Texas Instruments SN74AHCT174D

Overview

SN74AHCT174D from Texas Instruments is a positive-edge-triggered hex D-type flip-flop with asynchronous active-low clear, designed for synchronous data latching in digital logic systems. It features six independent D-flip-flop channels, TTL-compatible inputs (VIH = 2 V, VIL = 0.8 V), 5-V supply operation (4.5–5.5 V), and guaranteed 100 MHz maximum clock frequency at CL = 15 pF - used in buffer/register applications requiring deterministic edge-triggered storage.

For engineers reviewing the SN74AHCT174D datasheet, SN74AHCT174D pinout, SN74AHCT174D application, or SN74AHCT174D equivalent, this device supports high-speed register staging, pattern generation, and shift register control where precise setup/hold timing (tsu = 5 ns, th = 0 ns) and low propagation delay (tPLH = 5.8 ns typical) are critical to system-level timing integrity.

Technical Context

This IC implements six independent D-type latches synchronized to the rising edge of CLK, with a shared asynchronous CLR input that forces all Q outputs low regardless of clock state. Each channel operates with single-rail CMOS-compatible outputs capable of ±8 mA drive strength under 5-V supply conditions.

Its TTL-voltage-compatible inputs allow direct interfacing with legacy 5-V TTL logic families without level-shifting, while its latch-up immunity (>250 mA per JESD17) and ESD robustness (±2000 V HBM) support reliable operation in industrial control and instrumentation environments.

Key Specifications

Pinout & Package

SN74AHCT174D is housed in a 16-pin SOIC (D) package measuring 9.9 mm × 6.0 mm (body: 9.00 mm × 3.90 mm), with 1.27-mm lead pitch and gull-wing leads suitable for reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT174D, SN74AHC174D sacrifices TTL input compatibility for reduced power and tighter noise margins, while 74LV174D trades 5-V operation for speed and efficiency in 3.3-V domains - neither offers drop-in replacement capability without voltage or interface redesign.

Availability

SN74AHCT174D is available at Aetrix Electronics and suitable for industrial control systems, test equipment design, and programmable logic interface applications requiring stable component supply and long-term obsolescence management.

Supply support for SN74AHCT174D 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 U.S.-based semiconductor company founded in 1930, specializing in analog and embedded processing solutions with broad industrial, automotive, and communications product portfolios.

The SN74AHCT174D belongs to TI's 74AHCT logic family - engineered for seamless 5-V TTL-to-CMOS interfacing in legacy system upgrades, industrial PLCs, and instrumentation where signal integrity and backward compatibility are mandatory.

FAQ

What is the function of the CLR pin on the SN74AHCT174D?

The CLR (pin 1) is an asynchronous active-low clear input that forces all six Q outputs (pins 2, 5, 7, 10, 12, 15) to logic low immediately, regardless of the CLK state or timing. This function is critical for system initialization and fault recovery in the SN74AHCT174D, and it operates independently of the clock edge - making it ideal for emergency stop circuits or power-on reset sequences in industrial hardware using the SN74AHCT174D.

Does the SN74AHCT174D support mixed-voltage operation between 3.3 V and 5 V?

No - the SN74AHCT174D is specified only for 4.5–5.5 V supply operation and requires TTL-compatible input voltages (VIH ≥ 2 V, VIL ≤ 0.8 V). While its outputs swing rail-to-rail (0 V to VCC), it cannot accept 3.3-V logic inputs reliably without external level shifting, and its internal circuitry is not characterized below 4.5 V. Therefore, SN74AHCT174D must be used in strictly 5-V systems or with interface buffers when connecting to 3.3-V controllers.

What is the minimum setup time required for data inputs on the SN74AHCT174D?

The SN74AHCT174D requires a minimum data setup time (tsu) of 5 ns before the rising edge of CLK at TA = 25°C and VCC = 5 V. This specification ensures reliable capture of D-input states into the flip-flop registers. At worst-case industrial temperature (–40°C to +85°C) and supply (4.5 V), the datasheet maintains tsu = 5 ns - meaning timing-critical designs using the SN74AHCT174D must guarantee D-input stability for at least 5 ns prior to each CLK↑ transition.

Can unused inputs on the SN74AHCT174D be left floating?

No - all unused inputs on the SN74AHCT174D must be tied to a defined logic level (VCC or GND) to prevent undefined output states, increased power consumption, and potential oscillation. The datasheet explicitly mandates this for proper device operation. For example, if only three D inputs are used, the remaining three D pins and the unused portion of the CLR net must be terminated - directly tying them to VCC or GND ensures predictable behavior and avoids noise coupling in systems deploying the SN74AHCT174D.

Is the SN74AHCT174D pin-compatible with other 74-series hex D-flip-flops like the 74LS174?

Yes - the SN74AHCT174D shares identical pinout (16-pin SOIC), terminal assignments, and functional block diagram with industry-standard 74LS174 and 74HC174 devices. However, electrical characteristics differ: SN74AHCT174D offers TTL-compatible inputs and CMOS outputs, whereas 74LS174 uses bipolar inputs and outputs. Thus, while PCB layout is interchangeable, direct substitution requires verification of drive strength, timing, and supply compatibility - especially when replacing 74LS174 with SN74AHCT174D in legacy 5-V systems.