Texas Instruments SN74HCT652DWE4

Overview

SN74HCT652DWE4 from Texas Instruments is an octal bus transceiver with dual D-type registers and 3-state outputs, operating at 4.5 V to 5.5 V. It supports real-time or stored data transfer between A and B 8-bit buses, provides ±6-mA output drive at 5 V, features typical propagation delay of 12 ns (VCC = 5.5 V, CL = 50 pF), and enables independent clocking (CLKAB/CLKBA) and select control (SAB/SBA) for flexible bus management in industrial control backplanes.

For engineers reviewing the SN74HCT652DWE4 datasheet, SN74HCT652DWE4 pinout, SN74HCT652DWE4 application, or SN74HCT652DWE4 equivalent, key selection criteria include bidirectional register-controlled data routing, TTL-compatible inputs, 3-state output isolation timing (ten/tdis ≤ 55 ns), and SOIC-24 package compatibility with legacy 74HCT logic designs.

Technical Context

The SN74HCT652DWE4 integrates two independent 8-bit D-type flip-flop registers with separate clock (CLKAB, CLKBA) and select (SAB, SBA) inputs, enabling concurrent or staggered storage of A- or B-bus data. Its dual 3-state output enables (OEAB, OEBA) allow isolated bidirectional bus driving without contention.

Real-time transfer occurs when SAB/SBA = L, passing data transparently; stored-data transfer activates when SAB/SBA = H, outputting registered values. Clock edges trigger storage regardless of OE/S state, and output disable timing is guaranteed under 55 ns (VCC = 5.5 V, CL = 50 pF).

Key Specifications

Pinout & Package

SN74HCT652DWE4 is housed in a 24-pin SOIC (DW) package with 1.27-mm pitch, 7.5-mm body width, and RoHS-compliant NiPdAu lead finish (MSL Level-1, 260°C peak reflow). Pin 1 is located at quadrant Q1 per tape-and-reel orientation standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT245DW and 74ACT16543DLR, the SN74HCT652DWE4 uniquely delivers register-controlled bus multiplexing in a legacy-compatible SOIC-24 footprint, making it irreplaceable for maintaining existing industrial hardware while adding diagnostic storage capability without layout changes.

Availability

SN74HCT652DWE4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, PLC I/O modules, legacy bus extenders, and test equipment data capture interfaces requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT652DWE4 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 industrial-grade product validation and manufacturing excellence.

The SN74HCT652DWE4 belongs to TI's 74HCT logic family, designed specifically for robust 5-V mixed-signal systems requiring TTL compatibility, low power, and deterministic timing in harsh electromagnetic environments.

FAQ

What is the maximum clock frequency supported by the SN74HCT652DWE4?

The SN74HCT652DWE4 supports a maximum clock frequency of 22 MHz at VCC = 5.5 V and TA = 25°C (CL = 50 pF), as specified in the timing requirements table. This limit derives from minimum pulse width (tw = 23 ns) and setup/hold timing constraints. At lower supply voltages or elevated temperatures, the usable frequency decreases-e.g., 17 MHz at VCC = 4.5 V. The SN74HCT652DWE4 must not be operated beyond these validated limits to ensure reliable register capture and bus transfer.

How does the SN74HCT652DWE4 handle power-up sequencing to avoid bus contention?

The SN74HCT652DWE4 requires external biasing to guarantee high-impedance outputs during power-up: OEBA must be tied to VCC via a pullup resistor and OEAB to GND via a pulldown resistor. This configuration forces both output directions into 3-state before internal logic stabilizes. The resistor value must respect driver current limits-TI recommends ≥10 kΩ for standard CMOS drivers. Without this, undefined OE states may cause short-circuits between A and B buses during ramp-up, risking damage or system lockup.

Can the SN74HCT652DWE4 operate with mixed-voltage interfaces, such as 3.3-V controllers driving its inputs?

No-the SN74HCT652DWE4 inputs are strictly TTL-voltage compatible (VIH ≥ 2.0 V, VIL ≤ 0.8 V at VCC = 4.5–5.5 V) and not 3.3-V tolerant. Driving its inputs directly from a 3.3-V microcontroller risks marginal VIH margin (2.0 V vs. 3.3 V × 0.7 = 2.31 V nominal) and violates recommended operating conditions. A level-shifter or HCT-series buffer (e.g., SN74HCT125) is required for reliable interfacing. The SN74HCT652DWE4 itself must be powered at 5 V to meet its specified timing and drive performance.

What is the function of the NC (no-connect) pins on the SN74HCT652DWE4 SOIC package?

The SN74HCT652DWE4 SOIC (DW) package has no NC pins-every pin (1–24) is assigned a defined electrical function per the official TI datasheet SCLS179D. Claims of NC pins arise from misreading the FK (LCCC) or JT (CDIP) package diagrams, which do include NC positions. For SN74HCT652DWE4, all 24 pins are active: A1–A8, B1–B8, CLKAB, CLKBA, SAB, SBA, OEAB, OEBA, VCC, and GND. Leaving any pin unconnected violates TI's recommendation that unused inputs be tied to VCC or GND.

Does the SN74HCT652DWE4 support simultaneous clocking of both A and B registers?

Yes-but only when SAB and SBA are both low (real-time mode). In stored-data mode (SAB = SBA = H), clocks must be staggered: CLKAB and CLKBA cannot rise simultaneously, as the internal logic requires sequential register loading to avoid metastability. The datasheet explicitly states "Select control = H: clocks must be staggered to load both registers." Simultaneous clocks in stored mode may result in unpredictable data capture or bus glitches, so design must enforce ≥5 ns skew between CLKAB↑ and CLKBA↑ when SAB/SBA = H.