Texas Instruments CD74HCT652M

Overview

CD74HCT652M from Texas Instruments is a non-inverting, three-state octal bus transceiver/register IC with independent A/B bus registers, 4.5V–5.5V operation, and -55°C to +125°C temperature range. It supports real-time or stored data transfer via SAB/SBA select control and drives up to 15 LSTTL loads. Used in high-reliability industrial backplane and bidirectional data bus management systems.

For engineers reviewing the CD74HCT652M datasheet, CD74HCT652M pinout, CD74HCT652M application, or CD74HCT652M equivalent, key selection criteria include its HCT-level LSTTL input compatibility (VIH ≥ 2.0 V, VIL ≤ 0.8 V), 15pF load propagation delay of 15 ns (typ), three-state enable timing (tPZL/tPLZ = 14 ns typ), and dual-clock register architecture enabling simultaneous A/B bus storage.

Technical Context

The CD74HCT652M implements edge-triggered D-type flip-flops for both A and B buses, with separate CAB and CBA clocks allowing independent register loading. Its select-control logic (SAB/SBA) eliminates multiplexer glitches during transitions between real-time and stored data paths.

It features two independent three-state output enables (OEAB, OEBA) and operates strictly within 4.5–5.5 V, ensuring direct compatibility with legacy LSTTL logic while maintaining CMOS power efficiency. Input leakage remains ≤±1 µA across full temperature range, and output drive capability is specified at ±25 mA per pin under valid VO conditions.

Key Specifications

Pinout & Package

CD74HCT652M uses a 24-pin SOIC (DW) package with 1.27 mm pitch, 7.5 mm body width, and JEDEC MS-013 compliant footprint. Thermal resistance θJA = 46°C/W enables stable operation at full temperature range without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT652N, CD74HCT652M offers superior temperature range (-55°C to +125°C vs. 0°C to +70°C) and lower quiescent current, while 74LVX652M cannot substitute without system-level voltage rearchitecture.

Availability

CD74HCT652M is available at Aetrix Electronics and suitable for industrial backplane bus management, military data acquisition systems, automotive ECU diagnostics, and test equipment digital pattern generation requiring stable component supply across extended temperature ranges.

Supply support for CD74HCT652M 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 decades of heritage in high-reliability logic families.

The CD74HCT652M belongs to TI's legacy High-Speed CMOS (HCT) logic portfolio, engineered specifically for drop-in replacement of LSTTL in mission-critical 5 V systems demanding wide temperature operation and low power.

FAQ

What is the maximum clock frequency supported by CD74HCT652M for register storage operations?

The CD74HCT652M supports a maximum clock frequency of 17 MHz at -55°C to +125°C (CL = 50 pF) and up to 25 MHz at 25°C. At CL = 15 pF and 5 V, the datasheet specifies fMAX = 45 MHz for real-time bus transfer mode. These values derive directly from setup/hold time and propagation delay limits under worst-case temperature and load conditions.

Does CD74HCT652M support simultaneous storage of data on both A and B buses?

Yes, CD74HCT652M supports simultaneous storage: a low-to-high transition on both CAB and CBA clocks (with OEAB and OEBA inactive or configured appropriately) latches data from A0–A7 and B0–B7 into their respective internal D-type flip-flops. The function table explicitly lists "Store A and B Data" as an enabled operation when OEAB and OEBA are both low.

Can CD74HCT652M operate with a 3.3 V supply?

No, CD74HCT652M is an HCT-type device specified only for 4.5 V to 5.5 V operation. Applying 3.3 V violates its absolute minimum VCC rating and will result in undefined logic thresholds, increased propagation delay, and potential failure to meet VIH/VIL specifications. For 3.3 V systems, consider LV or LVC family alternatives-not CD74HCT652M.

What is the purpose of the SAB and SBA pins on CD74HCT652M?

The SAB and SBA pins on CD74HCT652M control data source selection: LOW selects real-time data from the opposite bus (e.g., SAB = LOW enables real-time B→A transfer), while HIGH selects data previously stored in the corresponding register (e.g., SAB = HIGH enables stored B→A transfer). This dual-mode operation is implemented with glitch-free combinational logic to prevent bus contention during transitions.

Is CD74HCT652M pin-compatible with CD74HC652EN?

No, CD74HCT652M (24-pin SOIC) is not pin-compatible with CD74HC652EN (24-pin PDIP) due to differing package footprints and thermal pad configurations-though both share identical pin numbering and electrical functionality. Mechanical mounting, solder reflow profile, and PCB layout must be redesigned when substituting between SOIC and PDIP packages, even for the same logic function.