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Home > Products > Integrated Circuits (ICs) > Logic > Flip Flops

Texas Instruments SN74AC74D

Name: SN74AC74D
Brand: Texas Instruments
SKU: SN74AC74D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74AC74D

Manufacturer:: Texas Instruments

Category:: Flip Flops

Package:: 14-SOIC (0.154", 3.90mm Width)

Datasheet:: SN74AC74D.pdf

Description:: IC FF D-TYPE DUAL 1BIT 14SOIC

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74AC74D from Texas Instruments is a dual positive-edge-triggered D-type flip-flop IC with independent asynchronous clear (CLR) and preset (PRE) inputs per channel, operating across 2V–6V V_CC, delivering ≤10ns propagation delay at 5V, and supporting clock division by 2/4 in digital control logic and switch debouncing circuits.

For engineers reviewing the SN74AC74D datasheet, SN74AC74D pinout, SN74AC74D application, or SN74AC74D equivalent, this page provides verified functional role, SOIC-14 package mapping, timing-critical parameters (t_PLH/t_PHL, f_max, t_su), and real-world toggle-switch and clock-division use cases - all confirmed against TI's SCAS521H production data sheet (Rev H, June 2025).

Technical Context

The SN74AC74D implements two fully independent CMOS D-type flip-flops, each with separate active-low asynchronous PRE and CLR inputs, non-inverted (Q) and inverted (Q̅) outputs, and edge-sensitive CLK inputs. Its balanced push-pull output stage supports ±24mA drive at 4.5V while maintaining rail-to-rail voltage compliance.

It operates under standard CMOS input logic with VIH/VIL thresholds tied to V_CC (e.g., VIH = 3.15V at V_CC = 4.5V), requires no external pull resistors on unused inputs when tied directly to V_CC or GND, and exhibits latch-up immunity per JEDEC JESD78.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	2V to 6V - enables direct interface with 3.3V and 5V logic families without level shifters
Max Propagation Delay	10ns at V_CC = 5V - ensures reliable operation in high-speed synchronous logic up to 125MHz f_max
Output Drive	±24mA at V_CC = 4.5V - sufficient to drive multiple 74AC inputs or small capacitive loads (<50pF)
Input Voltage Tolerance	Accepts up to 6V regardless of V_CC - allows mixed-voltage system interfacing and hot-swap compatibility
Setup/Hold Times	t_su = 3ns, t_h = 0.5ns at 5V - minimal timing margin required for clean edge-triggered sampling
Power Dissipation Cap.	C_pd = 45pF at 3.3V/1MHz - enables accurate dynamic power estimation in battery-sensitive designs

Pinout & Package

SN74AC74D is supplied in a 14-pin SOIC (D) package measuring 8.65mm × 6mm (body: 8.65mm × 3.9mm), with gull-wing leads and standard JEDEC MS-012AC footprint.

Pin/Terminal	Circuit Role	Design Meaning
1 CLR	Channel 1 Clear Input (active low)	Asynchronously forces Q₁ = LOW, Q̅₁ = HIGH - used for hardware reset independent of clock
2 D₁	Channel 1 Data Input	Samples value on rising CLK edge; ties to Q̅₁ for toggle mode
3 CLK₁	Channel 1 Clock Input (positive edge)	Edge-triggered sampling point - must meet ∆t/∆v ≤ 8 ns/V for reliable operation
4 PRE₁	Channel 1 Preset Input (active low)	Asynchronously forces Q₁ = HIGH, Q̅₁ = LOW - used for known power-on state initialization
5 Q₁	Channel 1 Non-Inverted Output	Primary logic output; drives downstream gates or LEDs with rail-aligned swing
6 Q̅₁	Channel 1 Inverted Output	Complementary signal; enables toggle configuration when fed back to D₁
7 GND	Ground Reference	Common return path for all I/O and supply currents; requires low-impedance PCB plane
8 Q̅₂	Channel 2 Inverted Output	Independent complement of Q₂; usable as second toggle output or status indicator
9 Q₂	Channel 2 Non-Inverted Output	Second independent output; electrically isolated from Channel 1 except shared V_CC/GND
10 PRE₂	Channel 2 Preset Input (active low)	Separate preset control - allows asymmetric initialization of dual channels
11 CLK₂	Channel 2 Clock Input (positive edge)	Independent clock domain - supports dual-rate or phase-shifted timing
12 D₂	Channel 2 Data Input	Independent data path; may be driven by Q₁ or external source
13 CLR₂	Channel 2 Clear Input (active low)	Independent reset - enables selective channel clearing without affecting Channel 1
14 V_CC	Positive Supply	Single-supply rail (2–6V); bypass capacitor (0.1µF) required adjacent to pin for noise immunity

