Texas Instruments SN74AHCT245NS

Overview

SN74AHCT245NS from Texas Instruments is an 8-bit non-inverting bidirectional bus transceiver with 3-state outputs, designed for level-shifting and bus isolation in mixed-voltage digital systems. It features independent direction (DIR) and output enable (OE) controls, TTL-compatible inputs (V_IL = 0.8 V max, V_IH = 2.0 V min at V_CC = 4.5–5.5 V), and supports operation from −40 °C to +85 °C. It is commonly used in microcontroller peripheral interfacing, memory expansion buses, and industrial control backplanes.

For engineers reviewing the SN74AHCT245NS datasheet, SN74AHCT245NS pinout, SN74AHCT245NS application, or SN74AHCT245NS equivalent, this page delivers verified functional specifications, validated pin roles, confirmed thermal and timing behavior across temperature, and real-world substitution guidance - all grounded in TI's official SN74AHCT245 data sheet (SCAS555G, revised April 2022).

Technical Context

The SN74AHCT245NS implements a dual-rail octal transceiver architecture with separate A- and B-side I/O banks, enabling bidirectional data flow under DIR control and high-impedance tri-state output when OE is HIGH. Its TTL-input thresholds ensure compatibility with legacy 5 V logic families while maintaining CMOS output drive strength (±24 mA per channel at V_CC = 4.5–5.5 V).

Propagation delay is specified at 10 ns typical (A→B or B→A, V_CC = 5 V, C_L = 50 pF), with enable/disable times of 12 ns (t_en) and 13 ns (t_dis). Input clamping diodes allow safe interface to voltages exceeding V_CC when current-limited, supporting hot-swap and mixed-supply system design.

Key Specifications

Pinout & Package

SN74AHCT245NS uses the SO-20 (Small Outline, 20-pin, 0.300″ wide) package per TI's SCAS555G datasheet. Body dimensions: 12.8 mm × 7.5 mm × 2.35 mm; lead pitch: 1.27 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT245NS, SN74HCT245N offers identical logic behavior but lacks surface-mount compatibility and speed margin, while 74LVC245APW enables compact 3.3 V designs but introduces voltage-domain incompatibility - making SN74AHCT245NS the sole validated choice for industrial 5 V bidirectional bus extension.

Availability

SN74AHCT245NS is available at Aetrix Electronics and suitable for microcontroller peripheral expansion, memory bus isolation, industrial backplane interface, and legacy system signal translation requiring stable component supply and long-term industrial-grade availability.

Supply support for SN74AHCT245NS 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 specializing in analog, embedded processing, and logic solutions, with decades of leadership in industry-standard logic families.

The SN74AHCT245NS belongs to TI's 74AHCT logic series, engineered specifically for robust 5 V TTL-to-CMOS interfacing in industrial control, test equipment, and legacy system upgrades where reliability and interoperability are critical.

FAQ

What is the supply voltage range for SN74AHCT245NS?

The SN74AHCT245NS operates exclusively from a 4.5 V to 5.5 V supply. It is not rated for 3.3 V or lower operation, and applying voltages outside this range may cause permanent damage or undefined behavior. The device draws <100 µA quiescent current at 25 °C, and its output drive remains stable across the full 4.5–5.5 V window, ensuring consistent timing and noise margins in 5 V systems. Always use local 0.1 µF ceramic decoupling at the V_CC pin of SN74AHCT245NS.

Is SN74AHCT245NS pin-compatible with SN74HC245 or SN74HCT245?

Yes, SN74AHCT245NS shares identical pinout, function table, and SO-20 footprint with SN74HC245 and SN74HCT245. However, SN74AHCT245NS has tighter AC specifications - including faster propagation delay (10 ns typical vs. 12–18 ns) and improved noise immunity - due to its advanced AHCT process. All three support the same DIR/OE control scheme and 3-state behavior, but SN74AHCT245NS is optimized for higher-speed 5 V bus applications where timing margin is critical.

Can SN74AHCT245NS interface between 3.3 V and 5 V logic domains?

No, SN74AHCT245NS does not support true level translation. Its inputs are TTL-compatible (2.0 V V_IH, 0.8 V V_IL) but require a 5 V supply; it cannot safely accept 3.3 V logic highs as valid inputs without risk of marginal switching or increased static current. For 3.3 V ↔ 5 V translation, use purpose-built devices like TXB0108 or SN74AVCH series. SN74AHCT245NS is intended for unidirectional 5 V bus extension, not cross-voltage domain bridging.

What is the maximum data rate supported by SN74AHCT245NS?

Based on its 10 ns typical propagation delay and 13 ns maximum disable time at 125 °C, SN74AHCT245NS supports reliable operation up to 50 MHz for burst-mode transfers and ≤25 MHz for sustained synchronous bus protocols (e.g., parallel memory access). Real-world throughput depends on trace length, load capacitance, and slew rate; TI characterizes performance with 50 pF load and 1.27 mm pitch routing. For continuous 50 MHz operation, maintain C_L ≤ 30 pF and use controlled-impedance traces.

Does SN74AHCT245NS include ESD protection?

Yes, SN74AHCT245NS incorporates on-die ESD protection meeting JEDEC JESD22-A114F (Human Body Model > 2000 V) and JESD22-A115-A (Machine Model > 200 V). This protection covers all I/O pins and is effective against typical handling and board-level discharge events. However, it does not replace system-level TVS diodes for surge-prone interfaces (e.g., backplanes or connectors). Always observe proper grounding and avoid floating inputs - unused pins should be tied to GND or V_CC to prevent latch-up in SN74AHCT245NS.