Texas Instruments SN74HCT74DRE4

Overview

SN74HCT74DRE4 from Texas Instruments is a dual D-type positive-edge-triggered flip-flop with independent preset (PRE) and clear (CLR) inputs, operating at 4.5–5.5 V supply voltage, delivering 17 ns typical propagation delay (tpd), ±4-mA output drive at 5 V, and supporting TTL-voltage-compatible inputs for reliable interfacing in synchronous logic systems.

For engineers reviewing the SN74HCT74DRE4 datasheet, SN74HCT74DRE4 pinout, SN74HCT74DRE4 application, or SN74HCT74DRE4 equivalent, this device serves as a foundational building block in clock-synchronized data latching, state storage, and edge-triggered control circuits where deterministic timing, low power (≤40 μA ICC), and robust noise immunity are required.

Technical Context

The SN74HCT74DRE4 implements two functionally identical, electrically isolated D-type flip-flops sharing no internal coupling-each responds independently to its own CLK, D, PRE, and CLR signals. Triggering occurs on the positive-going edge of CLK at a defined voltage threshold (not dependent on slew rate), while asynchronous PRE and CLR override clocked behavior by forcing Q to high or low regardless of other inputs.

Its HCT logic family ensures CMOS-level power efficiency with TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V at VCC = 4.5–5.5 V), enabling direct interface with legacy 74LS and 74F series without level-shifting. Output drive capability (±4 mA at 5 V) supports fan-out to up to 10 LSTTL loads under specified conditions.

Key Specifications

Pinout & Package

SN74HCT74DRE4 is housed in a 14-pin SOIC (D) package with nominal body dimensions of 8.65 mm × 3.90 mm and maximum height of 1.75 mm, optimized for surface-mount assembly and IPC-7351-compliant land patterns.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual D-type flip-flop applications.

Compared with SN74HC74DR and 74LVC74AD,118, the SN74HCT74DRE4 uniquely delivers guaranteed TTL input compatibility at 5 V with sub-20 ns timing and <40 μA quiescent current-making it the optimal choice for retrofitting or maintaining legacy 5-V logic systems without redesigning interface networks.

Availability

SN74HCT74DRE4 is available at Aetrix Electronics and suitable for industrial control logic, digital signal sampling, state machine sequencing, and glitch-free clock division requiring stable component supply and long-term production continuity.

Supply support for SN74HCT74DRE4 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, automotive, and communications markets.

The SN74HCT74DRE4 belongs to TI's 74HCT logic family-designed specifically to bridge TTL and CMOS technologies by combining CMOS power efficiency with TTL input voltage thresholds for seamless interoperability in mixed-signal 5-V systems.

FAQ

What is the maximum clock frequency supported by SN74HCT74DRE4?

The SN74HCT74DRE4 supports a maximum clock frequency of 24 MHz at VCC = 5.5 V and TA = 25 °C, derived from its 17 ns typical propagation delay and verified switching characteristics in the official datasheet. At 4.5 V, fmax reduces to 22 MHz due to slower internal switching speeds. System-level timing must account for board-level skew and load capacitance.

Does SN74HCT74DRE4 require external pull-up resistors on PRE and CLR pins?

No, SN74HCT74DRE4 does not require external pull-up resistors on PRE or CLR pins. These inputs are active-low and internally designed to be driven directly by logic outputs or switches. However, unused PRE/CLR inputs must be tied to VCC (not left floating) to prevent unintended triggering, per TI's application guidance in SCBA004.

Can SN74HCT74DRE4 operate reliably at 3.3 V supply voltage?

No, SN74HCT74DRE4 is not rated for 3.3 V operation. Its recommended operating range is strictly 4.5 V to 5.5 V. At 3.3 V, input thresholds (VIH = 2 V, VIL = 0.8 V) become non-compliant, and output drive strength degrades significantly-potentially causing logic failures. For 3.3-V systems, consider SN74LVC74A or SN74AHC74 instead.

What is the thermal resistance (RθJA) of SN74HCT74DRE4 in its SOIC package?

The junction-to-ambient thermal resistance (RθJA) for SN74HCT74DRE4 in the SOIC (D) package is 138.7 °C/W, as specified in the October 2022 revision (SCLS169G) of the datasheet. This value assumes standard JEDEC 2-layer board conditions; actual thermal performance improves with added copper pour or airflow.

How does SN74HCT74DRE4 handle simultaneous assertion of PRE and CLR?

When both PRE and CLR are low simultaneously, SN74HCT74DRE4 forces Q and Q̅ to logic high (non-stable state), as documented in the Function Table (Table 7-1). This condition is transient: upon release of either PRE or CLR, the output reverts to the state dictated by the remaining active control signal-or resumes clocked operation if both return high.