Texas Instruments SN74HCT74NE4

Overview

SN74HCT74NE4 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 such as digital counters and state machines.

For engineers reviewing the SN74HCT74NE4 datasheet, SN74HCT74NE4 pinout, SN74HCT74NE4 application, or SN74HCT74NE4 equivalent, key selection criteria include its PDIP-14 package compatibility with through-hole prototyping, guaranteed 5-V operation with LSTTL load drive capability, and dual independent flip-flop architecture enabling clock-synchronized data latching and reset/preset control in industrial control and instrumentation circuits.

Technical Context

The SN74HCT74NE4 implements two electrically isolated D-type flip-flops sharing no internal signal paths; each responds independently to its own CLK, D, PRE, and CLR inputs. Clock triggering occurs at a fixed voltage threshold (~1.3 V), not dependent on input slew rate, ensuring robust edge detection across temperature and voltage variations.

Each flip-flop features asynchronous active-low PRE and CLR inputs that override clocked data transfer, allowing immediate set/reset regardless of CLK or D state. When both PRE and CLR are high, data at D is transferred to Q on the rising edge of CLK, provided setup (14 ns min at 5.5 V) and hold (0 ns) timing requirements are met.

Key Specifications

Pinout & Package

SN74HCT74NE4 uses a 14-pin plastic dual in-line package (PDIP) with 19.31 mm × 6.35 mm body size and 2.54 mm lead pitch, optimized for through-hole mounting and manual prototyping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HCT74NE4, SN74HCT74DRE4 offers superior thermal performance in compact layouts but requires SMT infrastructure, while 74HCT74N provides identical functionality with updated environmental compliance - making SN74HCT74NE4 optimal for legacy repair, hand-soldered prototypes, and industrial field-replaceable units.

Availability

SN74HCT74NE4 is available at Aetrix Electronics and suitable for industrial control sequencing, digital test equipment, serial-to-parallel conversion, and state machine implementation requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT74NE4 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 90 years of innovation in industrial, automotive, and communications electronics.

The SN74HCT74NE4 belongs to TI's 74HCT logic family, designed specifically to bridge TTL and CMOS domains with 5-V operation, TTL-compatible inputs, and low-power CMOS outputs for reliable interoperability in mixed-technology systems.

FAQ

What is the maximum clock frequency supported by SN74HCT74NE4?

SN74HCT74NE4 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, the maximum frequency drops to 22 MHz due to slower internal switching. This rating assumes proper load conditions (CL = 50 pF) and valid setup/hold timing margins.

Does SN74HCT74NE4 require external pull-up resistors on PRE and CLR inputs?

No, SN74HCT74NE4 does not require external pull-up resistors on PRE and CLR inputs because these are active-low, TTL-compatible inputs with defined voltage thresholds (VIL ≤ 0.8 V, VIH ≥ 2 V). When left unasserted, they must be tied to VCC (not floating) per TI's application guidance - a direct connection suffices; no resistor is needed unless noise immunity in high-EMI environments justifies adding one.

Can SN74HCT74NE4 operate reliably at 3.3 V?

No, SN74HCT74NE4 cannot operate reliably at 3.3 V. Its recommended operating voltage 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 operation results in undefined logic levels, increased propagation delay, and potential failure to meet setup/hold timing - use SN74LVC74A or similar 3.3-V logic for that voltage domain.

How many LSTTL loads can SN74HCT74NE4 drive per output?

SN74HCT74NE4 can drive up to 10 LSTTL loads per output, as specified in its datasheet features. This is enabled by its ±4-mA output drive capability at 5 V, which matches the aggregate input current requirement of 10 LSTTL inputs (each drawing ~0.4 mA high, 1.6 mA low). Exceeding this count risks violating VOH/VOL specifications and timing margins.

Is SN74HCT74NE4 pin-compatible with SN74LS74A?

Yes, SN74HCT74NE4 is pin-compatible with SN74LS74A in the PDIP-14 package - both share identical pin assignments for VCC, GND, CLK, D, PRE, CLR, Q, and Q̅ across two independent channels. However, SN74HCT74NE4 draws significantly less quiescent current (40 μA vs. ~8 mA) and offers higher noise immunity, making it a direct drop-in replacement in most 5-V TTL systems where power and thermal constraints exist.