Key Features

Feature	Design Value
Dual independent flip-flops	Enables two concurrent synchronous functions (e.g., dual clock dividers or parallel toggle stages) in one SOIC-14 package
Asynchronous PRE/CLR per channel	Allows deterministic power-on initialization and emergency reset without waiting for clock edges
2V–6V wide V_CC range	Eliminates need for dedicated level translators in mixed-voltage systems (e.g., 3.3V MCU controlling 5V peripherals)
≤10ns t_pd at 5V	Supports 125MHz maximum clock frequency - suitable for high-speed counters and state machines
CMOS push-pull outputs	Provides symmetrical sourcing/sinking (±24mA), enabling robust driving of transmission lines or capacitive loads

Applications

Toggle Switch Emulation	Binary Clock Division
Use Scenario: Replacing mechanical toggle switches in space-constrained industrial HMI panels using momentary push buttons. IC Role / Device Role / Timing Role: SN74AC74D configured as a toggle flip-flop (D₁ → Q̅₁ feedback) with Schmitt-triggered CLK input for switch debouncing. Use Value: Reduces BOM cost and improves long-term reliability by eliminating moving parts while maintaining user-intuitive on/off behavior.	Use Scenario: Generating half-frequency clock signals for peripheral interfaces (e.g., UART baud rate derivation from master oscillator). IC Role / Device Role / Timing Role: SN74AC74D Channel 1 used as divide-by-2 counter; Q₁ output serves as synchronized 50% duty-cycle clock. Use Value: Provides glitch-free, edge-aligned division without external RC networks or software overhead - critical for timing-critical serial protocols.
Power-On State Control	LED Status Sequencing
Use Scenario: Ensuring predictable initial states in automotive body-control modules after cold start or brown-out recovery. IC Role / Device Role / Timing Role: SN74AC74D PRE/CLR pins driven by RC-based power-on reset circuit to force Q₁ = LOW and Q₂ = HIGH at startup. Use Value: Guarantees defined logic levels before firmware execution begins - prevents spurious actuator activation or bus contention.	Use Scenario: Driving multi-LED status indicators in network equipment with sequential on/off patterns (e.g., link/activity/activity/error). IC Role / Device Role / Timing Role: SN74AC74D dual outputs control two LEDs directly; cascaded CLK inputs create progressive timing shifts. Use Value: Enables hardware-based visual sequencing without MCU GPIO or timer resources - reduces firmware complexity and latency.

Toggle Switch Emulation

Binary Clock Division

Use Scenario: Replacing mechanical toggle switches in space-constrained industrial HMI panels using momentary push buttons.

IC Role / Device Role / Timing Role: SN74AC74D configured as a toggle flip-flop (D₁ → Q̅₁ feedback) with Schmitt-triggered CLK input for switch debouncing.

Use Value: Reduces BOM cost and improves long-term reliability by eliminating moving parts while maintaining user-intuitive on/off behavior.

Use Scenario: Generating half-frequency clock signals for peripheral interfaces (e.g., UART baud rate derivation from master oscillator).

IC Role / Device Role / Timing Role: SN74AC74D Channel 1 used as divide-by-2 counter; Q₁ output serves as synchronized 50% duty-cycle clock.

Use Value: Provides glitch-free, edge-aligned division without external RC networks or software overhead - critical for timing-critical serial protocols.

Power-On State Control

LED Status Sequencing

Use Scenario: Ensuring predictable initial states in automotive body-control modules after cold start or brown-out recovery.

IC Role / Device Role / Timing Role: SN74AC74D PRE/CLR pins driven by RC-based power-on reset circuit to force Q₁ = LOW and Q₂ = HIGH at startup.

Use Value: Guarantees defined logic levels before firmware execution begins - prevents spurious actuator activation or bus contention.

Use Scenario: Driving multi-LED status indicators in network equipment with sequential on/off patterns (e.g., link/activity/activity/error).

IC Role / Device Role / Timing Role: SN74AC74D dual outputs control two LEDs directly; cascaded CLK inputs create progressive timing shifts.

