Texas Instruments SN74HCT74DRG4

Overview

SN74HCT74DRG4 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 V–5.5 V supply voltage, delivering ±4-mA output drive at 5 V, and achieving typical propagation delay of 17 ns. It functions as a synchronous storage element in digital control logic, clock-domain synchronization, and state-machine sequencing in industrial PLC modules.

For engineers reviewing the SN74HCT74DRG4 datasheet, SN74HCT74DRG4 pinout, SN74HCT74DRG4 application, or SN74HCT74DRG4 equivalent, key selection criteria include TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V), low quiescent current (ICC ≤ 40 μA), dual independent flip-flop architecture, and SOIC-14 package compatibility with standard 5-V logic systems.

Technical Context

The SN74HCT74DRG4 implements two electrically isolated D-type latches triggered on the rising edge of CLK, each with asynchronous active-low PRE and CLR inputs that override clocked data transfer. Its CMOS HCT process ensures TTL-level input compatibility while maintaining CMOS power efficiency and noise immunity.

Timing behavior is defined by setup time (tsu = 14 ns @ 5.5 V), hold time (th = 0 ns), and propagation delay (tpd = 17 ns typ @ 5.5 V, CLK→Q). Output switching characteristics are specified under CL = 50 pF load, with guaranteed fan-out of 10 LSTTL loads and ±25-mA absolute maximum output current.

Key Specifications

Pinout & Package

SN74HCT74DRG4 is housed in a 14-pin SOIC (D) package measuring 8.65 mm × 3.90 mm with 1.27-mm lead pitch and 1.75-mm maximum height. The package is RoHS-compliant, moisture-sensitive level 1, and rated for reflow up to 260 °C.

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 MC74HC74ADTR2G, SN74HCT74DRG4 uniquely guarantees TTL-compatible input thresholds at 5 V, enabling plug-in replacement in legacy 74LS-based systems without redesign, while maintaining lower ICC than standard LS devices and tighter timing control than general-purpose HC variants.

Availability

SN74HCT74DRG4 is available at Aetrix Electronics and suitable for industrial control sequencing, digital clock division, microcontroller GPIO expansion, and power-up state initialization requiring stable component supply and long-term production continuity.

Supply support for SN74HCT74DRG4 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 ICs, with over 50 years of innovation in industrial, automotive, and communications markets.

The SN74HCT74DRG4 belongs to TI's 74HCT logic family, engineered specifically for 5-V TTL-to-CMOS bridging in industrial control, instrumentation, and legacy system upgrades where input compatibility and noise immunity are critical.

FAQ

What is the maximum clock frequency supported by SN74HCT74DRG4?

The SN74HCT74DRG4 supports a maximum clock frequency of 24 MHz at VCC = 5.5 V and TA = 25 °C, based on its guaranteed 18 ns minimum clock pulse width and 17 ns typical propagation delay. At 4.5 V, fmax drops to 22 MHz. These values assume CL = 50 pF and proper power supply decoupling with a 0.1-μF capacitor.

Does SN74HCT74DRG4 require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of SN74HCT74DRG4 must be tied to VCC or GND to prevent floating states that cause excessive ICC, erratic switching, or ESD susceptibility. TI recommends connecting unused PRE/CLR inputs to VCC (inactive high) and unused D inputs to GND or VCC depending on desired default state, per SCBA004 application report.

Can SN74HCT74DRG4 operate reliably at 3.3 V supply voltage?

No - SN74HCT74DRG4 is specified only for 4.5 V to 5.5 V operation. At 3.3 V, VIH and VIL thresholds become undefined, input transition behavior degrades, and output drive falls outside specification. For 3.3-V systems, use SN74LVC74A or SN74AUP1G74 instead.

What is the meaning of the 'G4' suffix in SN74HCT74DRG4?

The 'G4' suffix in SN74HCT74DRG4 indicates Green (RoHS-compliant, lead-free) packaging with NiPdAu (nickel-palladium-gold) lead finish and compliance with JEDEC J-STD-020 moisture sensitivity level 1. It confirms the device meets TI's current environmental standards and is qualified for standard 260 °C reflow profiles.

How does the asynchronous preset/clear functionality behave when both PRE and CLR are low simultaneously?

When both PRE and CLR are low on the same channel of SN74HCT74DRG4, the outputs enter a metastable nonstable state (Q = Q̅ = HIGH), as documented in the function table. This condition resolves unpredictably upon release; TI advises avoiding simultaneous assertion and using priority encoding or external logic to prevent it in production designs.