Texas Instruments SN74HCT74NG4

Overview

SN74HCT74NG4 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 ±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 within industrial PLCs and instrumentation interfaces.

For engineers reviewing the SN74HCT74NG4 datasheet, SN74HCT74NG4 pinout, SN74HCT74NG4 application, or SN74HCT74NG4 equivalent, key selection criteria include TTL-compatible input thresholds (VIH = 2 V, VIL = 0.8 V), low 40-μA max ICC quiescent current, and guaranteed setup/hold timing (tsu = 14 ns, th = 0 ns at 5.5 V) for reliable edge-triggered data capture in noise-resilient 5-V logic systems.

Technical Context

The SN74HCT74NG4 implements two electrically isolated D-type flip-flops sharing no internal signal paths, each with asynchronous active-low PRE and CLR inputs that override clocked operation. Its CMOS HCT architecture ensures TTL-voltage compatibility while maintaining CMOS power efficiency and noise immunity.

Triggering occurs on the positive-going edge of CLK at a defined voltage threshold (~1.3 V), independent of input rise time, and data transfer requires only 14 ns setup time before CLK↑ at 5.5 V - enabling robust operation in mixed-signal environments where clock jitter or slow edges may occur.

Key Specifications

Pinout & Package

Packaged in 14-pin PDIP (Plastic Dual In-line Package) with 19.31 mm × 6.35 mm body size and through-hole mounting compatibility. Pin 1 marked by notch or dot; pin 7 = GND, pin 14 = VCC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT74DR and 74HCT74D,653, the SN74HCT74NG4 provides direct through-hole compatibility for manual assembly and field replacement, while retaining identical logic functionality and timing - making it indispensable for maintenance, education, and low-volume industrial control boards where soldering flexibility matters.

Availability

SN74HCT74NG4 is available at Aetrix Electronics and suitable for industrial control sequencing, digital signal synchronization, test equipment logic control, and legacy system interface bridge applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT74NG4 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 and automotive electronics.

The SN74HCT74NG4 belongs to TI's 74HCT logic family, designed specifically for TTL-to-CMOS interfacing in industrial control, instrumentation, and legacy system upgrades where robust 5-V operation and noise immunity are critical.

FAQ

What is the maximum clock frequency supported by SN74HCT74NG4?

The SN74HCT74NG4 supports up to 24 MHz maximum clock frequency at VCC = 5.5 V and TA = 25 °C, as specified in its switching characteristics table. This limit derives from the 17 ns typical propagation delay and required setup/hold timing margins. At lower supply voltages (e.g., 4.5 V), maximum frequency reduces to 22 MHz due to increased tpd.

Does SN74HCT74NG4 require external pull-up resistors on PRE and CLR inputs?

No - SN74HCT74NG4 does not require external pull-up resistors on PRE and CLR inputs when actively driven, but unused PRE/CLR pins must be tied to VCC (logic high) to prevent floating states. The device specifies VIH ≥ 2.0 V and VIL ≤ 0.8 V, and internal input structure ensures stable high-impedance behavior only when externally biased.

Can SN74HCT74NG4 operate reliably at 3.3 V supply voltage?

No - SN74HCT74NG4 is not specified for 3.3 V operation. Its recommended operating range is strictly 4.5 V to 5.5 V, and absolute maximum ratings prohibit sustained operation below 4.5 V. Attempting 3.3 V supply risks failure to meet VIH/VIL thresholds, increased propagation delay, and potential functional instability.

What is the thermal resistance (RθJA) of SN74HCT74NG4 in its PDIP package?

The SN74HCT74NG4 in PDIP (N) package has a junction-to-ambient thermal resistance (RθJA) of 61.1 °C/W, as documented in Section 5.3 of the datasheet. This value assumes standard JEDEC High-K board conditions and confirms suitability for natural-convection cooling in industrial enclosures without forced airflow.

How does the asynchronous clear function behave relative to clock timing in SN74HCT74NG4?

In SN74HCT74NG4, asserting CLR low immediately forces Q = L and Q̅ = H, regardless of CLK state, D input, or setup/hold timing - this action is fully asynchronous and requires no clock edge. Once CLR returns high, the flip-flop resumes normal edge-triggered operation on the next CLK↑, provided setup time is met.