be tied to VCC/GND; however, TI recommends fixing DIR to a known state (e.g., via pull-up/pull-down) to prevent metastability. The SN74ABT245BNSR's built-in power-up 3-state circuitry automatically places outputs in high-Z if OE is indeterminate during VCC ramp, but external biasing remains best practice for deterministic behavior.

Does the SN74ABT245BNSR support mixed-voltage operation between 3.3 V and 5 V buses?

No, the SN74ABT245BNSR is strictly a 5-V device with VCC range 4.5–5.5 V and TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V). While its outputs swing rail-to-rail and can drive 3.3-V inputs with appropriate series termination, it cannot accept 3.3-V logic levels on A/B ports without risking marginal VIH compliance. For true mixed-voltage translation, TI recommends dedicated level-shifting devices such as the SN74AVC4T245 or SN74LVC8T245, which are explicitly characterized for 3.3-V ↔ 5-V operation.

What is the thermal pad configuration for the SN74ABT245BNSR package?

Unlike QFN or VQFN packages, the SOP-NS (NS) package used by the SN74ABT245BNSR has no exposed thermal pad. Heat dissipation occurs solely through the leads and plastic body. The specified θJA of 60°C/W assumes standard JEDEC 2S2P test board conditions (2-layer PCB, 2-oz copper, 1-inch² copper area per lead). For high-duty-cycle applications, designers should provide adequate copper pour on both layers connected to GND and VCC pins, and avoid excessive trace length on power/ground paths to maintain thermal performance.

Can the SN74ABT245BNSR replace the older SN74LS245 in existing designs?

Yes, the SN74ABT245BNSR is a direct functional and pin-compatible upgrade to the SN74LS245, offering identical 20-pin SOP-NS pinout, same DIR/OE control logic, and compatible 5-V TTL voltage levels. Key improvements include 2× higher drive strength (64 mA vs. 24 mA sink), lower ground bounce (<1 V vs. ~1.5 V), enhanced ESD protection (2000-V HBM), and guaranteed hot-swap operation via Ioff. No PCB changes are required, though decoupling capacitor placement should be verified due to higher peak currents.