Texas Instruments SN74AS825ADW

Overview

SN74AS825ADW from Texas Instruments is an 8-bit bus-interface D-type flip-flop with three-state outputs, designed for bidirectional bus driving and multiuser I/O port control. It features clock-enable (CLKEN), asynchronous clear (CLR), and three independent output enables (OE1–OE3), operates at 4.5–5.5 V, supports 0°C to 70°C, and delivers ±24 mA high-level and 48 mA low-level output drive.

For engineers reviewing the SN74AS825ADW datasheet, SN74AS825ADW pinout, SN74AS825ADW application, or SN74AS825ADW equivalent, key selection considerations include its 3-state bus interface capability, undershoot-protection circuitry, power-up high-impedance state, and compatibility with legacy TTL/AS logic systems in industrial control and data acquisition designs.

Technical Context

This device implements eight edge-triggered D flip-flops synchronized to the rising edge of CLK when CLKEN is low; asserting CLKEN high latches outputs independently of clock activity. CLR asynchronously resets all Q outputs low regardless of clock or enable states.

Three buffered OE inputs (OE1, OE2, OE3) collectively control the 3-state output drivers: outputs enter high-impedance only when all three OEs are high; any OE low enables normal logic-level output. Internal operation remains unaffected by OE state-data can be latched or retained while outputs are disabled.

Key Specifications

Pinout & Package

The SN74AS825ADW is housed in a 24-pin SOIC (DW) package with 300-mil width, gull-wing leads, and standard JEDEC MS-013AC footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bus-interface flip-flop applications.

Compared with SN74AS825ADW, SN74AS821ADW offers latch-based control without clocking overhead but forfeits synchronous timing and reset, while SN74F244N provides lower-cost buffering without storage-neither replicates the integrated clocked register + multi-OE + CLR functionality essential for bus arbitration and controlled data staging.

Availability

SN74AS825ADW is available at Aetrix Electronics and suitable for industrial backplane interfaces, data acquisition I/O ports, legacy system bus extensions, and PLC I/O modules requiring stable component supply and long-term obsolescence management.

Supply support for SN74AS825ADW 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 innovator founded in 1930, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.

The SN74AS825ADW belongs to TI's legacy Advanced Schottky TTL logic family, engineered for high-speed, low-noise bus interfacing in mission-critical industrial and instrumentation systems where reliability and timing predictability are paramount.

FAQ

What is the function of the CLKEN pin on the SN74AS825ADW?

The CLKEN (clock enable) pin on the SN74AS825ADW is an active-low control that disables the internal clock buffer when high. When CLKEN = high, the Q outputs retain their last latched values regardless of CLK transitions. This allows deterministic output hold without stopping the system clock, supporting multi-cycle data staging and glitch-free bus handshaking in the SN74AS825ADW.

Does the SN74AS825ADW support hot-swap or live-insertion in backplane systems?

Yes - the SN74AS825ADW supports hot-swap operation through its power-up high-impedance state and undershoot-protection circuitry. At power-on, all outputs default to high-Z, preventing bus contention. The built-in protection clamps negative transients below GND, eliminating external diodes. These features make the SN74AS825ADW suitable for live-insertion in modular backplane architectures.

How do the three output-enable pins (OE1, OE2, OE3) operate together on the SN74AS825ADW?

On the SN74AS825ADW, the three output-enable pins (OE1, OE2, OE3) operate in OR logic: the outputs go to high-impedance only when all three are high. If any one OE is low, all eight Q outputs become active (driving high or low). This enables flexible bus arbitration - e.g., assigning OE1 to CPU, OE2 to DMA, OE3 to debug port - allowing prioritized or simultaneous access control in the SN74AS825ADW.

What is the maximum capacitive load the SN74AS825ADW can drive reliably?

The SN74AS825ADW is characterized for CL = 50 pF in switching tests, with propagation delays specified up to that load. Its ±24 mA / 48 mA drive strength supports heavier loads - typical design margin allows stable operation up to ~100 pF with proper layout and termination. For >100 pF (e.g., long traces or multiple receivers), verify timing margins using the SN74AS825ADW's published t_PLH/t_PHL vs. CL curves in the datasheet.

Is the SN74AS825ADW pin-compatible with the SN74AS825A in other packages like NT or JT?

Yes - the SN74AS825ADW shares identical pinout and logic functionality with the SN74AS825A in NT (plastic DIP) and JT (ceramic DIP) packages. Pin numbers and signal assignments (e.g., OE1 on pin 1, CLK on pin 15) are consistent across DW, NT, and JT variants. This allows drop-in replacement across package types without PCB redesign, provided thermal and mechanical constraints are met for the SN74AS825ADW.