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Texas Instruments SN74LS74AD
- Part No.:
- SN74LS74AD
- Manufacturer:
- Texas Instruments
- Category:
- Flip Flops
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS74AD.pdf
- Description:
- IC FF D-TYPE DUAL 1BIT 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,699
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Product details
Overview
SN74LS74AD from Texas Instruments is a dual D-type positive-edge-triggered flip-flop in SOIC-14 package, operating from 4.75 V to 5.25 V with typical propagation delay of 15 ns and maximum clock frequency of 30 MHz. It features complementary Q and Q̅ outputs per section, independent preset and clear inputs, and is used in synchronous logic control, data latching, and clock division circuits in industrial control panels and legacy instrumentation.
For engineers reviewing the SN74LS74AD datasheet, SN74LS74AD pinout, SN74LS74AD application, or SN74LS74AD equivalent, this page delivers verified functional specifications, validated pin assignments, confirmed TTL-compatible input thresholds, real-world timing constraints, and direct alternative options for legacy system maintenance and redesign.
Technical Context
The SN74LS74AD implements two independent edge-triggered D flip-flops with asynchronous active-low preset (PR̅) and clear (CLR̅) inputs. Each section responds only on the rising edge of the clock (CLK), ensuring deterministic state capture synchronized to system timing.
It belongs to the 74LS logic family, delivering standard TTL voltage levels (VIH = 2.0 V min, VIL = 0.8 V max), fan-out of 20 LS-TTL loads, and guaranteed operation across 0°C to 70°C ambient temperature. Its internal structure uses bipolar Schottky-clamped transistors for speed-power optimization.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS (Low-power Schottky TTL) - ensures compatibility with legacy TTL systems and predictable noise margins. |
| Supply Voltage | 4.75 V to 5.25 V - requires stable +5 V rail; operation outside this range risks metastability or latch-up. |
| Propagation Delay | 15 ns (typ) at VCC = 5 V, CL = 15 pF - defines minimum clock-to-output timing for synchronous design margining. |
| Maximum Clock Frequency | 30 MHz - sets upper bound for reliable toggle rate in counter or register applications. |
| Input Thresholds | VIH = 2.0 V min, VIL = 0.8 V max - enables interoperability with 5 V CMOS outputs and microcontroller GPIOs. |
| Output Drive | IOL = 8 mA, IOH = –0.4 mA - supports direct driving of LEDs, small relays, or cascaded LS inputs without buffering. |
Pinout & Package
SN74LS74AD is housed in a 14-pin SOIC (D) package, 3.90 mm wide, 8.65 mm long, and 1.75 mm maximum height, with 1.27 mm pitch and gull-wing leads. Pin 1 is marked by a beveled corner or notch on the package top.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (1CLR̅) | Asynchronous clear input (Section 1) | Active-low reset: forces Q1 = 0, Q̅1 = 1 regardless of clock or D1 state. |
| 2 (1D) | Data input (Section 1) | Samples value on rising CLK edge; determines next-state Q1 output. |
| 3 (1CLK) | Clock input (Section 1) | Positive-edge-triggered; transition from low to high captures 1D into Q1. |
| 4 (1Q̅) | Inverted output (Section 1) | Complement of Q1; provides logical inversion without external gate. |
| 5 (1Q) | True output (Section 1) | Primary stored state output; drives downstream logic or indicators. |
| 6 (2Q) | True output (Section 2) | Independent storage element output; electrically isolated from Section 1. |
| 7 (GND) | Ground reference | Return path for all internal currents; must be low-impedance and decoupled near VCC pin. |
| 8 (2Q̅) | Inverted output (Section 2) | Complement of Q2; enables differential signaling or XOR-based feedback. |
| 9 (2CLK) | Clock input (Section 2) | Independent edge-sensitive trigger; allows separate clock domains per section. |
| 10 (2D) | Data input (Section 2) | Independent data path; supports dual-channel latching in single IC. |
| 11 (2CLR̅) | Asynchronous clear input (Section 2) | Independent reset control; avoids global reset when only one section needs clearing. |
| 12 (2PR̅) | Asynchronous preset input (Section 2) | Active-low set: forces Q2 = 1, Q̅2 = 0 independently of clock or D2. |
| 13 (1PR̅) | Asynchronous preset input (Section 1) | Independent set control; enables initialization to known state without clock dependency. |
| 14 (VCC) | Positive supply | +5 V power rail; requires 0.1 µF ceramic decoupling capacitor placed within 5 mm. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent D flip-flops | Enables two-bit storage or parallel data capture in one 14-pin SOIC footprint, reducing board space vs discrete solutions. |
| Asynchronous preset and clear | Allows immediate initialization or reset without waiting for clock edge-critical for power-on sequencing and fault recovery. |
| Positive-edge clock triggering | Eliminates race conditions in synchronous designs by sampling input only at defined rising transitions. |
| TTL-compatible input thresholds | Guarantees interoperability with legacy 74-series logic, microcontrollers, and FPGA I/O banks configured for 5 V TTL. |
| SOIC-14 RoHS-compliant packaging | Supports automated SMT assembly with standard reflow profiles (Level-1-260°C-UNLIM); lead finish is NiPdAu. |
Applications
| Industrial Control Logic | Digital Instrumentation |
|---|---|
Use Scenario: Latching sensor status (e.g., limit switch closure) in PLC I/O modules until acknowledged by host controller. IC Role / Device Role / Timing Role: Dual D flip-flop acts as edge-triggered input register, capturing momentary events on rising CLK synchronized to scan cycle. Use Value: Prevents missed pulses during fast scan intervals; PR̅/CLR̅ enable hardware-initiated reset without software intervention. |
Use Scenario: Debouncing front-panel pushbuttons in digital multimeters and oscilloscope user interfaces. IC Role / Device Role / Timing Role: Each section implements a 2-stage synchronizer: first stage samples raw button signal, second stage validates stable state after 2–3 ms. Use Value: Eliminates contact bounce artifacts using only internal flip-flops-no external RC networks or firmware delays required. |
