Texas Instruments SN74HCT74PWT

Overview

SN74HCT74PWT 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 circuits.

For engineers reviewing the SN74HCT74PWT datasheet, SN74HCT74PWT pinout, SN74HCT74PWT application, or SN74HCT74PWT equivalent, this page provides verified functional identity, TSSOP-14 package mapping, timing parameters under 5-V operation, TTL-compatible input thresholds, and validated alternative options for logic-level storage design.

Technical Context

The SN74HCT74PWT implements two electrically isolated D-type flip-flops, each triggered on the rising edge of CLK while PRE and CLR operate asynchronously-low-active set/reset overrides clock and data. Its CMOS HCT process ensures TTL-voltage compatibility (VIH = 2 V, VIL = 0.8 V) without external level-shifting.

It supports stable latching under recommended conditions: 4.5–5.5 V VCC, –40°C to +85°C ambient, with setup time (tsu) of 14 ns and hold time (th) of 0 ns at 5.5 V, enabling reliable sampling in moderate-speed digital systems up to 24 MHz maximum clock frequency.

Key Specifications

Pinout & Package

TSSOP-14 package (PW), 5.00 mm × 4.40 mm body size, 0.65-mm lead pitch, 1.2-mm max height; RoHS-compliant, NIPDAU lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC74PWR and 74LVC74APW,118, the SN74HCT74PWT uniquely guarantees TTL-level input compatibility across its full 4.5–5.5 V range while maintaining industrial temperature rating and proven reliability in legacy 5-V control systems - making it the optimal choice where backward compatibility and deterministic timing are non-negotiable.

Availability

SN74HCT74PWT is available at Aetrix Electronics and suitable for industrial PLC input latching, digital clock division, motor phase sequencing, and FSM register applications requiring stable component supply and long-term production continuity.

Supply support for SN74HCT74PWT 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 SN74HCT74PWT belongs to TI's 74HCT logic family, engineered specifically for seamless integration between TTL and CMOS systems - delivering robust noise immunity, low power, and guaranteed 5-V interoperability in mission-critical control logic.

FAQ

What is the maximum clock frequency supported by SN74HCT74PWT?

The SN74HCT74PWT supports a maximum clock frequency of 24 MHz at VCC = 5.5 V and TA = 25°C, as specified in the Switching Characteristics table. At 4.5 V, fmax drops to 22 MHz. This limit derives from propagation delay (tpd ≤ 40 ns) and setup/hold timing constraints - exceeding it risks metastability or incorrect state capture in the SN74HCT74PWT.

Does SN74HCT74PWT require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of the SN74HCT74PWT must be terminated to either VCC or GND to prevent floating states that cause excessive ICC, erratic outputs, or ESD susceptibility. TI explicitly recommends tying unused PRE, CLR, D, or CLK pins to defined logic levels per Application Report SCBA004; leaving them open violates recommended operating conditions for the SN74HCT74PWT.

Can SN74HCT74PWT operate reliably at 3.3 V supply voltage?

No - the SN74HCT74PWT is specified only for 4.5–5.5 V operation. At 3.3 V, VIH (2.0 V) and VIL (0.8 V) thresholds become unmet relative to rail, causing undefined input interpretation and potential latch-up. For 3.3-V systems, use SN74LVC74A or SN74AHC74 instead; the SN74HCT74PWT is not rated or characterized below 4.5 V.

What is the purpose of the NC (no-connect) pin on SN74HCT74PWT?

The SN74HCT74PWT has no NC pin - all 14 pins are functional, as confirmed by the Pin Configuration diagram and Function Table in the official datasheet. Misidentification may arise from generic package drawings; the TSSOP-14 variant used in SN74HCT74PWT assigns every pin to a defined role (D, CLK, PRE, CLR, Q, Q̅, VCC, GND). There is no NC pin in the SN74HCT74PWT pinout.

How does the asynchronous clear (CLR) function interact with the clock signal in SN74HCT74PWT?

In the SN74HCT74PWT, CLR operates asynchronously: asserting CLR low immediately forces Q = L and Q̅ = H, overriding any concurrent CLK activity or D input state. This action occurs independently of clock edges, setup/hold windows, or timing margins - making CLR effective for immediate fault recovery or power-on reset, regardless of ongoing clock transitions in the SN74HCT74PWT.