Texas Instruments SN74HC623DW

Overview

SN74HC623DW from Texas Instruments is an octal bus transceiver IC designed for asynchronous two-way data communication between parallel buses in digital systems. It features dual 3-state enable controls (OEAB/OEBA), ±6-mA output drive at 5 V, 8 ns typical propagation delay, and operates across 2 V to 6 V supply range - enabling use in mixed-voltage industrial control backplanes and legacy TTL-to-CMOS interface bridging.

For engineers reviewing the SN74HC623DW datasheet, SN74HC623DW pinout, SN74HC623DW application, or SN74HC623DW equivalent, key selection considerations include bidirectional bus isolation timing, simultaneous latch capability via dual-enable activation, high-current 3-state output compatibility with LSTTL loads, and SOIC-20 thermal performance (θ_JA = 58°C/W).

Technical Context

The SN74HC623DW implements true CMOS logic with Schmitt-trigger–free inputs and complementary push-pull outputs. Its dual-output-enable architecture supports four distinct operational modes: A→B transmission, B→A transmission, full bus isolation, and lock-bus-latch mode when both OEAB and OEBA are low - enabling transparent data retention without external storage.

Propagation delay (t_pd) is specified at 8 ns (typical) under 4.5 V/50 pF conditions, while enable/disable times (t_en/t_dis) range from 20 ns to 63 ns depending on V_CC and load. Input transition rate limits (Δt/Δv) are defined down to 400 ns/V at 6 V, ensuring robust noise immunity in electrically noisy environments.

Key Specifications

Pinout & Package

SN74HC623DW is housed in a 20-pin SOIC (DW) package with 1.27 mm pitch, 7.6 mm body width, and 2.65 mm maximum height - compatible with standard surface-mount reflow profiles (MSL Level-1, 260°C peak).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC623DW, SN74HCT623DW offers guaranteed TTL-compatible inputs but sacrifices V_CC-scalable thresholds, while 74LCX623M delivers faster switching at lower voltage but omits the critical lock-bus-latch feature needed for fault-tolerant industrial designs.

Availability

SN74HC623DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy system bus bridges, and hot-swappable module interconnects requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SN74HC623DW 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 logic solutions with over 50 years of innovation in industrial-grade interface ICs.

The SN74HC623DW belongs to TI's 74HC high-speed CMOS logic family, engineered for robust bidirectional data transfer in electrically noisy, thermally demanding industrial and automation systems.

FAQ

What is the maximum recommended operating temperature for SN74HC623DW?

The SN74HC623DW is rated for continuous operation from –40°C to +85°C ambient temperature. This industrial-grade specification ensures reliable performance in factory-floor control cabinets, motor drive enclosures, and outdoor telecom infrastructure where thermal cycling and elevated ambient temperatures are common. The SOIC-DW package's θ_JA of 58°C/W supports adequate heat dissipation without forced airflow in most PCB layouts.

Does SN74HC623DW support simultaneous bidirectional data flow?

No, SN74HC623DW does not support true simultaneous bidirectional flow on the same bus pair. It operates in one direction at a time - either A→B or B→A - controlled by OEAB and OEBA. However, when both enables are asserted low, it enters lock-bus-latch mode where both A and B buses retain their last valid states, effectively holding data without active transmission.

Can SN74HC623DW replace SN74LS623 in existing designs?

SN74HC623DW can replace SN74LS623 in many cases due to pin compatibility and identical function, but requires attention to supply voltage (LS uses 5 V only; HC supports 2–6 V) and input thresholds (HC uses CMOS-level, not TTL-level). Output drive is lower (±6 mA vs ±8 mA for LS), so verify load compatibility. No PCB changes are needed if V_CC remains at 5 V and fanout is ≤15 LSTTL units.

What is the purpose of the lock-bus-latch feature in SN74HC623DW?

The lock-bus-latch feature activates when both OEAB and OEBA are driven low, causing each output to reinforce its corresponding input. With all other drivers on both buses in high-impedance state, the 16 bus lines retain their last logic states - enabling safe hold-mode operation during system reset, fault isolation, or diagnostic freeze without external latches or power loss.

Is SN74HC623DW RoHS compliant and lead-free?

Yes, SN74HC623DW is RoHS compliant and features NiPdAu (NIPDAU) lead finish. It meets JEDEC MSL Level-1 moisture sensitivity rating with unlimited floor life at ≤30°C/60% RH, and is qualified for standard Pb-free reflow profiles up to 260°C peak temperature - fully compatible with modern lead-free manufacturing processes.