onsemi 74ACT245SC_NL

Overview

74ACT245SC_NL from Fairchild Semiconductor (manufactured by Rochester Electronics) is an octal non-inverting bidirectional transceiver with 3-STATE outputs, designed for bus interface applications between TTL/CMOS systems and data buses. It features TTL-compatible inputs, ±24mA output drive capability at both A and B ports, 4.5V–5.5V supply operation, and supports bidirectional data flow controlled by T/R and OE pins. It is commonly used in microprocessor bus buffering and level translation.

For engineers reviewing the 74ACT245SC_NL datasheet, pinout, applications, or equivalent options, key selection criteria include its 3-STATE bidirectional control logic, TTL-compatible input thresholds (VIH = 2.0V min, VIL = 0.8V max at VCC = 4.5V), propagation delay ≤8.0 ns (tPLH/tPHL), output enable/disable timing, and SOIC-20 package compatibility with JEDEC MS-013.

Technical Context

The 74ACT245SC_NL implements eight independent bidirectional buffer channels, each controlled by a shared Transmit/Receive (T/R) signal to determine data direction (A→B on T/R = HIGH; B→A on T/R = LOW) and a global Output Enable (OE) input that places all A and B I/Os into high-impedance state when HIGH. Its ACT logic family ensures TTL-compatible input thresholds while maintaining CMOS-level noise immunity and low ICC.

It operates strictly within 4.5V–5.5V VCC, delivering VOH ≥4.4V (IOH = −24mA) and VOL ≤0.44V (IOL = 24mA) across −40°C to +85°C, with input leakage ≤±1.0 µA and I/O leakage ≤±3.0 µA. Propagation delays are characterized at CL = 50pF and specified for both tPLH and tPHL paths, with output enable/disable times tightly bounded (tPZH ≤11.0 ns, tPHZ ≤11.0 ns).

Key Specifications

Pinout & Package

74ACT245SC_NL is housed in a 20-lead Small Outline Integrated Circuit (SOIC) package per JEDEC MS-013, 0.300" wide, with gull-wing leads and standard land pattern SOIC127P1030X265-20L.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74ACT245SC_NL, 74ACT245SCX offers identical performance in tape-and-reel format for SMT scalability, while SN74ACT245N provides the same core functionality in a through-hole PDIP package-enabling design flexibility across assembly methods without compromising bus timing, drive strength, or logic compatibility.

Availability

74ACT245SC_NL is available at Aetrix Electronics and suitable for microprocessor bus buffering, memory interface translation, legacy system bus expansion, and industrial I/O module communication requiring stable component supply and long-term industrial temperature support.

Supply support for 74ACT245SC_NL 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

Fairchild Semiconductor (now part of ON Semiconductor) is a historically significant analog and logic IC manufacturer known for pioneering high-performance TTL-compatible CMOS families like ACT.

The 74ACT245SC_NL belongs to Fairchild's ACT logic series, engineered specifically for high-speed, low-power bus interface applications demanding TTL input compatibility, robust drive strength, and precise 3-STATE timing in industrial environments.

FAQ

What is the supply voltage range for the 74ACT245SC_NL?

The 74ACT245SC_NL operates exclusively within a 4.5V to 5.5V VCC range, as defined in its Recommended Operating Conditions. This tight window ensures TTL-compatible input thresholds and guaranteed 24mA output drive. Operation outside this range risks undefined logic states, degraded timing, or potential damage per Absolute Maximum Ratings (−0.5V to +7.0V is stress-only, not operational).

How does the T/R pin control data direction in the 74ACT245SC_NL?

In the 74ACT245SC_NL, the T/R pin is an active-HIGH control: when T/R = HIGH and OE = LOW, data flows from A0–A7 to B0–B7; when T/R = LOW and OE = LOW, data flows from B0–B7 to A0–A7. The 74ACT245SC_NL does not support simultaneous bidirectional operation - direction is statically set per transaction cycle.

Is the 74ACT245SC_NL pin-compatible with the 74AC245 series?

Yes, the 74ACT245SC_NL shares identical pinout, package (SOIC-20), and functional block diagram with the 74AC245SC, but differs electrically: 74ACT245SC_NL has TTL-compatible inputs (VIH = 2.0V min), whereas 74AC245SC requires higher VIH (2.1V min at VCC = 3.0V). Swapping them may cause marginal logic recognition in mixed-voltage systems.

What is the maximum capacitive load the 74ACT245SC_NL can drive reliably?

The 74ACT245SC_NL AC specifications are characterized at CL = 50pF, with propagation delay and timing parameters guaranteed under that condition. While it can physically drive higher capacitance, exceeding 50pF increases propagation delay nonlinearly and may violate setup/hold timing in high-speed buses. For >50pF loads, verify timing margins using actual layout parasitics and worst-case VCC/temperature conditions.

Does the 74ACT245SC_NL support hot insertion or live bus swapping?

No, the 74ACT245SC_NL is not designed for hot insertion. Its Absolute Maximum Ratings specify no protection against voltage overshoot or current surge during live connection. Applying VCC or signals before power stabilization may exceed IIK/IOK limits (±20mA), risking latch-up or permanent damage. Always power-sequence VCC before applying I/O signals.