Texas Instruments SN74AS823ADW

Overview

SN74AS823ADW from Texas Instruments is a 9-bit bus-interface D-type flip-flop with noninverting 3-state outputs, designed for high-capacitance bus driving in industrial control and legacy computing systems. It operates at 4.5–5.5 V, supports 0°C to 70°C ambient, delivers ±24 mA output drive, and features independent asynchronous clear (CLR) and output-enable (OE) controls.

For engineers reviewing the SN74AS823ADW datasheet, SN74AS823ADW pinout, SN74AS823ADW application, or SN74AS823ADW equivalent, key selection criteria include 9-bit parallel data latching, TTL-compatible input thresholds, undershoot-protection circuitry, power-up high-impedance state, and compatibility with 24-pin SOIC (DW) packaging for space-constrained PCB layouts.

Technical Context

The SN74AS823ADW implements nine edge-triggered D-type flip-flops synchronized to the rising edge of CLK when CLKEN is low; CLKEN high disables clock propagation and holds Q outputs. CLR operates asynchronously to force all Q outputs low regardless of clock or enable states.

OE controls output driver stage independently-asserting OE high places all nine Q outputs in high-impedance (Z) state without affecting internal latch operation, enabling bidirectional bus sharing and hot-swap capability. Inputs are buffered to reduce DC loading on upstream logic.

Key Specifications

Pinout & Package

SN74AS823ADW uses a 24-pin SOIC (DW) package with 300-mil width, gull-wing leads, and JEDEC MS-013AC compliant footprint. Pin 1 is marked by notch or dot; pin numbering follows standard counter-clockwise convention from top-left corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 9-bit bus-interface flip-flop applications.

Compared with SN74AS824ADW, SN74AS823ADW preserves native data polarity without external inverters; compared with AM29823PC, it offers assured long-term sourcing, updated reliability data, and consistent SOIC-DW packaging with RoHS-compliant lead finish.

Availability

SN74AS823ADW is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy ISA bus extensions, and avionics data acquisition systems requiring stable component supply, long lifecycle support, and verified 24-pin SOIC compatibility.

Supply support for SN74AS823ADW 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial and aerospace heritage.

The SN74AS823ADW belongs to TI's legacy AS-series TTL logic family, engineered for high-speed, low-noise bus interfacing in mission-critical industrial and defense systems where reliability and timing precision are paramount.

FAQ

What is the maximum clock frequency supported by the SN74AS823ADW?

The SN74AS823ADW does not specify a maximum clock frequency in its datasheet; instead, timing is defined by minimum pulse widths and setup/hold times. With t_w(CLK) ≥ 8 ns (high/low), the practical maximum toggle rate is approximately 62.5 MHz. For reliable operation, design margins should maintain ≥10 ns clock period to accommodate propagation delays and board-level skew. The SN74AS823ADW is optimized for synchronous bus applications up to 50 MHz.

Does the SN74AS823ADW support hot-swap or live-insertion on a powered bus?

Yes - the SN74AS823ADW supports controlled hot-swap operation via its OE pin. When OE is held high (disabled), all nine Q outputs enter high-impedance state before power is applied, preventing bus contention. Its undershoot-protection circuitry also limits negative transients during insertion. However, VCC must ramp monotonically and meet recommended operating conditions before asserting CLK or data; external sequencing is recommended for full compliance.

Can the SN74AS823ADW be used with 3.3 V logic systems?

No - the SN74AS823ADW is a 5 V-only TTL device requiring VCC = 4.5–5.5 V and VIH = 2.0 V minimum. Driving its inputs from 3.3 V logic may result in marginal or non-functional high-level recognition. Interfacing with 3.3 V systems requires level-shifting buffers such as SN74LVC4245A or discrete resistor-divider networks validated for VIH/VIL margins. The SN74AS823ADW itself is not 3.3 V tolerant.

What is the purpose of the NC pins on the SN74AS823ADW DW package?

The SN74AS823ADW DW package has no NC (no-connect) pins - all 24 pins are assigned functions as shown in the official pinout diagram. Confusion may arise from SN74AS824A DW top-view diagrams where pins 4 and 26 are marked NC, but those do not apply to SN74AS823ADW. For SN74AS823ADW, every pin from 1 to 24 serves a defined role: nine D inputs, nine Q outputs, plus CLK, CLKEN, OE, CLR, VCC, and GND.

How does the SN74AS823ADW handle simultaneous assertion of CLR and OE?

When both CLR (pin 10) and OE (pin 24) are asserted low, the SN74AS823ADW drives all nine Q outputs low (logic 0) - CLR takes precedence over OE in determining output state. OE only controls whether outputs are actively driven or placed in high-Z; it does not override the logic value established by CLR or clocked data. Thus, CLR = L forces Q = L regardless of OE state, and OE = L then actively drives that low state onto the bus.