| Legacy System Repair | Education & Lab Training |
Use Scenario: Replacing failed 74LS74 variants in discontinued test equipment where PCB layout prohibits package change. IC Role / Device Role / Timing Role: Drop-in functional replacement for SN74LS74ADR/SN74LS74AN in existing SOIC footprints. Use Value: Maintains identical timing, drive strength, and voltage thresholds-no schematic or firmware modification needed. |
Use Scenario: Teaching sequential logic fundamentals in university electronics labs using breadboard-based experiments. IC Role / Device Role / Timing Role: Core component in clocked counters, shift registers, and finite-state machine implementations. Use Value: Clear pinout, robust noise immunity, and predictable edge-trigger behavior make it ideal for student debugging and oscilloscope verification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual D flip-flop applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS74ADR | Same electrical specs and pinout; differs only in tape-and-reel packaging (2500 pcs/reel vs SN74LS74AD's obsolete status). | Identical use in new designs; preferred for volume production due to active status and full TI support. | Select SN74LS74ADR for new designs requiring guaranteed long-term availability and TI-backed documentation. |
| SN74LS74ANSR | SOIC-14 variant with same logic function but SOP (NS) package; slightly larger body (8.1 mm × 10.4 mm vs 3.9 mm × 8.65 mm) and different land pattern. | Requires PCB footprint change; suitable only when NS package is already standardized in the design ecosystem. | Choose SN74LS74ANSR only if SOP-14 is mandated by existing assembly lines or legacy board reuse constraints. |
Compared with SN74LS74AD, SN74LS74ADR offers assured supply continuity and identical performance, while SN74LS74ANSR trades compactness for compatibility with SOP-based manufacturing-neither is pin-compatible without layout revision, but both deliver functionally equivalent dual D flip-flop behavior.
Availability
SN74LS74AD is available at Aetrix Electronics and suitable for industrial control logic, digital instrumentation, legacy system repair, and educational lab training requiring stable component supply and verified TTL-level compatibility.
Supply support for SN74LS74AD 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, embedded processing, and logic ICs with broad industrial and automotive qualification.
The SN74LS74AD belongs to TI's legacy 74LS logic product line, designed for backward compatibility with 1970s–1990s TTL-based systems while maintaining manufacturability and reliability for maintenance and retrofit applications.
FAQ
What is the operating temperature range for SN74LS74AD?
The SN74LS74AD is specified for commercial-grade operation from 0°C to +70°C ambient temperature. This range aligns with standard industrial environments and indoor instrumentation use cases. It does not support extended or military temperature ranges; for –40°C to +85°C operation, consider SN74LS74ADR with identical functionality and broader qualification.
Is SN74LS74AD pin-compatible with SN74LS74AN?
Yes, SN74LS74AD is pin-compatible with SN74LS74AN-the same 14-pin dual-in-line pinout applies-but they differ in package type: SN74LS74AD uses SOIC (D), while SN74LS74AN uses PDIP (N). Mechanical mounting and PCB footprint are not interchangeable, though logic function, timing, and electrical behavior are identical.
Does SN74LS74AD support 3.3 V logic interfacing?
No, SN74LS74AD is not 3.3 V compatible. It requires a 4.75 V to 5.25 V supply and has TTL input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). Direct connection to 3.3 V CMOS outputs may result in marginal VIH margin; level-shifting or buffer ICs are recommended for mixed-voltage systems.
What is the maximum fan-out capability of SN74LS74AD?
The SN74LS74AD supports a fan-out of 20 LS-TTL loads per output. This means each Q or Q̅ output can reliably drive up to 20 inputs of other 74LS-series devices. Exceeding this load increases propagation delay and may cause logic errors; buffer stages are required for higher fan-out demands.
Can SN74LS74AD replace SN74S74 in existing designs?
SN74LS74AD can functionally replace SN74S74 in most applications, but with trade-offs: SN74S74 offers faster propagation delay (~5 ns) and higher drive strength, while SN74LS74AD consumes less power and runs cooler. Verify timing margins and output loading in the target circuit before substitution.
SN74LS74AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- 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:
- 33 MHz
- Max Propagation Delay @ V, Max CL:
- 40ns @ 5V, 15pF
- Trigger Type:
- Positive Edge
- Current - Output High, Low:
- 400µA, 8mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Current - Quiescent (Iq):
- 8 mA
- Input Capacitance:
- -
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
SN74LS74AD FAQ
1.How can I place an order for SN74LS74AD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS74AD 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 SN74LS74AD reliable?
The price and inventory of SN74LS74AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS74AD is usually 5 days.
3.What payment methods are accepted for SN74LS74AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS74AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS74AD?
SN74LS74AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS74AD 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 SN74LS74AD?
For technical support, including SN74LS74AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS74AD requirements.
6.How does Aetrix verify that SN74LS74AD is sourced from the original manufacturer or authorized distributors?
All SN74LS74AD 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 SN74LS74AD meets industry standards.
7.What is the process for return or replacement of SN74LS74AD?
All SN74LS74AD units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS74AD, 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 SN74LS74AD part is unused and in its original packaging.
Return procedure for SN74LS74AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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