Texas Instruments SN74HC74DBRG4

Overview

SN74HC74DBRG4 from Texas Instruments is a dual D-type positive-edge-triggered flip-flop with independent asynchronous preset and clear inputs per channel, operating across 2 V to 6 V supply voltage and -40°C to +85°C temperature range. It delivers 39 ns typical propagation delay (VCC = 6 V), supports fanout of up to 10 LSTTL loads, and is used in clock division and momentary-to-toggle switch conversion circuits.

For engineers reviewing the SN74HC74DBRG4 datasheet, SN74HC74DBRG4 pinout, SN74HC74DBRG4 application, or SN74HC74DBRG4 equivalent, this device serves as a foundational building block for synchronous logic design, edge-triggered state storage, and low-power digital control where precise timing and dual-channel independence are required.

Technical Context

The SN74HC74DBRG4 implements two fully independent CMOS D-type flip-flops, each with separate asynchronous active-low preset (PRE) and clear (CLR) inputs, and a shared positive-edge-sensitive clock input per channel. Its functional behavior is defined by a verified truth table specifying Q/Q states under all PRE/CLR/CLK/D combinations, including metastability-aware hold-time-zero operation.

It uses standard CMOS inputs with ≤10 pF input capacitance and balanced push-pull outputs capable of sourcing/sinking ±4 mA (VCC = 4.5 V) or ±5.2 mA (VCC = 6 V), enabling direct interfacing with LSTTL loads while maintaining rail-to-rail output swing and low static current (≤40 µA at VCC = 6 V).

Key Specifications

Pinout & Package

SN74HC74DBRG4 is packaged in a 14-pin SSOP (Shrink Small Outline Package) with nominal body size 6.50 mm × 5.30 mm and 0.65 mm lead pitch. This surface-mount package supports automated assembly and offers improved thermal resistance (RθJA = 107.7 °C/W) versus SOIC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC74DBRG4, SN74HCT74DBR offers superior TTL input compatibility at the cost of higher quiescent current, while MC74HC74ADTR2G trades thermal performance for reduced PCB footprint - both require validation of layout thermal relief and signal integrity in high-density designs.

Availability

SN74HC74DBRG4 is available at Aetrix Electronics and suitable for industrial control panels, test equipment interfaces, and consumer appliance timing circuits requiring stable component supply and long-term production continuity.

Supply support for SN74HC74DBRG4 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.

SN74HC74DBRG4 belongs to the 74HC high-speed CMOS logic product line, designed specifically for low-power, pin-compatible replacements of legacy TTL logic in industrial, automotive, and communications systems.

FAQ

What is the maximum clock frequency supported by SN74HC74DBRG4?

The SN74HC74DBRG4 supports a maximum clock frequency of 29 MHz at VCC = 6 V and TA = –40°C to +85°C, as specified in the switching characteristics table. At VCC = 4.5 V, the guaranteed maximum is 25 MHz. These values assume proper setup/hold timing and load conditions ≤70 pF; exceeding them may cause metastability or timing violations in the SN74HC74DBRG4.

Does SN74HC74DBRG4 require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of SN74HC74DBRG4 must be terminated to either VCC or GND to prevent floating states that cause excessive current draw or erratic operation. TI recommends 10-kΩ resistors for default HIGH (pull-up) or LOW (pull-down) biasing; direct connection is acceptable if the input is permanently unused. Leaving inputs unconnected violates the SN74HC74DBRG4 functional specification.

Can SN74HC74DBRG4 drive LSTTL loads directly?

Yes - SN74HC74DBRG4 is explicitly rated to support fanout of up to 10 LSTTL loads. Its output drive strength (±4 mA at VCC = 4.5 V, ±5.2 mA at VCC = 6 V) meets LSTTL input current requirements (IIH ≤ 20 µA, IIL ≤ 0.4 mA), enabling direct interface without buffers. However, total capacitive load should remain ≤70 pF to maintain SN74HC74DBRG4 timing compliance.

What is the purpose of the PRE and CLR pins on SN74HC74DBRG4?

The PRE (preset) and CLR (clear) pins on SN74HC74DBRG4 provide asynchronous, active-low control over each flip-flop's output state: PRE forces Q = HIGH / Q = LOW, while CLR forces Q = LOW / Q = HIGH - both independent of the clock signal. These pins enable deterministic power-on initialization, emergency reset, or mode forcing in the SN74HC74DBRG4 without waiting for clock edges.

Is SN74HC74DBRG4 compatible with 3.3 V logic systems?

Yes - SN74HC74DBRG4 operates down to 2 V supply voltage and features CMOS input thresholds scalable with VCC (e.g., VIH ≈ 0.7×VCC). At VCC = 3.3 V, it reliably accepts 3.3 V logic-high signals and produces rail-aligned outputs, making it fully interoperable with 3.3 V microcontrollers and FPGAs without level-shifting circuitry in the SN74HC74DBRG4 signal path.