STMicroelectronics M74HCT652B1R

Overview

M74HCT652B1R from STMicroelectronics is an octal bus transceiver and register with 3-state outputs, implementing bidirectional data flow between two 8-bit buses (A1–A8 and B1–B8) with edge-triggered clock control (CAB/CBA), dual select inputs (SAB/SBA), and independent direction/enable logic (GAB/GBA). It operates at up to 55 MHz (typ.) at VCC = 4.5 V, delivers symmetrical ±6 mA output drive, and maintains TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V).

For engineers reviewing the M74HCT652B1R datasheet, M74HCT652B1R pinout, M74HCT652B1R application, or M74HCT652B1R equivalent, this device supports real-time or registered data transfer in memory-mapped I/O, bus isolation, and buffered address/data multiplexing - with precise setup/hold timing (ts = 3 ns, th = 5 ns), low quiescent current (ICC ≤ 4 µA), and high-impedance output enable/disable times under 44 ns.

Technical Context

The M74HCT652B1R integrates eight D-type flip-flops with dual-clock architecture (CAB for A→B, CBA for B→A), enabling synchronous storage of bus data independent of GAB/GBA enable states. Its control logic decouples data routing (via SAB/SBA) from direction (GAB/GBA) and storage (clock edges), allowing simultaneous real-time pass-through and register capture.

It features symmetrical output impedance (|IOH| = |IOL| ≥ 6 mA), balanced propagation delays (tPLH ≅ tPHL), and TTL-compatible input thresholds - ensuring interoperability with legacy 74-series logic while delivering CMOS-level power efficiency and noise immunity across –55°C to +125°C operation.

Key Specifications

Pinout & Package

Package: Plastic DIP-24 (0.300" wide), 24-pin dual in-line package with 2.54 mm pitch; RoHS-compliant, through-hole mountable.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT652N and 74VHC652M, the M74HCT652B1R offers the highest guaranteed speed (55 MHz typ), lowest quiescent current (4 µA max), and widest operating temperature range (–55°C to +125°C), making it optimal for high-reliability industrial and automotive bus interface applications.

Availability

M74HCT652B1R is available at Aetrix Electronics and suitable for memory-mapped I/O interfaces, microcontroller bus isolation, and address/data demultiplexing requiring stable component supply, long-term obsolescence management, and consistent DIP-24 through-hole form factor.

Supply support for M74HCT652B1R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The M74HCT652B1R belongs to ST's HCT logic family - engineered for TTL-compatible operation with CMOS power efficiency, targeting robust, pin-accurate replacements for legacy 74-series logic in industrial control and instrumentation systems.

FAQ

What is the maximum clock frequency supported by M74HCT652B1R?

The M74HCT652B1R supports a typical maximum clock frequency of 55 MHz at VCC = 4.5 V and CL = 50 pF. This value is specified under standard test conditions; actual achievable frequency depends on load capacitance, PCB trace inductance, and supply stability. The device guarantees functional operation up to 31 MHz across its full temperature range (–55°C to +125°C).

Can M74HCT652B1R operate with a 3.3 V supply?

No - the M74HCT652B1R is designed for 4.5–5.5 V operation only. Its input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and output drive strength are characterized exclusively within this range. Using 3.3 V violates recommended operating conditions and risks unreliable logic levels, increased propagation delay, and potential failure to meet AC specifications.

How does the real-time versus registered data selection work?

Real-time transfer occurs when SAB or SBA is low, passing bus data directly without storage. Registered transfer occurs when SAB or SBA is high, outputting the most recently clocked data from internal D flip-flops. Clock edges (CAB/CBA) capture data regardless of select state - enabling simultaneous real-time forwarding and register update in one cycle.

Is thermal derating required for continuous operation at 85°C?

Yes - the absolute maximum power dissipation is 500 mW at 65°C, derating linearly by 10 mW/°C above that point. At 85°C, maximum allowable power drops to 300 mW. Designers must verify total dynamic + static power (ICC × VCC + CPD × VCC × fIN) remains below this limit, especially under worst-case bus toggle conditions and heavy capacitive loading.