Use Value: Enables hardware-based visual sequencing without MCU GPIO or timer resources - reduces firmware complexity and latency.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HC74DR	Slower max speed (36MHz vs 125MHz), higher t_pd (27ns @ 4.5V), lower drive (±5.2mA)	Better suited for low-power, low-frequency applications where AC speed is unnecessary	Select SN74HC74DR only if system clock ≤ 25MHz and drive requirements < ±6mA
74LVC74AD	Narrower V_CC range (1.65–5.5V), faster t_pd (5.5ns @ 3.3V), same pinout	Optimized for 3.3V-only systems with tighter timing budgets and lower supply headroom	Choose 74LVC74AD when operating exclusively at 3.3V and requiring sub-6ns propagation delay

Compared with SN74HC74DR and 74LVC74AD, the SN74AC74D uniquely balances wide voltage operation (2–6V), high-speed performance (125MHz), and robust drive strength (±24mA), making it optimal for mixed-voltage industrial control and legacy 5V design reuse.

Availability

SN74AC74D is available at Aetrix Electronics and suitable for industrial automation controllers, test equipment timing modules, and embedded HMI interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74AC74D 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 50 years of innovation in high-reliability logic families.

The SN74AC74D belongs to TI's AC-series advanced CMOS logic family, designed for high-speed, low-noise digital control in industrial, automotive, and communications infrastructure where rail-to-rail operation and timing precision are critical.

FAQ

What is the maximum clock frequency supported by the SN74AC74D?

The SN74AC74D supports a maximum clock frequency of 125MHz at V_CC = 5V ± 0.5V, as specified in Section 5.6 of the SCAS521H datasheet. This is derived from minimum pulse width (5ns) and setup/hold timing constraints. At 3.3V, the rated f_max is 95MHz. Operation beyond these values risks metastability or incorrect state capture.

Can the SN74AC74D operate reliably at 3.3V supply voltage?

Yes, the SN74AC74D is fully specified for 3.3V operation (V_CC = 3.3V ± 0.3V), with guaranteed parameters including t_pd ≤ 13.5ns, f_max ≥ 95MHz, and VIH/VIL thresholds scaled to V_CC. Its 2V–6V range makes it interoperable with both 3.3V and 5V logic families without level translation.

How should unused inputs on the SN74AC74D be handled?

All unused inputs on the SN74AC74D must be terminated to either V_CC or GND - never left floating. TI explicitly mandates this in Section 5.2 to prevent excessive current draw, oscillation, or undefined output states. Direct connection is preferred; if dynamic control is needed, a 10kΩ pull-up or pull-down resistor is recommended.

Does the SN74AC74D have built-in ESD protection?

The SN74AC74D incorporates internal clamp diodes on all inputs and outputs (per Figure 7-2 in SCAS521H), providing ±20mA input/output clamp current protection. However, TI warns that voltages beyond Absolute Maximum Ratings (−0.5V to V_CC + 0.5V) can still cause permanent damage - external ESD safeguards remain essential in handling and PCB layout.

Is the SN74AC74D pin-compatible with other 74xx74 variants?

The SN74AC74D shares the standard 14-pin SOIC (D) footprint and identical pinout with SN74HC74, SN74LS74, and 74LVC74A, enabling drop-in replacement in most cases. However, differences in V_CC range, speed, and drive strength require verification of timing and loading in the target application before substitution.

SN74AC74D Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74AC

Package/Case:: 14-SOIC (0.154", 3.90mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Function:: Set(Preset) and Reset

Type:: D-Type

Output Type:: Complementary

Number of Elements:: 2

Number of Bits per Element:: 1

Clock Frequency:: 160 MHz

Max Propagation Delay @ V, Max CL:: 6ns @ 5V, 50pF

Trigger Type:: Positive Edge

Current - Output High, Low:: 24mA, 24mA

Voltage - Supply:: 2V ~ 6V

Current - Quiescent (Iq):: 2 µA

Input Capacitance:: 3 pF

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 14-SOIC

SN74AC74D FAQ

1.How can I place an order for SN74AC74D through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74AC74D on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN74AC74D reliable?

The price and inventory of SN74AC74D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AC74D is usually 5 days.

3.What payment methods are accepted for SN74AC74D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AC74D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74AC74D?

SN74AC74D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74AC74D order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN74AC74D?

For technical support, including SN74AC74D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AC74D requirements.

6.How does Aetrix verify that SN74AC74D is sourced from the original manufacturer or authorized distributors?

All SN74AC74D products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74AC74D meets industry standards.

7.What is the process for return or replacement of SN74AC74D?

All SN74AC74D units undergo pre-shipment inspection (PSI). If there is an issue with SN74AC74D, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN74AC74D part is unused and in its original packaging.

Return procedure for SN74AC74D:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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